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

smoko roomcewh Published the article • 0 comments • 21 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 • 10758 views • 2016-07-05 09:33 • 来自相关话题

http://freecollegeschedulemaker.com/

The Aromatic Thiols

winerycewh Published the article • 0 comments • 38 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 • 54 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 • 52 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 • 118 views • 2016-06-08 21:13 • 来自相关话题

Wine Industry Pumps

winerycewh Published the article • 0 comments • 56 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

La Crescent: A Winemaker’s Grape

vineyardcewh Published the article • 0 comments • 67 views • 2016-06-04 19:48 • 来自相关话题

May 12, 2013 by Katie Cook
 
The first time I had a glass of wine made from La Crescent, I was completely blown away.

Reminiscent of an aromatic white that might come from Germany or Austria, my mind started spinning with all the potential this grape has for winemakers in Minnesota. The high acidity makes it relatively versatile for various winemaking styles from dry to sweet or even fortified dessert wines, while the tropical fruit and floral aroma make it an easy sell to consumers.[John Thull, vineyard manager and Katie Cook, enology project leader, The University of Minnesota]John Thull, vineyard manager, and Katie Cook, enology project leader, The University of Minnesota

The La Crescent grape originated from a cross between St. Pepin and ES 6-8-25, both selections from the breeding program of Elmer Swenson. It has a complex lineage in which the French hybrid ‘Seyval Blanc’ and V. vinifera ‘Muscat Hamburg’ play a role. Its aromatic profile leans towards muscat, but I’ve also encountered examples that are so fruit-forward that the aroma is reminiscent of the children’s cereal with a toucan on the label.

Surprisingly, an example I had from Iowa so resembled an herbaceous Sauvignon Blanc, that I had a hard time believing that it was a 100% varietal wine (it was fermented using a thiol-producing yeast).

There is, however, a dark side to such a seemingly perfect cold-hardy wine grape. The vine itself isn’t always pretty to look at – its procumbent growth habit making it look as though it is always weeping, and the leaves and fruit can show some disease.

It has moderate resistance to powdery mildew and black rot, but it is susceptible to downy mildew and foliar phylloxera. It’s not a vine for growers who plan to be weekend warriors, as anti-fungal sprays need to be well-timed with bud-break, bloom, and high disease situations (rainfall and humidity) throughout the spring.

The high-vigor canopy also needs to be managed throughout the growing season to allow for good air-circulation. It’s a vine that will punish growers who don’t use good practices. In addition, poor fruit set and late season berry shelling can be troublesome in certain vintages or on particular vineyard sites (though the exact cause is unknown).

The viticultural challenges of La Crescent have unfortunately caused some growers to give up on this variety entirely. I say “unfortunately” because even though I’ve outlined some scary prospects, these aren’t unmanageable problems. Botrytis and berry splitting are non-existent, and own-rooted vines are long-lived.[The La Crescent Grape, developed at the University of Minnesota]The La Crescent Grape, developed at the University of Minnesota

Although La Crescent is a difficult cold-hardy vine when compared to say, Frontenac, in the wide world of viticulture, it is still relatively easy to manage. It is also extremely cold-hardy – tolerating temperatures as cold as -36°F (-38°C) in early February with only minor bud loss. This characteristic, along with the quality of the fruit, means that it is definitely a grape that northern growers should not turn away. It is truly a winemaker’s grape, but one that growers shouldn’t give up on for all its difficulties.

To this day, whenever I’m introducing someone to Minnesota wines, the first wine I tend to start with is one made from La Crescent. Even though Marquette is getting lots of hype, its lack of tannins and its high relative acidity for a red grape still cause wine drinkers to find it “unusual” if they are accustomed to drinking Malbec or Cabernet Sauvignon.

However, La Crescent, when done well, can easily be confused for a Moscato or perhaps a Grüner-Veltiner wine. It’s floral, fruit-forward, and citrusy. Served chilled it’s a perfect wine to serve in the summertime. It also tends to be made in somewhat of an off-dry style rather than bone dry, which is an approachable style to many.

The sugar and acid levels tend to be relatively high when compared to V. vinifera grapes. Sugar levels at harvest average around 25° brix, while acid levels average about 12 g/L, thus the wine is very well-suited towards an off-dry to sweet wine. Because late-season berry shelling can be an issue, making a late-harvest or ice wine comes with risks. Nonetheless, winemakers utilizing cryo-extraction methods or drying the grapes to further concentrate the sugars have been awarded with high-quality, award winning dessert wines. I dare anyone to pick up a bottle and see if they aren’t smitten by its charms.

For more information: http://grapes.umn.edu/LaCrescent/

Katie Cook is the enology project leader at the University of Minnesota and the author of the University of Minnesota Enology Blog 
 
reference: http://midwestwinepress.com/20 ... rape/ 查看全部
May 12, 2013 by Katie Cook
 
The first time I had a glass of wine made from La Crescent, I was completely blown away.

Reminiscent of an aromatic white that might come from Germany or Austria, my mind started spinning with all the potential this grape has for winemakers in Minnesota. The high acidity makes it relatively versatile for various winemaking styles from dry to sweet or even fortified dessert wines, while the tropical fruit and floral aroma make it an easy sell to consumers.[John Thull, vineyard manager and Katie Cook, enology project leader, The University of Minnesota]John Thull, vineyard manager, and Katie Cook, enology project leader, The University of Minnesota

The La Crescent grape originated from a cross between St. Pepin and ES 6-8-25, both selections from the breeding program of Elmer Swenson. It has a complex lineage in which the French hybrid ‘Seyval Blanc’ and V. vinifera ‘Muscat Hamburg’ play a role. Its aromatic profile leans towards muscat, but I’ve also encountered examples that are so fruit-forward that the aroma is reminiscent of the children’s cereal with a toucan on the label.

Surprisingly, an example I had from Iowa so resembled an herbaceous Sauvignon Blanc, that I had a hard time believing that it was a 100% varietal wine (it was fermented using a thiol-producing yeast).

There is, however, a dark side to such a seemingly perfect cold-hardy wine grape. The vine itself isn’t always pretty to look at – its procumbent growth habit making it look as though it is always weeping, and the leaves and fruit can show some disease.

It has moderate resistance to powdery mildew and black rot, but it is susceptible to downy mildew and foliar phylloxera. It’s not a vine for growers who plan to be weekend warriors, as anti-fungal sprays need to be well-timed with bud-break, bloom, and high disease situations (rainfall and humidity) throughout the spring.

The high-vigor canopy also needs to be managed throughout the growing season to allow for good air-circulation. It’s a vine that will punish growers who don’t use good practices. In addition, poor fruit set and late season berry shelling can be troublesome in certain vintages or on particular vineyard sites (though the exact cause is unknown).

The viticultural challenges of La Crescent have unfortunately caused some growers to give up on this variety entirely. I say “unfortunately” because even though I’ve outlined some scary prospects, these aren’t unmanageable problems. Botrytis and berry splitting are non-existent, and own-rooted vines are long-lived.[The La Crescent Grape, developed at the University of Minnesota]The La Crescent Grape, developed at the University of Minnesota

Although La Crescent is a difficult cold-hardy vine when compared to say, Frontenac, in the wide world of viticulture, it is still relatively easy to manage. It is also extremely cold-hardy – tolerating temperatures as cold as -36°F (-38°C) in early February with only minor bud loss. This characteristic, along with the quality of the fruit, means that it is definitely a grape that northern growers should not turn away. It is truly a winemaker’s grape, but one that growers shouldn’t give up on for all its difficulties.

To this day, whenever I’m introducing someone to Minnesota wines, the first wine I tend to start with is one made from La Crescent. Even though Marquette is getting lots of hype, its lack of tannins and its high relative acidity for a red grape still cause wine drinkers to find it “unusual” if they are accustomed to drinking Malbec or Cabernet Sauvignon.

However, La Crescent, when done well, can easily be confused for a Moscato or perhaps a Grüner-Veltiner wine. It’s floral, fruit-forward, and citrusy. Served chilled it’s a perfect wine to serve in the summertime. It also tends to be made in somewhat of an off-dry style rather than bone dry, which is an approachable style to many.

The sugar and acid levels tend to be relatively high when compared to V. vinifera grapes. Sugar levels at harvest average around 25° brix, while acid levels average about 12 g/L, thus the wine is very well-suited towards an off-dry to sweet wine. Because late-season berry shelling can be an issue, making a late-harvest or ice wine comes with risks. Nonetheless, winemakers utilizing cryo-extraction methods or drying the grapes to further concentrate the sugars have been awarded with high-quality, award winning dessert wines. I dare anyone to pick up a bottle and see if they aren’t smitten by its charms.

For more information: http://grapes.umn.edu/LaCrescent/

Katie Cook is the enology project leader at the University of Minnesota and the author of the University of Minnesota Enology Blog 
 
reference: http://midwestwinepress.com/20 ... rape/

Crabtree effect

winerycewh Published the article • 0 comments • 63 views • 2016-05-22 22:36 • 来自相关话题

From Wikipedia, the free encyclopediaSee also: Evolution of aerobic fermentation

Named after the English biochemist Herbert Grace Crabtree, the Crabtree effect describes the phenomenon whereby the yeast, Saccharomyces cerevisiae, produces ethanol (alcohol) in aerobic conditions and high external glucose concentrations rather than producing biomass via the tricarboxylic acid (TCA) cycle, the usual process occurring aerobically in most yeasts e.g. Kluyveromyces spp[1]. This phenomenon is observed in most species of the Saccharomyces, Schizosaccharomyces, Debaryomyces, Brettanomyces, Torulopsis, Nematospora, and Nadsonia genera.[2] Increasing concentrations of glucose accelerates glycolysis (the breakdown of glucose) which results in the production of appreciable amounts of ATP through substrate-level phosphorylation. This reduces the need of oxidative phosphorylation done by the TCA cycle via the electron transport chain and therefore decreases oxygen consumption. The phenomenon is believed to have evolved as a competition mechanism (due to the antiseptic nature of ethanol) around the time when the first fruits on Earth fell from the trees.[1] The crabtree effect works by repressing respiration by the fermentation pathway, dependent on the substrate.[2] 查看全部

From Wikipedia, the free encyclopediaSee also: Evolution of aerobic fermentation

Named after the English biochemist Herbert Grace Crabtree, the Crabtree effect describes the phenomenon whereby the yeast, Saccharomyces cerevisiae, produces ethanol (alcohol) in aerobic conditions and high external glucose concentrations rather than producing biomass via the tricarboxylic acid (TCA) cycle, the usual process occurring aerobically in most yeasts e.g. Kluyveromyces spp[1]. This phenomenon is observed in most species of the Saccharomyces, Schizosaccharomyces, Debaryomyces, Brettanomyces, Torulopsis, Nematospora, and Nadsonia genera.[2] Increasing concentrations of glucose accelerates glycolysis (the breakdown of glucose) which results in the production of appreciable amounts of ATP through substrate-level phosphorylation. This reduces the need of oxidative phosphorylation done by the TCA cycle via the electron transport chain and therefore decreases oxygen consumption. The phenomenon is believed to have evolved as a competition mechanism (due to the antiseptic nature of ethanol) around the time when the first fruits on Earth fell from the trees.[1] The crabtree effect works by repressing respiration by the fermentation pathway, dependent on the substrate.[2]

Brettanomyces Character in Wine ©Richard Gawel

winerycewh Published the article • 0 comments • 70 views • 2016-05-22 22:27 • 来自相关话题

Introduction

The desirability or otherwise of the wine character known as "Brett" is one of the most controversial issues of recent times. Arguments have been made for Brett character being a complexing and a legitimate expression of natural, uncomplicated winemaking, while others view it simply as an unattractive wine fault that results from poor winery hygiene and sloppy winemaking. 

[Brettanomyces forming pseudomycelium on oak]
Figure 1: Brettanomyces bruxellensis forming pseudomycelium
© 2004 High Power Ultrasonics Pty Ltd

The Aroma and Flavour of Brett Character

But what is Brett character and how and why does it appear in some wines? The wine character described as "Bretty" comes in various forms. It is the combined result of the creation of a number of compounds by the yeast Brettanomyces bruxellensis, and its close relative, Dekkera bruxulensis. The three most important known aroma active compounds are 1) 4-ethyl phenol (4-ep), which has been variously described as having the aromas of Band-aids®, antiseptic and horse stable 2) 4-ethyl guaiacol (4-eg) which has a rather pleasant aroma of smoked bacon, spice or cloves and 3) isovaleric acid which has an unpleasant smell of sweaty animals, cheese and rancidity. Other characters associated with Brett include wet dog, creosote, burnt beans, rotting vegetation, plastic and (but not exclusively caused by Brett) mouse cage aroma and vinegar.

The Formation of Brett Character in Wine

Brettanomyces has been isolated from the outside of grapes and from winery equipment. However its, favoured winery haunt is the oak barrel as it often provides for conditions that strongly favours its growth.

Certain conditions are known to favour the growth of Brettanomyces during winemaking. If low free sulfur dioxide levels are coupled with high wine pH and warm temperatures during barrel maturation, then issues may arise. If older oak is used and the wine has a reasonable amount of dissolved oxygen, …. look out! Furthermore it is thought that Brett can also multiply after bottling if the wine contains residual fermentable sugars, a situation made more likely if the wine was minimally filtered. Lets look at the why's of these factors.

Brettanomyces proliferates under warm cellaring conditions. Twenty degrees C is an ideal temperature, with even small reductions in temperature seriously hamper its growth. Sulfur dioxide is an anti-microbial agent that is added by winemakers throughout the winemaking process. If it is added in sufficient amounts, and the pH of the wine is reasonably high (SO2 is more effective at higher acidity levels), then the growth of Brett will be retarded. On the other hand, high alcohol levels and the existence of even small amounts of fermentable sugars such as glucose suit the growth of Brett, as they are its preferred source of energy for growth. Some recent research under laboratory conditions suggest that Brett does not grow at alcohol levels above 13%. However, this result is not consistent with the observation that many wines with alcohols far in excess of this have gone bretty under winery conditions.

Filtering the wine before bottling can reduce the numbers of Brett cells, and hence the incidence of Brett character that develops in the bottle. However, there is anecdotal evidence that filtered wines that are sound at the time of bottling can randomly become infected with Brettanomyces after a period of time, probably as a result of the bottled wine containing residual sugar and being stored in warm conditions.

It is widely acknowledged that the majority of wines with Brett character, became that way during the period of barrel maturation, particularly if second use (or older) oak barrels were used. Brett can colonise a barrel between fills, and can begin to reproduce when the barrel is refilled with new wine. Figure 1 shows Brett extending pseudomycilium into the surface of an oak stave. Topping up barrels with a wine which contains Brett cells, may also contribute to those barrels 'going Bretty'. Shaving and re-toasting the inside of re-used barrels significantly reduces the incidence of Brett growth. However, it is also worth noting that the use of new barrels does not guarantee that Brett will not appear. Recent work in California has shown that new barrels filled with sterilised wine can still sustain populations of Brett high enough to produce above threshold levels of 4-ep. 

But why does oak maturation particularly favour Brett growth? Firstly, Brett is a slow growing yeast that does not compete well against other micro-organisms. During alcoholic fermentation the wine yeast Saccharomyces out easily out-competes it. Two possible reasons are that it naturally grows slower than Saccharomyces, and that it prefers aerobic conditions for growth. During primary ferment, the wine is saturated with carbon dioxide which makes for a hostile environment for Brettanomyces. On the other hand, barrel maturation is a step in conventional winemaking that provides both the time and the lack of competition needed for Brett to successfully grow to levels which results in sensory modification to the wine. Wines stored in barrel are usually lower in SO2 and are kept warmer than at any other time (other than during ferment of course). This is necessary so as to encourage malolactic fermentation (MLF). Lastly, the necessary processes of racking off lees and regularly topping up barrels ensures that there are always reasonable levels of dissolved oxygen in the wine. For all these reasons, it is thought that the time between the completion of primary fermentation and the start of MLF this is the most likely time that Brett multiplies and produces brettiness in wine.



Brettanomyces Character is Seen Primarily in Red Wine. Why?

One final matter concerning Brett is rarely mentioned. It occurs almost exclusively in red wines. Why is this so? Red wines have a much higher level of tannin like substances called coumaric and ferulic acid than do white wines as they are extracted from the skins of grapes during red wine fermentation. The wine yeastSaccharomyces and some lactic acid bacteria such as Lactobacillis have enzymes which degrade these acids to weakly smelling intermediates called 4-vinyl phenol and 4-vinyl guaiacol (Step 1 of Figure 2). These compounds are then enzymatically degraded over a period of months by Brettanomyces to the strong smelling 4-ethyl phenol and 4-ethyl guaiacol respectively (Step 2 of Figure 2). Incidentally Brettanomyces is the only major micro-organism in wine that has the ability to transform 4-vinyl-phenol into the potent band-aid® smelling, 4-ethyl phenol. Hence 4-ethyl phenol is rightly considered to be the "trademark" aroma ofBrettanomyces growth in wine. Where you find 4-ethyl phenol you will invariably find Brett, and vice versa.

Surveys of Australian wines have shown that detectable levels of 4-ethyl phenol is more likely to be seen in darker coloured wines, with Shiraz and Cabernet wines than wines made from either Pinot noir and Grenache. The reason for this is unclear, but may involve the coumarates which are a form of coloured anthocyanins found in red wines.

[Formation of 4-ethyl phenol in wine]
Figure 2: Pathway to the formation of 4-ethyl phenol and 4-ethyl guaiacol in wine


The Prevalence of Brett Character

Has Brett character become apparently more prevalent in recent years? Some commentators believe that we have simply become more aware of it and that it has always been around. I am sure that there is some truth in this. Upon personal reflection, I feel that classic Hunter Shiraz with its 'sweaty saddle' aroma and flavour is a very likely case in point. However, in my opinion, the overpowering, fruit destroying, antiseptic like aromas and flavours that are now occasionally encountered in wines sourced from every winemaking region of Australia is a relatively new phenomenon. The trend in this country today is to produce red wines picked from riper grapes. In addition to maximizing flavour development in some varieties, this also results in wines that are on average higher in pH and alcohol. Furthermore, residual sweetness is being retained in some commercial red wines in an attempt to fill out the palate and to give it greater apparent fruitiness. These trends together with the use of minimal SO2 and filtration, has enhanced the conditions under which Brett is retained and thrives.

The Desirability or Otherwise of Brett Character in Wine

But is the action of Brett desirable? In my humble opinion, the answer depends on degree. As well as producing a band-aid aroma, Brett can create an array of 'interesting' smells that can excite those that are inclined to be excited by them. Furthermore, the ratio of the rather unattractive 4-ethyl phenol to the rather pleasant smelling 4-ethyl guaiacol varies substantially from wine to wine, with reports varying from 3:1 to over 40:1. In the latter case, it is highly likely that the wine would smell like the inside of a band-aid box, while in the former, the aroma would in all likelihood be far more spicy and savoury like. The reason for these differences between wines are not completely understood but are likely to be either due to differing ratios between wines coumaric and ferulic acids (the respective precursors of 4-ep and 4-eg), or to different strains of Brettanomyces being more effective in producing one compound relative to the other. Very recent research with five different strains of Brettanomyces has not lent much support to the latter possibility. Under laboratory conditions the different strains produced roughly equal proportions of 4-ep to 4-eg in the same red wine. But the search for strains of Brett which may be low 4-ep producers will no doubt continue.

In some wine growing regions such as Bordeaux, the Rhone and, dare I say it, the Hunter Valley, it is now acknowledged that some wine producers have developed 'house styles' over time that have actually been defined by some form of Brett character. Many of these producers, or the media, or both, have naively attributed these unusual and sometimes complexing characters to being 'an expression of the soil'. However, overwhelming scientific evidence in the form of elevated 4-ethyl phenol levels in their wines have forced them to admit to the less romantic notions of the microbiological origin of these characters. This is not to say that they necessarily will, or indeed should, do anything different in the future, as many Bretty house styles have become widely accepted and in some cases revered by the wine tasting public. But in the cases where a wine smells more of a hospital ward than it does wine, surely the wine-maker should begin to reflect on what wine drinkers seriously value. That is, real fruit and real complexity. Unfortunately some winemakers (possibly in an attempt to save their career), have attributed the accidental making of overtly Bretty wines as a serious attempt at making something different and complex. Wine diversity is a wonderful thing and should be encouraged in the face of continued 'internationalisation' of wines. But as Pascal Chattonet once argued. Brettyiness has nothing to do with a wines 'typicity' as claimed by some French wine producers. His counterclaim is that wines that are overly Bretty do indeed smell and taste much the same, so overt Brettyness mitigates against 'typicity' and diversity. I'm in Pascal's camp. Real 'typicity' and 'expression' indeed come from the fruit. A message that I hope is not lost on the winemaking fraternity.

This work was presented at the Australian Society of Wine Education National Convention. Hunter Valley, Australia. 4th-6th of June 2004. 
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Introduction

The desirability or otherwise of the wine character known as "Brett" is one of the most controversial issues of recent times. Arguments have been made for Brett character being a complexing and a legitimate expression of natural, uncomplicated winemaking, while others view it simply as an unattractive wine fault that results from poor winery hygiene and sloppy winemaking. 

[Brettanomyces forming pseudomycelium on oak]
Figure 1: Brettanomyces bruxellensis forming pseudomycelium
© 2004 High Power Ultrasonics Pty Ltd

The Aroma and Flavour of Brett Character

But what is Brett character and how and why does it appear in some wines? The wine character described as "Bretty" comes in various forms. It is the combined result of the creation of a number of compounds by the yeast Brettanomyces bruxellensis, and its close relative, Dekkera bruxulensis. The three most important known aroma active compounds are 1) 4-ethyl phenol (4-ep), which has been variously described as having the aromas of Band-aids®, antiseptic and horse stable 2) 4-ethyl guaiacol (4-eg) which has a rather pleasant aroma of smoked bacon, spice or cloves and 3) isovaleric acid which has an unpleasant smell of sweaty animals, cheese and rancidity. Other characters associated with Brett include wet dog, creosote, burnt beans, rotting vegetation, plastic and (but not exclusively caused by Brett) mouse cage aroma and vinegar.

The Formation of Brett Character in Wine

Brettanomyces has been isolated from the outside of grapes and from winery equipment. However its, favoured winery haunt is the oak barrel as it often provides for conditions that strongly favours its growth.

Certain conditions are known to favour the growth of Brettanomyces during winemaking. If low free sulfur dioxide levels are coupled with high wine pH and warm temperatures during barrel maturation, then issues may arise. If older oak is used and the wine has a reasonable amount of dissolved oxygen, …. look out! Furthermore it is thought that Brett can also multiply after bottling if the wine contains residual fermentable sugars, a situation made more likely if the wine was minimally filtered. Lets look at the why's of these factors.

Brettanomyces proliferates under warm cellaring conditions. Twenty degrees C is an ideal temperature, with even small reductions in temperature seriously hamper its growth. Sulfur dioxide is an anti-microbial agent that is added by winemakers throughout the winemaking process. If it is added in sufficient amounts, and the pH of the wine is reasonably high (SO2 is more effective at higher acidity levels), then the growth of Brett will be retarded. On the other hand, high alcohol levels and the existence of even small amounts of fermentable sugars such as glucose suit the growth of Brett, as they are its preferred source of energy for growth. Some recent research under laboratory conditions suggest that Brett does not grow at alcohol levels above 13%. However, this result is not consistent with the observation that many wines with alcohols far in excess of this have gone bretty under winery conditions.

Filtering the wine before bottling can reduce the numbers of Brett cells, and hence the incidence of Brett character that develops in the bottle. However, there is anecdotal evidence that filtered wines that are sound at the time of bottling can randomly become infected with Brettanomyces after a period of time, probably as a result of the bottled wine containing residual sugar and being stored in warm conditions.

It is widely acknowledged that the majority of wines with Brett character, became that way during the period of barrel maturation, particularly if second use (or older) oak barrels were used. Brett can colonise a barrel between fills, and can begin to reproduce when the barrel is refilled with new wine. Figure 1 shows Brett extending pseudomycilium into the surface of an oak stave. Topping up barrels with a wine which contains Brett cells, may also contribute to those barrels 'going Bretty'. Shaving and re-toasting the inside of re-used barrels significantly reduces the incidence of Brett growth. However, it is also worth noting that the use of new barrels does not guarantee that Brett will not appear. Recent work in California has shown that new barrels filled with sterilised wine can still sustain populations of Brett high enough to produce above threshold levels of 4-ep. 

But why does oak maturation particularly favour Brett growth? Firstly, Brett is a slow growing yeast that does not compete well against other micro-organisms. During alcoholic fermentation the wine yeast Saccharomyces out easily out-competes it. Two possible reasons are that it naturally grows slower than Saccharomyces, and that it prefers aerobic conditions for growth. During primary ferment, the wine is saturated with carbon dioxide which makes for a hostile environment for Brettanomyces. On the other hand, barrel maturation is a step in conventional winemaking that provides both the time and the lack of competition needed for Brett to successfully grow to levels which results in sensory modification to the wine. Wines stored in barrel are usually lower in SO2 and are kept warmer than at any other time (other than during ferment of course). This is necessary so as to encourage malolactic fermentation (MLF). Lastly, the necessary processes of racking off lees and regularly topping up barrels ensures that there are always reasonable levels of dissolved oxygen in the wine. For all these reasons, it is thought that the time between the completion of primary fermentation and the start of MLF this is the most likely time that Brett multiplies and produces brettiness in wine.



Brettanomyces Character is Seen Primarily in Red Wine. Why?

One final matter concerning Brett is rarely mentioned. It occurs almost exclusively in red wines. Why is this so? Red wines have a much higher level of tannin like substances called coumaric and ferulic acid than do white wines as they are extracted from the skins of grapes during red wine fermentation. The wine yeastSaccharomyces and some lactic acid bacteria such as Lactobacillis have enzymes which degrade these acids to weakly smelling intermediates called 4-vinyl phenol and 4-vinyl guaiacol (Step 1 of Figure 2). These compounds are then enzymatically degraded over a period of months by Brettanomyces to the strong smelling 4-ethyl phenol and 4-ethyl guaiacol respectively (Step 2 of Figure 2). Incidentally Brettanomyces is the only major micro-organism in wine that has the ability to transform 4-vinyl-phenol into the potent band-aid® smelling, 4-ethyl phenol. Hence 4-ethyl phenol is rightly considered to be the "trademark" aroma ofBrettanomyces growth in wine. Where you find 4-ethyl phenol you will invariably find Brett, and vice versa.

Surveys of Australian wines have shown that detectable levels of 4-ethyl phenol is more likely to be seen in darker coloured wines, with Shiraz and Cabernet wines than wines made from either Pinot noir and Grenache. The reason for this is unclear, but may involve the coumarates which are a form of coloured anthocyanins found in red wines.

[Formation of 4-ethyl phenol in wine]
Figure 2: Pathway to the formation of 4-ethyl phenol and 4-ethyl guaiacol in wine


The Prevalence of Brett Character

Has Brett character become apparently more prevalent in recent years? Some commentators believe that we have simply become more aware of it and that it has always been around. I am sure that there is some truth in this. Upon personal reflection, I feel that classic Hunter Shiraz with its 'sweaty saddle' aroma and flavour is a very likely case in point. However, in my opinion, the overpowering, fruit destroying, antiseptic like aromas and flavours that are now occasionally encountered in wines sourced from every winemaking region of Australia is a relatively new phenomenon. The trend in this country today is to produce red wines picked from riper grapes. In addition to maximizing flavour development in some varieties, this also results in wines that are on average higher in pH and alcohol. Furthermore, residual sweetness is being retained in some commercial red wines in an attempt to fill out the palate and to give it greater apparent fruitiness. These trends together with the use of minimal SO2 and filtration, has enhanced the conditions under which Brett is retained and thrives.

The Desirability or Otherwise of Brett Character in Wine

But is the action of Brett desirable? In my humble opinion, the answer depends on degree. As well as producing a band-aid aroma, Brett can create an array of 'interesting' smells that can excite those that are inclined to be excited by them. Furthermore, the ratio of the rather unattractive 4-ethyl phenol to the rather pleasant smelling 4-ethyl guaiacol varies substantially from wine to wine, with reports varying from 3:1 to over 40:1. In the latter case, it is highly likely that the wine would smell like the inside of a band-aid box, while in the former, the aroma would in all likelihood be far more spicy and savoury like. The reason for these differences between wines are not completely understood but are likely to be either due to differing ratios between wines coumaric and ferulic acids (the respective precursors of 4-ep and 4-eg), or to different strains of Brettanomyces being more effective in producing one compound relative to the other. Very recent research with five different strains of Brettanomyces has not lent much support to the latter possibility. Under laboratory conditions the different strains produced roughly equal proportions of 4-ep to 4-eg in the same red wine. But the search for strains of Brett which may be low 4-ep producers will no doubt continue.

In some wine growing regions such as Bordeaux, the Rhone and, dare I say it, the Hunter Valley, it is now acknowledged that some wine producers have developed 'house styles' over time that have actually been defined by some form of Brett character. Many of these producers, or the media, or both, have naively attributed these unusual and sometimes complexing characters to being 'an expression of the soil'. However, overwhelming scientific evidence in the form of elevated 4-ethyl phenol levels in their wines have forced them to admit to the less romantic notions of the microbiological origin of these characters. This is not to say that they necessarily will, or indeed should, do anything different in the future, as many Bretty house styles have become widely accepted and in some cases revered by the wine tasting public. But in the cases where a wine smells more of a hospital ward than it does wine, surely the wine-maker should begin to reflect on what wine drinkers seriously value. That is, real fruit and real complexity. Unfortunately some winemakers (possibly in an attempt to save their career), have attributed the accidental making of overtly Bretty wines as a serious attempt at making something different and complex. Wine diversity is a wonderful thing and should be encouraged in the face of continued 'internationalisation' of wines. But as Pascal Chattonet once argued. Brettyiness has nothing to do with a wines 'typicity' as claimed by some French wine producers. His counterclaim is that wines that are overly Bretty do indeed smell and taste much the same, so overt Brettyness mitigates against 'typicity' and diversity. I'm in Pascal's camp. Real 'typicity' and 'expression' indeed come from the fruit. A message that I hope is not lost on the winemaking fraternity.

This work was presented at the Australian Society of Wine Education National Convention. Hunter Valley, Australia. 4th-6th of June 2004. 
www.aswe.org.au