Grape Breeding 101-Lon J. Rombough

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In trying for the “perfect” wine there are many factors to deal with. The culture of the vine can only be adjusted so much — soil, pruning, training and microclimate all have their limits. The part you can most control is your choice of grape variety. There are enough varieties in the world that most winemakers find at least one that works well enough to suit them, but for others no grape is “just right.”   

The solution? Breed your own grapes. Grape breeding doesn’t take a college degree or special equipment, and while there is no absolute guarantee you will create a wine grape perfect for your climate, odds are good the result will be worthwhile. Add the fact that it will be your own creation, and breeding can be immensely satisfying.

Grape Biology Basics

First, it helps to know a little bit about grape biology. Grapes bloom differently than other flowers. Grape petals are green, and instead of blooming they detach at the bottom, coming off the flower as a cap. Because of their appearance, the unopened buds are often mistaken for small green grapes.  All wild grape species are dioecious — each vine has either male or female flowers. The male flowers have fully developed anthers (the pollen-bearing organs), but little or no ovary or pistil. Female flowers have a large, well-developed ovary and pistil, and while the anthers are nearly as large as those of the males, they are reflexed under the flower (they curve down and under) and any pollen they produce is sterile. Pollination is  by wind and insects, such as small flies.

Most cultivated grapes have “perfect flowers,” with a normal ovary and pistil and fully developed, upright anthers. (In other words, they are both male and female.) This means that cultivated grapes are mostly able to set fruit by self-fertilization, with a few exceptions. Some older varieties have female flowers, but had such good qualities that they were not discarded when perfect-flowered types came along, and must be planted near perfect-flowered types to set a crop.

Each flower in a cluster of a perfect-flowered or a female-flowered variety can “set” and become a single grape. However, in most varieties only 20 percent of the flowers set, at most. Any more than that and the grapes are packed so tightly on the mature cluster that they crush and split each other. In well-filled clusters, 10 to 15 percent of the flowers become berries. It’s worth nothing that here are varieties that appear to be perfect-flowered but have weak pollen. These varieties don’t set good crops unless a second variety is planted near them. There are also female-flowered types that can set full clusters of small seedless berries if they are not pollinated by another.

None of the common commercial varieties has these traits, but they do show up often enough to be worth noting. Just about all the grapes you are apt to buy in nurseries are perfect flowered and will self-fertilize — be both the “mother” and “father.” The most important aspect of breeding grapes is controlled pollination — making sure you know what the parents of your seedlings are.

The method used by commercial and university breeders is to emasculate the flowers, which involves removing the cap with  fine tweezers in a way that pulls off the anthers without harming the ovary or pistil. It’s not especially hard to learn, but it can be tedious and time-consuming. Instead, here are simpler methods that, while not always as exact, will still give a beginner a good chance of success. 

Growing seedlings

If you’ve found a grape that mostly suits you, it may be  worthwhile to grow seedlings of it. Even though most commercial grapes are self-pollinating, grapes have a lot of variation in their genes. Plant a hundred seeds and none of the seedlings will be exactly like the original variety. This means that a seedling of that “almost perfect” grape could inherit a combination of genes that corrects the problem you have with it. For example, if a grape is late-ripening for you, odds are good that some of its seedlings will ripen earlier.

This method only works if a trait is present in the grape to start with. If you plant seed of a grape that is white, odds are good all the seedlings will have white fruit, unless pollen of a red grape somehow reached a flower. If a variety has no resistance to mildew, the seedlings are unlikely to have any either. However, if a grape has some resistance to mildew, it’s possible that a seedling could inherit a new combination of genes and wind up with greater resistance.

Also, for many traits it’s possible that there may be hidden “recessive” genes that will surprise you. For instance, Cabernet is a blue grape, but it can produce seedlings with white fruit because it has recessive genes for that fruit color.

Remember that more than a few traits are reshuffled in the seedlings — dozens are recombined in any one offspring. This means  an improvement in one trait might be offset by a weakness in another. To beat the odds, it is usually necessary to grow a lot of seedlings to find one that has all the traits you want. There is no set number, but 100 seedlings is a good baseline. With that many, you may or may not find what you want, but you will almost surely find enough to help decide if it’s worth growing more seedlings. If nothing in the 100 comes even close, odds are that you won’t find what you want in a larger group. The easiest thing about this method is that seed can be collected from the bottom of the fermentation tank during winemaking — seed isn’t harmed by fermentation — so getting a quantity of seed to work with is simple. (I’ll explain how to grow seeds shortly.)

Let’s walk through what you can expect with this and other breeding methods. Pick any nice ripe cluster of grapes (or collect seed as above) and remove the seeds from the fruit. Let’s say we’re working with Marechal Foch. First, grow the seedlings out. Now let’s start eliminating some. Twenty-five of the 100 seedlings (for example) get powdery mildew, when Foch itself does not. Remove those. Of the remaining 75, 10 get more black rot than Foch. Out. Of the remaining 65, five are runts or slow-growing. Out. By the time you have taken out all the poor-growing, diseased types, you are probably down to 50 or less of the original 100. Train them up to have one good cane. End of first year.

With good care, many can start to bear the second year. It’s possible that 20 or more will have female flowers. You might keep those for further breeding, but they are out as varieties since they would have to be pollinated by a second variety to bear fruit. Down to 30. When the first crop ripens, you will probably eliminate some as ripening at the wrong time — too late (or less likely) too early. Eliminate 10-15. Some may be removed for problems like fruit rot. Now you are down to about 15 or less from your original 100. If there is at least 5 pounds of fruit, you can make a sample batch of wine. That will eliminate more of the seedlings for poor quality. If not enough fruit, try again the next year.

By the time all seedlings have borne fruit you have eliminated just about everything, and if all went well, you will have about one seedling of the original 100 that either has everything you want, or is close enough to it to show that you could grow a larger number of seedlings — say 300 — and probably find just what you wanted. You have spent anywhere from five to ten years to get to this stage, though you might find a good seedling within three years under ideal conditions. Even at that, it would be wise to make wine from your “find” for at least three years to be sure it will be consistent. 

Crossing grape varieties

When a variety lacks a trait altogether, it’s necessary to cross it with another that has what you want and hope everything will recombine the right way in a seedling. Crossing two varieties takes a bit more work than just growing seeds from one grape, but there are easy “shortcut” methods. First, choose the parents. Pick varieties that either reinforce each other  in desirable traits, or complement each other for strengths and weaknesses. Avoid crossing parents that reinforce each other negatively — both  are susceptible to the same disease, for instance. If yours is a disease-ridden climate, having both parents resistant to disease helps ensure healthy offspring. One resistant and one susceptible parent are more likely to yield an intermediate offspring than a fully resistant one, though a trait can be fully dominant. As a case in point,  crossing a very cold-hardy grape with a relatively tender grape can still give offspring with  good cold hardiness. Legendary breeder Elmer Swenson, for example, crossed Minnesota #78 with S. 11803. While #78 is hardy to more than -40° F,  S. 11803 is as tender as pure vinifera. Yet, the result, Swenson Red, is hardy to -30° F.

If you want an  idea beforehand of what you will get, the inheritance of most of the important traits of grapes has been worked out and can be researched, but  you’ll get results even if you don’t know exactly what to expect. A “quick and dirty” way to make crosses is to have the parents growing  side-by-side, in the ground or in pots. They should bloom at the same time to try this.

Train canes from each vine so they can be intertwined. When the shoots bearing flower clusters come out, tie them together so the clusters  are together. This will ensure that a large proportion of the flowers will get pollen from the other variety. If you want to be sure the two are crossing, look for a trait in one that can act as a marker — red  tendrils, unusual leaf shape — that the other variety lacks. Then when  you grow the seed of the other variety, any seedlings that have the trait can be assumed to have inherited it from the “marker” variety. You can grow the seed from both clusters, since either could have gotten pollen from the other.

A simple method used by many grape breeders is to use female flowered varieties as the female parent. Females are much easier to use in breeding and breeders often save good ones for that purpose. For instance, the aforementioned MN #78 has female flowers. With such vines, all you need do is bag the flower clusters with a bag before they bloom (see illustration). At the same time, put bags on clusters of the variety you want to use as the male parent, before the flowers bloom. Bag at least twice as many clusters of the variety to be used for pollen as the variety with female flowers. Peek in the bags daily in the morning, and when the female flower cluster is in bloom (at least 50 percent of the flowers are open), find a cluster in full bloom from the male variety. Snip the “male” cluster and drop it into the bag on the female cluster. Shake the bag gently. This will get pollen on most of the open female flowers and they will be fertilized and set seed. For insurance, give the bag a shake every morning for about three days to pollinate any late-blooming flowers on the female cluster. Don’t worry if a lot of the flowers don’t set — on most grapes only 10 to 20 percent will set, at best.  
    
Growing grape seed

Seed is mature enough to grow when the berries turn color. Cut the berries in half and remove the seeds. Put them in water; any that float are hollow and won’t  grow. Mix the fresh seed with a tablespoon of moist peat per 100 seeds, then place the mixture in a Ziploc bag and store it in the refrigerator. It should be cold, but not freezing. This is called “stratification” and it induces dormancy. Three months at 32 to 45° F is enough to stratify grape seed. The seed will stay dormant if you need to hold it longer, even until the next year.

Seed can be planted in two-inch square pots (one per pot) or in flats, in a greenhouse or cold frame. At temperatures of 75° F by day and 65° F at night, seed will start to emerge in two to four weeks. Once germination starts, seedlings will come up in as little as a week, though it can take as long as a month. Anywhere from 30 to 90 percent will germinate. Seeds that don’t germinate the first time can be put back in the refrigerator and more will grow after a second treatment. Some of the seedlings from these double-stratified seeds can be unusually strong and vigorous. The American species Vitis riparia and V. rupestris, and varieties that contain them (many of the French hybrids), give a faster germination rate and a larger percentage of seedlings the first time than labrusca, vinifera and  similar species.

Set out the seedlings after they have at least six true leaves and all danger of frost has passed. They can be planted six inches apart in a nursery row the first year, then moved to a test row the next year while still dormant, or planted directly in a test row at two to three  feet apart. (A test row is trellised similar to a regular one, but has only one wire.) Starting seedlings in a nursery allows you to eliminate obvious poor ones before putting them in the test row, but transplanting means more time before they come into bearing. Planting directly in a test row means you can bring the seedlings into bearing sooner, but takes more space and requires extra care.

Train seedlings to one good, short cane on the wire. At two- to three-foot spacing, you won’t have room for much more anyway. Don’t coddle the seedlings — if  one is weak-growing or gets diseased, take it out. However, don’t judge everything the first year it bears. A vine that has a small crop the first year may improve.

Once the vine has at least five pounds of crop, you will need to make a wine sample from each seedling. Five pounds is enough to make a “tenth” (4/5 pint) for a wine test. A good rating system is 0 to 10, with 0 meaning wine that has a flaw due to  a winemaking error and 10 equaling the best. A 5 is equal to a standard  commercial wine. Test three years in  a row to be certain. A 5 or better all three years and the seedling is worth propagating for large-scale tests.

The slowest part of wine-grape breeding is testing your new creation. Ten years of winemaking with a new grape is just barely enough to be sure it’s quality is consistent and it grows well in different conditions. You might not get rich on your new variety, but you’ll find it a fulfilling experience. 

Lon J. Rombough lives in Oregon and learned grape breeding and winemaking at the University of California at Davis. He has been collecting, growing and breeding grapes for 40 years (he started young). He has written a book on grape growing based on his experiences and sells cuttings from his 200+ variety collection.  His Web site is http://www.bunchgrapes.com. 查看全部
In trying for the “perfect” wine there are many factors to deal with. The culture of the vine can only be adjusted so much — soil, pruning, training and microclimate all have their limits. The part you can most control is your choice of grape variety. There are enough varieties in the world that most winemakers find at least one that works well enough to suit them, but for others no grape is “just right.”   

The solution? Breed your own grapes. Grape breeding doesn’t take a college degree or special equipment, and while there is no absolute guarantee you will create a wine grape perfect for your climate, odds are good the result will be worthwhile. Add the fact that it will be your own creation, and breeding can be immensely satisfying.

Grape Biology Basics

First, it helps to know a little bit about grape biology. Grapes bloom differently than other flowers. Grape petals are green, and instead of blooming they detach at the bottom, coming off the flower as a cap. Because of their appearance, the unopened buds are often mistaken for small green grapes.  All wild grape species are dioecious — each vine has either male or female flowers. The male flowers have fully developed anthers (the pollen-bearing organs), but little or no ovary or pistil. Female flowers have a large, well-developed ovary and pistil, and while the anthers are nearly as large as those of the males, they are reflexed under the flower (they curve down and under) and any pollen they produce is sterile. Pollination is  by wind and insects, such as small flies.

Most cultivated grapes have “perfect flowers,” with a normal ovary and pistil and fully developed, upright anthers. (In other words, they are both male and female.) This means that cultivated grapes are mostly able to set fruit by self-fertilization, with a few exceptions. Some older varieties have female flowers, but had such good qualities that they were not discarded when perfect-flowered types came along, and must be planted near perfect-flowered types to set a crop.

Each flower in a cluster of a perfect-flowered or a female-flowered variety can “set” and become a single grape. However, in most varieties only 20 percent of the flowers set, at most. Any more than that and the grapes are packed so tightly on the mature cluster that they crush and split each other. In well-filled clusters, 10 to 15 percent of the flowers become berries. It’s worth nothing that here are varieties that appear to be perfect-flowered but have weak pollen. These varieties don’t set good crops unless a second variety is planted near them. There are also female-flowered types that can set full clusters of small seedless berries if they are not pollinated by another.

None of the common commercial varieties has these traits, but they do show up often enough to be worth noting. Just about all the grapes you are apt to buy in nurseries are perfect flowered and will self-fertilize — be both the “mother” and “father.” The most important aspect of breeding grapes is controlled pollination — making sure you know what the parents of your seedlings are.

The method used by commercial and university breeders is to emasculate the flowers, which involves removing the cap with  fine tweezers in a way that pulls off the anthers without harming the ovary or pistil. It’s not especially hard to learn, but it can be tedious and time-consuming. Instead, here are simpler methods that, while not always as exact, will still give a beginner a good chance of success. 

Growing seedlings

If you’ve found a grape that mostly suits you, it may be  worthwhile to grow seedlings of it. Even though most commercial grapes are self-pollinating, grapes have a lot of variation in their genes. Plant a hundred seeds and none of the seedlings will be exactly like the original variety. This means that a seedling of that “almost perfect” grape could inherit a combination of genes that corrects the problem you have with it. For example, if a grape is late-ripening for you, odds are good that some of its seedlings will ripen earlier.

This method only works if a trait is present in the grape to start with. If you plant seed of a grape that is white, odds are good all the seedlings will have white fruit, unless pollen of a red grape somehow reached a flower. If a variety has no resistance to mildew, the seedlings are unlikely to have any either. However, if a grape has some resistance to mildew, it’s possible that a seedling could inherit a new combination of genes and wind up with greater resistance.

Also, for many traits it’s possible that there may be hidden “recessive” genes that will surprise you. For instance, Cabernet is a blue grape, but it can produce seedlings with white fruit because it has recessive genes for that fruit color.

Remember that more than a few traits are reshuffled in the seedlings — dozens are recombined in any one offspring. This means  an improvement in one trait might be offset by a weakness in another. To beat the odds, it is usually necessary to grow a lot of seedlings to find one that has all the traits you want. There is no set number, but 100 seedlings is a good baseline. With that many, you may or may not find what you want, but you will almost surely find enough to help decide if it’s worth growing more seedlings. If nothing in the 100 comes even close, odds are that you won’t find what you want in a larger group. The easiest thing about this method is that seed can be collected from the bottom of the fermentation tank during winemaking — seed isn’t harmed by fermentation — so getting a quantity of seed to work with is simple. (I’ll explain how to grow seeds shortly.)

Let’s walk through what you can expect with this and other breeding methods. Pick any nice ripe cluster of grapes (or collect seed as above) and remove the seeds from the fruit. Let’s say we’re working with Marechal Foch. First, grow the seedlings out. Now let’s start eliminating some. Twenty-five of the 100 seedlings (for example) get powdery mildew, when Foch itself does not. Remove those. Of the remaining 75, 10 get more black rot than Foch. Out. Of the remaining 65, five are runts or slow-growing. Out. By the time you have taken out all the poor-growing, diseased types, you are probably down to 50 or less of the original 100. Train them up to have one good cane. End of first year.

With good care, many can start to bear the second year. It’s possible that 20 or more will have female flowers. You might keep those for further breeding, but they are out as varieties since they would have to be pollinated by a second variety to bear fruit. Down to 30. When the first crop ripens, you will probably eliminate some as ripening at the wrong time — too late (or less likely) too early. Eliminate 10-15. Some may be removed for problems like fruit rot. Now you are down to about 15 or less from your original 100. If there is at least 5 pounds of fruit, you can make a sample batch of wine. That will eliminate more of the seedlings for poor quality. If not enough fruit, try again the next year.

By the time all seedlings have borne fruit you have eliminated just about everything, and if all went well, you will have about one seedling of the original 100 that either has everything you want, or is close enough to it to show that you could grow a larger number of seedlings — say 300 — and probably find just what you wanted. You have spent anywhere from five to ten years to get to this stage, though you might find a good seedling within three years under ideal conditions. Even at that, it would be wise to make wine from your “find” for at least three years to be sure it will be consistent. 

Crossing grape varieties

When a variety lacks a trait altogether, it’s necessary to cross it with another that has what you want and hope everything will recombine the right way in a seedling. Crossing two varieties takes a bit more work than just growing seeds from one grape, but there are easy “shortcut” methods. First, choose the parents. Pick varieties that either reinforce each other  in desirable traits, or complement each other for strengths and weaknesses. Avoid crossing parents that reinforce each other negatively — both  are susceptible to the same disease, for instance. If yours is a disease-ridden climate, having both parents resistant to disease helps ensure healthy offspring. One resistant and one susceptible parent are more likely to yield an intermediate offspring than a fully resistant one, though a trait can be fully dominant. As a case in point,  crossing a very cold-hardy grape with a relatively tender grape can still give offspring with  good cold hardiness. Legendary breeder Elmer Swenson, for example, crossed Minnesota #78 with S. 11803. While #78 is hardy to more than -40° F,  S. 11803 is as tender as pure vinifera. Yet, the result, Swenson Red, is hardy to -30° F.

If you want an  idea beforehand of what you will get, the inheritance of most of the important traits of grapes has been worked out and can be researched, but  you’ll get results even if you don’t know exactly what to expect. A “quick and dirty” way to make crosses is to have the parents growing  side-by-side, in the ground or in pots. They should bloom at the same time to try this.

Train canes from each vine so they can be intertwined. When the shoots bearing flower clusters come out, tie them together so the clusters  are together. This will ensure that a large proportion of the flowers will get pollen from the other variety. If you want to be sure the two are crossing, look for a trait in one that can act as a marker — red  tendrils, unusual leaf shape — that the other variety lacks. Then when  you grow the seed of the other variety, any seedlings that have the trait can be assumed to have inherited it from the “marker” variety. You can grow the seed from both clusters, since either could have gotten pollen from the other.

A simple method used by many grape breeders is to use female flowered varieties as the female parent. Females are much easier to use in breeding and breeders often save good ones for that purpose. For instance, the aforementioned MN #78 has female flowers. With such vines, all you need do is bag the flower clusters with a bag before they bloom (see illustration). At the same time, put bags on clusters of the variety you want to use as the male parent, before the flowers bloom. Bag at least twice as many clusters of the variety to be used for pollen as the variety with female flowers. Peek in the bags daily in the morning, and when the female flower cluster is in bloom (at least 50 percent of the flowers are open), find a cluster in full bloom from the male variety. Snip the “male” cluster and drop it into the bag on the female cluster. Shake the bag gently. This will get pollen on most of the open female flowers and they will be fertilized and set seed. For insurance, give the bag a shake every morning for about three days to pollinate any late-blooming flowers on the female cluster. Don’t worry if a lot of the flowers don’t set — on most grapes only 10 to 20 percent will set, at best.  
    
Growing grape seed

Seed is mature enough to grow when the berries turn color. Cut the berries in half and remove the seeds. Put them in water; any that float are hollow and won’t  grow. Mix the fresh seed with a tablespoon of moist peat per 100 seeds, then place the mixture in a Ziploc bag and store it in the refrigerator. It should be cold, but not freezing. This is called “stratification” and it induces dormancy. Three months at 32 to 45° F is enough to stratify grape seed. The seed will stay dormant if you need to hold it longer, even until the next year.

Seed can be planted in two-inch square pots (one per pot) or in flats, in a greenhouse or cold frame. At temperatures of 75° F by day and 65° F at night, seed will start to emerge in two to four weeks. Once germination starts, seedlings will come up in as little as a week, though it can take as long as a month. Anywhere from 30 to 90 percent will germinate. Seeds that don’t germinate the first time can be put back in the refrigerator and more will grow after a second treatment. Some of the seedlings from these double-stratified seeds can be unusually strong and vigorous. The American species Vitis riparia and V. rupestris, and varieties that contain them (many of the French hybrids), give a faster germination rate and a larger percentage of seedlings the first time than labrusca, vinifera and  similar species.

Set out the seedlings after they have at least six true leaves and all danger of frost has passed. They can be planted six inches apart in a nursery row the first year, then moved to a test row the next year while still dormant, or planted directly in a test row at two to three  feet apart. (A test row is trellised similar to a regular one, but has only one wire.) Starting seedlings in a nursery allows you to eliminate obvious poor ones before putting them in the test row, but transplanting means more time before they come into bearing. Planting directly in a test row means you can bring the seedlings into bearing sooner, but takes more space and requires extra care.

Train seedlings to one good, short cane on the wire. At two- to three-foot spacing, you won’t have room for much more anyway. Don’t coddle the seedlings — if  one is weak-growing or gets diseased, take it out. However, don’t judge everything the first year it bears. A vine that has a small crop the first year may improve.

Once the vine has at least five pounds of crop, you will need to make a wine sample from each seedling. Five pounds is enough to make a “tenth” (4/5 pint) for a wine test. A good rating system is 0 to 10, with 0 meaning wine that has a flaw due to  a winemaking error and 10 equaling the best. A 5 is equal to a standard  commercial wine. Test three years in  a row to be certain. A 5 or better all three years and the seedling is worth propagating for large-scale tests.

The slowest part of wine-grape breeding is testing your new creation. Ten years of winemaking with a new grape is just barely enough to be sure it’s quality is consistent and it grows well in different conditions. You might not get rich on your new variety, but you’ll find it a fulfilling experience. 

Lon J. Rombough lives in Oregon and learned grape breeding and winemaking at the University of California at Davis. He has been collecting, growing and breeding grapes for 40 years (he started young). He has written a book on grape growing based on his experiences and sells cuttings from his 200+ variety collection.  His Web site is http://www.bunchgrapes.com.

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cellar doorcewh Post a question • 1 person concerned • 0 replies • 17 views • 2016-09-12 23:16 • 来自相关话题

understanding wine lees by Bruce Zoecklein

winerycewh Published the article • 0 comments • 22 views • 2016-08-31 20:22 • 来自相关话题

The Nature of Wine Lees
During aging sur lie, yeast components are released into the wine. These macromolecules can positively influence structural integration, phenols (including tannins), body, aroma, oxygen buffering, and wine stability. Some macromolecules can provide a sense of sweetness as a result of bridging the sensory sensations between the phenolic elements, acidity, and alcohol, aiding in harmony and integration.
Mannoproteins in the yeast cell wall are bound to glucans (glucose polymers), which exist in wines as polysaccharide and protein moieties (Feuillat, 2003). They are released from the yeast cell wall by the action of an enzyme, β-1,3-glucanase. β-1,3-glucanase is active during yeast growth (fermentation) and during aging in the presence of non-multiplying yeast cells. Stirring increases the concentration (Feuillat, 1998).
Lees and mannoproteins can impact the following:

integration of mouthfeel elements by interaction between structural/textural features
reduction in the perception of astringency and bitterness (Escot et al., 2001; Saucier, 1997)
increasing wine body
encouraging the growth of malolactic bacteria and, possibly, yeasts
preventing bitartrate instability (Lubbers et al., 1993; Moine-Ledoux, 1996; Moine-Ledoux and Dubourdieu, 2002; Waters et al., 1994)
interacting with wine aroma (Lubbers et al., 1994)

The amount of mannoprotein released during fermentation is dependent on several factors, including the following:

Yeast strain: Large differences are noted among yeasts in the amount of mannoproteins produced during fermentation and released during autolysis.
Must turbidity: Generally, the more turbid the must, the lower the mannoprotein concentration (Guilloux-Benatier et al., 1995). Mannoproteins released during fermentation are more reactive than those released during the yeast autolysis process in modifying astringency. This helps provide additional justification for measuring the non-soluble solids of juice pre-fermentation.

Wines aged on lees with no fining have mannoproteins present, while those fined prior to aging have a large percentage of mannoproteins removed. Periodic stirring sur lie increases the mannoprotein concentration, and increases the rate of β-1,3-glucanase activity. Generally, yeast autolysis is relatively slow (in the absence of glucanase enzyme addition) and may require months or years to occur, limiting the mannoprotein concentration (Charpentier and Feuillat, 1993).
The impact of lees components such as polysaccharides on astringency can cause an increase in the wine’s volume or body. Lees contact is particularly effective at modifying wood tannin astringency by binding with free ellagic tannins (harsh tannins). Sur lie storage can reduce the free ellagic acid by as much as 60% (via precipitation), while increasing the percentage of ellagic tannins bound to polysaccharides by 24% (Ribéreau-Gayon et al., 2000).
In the Burgundy and other regions, red wines are aged on their lees in conjunction with the addition of exogenous β ‑1,3-glucanase enzyme. This procedure is an attempt to release mannoproteins, which winemakers believe may enhance the suppleness of the wine, while reducing the perceived astringency.
Several alternative methods of increasing mannoprotein levels have been suggested (Feuillat, 2003), including the following:

selection and use of yeast which produce high levels of mannoproteins during the alcoholic fermentation
yeast which autolyze rapidly upon completion of alcoholic fermentation
addition of β-1,3-glucanase to wines stored on lees
addition of exogenous mannoproteins (proprietary products), prepared from yeast cell walls, to wines on lees

Lees Management Considerations.
Table 1 shows some important practical winemaking considerations regarding lees management.
During fermentation, the level of macromolecules continually rises, peaking at approximately 270 mg/L, by which time they contain 82% sugar and only 18% protein (Feuillat, 2003).
Guilloux‑Benatier et al. (1995) found a relationship between the degrees of must clarification and the amount of yeast macromolecules recovered in the wine. When the must was not clarified, there is no production of yeast macromolecules.
Table 1. Lees Management Considerations

Non-soluble solids level

Method of stirring

Frequency and duration of stirring

Type and size of vessel

Duration of lees contact

MLF

Timing and type of racking

SO2 timing and level of addition

Frequency of barrel topping

However, mild must clarification, such as cooling for 12 hours, increased the amount of yeast-produced macromolecule production by 76 mg/L, and heavy must clarification, such as bentonite fining, increased the production by 164 mg/L. Boivin et al. (1998) found that the amount of macromolecules produced will vary between 230 and 630 mg/L, and that they will contain 20 – 30% glucose and 70 – 80% mannose.
During lees contact, the composition of the wine changes as the yeast commence enzymatic hydrolysis of their cellular contents. One important feature is the process of proteolysis, whereby proteins are hydrolyzed to amino acids and peptides. These compounds result in an increase in the available nitrogen content of the wine. Amino acids can act as flavor precursors, possibly enhancing wine complexity and quality.
Yeast-derived macromolecules provide a sense of sweetness as a result of binding with wood phenols and organic acids, aiding in the harmony of a wine’s structural elements by softening tannins.
It is important to differentiate between light lees and heavy lees. Heavy lees can be defined as the lees which precipitate within 24 hours immediately post-fermentation. They are composed of large particles (greater than 100 micrometers) and consist of grape particulates, agglomerates of tartrate crystals, yeasts, bacteria, and protein-polysaccharide-tannin complexes.
Light lees, on the other hand, can be defined as those that precipitate from the wine more than 24 hours post-fermentation. These are composed mainly of small particles (1- 25 micrometers) of yeasts, bacteria, tartaric acid, protein-tannin complexes, and some polysaccharides.
There is no value in storing wine on heavy lees. Indeed, such storage can result in off aroma and flavors, and a depletion of sulfur dioxide. Light lees storage, however, can have a significant advantage in structural balance, complexity, and stability.
Lees stirring and the frequency of stirring is important, both as a practical and stylistic consideration. Feuillat and Charpentier (1998) have demonstrated that periodic stirring of the wine while on lees increases the mannoprotein level and the amount of yeast-derived amino acids, and that wines aged on their lees in barrel exhibit an increase in colloidal macromolecules.
Stirring generates an oxidative process which increases the acetaldehyde content, and which may increase the acetic acid concentration. Stirring also changes the sensory balance between fruit, yeast, and wood by enhancing the yeast component, and reducing the fruit and, to a lesser degree, the wood component.
Additionally, stirring may have the effect of enhancing secondary chemical reactions, possibly as the result of oxygen pick-up. Stuckey et al. (1991) demonstrated increases in both the total amino acid content and wine sensory score in wines stored for five months without stirring. The non-stirred wine was perceived to have greater fruit intensity.
MLF reduces the harshness of new oak and aids in the development of complex and mature flavors. Traditionally, stirring is continued until MLF is complete. After that, the lees are said to become more dense, which aids in clarification.
During barrel aging, what we are looking for is slow, well-managed, and controlled oxygenation. Some lees contact may allow for this oxygenation, and lees aid in the prevention of oxidation.
In Burgundy, wines are traditionally racked off the lees in March, usually the time when MLF is completed. Frequently this is an aerobic racking off the heavy lees, then back into wood on light lees, followed by an SO2 addition. Leaving the wine on the light lees helps to nourish the wine. The addition of SO2 helps to protect the wine from oxidation. A subsequent racking often occurs in early July, and is in the absence of air.
Timing of SO2 additions, and the quantity of SO2 added, are important stylistic considerations. Early use of SO2 increases the number of components that bind to subsequent additions of SO2. The addition of too much SO2 counters the wood flavors and limits oxidation reactions, while too little SO2 may allow the wine to become tired and over-aged.
Production considerations, such as the timing of MLF, the method of barrel storage, and time of bottling, are factors influencing SO2 levels. Barrel topping is an aerobic process that can result in excessive oxidation. Additionally, wines that spend a second winter in the cellar tend to lose their aroma unless the wine is particularly rich.
Delteil (2002) compared two red wines. One wine was barrel-stored on light lees for 9 months; the other, racked several times prior to barreling, was stored for the same period without lees. These two Syrah wines differed significantly in their palate and aroma profiles.
The wine stored sur lie had a much lower perception of astringency and a greater integration of the phenolic elements. The sur lie wine also had a lower perception of oak character, resulting in a higher perception of varietal fruit.
Lees contact is particularly effective at modifying wood tannin astringency by binding with free ellagic tannins, thus lowering the proportion of active tannins. Sur lie storage can reduce the free ellagic acid by as much as 60%, while increasing the percentage of ellagic tannins bound to polysaccharides by 24% (Ribéreau-Gayon et al., 2000).
The following is a review of the impact of lees on wines.

Lees, Color and Mouthfeel.High lees concentration can reduce color, as a function of adsorption onto the yeast cell surface.  Additionally, lees adsorb oxygen which can limit the anthocyanin-tannin polymerization, resulting in an increase in dry tannin perception. This may or may not be off-set by the release of lees components which can soften mouthfeel.

Lees and Wine Aroma. Aroma stabilization is dependent upon the hydrophobicity (ability to repel water molecules) of the aroma compounds. The protein component of the mannoprotein fraction is important for overall aroma stabilization (Lubbers et al., 1994). Such interactions can modify the volatility and aromatic intensity of wines.

When wine is aged on its lees with no fining, mannoproteins are present and are free to interact and to fortify the existing aroma components. When wines are fined prior to aging, mannoproteins are removed and will not be present to augment the existing aroma components. Additionally, when wines are cross‑flow filtered, eliminating a certain percentage of macromolecules, the loss of color intensity, aroma, and flavor can be noted.

Lees and Oak Bouquet. Lees modify oaky aromas, due to their ability to bind with wood-derived compounds such as vanillin, furfural, and methyl-octalactones.

Lees and Oxidative Buffering Capacity. Both lees and tannins act as reducing agents. During aging, lees release certain highly-reductive substances which limit wood-induced oxygenation. Wines have a higher oxidation-reduction potential in barrels than in tanks. Inside the barrel, this potential diminishes from the wine surface to the lees. Stirring helps to raise this potential.

This is a primary reason why wines stored in high-volume tanks should not be stored on their lees. Such storage can cause the release of “reductive” or sulfur-containing compounds. If there is a desire to store dry wines in tanks sur lie, it is recommended that the lees be stored in barrels for several months, then added back to the tank (Ribéreau-Gayon et al., 2000).

Lees and White Wine Protein Stability. The greater the lees contact, the lower the need for bentonite or other fining agents for protein stability. It is not believed that lees hydrolyze grape proteins, or that proteins are adsorbed by yeast. Rather, lees aging produces an additional mannoprotein, which somehow adds stability. The production of this mannoprotein is increased with temperature, time, and frequency of stirring.

Lees and Biological Stability. Guilloux‑Benatier et al. (2001) have studied the liberation of amino acids and glucose during barrel aging of Burgundy wine on its lees. Their studies were done with and without the addition of exogenous β‑1,3-glucanase preparations. They found little or no increase in amino acids in wine stored on lees, versus wine stored on lees with the addition of β‑1,3-glucanase.

Their most significant finding was an increase in glucose concentration, from 43 mg/L in the control wine, to 570 mg/L in wine stored on its lees, to 910 mg/L in wine stored on its lees with added β ‑1,3-glucanase. The finding of this relatively large amount of glucose led these authors to speculate that the growth of the spoilage yeast Brettanomycesin barreled wine may be stimulated by the availability of this carbon source.

Lees and Bitartrate Stability. Mannoproteins produced by yeast can act as crystalline inhibitors. The longer the lees contact time, the greater is the likelihood of potassium bitartrate stability.
 
reference:http://www.newworldwinemaker.com/2016/05/5715/ 查看全部
The Nature of Wine Lees
During aging sur lie, yeast components are released into the wine. These macromolecules can positively influence structural integration, phenols (including tannins), body, aroma, oxygen buffering, and wine stability. Some macromolecules can provide a sense of sweetness as a result of bridging the sensory sensations between the phenolic elements, acidity, and alcohol, aiding in harmony and integration.
Mannoproteins in the yeast cell wall are bound to glucans (glucose polymers), which exist in wines as polysaccharide and protein moieties (Feuillat, 2003). They are released from the yeast cell wall by the action of an enzyme, β-1,3-glucanase. β-1,3-glucanase is active during yeast growth (fermentation) and during aging in the presence of non-multiplying yeast cells. Stirring increases the concentration (Feuillat, 1998).
Lees and mannoproteins can impact the following:

integration of mouthfeel elements by interaction between structural/textural features
reduction in the perception of astringency and bitterness (Escot et al., 2001; Saucier, 1997)
increasing wine body
encouraging the growth of malolactic bacteria and, possibly, yeasts
preventing bitartrate instability (Lubbers et al., 1993; Moine-Ledoux, 1996; Moine-Ledoux and Dubourdieu, 2002; Waters et al., 1994)
interacting with wine aroma (Lubbers et al., 1994)

The amount of mannoprotein released during fermentation is dependent on several factors, including the following:

Yeast strain: Large differences are noted among yeasts in the amount of mannoproteins produced during fermentation and released during autolysis.
Must turbidity: Generally, the more turbid the must, the lower the mannoprotein concentration (Guilloux-Benatier et al., 1995). Mannoproteins released during fermentation are more reactive than those released during the yeast autolysis process in modifying astringency. This helps provide additional justification for measuring the non-soluble solids of juice pre-fermentation.

Wines aged on lees with no fining have mannoproteins present, while those fined prior to aging have a large percentage of mannoproteins removed. Periodic stirring sur lie increases the mannoprotein concentration, and increases the rate of β-1,3-glucanase activity. Generally, yeast autolysis is relatively slow (in the absence of glucanase enzyme addition) and may require months or years to occur, limiting the mannoprotein concentration (Charpentier and Feuillat, 1993).
The impact of lees components such as polysaccharides on astringency can cause an increase in the wine’s volume or body. Lees contact is particularly effective at modifying wood tannin astringency by binding with free ellagic tannins (harsh tannins). Sur lie storage can reduce the free ellagic acid by as much as 60% (via precipitation), while increasing the percentage of ellagic tannins bound to polysaccharides by 24% (Ribéreau-Gayon et al., 2000).
In the Burgundy and other regions, red wines are aged on their lees in conjunction with the addition of exogenous β ‑1,3-glucanase enzyme. This procedure is an attempt to release mannoproteins, which winemakers believe may enhance the suppleness of the wine, while reducing the perceived astringency.
Several alternative methods of increasing mannoprotein levels have been suggested (Feuillat, 2003), including the following:

selection and use of yeast which produce high levels of mannoproteins during the alcoholic fermentation
yeast which autolyze rapidly upon completion of alcoholic fermentation
addition of β-1,3-glucanase to wines stored on lees
addition of exogenous mannoproteins (proprietary products), prepared from yeast cell walls, to wines on lees

Lees Management Considerations.
Table 1 shows some important practical winemaking considerations regarding lees management.
During fermentation, the level of macromolecules continually rises, peaking at approximately 270 mg/L, by which time they contain 82% sugar and only 18% protein (Feuillat, 2003).
Guilloux‑Benatier et al. (1995) found a relationship between the degrees of must clarification and the amount of yeast macromolecules recovered in the wine. When the must was not clarified, there is no production of yeast macromolecules.
Table 1. Lees Management Considerations

Non-soluble solids level

Method of stirring

Frequency and duration of stirring

Type and size of vessel

Duration of lees contact

MLF

Timing and type of racking

SO2 timing and level of addition

Frequency of barrel topping

However, mild must clarification, such as cooling for 12 hours, increased the amount of yeast-produced macromolecule production by 76 mg/L, and heavy must clarification, such as bentonite fining, increased the production by 164 mg/L. Boivin et al. (1998) found that the amount of macromolecules produced will vary between 230 and 630 mg/L, and that they will contain 20 – 30% glucose and 70 – 80% mannose.
During lees contact, the composition of the wine changes as the yeast commence enzymatic hydrolysis of their cellular contents. One important feature is the process of proteolysis, whereby proteins are hydrolyzed to amino acids and peptides. These compounds result in an increase in the available nitrogen content of the wine. Amino acids can act as flavor precursors, possibly enhancing wine complexity and quality.
Yeast-derived macromolecules provide a sense of sweetness as a result of binding with wood phenols and organic acids, aiding in the harmony of a wine’s structural elements by softening tannins.
It is important to differentiate between light lees and heavy lees. Heavy lees can be defined as the lees which precipitate within 24 hours immediately post-fermentation. They are composed of large particles (greater than 100 micrometers) and consist of grape particulates, agglomerates of tartrate crystals, yeasts, bacteria, and protein-polysaccharide-tannin complexes.
Light lees, on the other hand, can be defined as those that precipitate from the wine more than 24 hours post-fermentation. These are composed mainly of small particles (1- 25 micrometers) of yeasts, bacteria, tartaric acid, protein-tannin complexes, and some polysaccharides.
There is no value in storing wine on heavy lees. Indeed, such storage can result in off aroma and flavors, and a depletion of sulfur dioxide. Light lees storage, however, can have a significant advantage in structural balance, complexity, and stability.
Lees stirring and the frequency of stirring is important, both as a practical and stylistic consideration. Feuillat and Charpentier (1998) have demonstrated that periodic stirring of the wine while on lees increases the mannoprotein level and the amount of yeast-derived amino acids, and that wines aged on their lees in barrel exhibit an increase in colloidal macromolecules.
Stirring generates an oxidative process which increases the acetaldehyde content, and which may increase the acetic acid concentration. Stirring also changes the sensory balance between fruit, yeast, and wood by enhancing the yeast component, and reducing the fruit and, to a lesser degree, the wood component.
Additionally, stirring may have the effect of enhancing secondary chemical reactions, possibly as the result of oxygen pick-up. Stuckey et al. (1991) demonstrated increases in both the total amino acid content and wine sensory score in wines stored for five months without stirring. The non-stirred wine was perceived to have greater fruit intensity.
MLF reduces the harshness of new oak and aids in the development of complex and mature flavors. Traditionally, stirring is continued until MLF is complete. After that, the lees are said to become more dense, which aids in clarification.
During barrel aging, what we are looking for is slow, well-managed, and controlled oxygenation. Some lees contact may allow for this oxygenation, and lees aid in the prevention of oxidation.
In Burgundy, wines are traditionally racked off the lees in March, usually the time when MLF is completed. Frequently this is an aerobic racking off the heavy lees, then back into wood on light lees, followed by an SO2 addition. Leaving the wine on the light lees helps to nourish the wine. The addition of SO2 helps to protect the wine from oxidation. A subsequent racking often occurs in early July, and is in the absence of air.
Timing of SO2 additions, and the quantity of SO2 added, are important stylistic considerations. Early use of SO2 increases the number of components that bind to subsequent additions of SO2. The addition of too much SO2 counters the wood flavors and limits oxidation reactions, while too little SO2 may allow the wine to become tired and over-aged.
Production considerations, such as the timing of MLF, the method of barrel storage, and time of bottling, are factors influencing SO2 levels. Barrel topping is an aerobic process that can result in excessive oxidation. Additionally, wines that spend a second winter in the cellar tend to lose their aroma unless the wine is particularly rich.
Delteil (2002) compared two red wines. One wine was barrel-stored on light lees for 9 months; the other, racked several times prior to barreling, was stored for the same period without lees. These two Syrah wines differed significantly in their palate and aroma profiles.
The wine stored sur lie had a much lower perception of astringency and a greater integration of the phenolic elements. The sur lie wine also had a lower perception of oak character, resulting in a higher perception of varietal fruit.
Lees contact is particularly effective at modifying wood tannin astringency by binding with free ellagic tannins, thus lowering the proportion of active tannins. Sur lie storage can reduce the free ellagic acid by as much as 60%, while increasing the percentage of ellagic tannins bound to polysaccharides by 24% (Ribéreau-Gayon et al., 2000).
The following is a review of the impact of lees on wines.

Lees, Color and Mouthfeel.High lees concentration can reduce color, as a function of adsorption onto the yeast cell surface.  Additionally, lees adsorb oxygen which can limit the anthocyanin-tannin polymerization, resulting in an increase in dry tannin perception. This may or may not be off-set by the release of lees components which can soften mouthfeel.

Lees and Wine Aroma. Aroma stabilization is dependent upon the hydrophobicity (ability to repel water molecules) of the aroma compounds. The protein component of the mannoprotein fraction is important for overall aroma stabilization (Lubbers et al., 1994). Such interactions can modify the volatility and aromatic intensity of wines.

When wine is aged on its lees with no fining, mannoproteins are present and are free to interact and to fortify the existing aroma components. When wines are fined prior to aging, mannoproteins are removed and will not be present to augment the existing aroma components. Additionally, when wines are cross‑flow filtered, eliminating a certain percentage of macromolecules, the loss of color intensity, aroma, and flavor can be noted.

Lees and Oak Bouquet. Lees modify oaky aromas, due to their ability to bind with wood-derived compounds such as vanillin, furfural, and methyl-octalactones.

Lees and Oxidative Buffering Capacity. Both lees and tannins act as reducing agents. During aging, lees release certain highly-reductive substances which limit wood-induced oxygenation. Wines have a higher oxidation-reduction potential in barrels than in tanks. Inside the barrel, this potential diminishes from the wine surface to the lees. Stirring helps to raise this potential.

This is a primary reason why wines stored in high-volume tanks should not be stored on their lees. Such storage can cause the release of “reductive” or sulfur-containing compounds. If there is a desire to store dry wines in tanks sur lie, it is recommended that the lees be stored in barrels for several months, then added back to the tank (Ribéreau-Gayon et al., 2000).

Lees and White Wine Protein Stability. The greater the lees contact, the lower the need for bentonite or other fining agents for protein stability. It is not believed that lees hydrolyze grape proteins, or that proteins are adsorbed by yeast. Rather, lees aging produces an additional mannoprotein, which somehow adds stability. The production of this mannoprotein is increased with temperature, time, and frequency of stirring.

Lees and Biological Stability. Guilloux‑Benatier et al. (2001) have studied the liberation of amino acids and glucose during barrel aging of Burgundy wine on its lees. Their studies were done with and without the addition of exogenous β‑1,3-glucanase preparations. They found little or no increase in amino acids in wine stored on lees, versus wine stored on lees with the addition of β‑1,3-glucanase.

Their most significant finding was an increase in glucose concentration, from 43 mg/L in the control wine, to 570 mg/L in wine stored on its lees, to 910 mg/L in wine stored on its lees with added β ‑1,3-glucanase. The finding of this relatively large amount of glucose led these authors to speculate that the growth of the spoilage yeast Brettanomycesin barreled wine may be stimulated by the availability of this carbon source.

Lees and Bitartrate Stability. Mannoproteins produced by yeast can act as crystalline inhibitors. The longer the lees contact time, the greater is the likelihood of potassium bitartrate stability.
 
reference:http://www.newworldwinemaker.com/2016/05/5715/

The Literature Review as stand-alone exercise: How To Do It

smoko roomcewh Published the article • 0 comments • 43 views • 2016-07-31 17:24 • 来自相关话题

Over the past two weeks, I’ve been on Twitter, looking at tweets mentioning the words “literature review”. And what happened isn’t what I expected: I didn’t see that many PhD students talking about the shortcomings of their own reviews. No. As I looked through the tweets, I saw dozens and dozens of undergraduate (and maybe some graduate) students lamenting that they had no idea how to do the literature review they were supposed to finish over the weekend.

First, wow. I didn’t know that university professors were asking that kind of assignment to undergraduates! This seems a bit harsh to me.

Second, I decided to go ahead and create this guide. I’m going to tell you how to finish your “stand alone” literature review (meaning, its an assignment for a college class and that won’t be a part of a thesis or dissertation) as easily, quickly and efficiently as possible. And at the end of this article, you will be able to download a PDF checklist of everything you need to do, with extra advice thrown in for good measure…

[Step-by-Step: How To do a Literature Review?]

So, PhD students, pass your way for today. And come back next week for something more tailored to your expectations.

As for the others, let’s dive in.

 

0/ Check that you know what a literature review is.

You can have a look here for a thorough definition + a pretty infographic!

 

1/ Make sure that you know what’s expected of you.

 Did you get an assignment sheet or did you write down the instructions? Can you compare notes with other students in your class? Can you go and ask your teach for more details? Here is a list of things you should check:

On which topic are you supposed to be doing your review?

How long should it be?

How many papers are you supposed to be reviewing?

What kind of papers are you allowed to include in your review? (Academic journal articles only? Book chapters? Newspaper articles? Blog posts?)

Do you need to include headings and subheadings?

Are you supposed to use a specific referencing style?

When is it due?

 

2/ Identify keywords around your topic

This is a crucial part that many students don’t know about. This will help you in the next step when you begin searching the literature.

So first, write down your topic. Let me show you with an example:

Role of a compression coil in a Firefly-class ship engine.

Then, identify the important keywords in your topic.

Here it would be “compression coil” and “Firefly-class ship”.

Then, try and think of all possible synonyms and variations on those terms.

Here we could have “compression spring”, “trace compression block”, “03-K64-Firefly”, “Serenity”…

For more info on how to find and use good keywords, have a look here.

 

3/ Begin your literature search

Usually, you will be able to use two separate resources: your library’s catalogue and bibliographic databases.

You can use your library’s catalogue to find books, DVDs, and other physical materials possessed by your library.

To find electronic materials, you will usually have to use electronic databases.

If you look around your library’s website, you should able to access some of those. If you don’t, ask your uni librarian!

I have a whole rubric on this blog to help you with searching a bibliographic database. So have a look at it if you can.

The gist of it is that you’re going to have to use the keywords you came up with to try and find relevant documents on your subject.

If you have any kind of trouble with his, please do go to your university library and ask for help. This is the very reason why there are reference librarians: to help you with that kind of stuff.

You can also send me a message (click on the “contact me” button on the right of your screen) or leave a comment and I’ll try to help you too.

 

4/ Read the documents you’ve found and take notes

You don’t have to read everything you’ve found: you need to identify which bits are truly interesting and then read only those. More info on that here.

Then, it’s absolutely crucial that you take thorough notes while reading: this is what’s going to keep you from unintentional plagiarism.

Try and sum up each paper. Keep those questions in mind:

What does this tell me about my topic?

What do you know about the author?

In which context was this text written? (For which public? In which historical / conceptual context?)

What kind of evidence does the author use? (Statistics? Historical sources? Philosophical arguments?…)

What are the strengths and weaknesses of the argument? Is it convincing?

 

5/ Decide on the structure of your review

You need to identify a few different themes about your topic.

If I come back to my example, I could have one part about the port compression coil and another about the starboard compression coil.

Or I could have different paragraphs about the different parts of a compression coil.

Or I could look at it from an historical point of view and describe its evolutions throughout the different series issued.

Or you could go first what it does / second how it can go wrong / third how to repair it.

You need to base yourself on the kind of information you found. And then you need to match specific ideas from those documents to the different themes you’ve identified. Try and not lose the references for each idea while doing that!

 

6/ Time to write

Okay, now all you need to do is to write your review.

It should look something like that:

Introduction
Theme 1
Theme 2
Theme 3
Conclusion

Your number of themes may vary, but make sure that all your parts are roughly equivalent in length. And don’t forget to write an introduction and a conclusion! I explain more about it over there.

It doesn’t have to be perfect, just write a first draft.

The important thing is that you need to reference each idea with the paper where you found it. Every time. So be super thorough! If you don’t know how to do your references, have a look on your library’s website: they probably have a help section explaining exactly how to do it.

 

7/ Editing and proofreading

Once you have written your first draft, it’s time to edit.

Re-read it and ask yourself those questions:

Did you say everything you wanted to say?

Does your structure make sense?

Did you express yourself clearly enough?

Is your paper evenly proportioned?

Is your tone formal enough for an academic context?

Did you cite all of the papers you intended to reference?

Make all changes you deem necessary. You can repeat this process several times if need be.

Then, it’s proofreading time! Check that your spell check doesn’t underline anything in red. Re-read yourself slowly (you can even print your paper to re-read it, you might see things that you didn’t see on screen!).

If you can, ask someone else to proofread your paper too. But do it yourself first, as a courtesy!

 

8/ Hand it out!

You’re done! Congratulations!

But first, you might want to have a look at the check-list I compiled for you. It will point at all the things you should check before handing out your paper.
 
reference
http://www.howtodoaliteraturer ... cise/ 查看全部
Over the past two weeks, I’ve been on Twitter, looking at tweets mentioning the words “literature review”. And what happened isn’t what I expected: I didn’t see that many PhD students talking about the shortcomings of their own reviews. No. As I looked through the tweets, I saw dozens and dozens of undergraduate (and maybe some graduate) students lamenting that they had no idea how to do the literature review they were supposed to finish over the weekend.

First, wow. I didn’t know that university professors were asking that kind of assignment to undergraduates! This seems a bit harsh to me.

Second, I decided to go ahead and create this guide. I’m going to tell you how to finish your “stand alone” literature review (meaning, its an assignment for a college class and that won’t be a part of a thesis or dissertation) as easily, quickly and efficiently as possible. And at the end of this article, you will be able to download a PDF checklist of everything you need to do, with extra advice thrown in for good measure…

[Step-by-Step: How To do a Literature Review?]

So, PhD students, pass your way for today. And come back next week for something more tailored to your expectations.

As for the others, let’s dive in.

 

0/ Check that you know what a literature review is.

You can have a look here for a thorough definition + a pretty infographic!

 

1/ Make sure that you know what’s expected of you.

 Did you get an assignment sheet or did you write down the instructions? Can you compare notes with other students in your class? Can you go and ask your teach for more details? Here is a list of things you should check:

On which topic are you supposed to be doing your review?

How long should it be?

How many papers are you supposed to be reviewing?

What kind of papers are you allowed to include in your review? (Academic journal articles only? Book chapters? Newspaper articles? Blog posts?)

Do you need to include headings and subheadings?

Are you supposed to use a specific referencing style?

When is it due?

 

2/ Identify keywords around your topic

This is a crucial part that many students don’t know about. This will help you in the next step when you begin searching the literature.

So first, write down your topic. Let me show you with an example:

Role of a compression coil in a Firefly-class ship engine.

Then, identify the important keywords in your topic.

Here it would be “compression coil” and “Firefly-class ship”.

Then, try and think of all possible synonyms and variations on those terms.

Here we could have “compression spring”, “trace compression block”, “03-K64-Firefly”, “Serenity”…

For more info on how to find and use good keywords, have a look here.

 

3/ Begin your literature search

Usually, you will be able to use two separate resources: your library’s catalogue and bibliographic databases.

You can use your library’s catalogue to find books, DVDs, and other physical materials possessed by your library.

To find electronic materials, you will usually have to use electronic databases.

If you look around your library’s website, you should able to access some of those. If you don’t, ask your uni librarian!

I have a whole rubric on this blog to help you with searching a bibliographic database. So have a look at it if you can.

The gist of it is that you’re going to have to use the keywords you came up with to try and find relevant documents on your subject.

If you have any kind of trouble with his, please do go to your university library and ask for help. This is the very reason why there are reference librarians: to help you with that kind of stuff.

You can also send me a message (click on the “contact me” button on the right of your screen) or leave a comment and I’ll try to help you too.

 

4/ Read the documents you’ve found and take notes

You don’t have to read everything you’ve found: you need to identify which bits are truly interesting and then read only those. More info on that here.

Then, it’s absolutely crucial that you take thorough notes while reading: this is what’s going to keep you from unintentional plagiarism.

Try and sum up each paper. Keep those questions in mind:

What does this tell me about my topic?

What do you know about the author?

In which context was this text written? (For which public? In which historical / conceptual context?)

What kind of evidence does the author use? (Statistics? Historical sources? Philosophical arguments?…)

What are the strengths and weaknesses of the argument? Is it convincing?

 

5/ Decide on the structure of your review

You need to identify a few different themes about your topic.

If I come back to my example, I could have one part about the port compression coil and another about the starboard compression coil.

Or I could have different paragraphs about the different parts of a compression coil.

Or I could look at it from an historical point of view and describe its evolutions throughout the different series issued.

Or you could go first what it does / second how it can go wrong / third how to repair it.

You need to base yourself on the kind of information you found. And then you need to match specific ideas from those documents to the different themes you’ve identified. Try and not lose the references for each idea while doing that!

 

6/ Time to write

Okay, now all you need to do is to write your review.

It should look something like that:

Introduction
Theme 1
Theme 2
Theme 3
Conclusion

Your number of themes may vary, but make sure that all your parts are roughly equivalent in length. And don’t forget to write an introduction and a conclusion! I explain more about it over there.

It doesn’t have to be perfect, just write a first draft.

The important thing is that you need to reference each idea with the paper where you found it. Every time. So be super thorough! If you don’t know how to do your references, have a look on your library’s website: they probably have a help section explaining exactly how to do it.

 

7/ Editing and proofreading

Once you have written your first draft, it’s time to edit.

Re-read it and ask yourself those questions:

Did you say everything you wanted to say?

Does your structure make sense?

Did you express yourself clearly enough?

Is your paper evenly proportioned?

Is your tone formal enough for an academic context?

Did you cite all of the papers you intended to reference?

Make all changes you deem necessary. You can repeat this process several times if need be.

Then, it’s proofreading time! Check that your spell check doesn’t underline anything in red. Re-read yourself slowly (you can even print your paper to re-read it, you might see things that you didn’t see on screen!).

If you can, ask someone else to proofread your paper too. But do it yourself first, as a courtesy!

 

8/ Hand it out!

You’re done! Congratulations!

But first, you might want to have a look at the check-list I compiled for you. It will point at all the things you should check before handing out your paper.
 
reference
http://www.howtodoaliteraturer ... cise/

Free Class Schedule Maker Online

smoko roomcewh Published the article • 0 comments • 17364 views • 2016-07-05 09:33 • 来自相关话题

http://freecollegeschedulemaker.com/

The Aromatic Thiols

winerycewh Published the article • 0 comments • 60 views • 2016-07-02 14:27 • 来自相关话题

At the AWITC technical conference in July, we attended an aroma and flavour compound workshop where we were given the opportunity to familiarize ourselves with a range of wine-related, good-bad-and-ugly aroma compounds. In a previous release we discussed the different compounds that contribute to green character in wine. This time we focus on one of the important fermentation aromas, the aromatic thiols.

These are sulphur-containing compounds, and are related by their chemistry to the negative ‘reductive aromas’ previously discussed. The most important fermentation thiols include:
3MHA: 3-mercaptohexylacetate. Passion fruit, gooseberry, guava and other tropical fruit aromas at lower levels, sweaty at higher levels. Sensory perception threshold 4ng/L3MH: 3-mercaptohexanol. Passion fruit, grapefruit and general citrus aromas. Sensory perception threshold 60ng/L4MMP: 4-mercapto-4-methylpentan-2-one. Box tree, broom, blackcurrant and cat urine aromas. Sensory perception threshold 0.8-3.0ng/L

These aromas contribute significantly to the aroma of Sauvignon blanc, but also form part of the fruit aromas of Cabernet Sauvignon, Merlot, Shiraz and Grenache, as well as other white varieties such as Chenin blanc, Riesling, Pinot gris and Gewurztraminer.

Fermentation thiols have their precursors in the grape and are released into wine to a greater or lesser degree depending on the way the grapes and juice are handled, both in the vineyard and the winery.

The 4MMP precursors develop earlier in the grape than those of 3MH and 3MHA. Thus timing of harvest can influence the relative concentration of the individual thiols in wine, and thus which of the aromas will be more dominant. Earlier harvesting favours higher concentrations of 4MMP in the resulting wine and the potential dominance of boxtree aromas, while later harvesting favours 3MH and 3MHA and the potential dominance of tropical and citrus aromas.

4MMP is found equally in skin and pulp while 3MH and 3MHA are found mainly near the skins. Thus skin damage e.g. by mechanical harvester, or during crushing may proportionately increase the levels of the 3MH and 3MHA precursors in the juice. The same is true for skin contact and the use of extraction enzymes. This proportionate increase in 3MH and 3MHA precursors may proportionately increase the levels of their thiols in the wine.

Yeast strain selection can significantly affect the concentration and relative proportion of the individual thiols. Many commercial strains have been specifically isolated to enhance thiol release into wine. Relatively higher fermentation temperatures may also favour the release of thiols.

Reductive processing and maturation conditions will favour the preservation of thiols in wine.

Note that, because they are chemically related to the volatile sulphur compounds, any CuSO4 fining will remove these desirable aromatics from wine.
reference: http://www.vinlab.com/blog/Details/4#.V3clf-wQjtg 查看全部
At the AWITC technical conference in July, we attended an aroma and flavour compound workshop where we were given the opportunity to familiarize ourselves with a range of wine-related, good-bad-and-ugly aroma compounds. In a previous release we discussed the different compounds that contribute to green character in wine. This time we focus on one of the important fermentation aromas, the aromatic thiols.

These are sulphur-containing compounds, and are related by their chemistry to the negative ‘reductive aromas’ previously discussed. The most important fermentation thiols include:
  • 3MHA: 3-mercaptohexylacetate. Passion fruit, gooseberry, guava and other tropical fruit aromas at lower levels, sweaty at higher levels. Sensory perception threshold 4ng/L
  • 3MH: 3-mercaptohexanol. Passion fruit, grapefruit and general citrus aromas. Sensory perception threshold 60ng/L
  • 4MMP: 4-mercapto-4-methylpentan-2-one. Box tree, broom, blackcurrant and cat urine aromas. Sensory perception threshold 0.8-3.0ng/L


These aromas contribute significantly to the aroma of Sauvignon blanc, but also form part of the fruit aromas of Cabernet Sauvignon, Merlot, Shiraz and Grenache, as well as other white varieties such as Chenin blanc, Riesling, Pinot gris and Gewurztraminer.

Fermentation thiols have their precursors in the grape and are released into wine to a greater or lesser degree depending on the way the grapes and juice are handled, both in the vineyard and the winery.

The 4MMP precursors develop earlier in the grape than those of 3MH and 3MHA. Thus timing of harvest can influence the relative concentration of the individual thiols in wine, and thus which of the aromas will be more dominant. Earlier harvesting favours higher concentrations of 4MMP in the resulting wine and the potential dominance of boxtree aromas, while later harvesting favours 3MH and 3MHA and the potential dominance of tropical and citrus aromas.

4MMP is found equally in skin and pulp while 3MH and 3MHA are found mainly near the skins. Thus skin damage e.g. by mechanical harvester, or during crushing may proportionately increase the levels of the 3MH and 3MHA precursors in the juice. The same is true for skin contact and the use of extraction enzymes. This proportionate increase in 3MH and 3MHA precursors may proportionately increase the levels of their thiols in the wine.

Yeast strain selection can significantly affect the concentration and relative proportion of the individual thiols. Many commercial strains have been specifically isolated to enhance thiol release into wine. Relatively higher fermentation temperatures may also favour the release of thiols.

Reductive processing and maturation conditions will favour the preservation of thiols in wine.

Note that, because they are chemically related to the volatile sulphur compounds, any CuSO4 fining will remove these desirable aromatics from wine.
reference: http://www.vinlab.com/blog/Details/4#.V3clf-wQjtg

Annual Cycle of the Grapevine

vineyardcewh Published the article • 0 comments • 74 views • 2016-06-13 05:02 • 来自相关话题

William Nail, The Connecticut Agricultural Experiment Station

Annual Growth Stages

Grapevines are deciduous, woody perennial plants, and their annual cycle is, in many ways, similar to other such plants. There are, however, some differences in managing grapevines cultivated for commercial production. Annual growth of grapevines is frequently described using Eichorn-Lorenz stages.

Dormancy

From leaf fall to the beginning of growth in spring, grapevines are dormant and consist entirely of woody tissue. Relatively little activity occurs during this period. Root growth can still occur unless soil temperatures are too cold to support growth. Cold hardiness within cultivars can vary depending on genetics, temperature, and temperature fluctuations. Many of the hybrid grape varieties are created to address the lack of hardiness in varieties of grapes in the species Vitis vinifera. As a result, hardiness varies considerably across varieties. In cold climates, hardy hybrid varieties are necessary for grape production.

Bud break

As temperatures warm in the spring, stored starch is converted to sugar and sap begins to move in the vine. This can be seen on warm spring days when pruning wounds begin to “bleed". As temperatures warm, buds begin to swell, then burst (break). The newly emerged shoots grow very rapidly, and will continue to do so for several weeks in the absence of stress. Soon clusterinflorescences become visible, usually opposite the third and fourth leaves on a shoot.

Bloom and fruit set

After a few weeks, depending on weather conditions, inflorescences begin to swell, and soon flowers open. The flowering period can be as short as a day or two under warm, dry conditions, or as long as a month under very cool, wet weather conditions. Most commercial grape cultivars are self-pollinating, so do not need a separate pollenizer cultivar. Grapevines are still mostly reliant on stored carbohydrates from the previous season for their energy at this point. After pollination, the flowers abscise and the newly-formed berries go through a rapid period of development due to cell division. Flower cluster primordia for the following season begin to originate in buds at this time, and will continue to develop until veraison. Leaves well exposed to sunlight during this time will result in morefruitful buds in the following growing season. Once the berries are well formed, cell division largely ceases and further berry growth is mostly due to cell expansion. Many leaves on each shoot are fully expanded, and the vine no longer depends on stored carbohydrates for its energy source. For the next few weeks, shoots and berries grow very rapidly.

Veraison and fruit maturation

Approximately five to seven weeks after fruit set, veraison begins. Berries expand further, begin to soften, and accumulate sugar. The color on red cultivars is readily apparent, while the visual indicators of maturity on white cultivars are more subtle. During the next four to six weeks, sugar, pigments, and other flavor compounds increase in the maturing fruit, while organic acids decrease and change forms. Unless there is an excess of water or fertility, shoot growth slows greatly or ceases. The bark of green shoots begins to turn brown from the base, becoming woody by the end of the period. This process is called lignification. On managed plantings, the veraison period ends with harvest.

Post-harvest

After harvest, grapevine leaves continue to photosynthesize until frost if temperatures are warm enough. This is a very important period for the vines to accumulate carbohydrates for future growth. As temperatures fall, vines gradually become more cold hardy, and sugars are converted to starch to be stored for the winter, mostly in perennial structures such as roots and trunks. After leaf fall, vines continue to acclimate to cold weather, but no more carbohydrate accumulation occurs.

Recommended Resources

Eichorn-Lorenz Stages in Shoot Development of the Grapevine

Stages of Grape Berry Development

Mullins, Michael G., Alain Bouquet, and Larry E. Williams. 1992. Biology of the Grapevine.Cambridge University Press, UK.

Growth Stages of Grapevines (diagrams), Canadian Ministry of Agriculture

Reviewed by William Shoemaker, University of Illinois
and Eric Stafne, Mississippi State University
 
reference: http://articles.extension.org/ ... evine 查看全部
William Nail, The Connecticut Agricultural Experiment Station

Annual Growth Stages

Grapevines are deciduous, woody perennial plants, and their annual cycle is, in many ways, similar to other such plants. There are, however, some differences in managing grapevines cultivated for commercial production. Annual growth of grapevines is frequently described using Eichorn-Lorenz stages.

Dormancy

From leaf fall to the beginning of growth in spring, grapevines are dormant and consist entirely of woody tissue. Relatively little activity occurs during this period. Root growth can still occur unless soil temperatures are too cold to support growth. Cold hardiness within cultivars can vary depending on genetics, temperature, and temperature fluctuations. Many of the hybrid grape varieties are created to address the lack of hardiness in varieties of grapes in the species Vitis vinifera. As a result, hardiness varies considerably across varieties. In cold climates, hardy hybrid varieties are necessary for grape production.

Bud break

As temperatures warm in the spring, stored starch is converted to sugar and sap begins to move in the vine. This can be seen on warm spring days when pruning wounds begin to “bleed". As temperatures warm, buds begin to swell, then burst (break). The newly emerged shoots grow very rapidly, and will continue to do so for several weeks in the absence of stress. Soon clusterinflorescences become visible, usually opposite the third and fourth leaves on a shoot.

Bloom and fruit set

After a few weeks, depending on weather conditions, inflorescences begin to swell, and soon flowers open. The flowering period can be as short as a day or two under warm, dry conditions, or as long as a month under very cool, wet weather conditions. Most commercial grape cultivars are self-pollinating, so do not need a separate pollenizer cultivar. Grapevines are still mostly reliant on stored carbohydrates from the previous season for their energy at this point. After pollination, the flowers abscise and the newly-formed berries go through a rapid period of development due to cell division. Flower cluster primordia for the following season begin to originate in buds at this time, and will continue to develop until veraison. Leaves well exposed to sunlight during this time will result in morefruitful buds in the following growing season. Once the berries are well formed, cell division largely ceases and further berry growth is mostly due to cell expansion. Many leaves on each shoot are fully expanded, and the vine no longer depends on stored carbohydrates for its energy source. For the next few weeks, shoots and berries grow very rapidly.

Veraison and fruit maturation

Approximately five to seven weeks after fruit set, veraison begins. Berries expand further, begin to soften, and accumulate sugar. The color on red cultivars is readily apparent, while the visual indicators of maturity on white cultivars are more subtle. During the next four to six weeks, sugar, pigments, and other flavor compounds increase in the maturing fruit, while organic acids decrease and change forms. Unless there is an excess of water or fertility, shoot growth slows greatly or ceases. The bark of green shoots begins to turn brown from the base, becoming woody by the end of the period. This process is called lignification. On managed plantings, the veraison period ends with harvest.

Post-harvest

After harvest, grapevine leaves continue to photosynthesize until frost if temperatures are warm enough. This is a very important period for the vines to accumulate carbohydrates for future growth. As temperatures fall, vines gradually become more cold hardy, and sugars are converted to starch to be stored for the winter, mostly in perennial structures such as roots and trunks. After leaf fall, vines continue to acclimate to cold weather, but no more carbohydrate accumulation occurs.

Recommended Resources

Eichorn-Lorenz Stages in Shoot Development of the Grapevine

Stages of Grape Berry Development

Mullins, Michael G., Alain Bouquet, and Larry E. Williams. 1992. Biology of the Grapevine.Cambridge University Press, UK.

Growth Stages of Grapevines (diagrams), Canadian Ministry of Agriculture

Reviewed by William Shoemaker, University of Illinois
and Eric Stafne, Mississippi State University
 
reference: http://articles.extension.org/ ... evine

Grapevine Sources and Sinks: Allocation of Photosynthate over the Growing Season

vineyardcewh Published the article • 0 comments • 72 views • 2016-06-13 04:57 • 来自相关话题

Tim Martinson, Cornell University

Carbon and sugars produced through photosynthesis, along with minerals from the soil, are allocated from ‘sources’ (active leaves) to ‘sinks’ to support vine growth, fruit development, and maintenance of the vine’s permanent structure (trunks, canes and roots). Where this photosynthate is allocated varies according to the time of the season and needs of the vines. Put another way, the strength of the various sinks to which photosynthates are allocated varies during seasonal vine development. It also is affected by nutrient availability and soil fertility, vine water status, additional stressors such as insects and disease, and crop load – the ratio of fruit to active leaf area. Understanding how allocation of photosynthate shifts over the growing season underpins many of the viticultural practices aimed at influencing vine growth and fruit development.
Dormant to bloom

Early vine growth relies on carbohydrate and nitrogen reserves stored in woody tissues, canes and roots. Starches are mobilized, first from the canes, cordons, and trunk, then from the roots, to the developing shoot tips until mature leaves are capable of becoming net exporters of photosynthate to support further shoot growth and development.
Bloom to fruit set

After flowers are pollinated and begin to set fruit, photosynthate allocation begins to transition from shoot tips to fruit clusters to support fruit growth. In addition, bloom is when the buds for next year’s crop start to form. By this time, reserves are largely depleted, and the vine becomes dependent solely on this year’s canopy to support further canopy development and shoot growth — as well as cluster development. Shoot tips and fruit compete as sinks for photosynthate. As evidence, it’s well known that if shoot tips are removed around bloom, increased allocation of photosynthate to clusters can increase fruit set, as the competing shoot tip sinks are temporarily eliminated.

Early fruit development

By fruit set, berries have already undergone cell division in their ovaries, and have about one-third of their final number of cells. Berries continue their development through cell division, while canopy development and root growth continues.
Lag phase

About a month after bloom, there is a temporary ‘lag’ in berry growth. At this time, cell division in berries is largely complete, and seeds are beginning to form within the ovaries of the berries. After this point, berries continue to grow through cell enlargement, and berries and seeds constitute an increasingly strong sink for photosynthate. Shoot growth should slow dramatically as more of the photosynthate is allocated to developing clusters.
Veraíson and after

Veraíson signals the start of fruit ripening. Fruit composition starts to change. There is a rapid expansion of berry volume and accumulation of soluble solids. Cells, which before veraíson expand through import of water through the xylem, continue expansion with water and solutes imported through the phloem. Acids – largely malate before veraíson — reach their peak at veraíson and get broken down via respiration, simultaneously with increased sugar accumulation. At this point, vines have a full canopy, and the developing and ripening fruit is the overwhelming sink for photosynthate produced by the leaves.
Periderm formation and dormancy

Also after veraíson, shoots begin to turn brown from the base of the shoot outward, as the water-resistant periderm forms. As the leaves start to senesce, carbon and nitrogen from leaves is mobilized out of them to support both fruit development and storage of reserves in canes, trunks and roots of the vine.
Harvest

Once the crop is removed, photosynthate produced by remaining leaves is converted to starches and moved into permanent parts of the vine for storage, which will again support early shoot growth and development during the next growing season.

Consequences for Management

Understanding this seasonal cycle of allocation helps explain seasonal variation in vine growth, the impact of stressors, and the effect of nutrient availability on various processes in the vineyard.
Water relations: Water stress from fruit set through the lag phase can limit cell division, shoot growth, and berry size. For wine grapes (and particularly reds), moderate stress at this time is often viewed as a positive – that limits excess vigor and shading, and facilitates the transition from vegetative growth to fruit development. For red varieties, smaller berries resulting from water stress increase the skin-to-pulp ratio, resulting in wines with deeper color and more concentrated flavors.This 'Pinot Noir' vineyard illustrates effects of excess fertility and undercropping on carbon allocation. Photographed on September 29 in New York, shoot tips are still actively growing, while clusters show evidence of uneven ripening. Note full green "Christmas" clusters that developed on secondary shoots. Photo by Tim Martinson, Cornell University.Excess water and nutrients: In contrast, excess water and nutrient availability (especially N) can delay the transition from vegetative growth to fruit development. Ideally, shoot growth should slow dramatically by about a month after fruit set. If excess water and nitrogen fuel continued shoot growth through and after veraíson, fruit quality suffers, and the transition to dormancy and winter hardiness also will be delayed.Active leaf area after harvest: A fundamental difference between cool and hot climate growing regions is the amount of time that active leaves remain on the vine after harvest. Warm-climate growers almost always have an extended amount of time after harvest with active leaves. In cooler climates, the amount of time that a grapevine canopy remains active after harvest is limited – and sometimes nonexistent. Removing the sink of ripening grape clusters redirects photosynthate towards replenishing vine reserves and supporting acclimation to winter low temperatures. This critical post-harvest time influences how resistant vines are to low winter temperatures and how early-season growth will progress in the following year.Vine balance: Finally, understanding carbon partitioning provides key insights into the concept of vine balance – that is, managing cropping levels and vine growth so that both are in balance with each other. Overcropped vines have more fruit and less leaf area to support development. At best, the finite amount of carbon produced by leaves is divided among too many clusters. At worst, overcropping also results in fewer leaves — and less photosynthate — to support a larger crop. Delayed maturity and unripe fruit can be results of a poorly balanced vine. Undercropped vines allocate too much photosynthate to vegetative growth. Without the sink of developing clusters to slow down shoot growth, canopies become dense and shaded — and often don’t stop growing until late in the season.

Understanding sources and sinks for carbon that leaves produce, and how they vary in time and in response to environment and vine management, is a key to effective vineyard management.
 
 
reference: http://articles.extension.org/ ... eason 查看全部
Tim Martinson, Cornell University

Carbon and sugars produced through photosynthesis, along with minerals from the soil, are allocated from ‘sources’ (active leaves) to ‘sinks’ to support vine growth, fruit development, and maintenance of the vine’s permanent structure (trunks, canes and roots). Where this photosynthate is allocated varies according to the time of the season and needs of the vines. Put another way, the strength of the various sinks to which photosynthates are allocated varies during seasonal vine development. It also is affected by nutrient availability and soil fertility, vine water status, additional stressors such as insects and disease, and crop load – the ratio of fruit to active leaf area. Understanding how allocation of photosynthate shifts over the growing season underpins many of the viticultural practices aimed at influencing vine growth and fruit development.
  • Dormant to bloom


Early vine growth relies on carbohydrate and nitrogen reserves stored in woody tissues, canes and roots. Starches are mobilized, first from the canes, cordons, and trunk, then from the roots, to the developing shoot tips until mature leaves are capable of becoming net exporters of photosynthate to support further shoot growth and development.
  • Bloom to fruit set


After flowers are pollinated and begin to set fruit, photosynthate allocation begins to transition from shoot tips to fruit clusters to support fruit growth. In addition, bloom is when the buds for next year’s crop start to form. By this time, reserves are largely depleted, and the vine becomes dependent solely on this year’s canopy to support further canopy development and shoot growth — as well as cluster development. Shoot tips and fruit compete as sinks for photosynthate. As evidence, it’s well known that if shoot tips are removed around bloom, increased allocation of photosynthate to clusters can increase fruit set, as the competing shoot tip sinks are temporarily eliminated.

Early fruit development

By fruit set, berries have already undergone cell division in their ovaries, and have about one-third of their final number of cells. Berries continue their development through cell division, while canopy development and root growth continues.
  • Lag phase


About a month after bloom, there is a temporary ‘lag’ in berry growth. At this time, cell division in berries is largely complete, and seeds are beginning to form within the ovaries of the berries. After this point, berries continue to grow through cell enlargement, and berries and seeds constitute an increasingly strong sink for photosynthate. Shoot growth should slow dramatically as more of the photosynthate is allocated to developing clusters.
  • Veraíson and after


Veraíson signals the start of fruit ripening. Fruit composition starts to change. There is a rapid expansion of berry volume and accumulation of soluble solids. Cells, which before veraíson expand through import of water through the xylem, continue expansion with water and solutes imported through the phloem. Acids – largely malate before veraíson — reach their peak at veraíson and get broken down via respiration, simultaneously with increased sugar accumulation. At this point, vines have a full canopy, and the developing and ripening fruit is the overwhelming sink for photosynthate produced by the leaves.
  • Periderm formation and dormancy


Also after veraíson, shoots begin to turn brown from the base of the shoot outward, as the water-resistant periderm forms. As the leaves start to senesce, carbon and nitrogen from leaves is mobilized out of them to support both fruit development and storage of reserves in canes, trunks and roots of the vine.
  • Harvest


Once the crop is removed, photosynthate produced by remaining leaves is converted to starches and moved into permanent parts of the vine for storage, which will again support early shoot growth and development during the next growing season.

Consequences for Management

Understanding this seasonal cycle of allocation helps explain seasonal variation in vine growth, the impact of stressors, and the effect of nutrient availability on various processes in the vineyard.
  • Water relations: Water stress from fruit set through the lag phase can limit cell division, shoot growth, and berry size. For wine grapes (and particularly reds), moderate stress at this time is often viewed as a positive – that limits excess vigor and shading, and facilitates the transition from vegetative growth to fruit development. For red varieties, smaller berries resulting from water stress increase the skin-to-pulp ratio, resulting in wines with deeper color and more concentrated flavors.This 'Pinot Noir' vineyard illustrates effects of excess fertility and undercropping on carbon allocation. Photographed on September 29 in New York, shoot tips are still actively growing, while clusters show evidence of uneven ripening. Note full green "Christmas" clusters that developed on secondary shoots. Photo by Tim Martinson, Cornell University.Excess water and nutrients: In contrast, excess water and nutrient availability (especially N) can delay the transition from vegetative growth to fruit development. Ideally, shoot growth should slow dramatically by about a month after fruit set. If excess water and nitrogen fuel continued shoot growth through and after veraíson, fruit quality suffers, and the transition to dormancy and winter hardiness also will be delayed.
  • Active leaf area after harvest: A fundamental difference between cool and hot climate growing regions is the amount of time that active leaves remain on the vine after harvest. Warm-climate growers almost always have an extended amount of time after harvest with active leaves. In cooler climates, the amount of time that a grapevine canopy remains active after harvest is limited – and sometimes nonexistent. Removing the sink of ripening grape clusters redirects photosynthate towards replenishing vine reserves and supporting acclimation to winter low temperatures. This critical post-harvest time influences how resistant vines are to low winter temperatures and how early-season growth will progress in the following year.
  • Vine balance: Finally, understanding carbon partitioning provides key insights into the concept of vine balance – that is, managing cropping levels and vine growth so that both are in balance with each other. Overcropped vines have more fruit and less leaf area to support development. At best, the finite amount of carbon produced by leaves is divided among too many clusters. At worst, overcropping also results in fewer leaves — and less photosynthate — to support a larger crop. Delayed maturity and unripe fruit can be results of a poorly balanced vine. Undercropped vines allocate too much photosynthate to vegetative growth. Without the sink of developing clusters to slow down shoot growth, canopies become dense and shaded — and often don’t stop growing until late in the season.


Understanding sources and sinks for carbon that leaves produce, and how they vary in time and in response to environment and vine management, is a key to effective vineyard management.
 
 
reference: http://articles.extension.org/ ... eason

what are Cava varieties?

Reply

winerycewh Replyed • 1 person concerned • 1 replies • 166 views • 2016-06-08 21:13 • 来自相关话题

Wine Industry Pumps

winerycewh Published the article • 0 comments • 78 views • 2016-06-07 17:50 • 来自相关话题

Pumps are used in many beverage and food process applications. For example, egg whites, honey, food oils, apple sauce, apple juice, donut glaze and pancake batter are all moved using pumps. Pumps can also be used to gently circulate fluid when fermenting high alcohol beer where oxygen is injected into the process to significantly reduce the fermentation time.

Pumps can provide a winemaker with the ability to transfer just-harvested grapes from a de-stemmer/crusher to the tank for fermentation. They can also be used for pump overs in fermentation tanks to allow for color enhancement on red wines and providing a way to move the juice from the tank to barrels for aging.

Pumps are also used to move the wine to the filtering process to remove sediment or solids and then to move the wine to the bottling line for packaging. Regardless of the style, pumps provide time savings to the winemaker and should be considered part of the wine production lifeline.

The winemaker should choose a pump that has the greatest versatility for the particular operation. A versatile pump—one that can run at variable speeds and provide a winery with multiple task fulfillment capabilities—is a cost advantage to a winemaker. Some other advantages of a versatile pump are self-priming, reversible flow, portability and ease of cleaning.

This article discusses some typical pumps found in the wine industry. However, they can also be used in other food and beverage industry segments. Pump styles can be offered in flow ranges from a trickle to hundreds of gallons per minute and with AC or DC voltages.

Pumps can be obtained as a pump alone, with the motor attached and or mounted on a cart for ease of movement within the winery. Some pumps offer low pressure and some can produce high discharge pressures. Picking the flow and pressure to meet the needs of the application is important for successful and continuous production.

Flexible Impeller Pumps
Flexible impeller pumps (FIPs) are self-priming with either wet or dry at start up. They offer gentle, smooth and variable flow rates. This design includes a flexible impeller that rotates in a fixed cavity. The use of an offset cam causes the vanes on the impeller to deflect, decreasing the cell volume initially.

When the vanes leave the cam contact, the volume increases between the vanes, and fluid is drawn into the larger cell cavity with the help of atmospheric pressure. As the impeller rotates, it reduces the cell volume at the discharge port on contact with the cam.

Each cavity then produces a nearly-even and perfect smooth flow and is repeated on each revolution of the impeller. These pumps can transfer solids suspended in liquid. They are reversible and can be mounted above or below the liquid source. The fluid has contact with the rubber flexible impeller and the interior of the body housing. Pump bodies and materials, preferably, should be manufactured from sanitary stainless steel with sanitary rubber compounds. These are positive displacement pumps.

A portable, flexible impeller pump used in wine production
Rotary Lobe Pumps & External Circumferential Piston Pumps
Rotary lobe pumps and external circumferential piston (ECP) pumps, positive displacement pumps, offer high efficiency, gentle pumping action and corrosion resistance. These pumps are reliable and can be cleaned in place (CIP) or steamed in place (SIP). Rotary lobe pumps are capable of handling thick or thin solids, liquids and paste products. Some models of rotary lobe pumps perform well on self-priming if wetted. They can produce significant pressure.

These pumps, like FIPs, can have the direction of fluid flow reversed. Run dry capability is possible if the seals are wetted during the run dry timeframe. Rotary lobe pumps have two alternating direction rotating rotors that mesh in operation. The fluid or product flows into the pump and is captured by the rotating lobes. The product is transferred in the cavities around the outside of the lobe body. The product does not effectively travel between the meshing actions of the two lobes. 

Centrifugal Pumps
Centrifugal pumps use gravity to push water into the pump cavity, and the high speed of the pump impeller then discharges the fluid from the discharge port. These pumps tend to be the most efficient with a smooth, pulse-free delivery. Minimal wear is associated with the pump components, the impeller and pump head are generally easily disassembled.

Most centrifugal pumps are small, but can produce a high volume of flow. Most can be obtained in AC and DC versions and are relatively inexpensive. The main draw back to centrifugal pumps is that they are not self-priming and may cavitate easily. The most common form of centrifugal pumps is a radial flow design.

Air-Operated Diaphragm Pumps
Air-operated diaphragm (AOD) pumps use air to power them. The pump design is self-priming, capable of handling high solids content, can run dry, is portable, explosion proof, has a high pumping efficiency and can deliver a variable flow rate and discharge pressure. One disadvantage is the requirement to have an air compressor on hand for use. This is a positive displacement pump.

Written by:
Keith Evans, Jabsco Flexible Impeller Pumps, Xylem, Inc.
Courtersy of: http://www.pump-zone.com/topics/pumps/pumps/wine-industry-pumps
 
reference: http://www.weg.net/nz/Media-Ce ... Pumps 查看全部
Pumps are used in many beverage and food process applications. For example, egg whites, honey, food oils, apple sauce, apple juice, donut glaze and pancake batter are all moved using pumps. Pumps can also be used to gently circulate fluid when fermenting high alcohol beer where oxygen is injected into the process to significantly reduce the fermentation time.

Pumps can provide a winemaker with the ability to transfer just-harvested grapes from a de-stemmer/crusher to the tank for fermentation. They can also be used for pump overs in fermentation tanks to allow for color enhancement on red wines and providing a way to move the juice from the tank to barrels for aging.

Pumps are also used to move the wine to the filtering process to remove sediment or solids and then to move the wine to the bottling line for packaging. Regardless of the style, pumps provide time savings to the winemaker and should be considered part of the wine production lifeline.

The winemaker should choose a pump that has the greatest versatility for the particular operation. A versatile pump—one that can run at variable speeds and provide a winery with multiple task fulfillment capabilities—is a cost advantage to a winemaker. Some other advantages of a versatile pump are self-priming, reversible flow, portability and ease of cleaning.

This article discusses some typical pumps found in the wine industry. However, they can also be used in other food and beverage industry segments. Pump styles can be offered in flow ranges from a trickle to hundreds of gallons per minute and with AC or DC voltages.

Pumps can be obtained as a pump alone, with the motor attached and or mounted on a cart for ease of movement within the winery. Some pumps offer low pressure and some can produce high discharge pressures. Picking the flow and pressure to meet the needs of the application is important for successful and continuous production.

Flexible Impeller Pumps
Flexible impeller pumps (FIPs) are self-priming with either wet or dry at start up. They offer gentle, smooth and variable flow rates. This design includes a flexible impeller that rotates in a fixed cavity. The use of an offset cam causes the vanes on the impeller to deflect, decreasing the cell volume initially.

When the vanes leave the cam contact, the volume increases between the vanes, and fluid is drawn into the larger cell cavity with the help of atmospheric pressure. As the impeller rotates, it reduces the cell volume at the discharge port on contact with the cam.

Each cavity then produces a nearly-even and perfect smooth flow and is repeated on each revolution of the impeller. These pumps can transfer solids suspended in liquid. They are reversible and can be mounted above or below the liquid source. The fluid has contact with the rubber flexible impeller and the interior of the body housing. Pump bodies and materials, preferably, should be manufactured from sanitary stainless steel with sanitary rubber compounds. These are positive displacement pumps.

A portable, flexible impeller pump used in wine production
Rotary Lobe Pumps & External Circumferential Piston Pumps
Rotary lobe pumps and external circumferential piston (ECP) pumps, positive displacement pumps, offer high efficiency, gentle pumping action and corrosion resistance. These pumps are reliable and can be cleaned in place (CIP) or steamed in place (SIP). Rotary lobe pumps are capable of handling thick or thin solids, liquids and paste products. Some models of rotary lobe pumps perform well on self-priming if wetted. They can produce significant pressure.

These pumps, like FIPs, can have the direction of fluid flow reversed. Run dry capability is possible if the seals are wetted during the run dry timeframe. Rotary lobe pumps have two alternating direction rotating rotors that mesh in operation. The fluid or product flows into the pump and is captured by the rotating lobes. The product is transferred in the cavities around the outside of the lobe body. The product does not effectively travel between the meshing actions of the two lobes. 

Centrifugal Pumps
Centrifugal pumps use gravity to push water into the pump cavity, and the high speed of the pump impeller then discharges the fluid from the discharge port. These pumps tend to be the most efficient with a smooth, pulse-free delivery. Minimal wear is associated with the pump components, the impeller and pump head are generally easily disassembled.

Most centrifugal pumps are small, but can produce a high volume of flow. Most can be obtained in AC and DC versions and are relatively inexpensive. The main draw back to centrifugal pumps is that they are not self-priming and may cavitate easily. The most common form of centrifugal pumps is a radial flow design.

Air-Operated Diaphragm Pumps
Air-operated diaphragm (AOD) pumps use air to power them. The pump design is self-priming, capable of handling high solids content, can run dry, is portable, explosion proof, has a high pumping efficiency and can deliver a variable flow rate and discharge pressure. One disadvantage is the requirement to have an air compressor on hand for use. This is a positive displacement pump.

Written by:
Keith Evans, Jabsco Flexible Impeller Pumps, Xylem, Inc.
Courtersy of: http://www.pump-zone.com/topics/pumps/pumps/wine-industry-pumps
 
reference: http://www.weg.net/nz/Media-Ce ... Pumps