MW Topic of the Week: Stabilization

Hi all

The topic this week is wine stabilization. There are been two direct questions on this recently

Why and how should wine be stabilized before bottling? (2010, and 2019 S1A)
How might protein and tartrate stability in wine be achieved, and managed? (2015)

Does anyone want to tackle the different methods of protein and tartrate stabilizing a wine? 

(I took a look at the examiner's report after my S1A and was surprised to see that the examiners didn't think microbial or color/colloid stability was in the scope of the first question.)

Cheers,

Sabrina

()

Parents
  • Hi all

    Here are my notes for these questions. To keep things manageable, I tried to focus on the "how" since this is explicitly called for in both questions. I didn't put these notes together in an hour. So keep in mind that this is probably too much information for an essay.

    Stability definition: the removal of components from wine to ensure that no undesirable physical or sensory properties develop for a given period of time under a given set of conditions.

    Cold stability definition: the ability of a wine to resist the precipitation of tartrates (Dr. Eric Wilkes, AWRI)

    Protein stability definition: the ability of a wine to resist the denaturation and aggregation of grape proteins

    Microbial stability definition: the removal or inhibition of microbes in wine to avoid refermentation

    WHY

    • Removal of calcium and potassium tartrate which can precipitate in bottle
    • Removal of proteins which can form haze in bottle
    • Removal of microbes (or microbial nutrients) to avoid refermentation in bottle
    • Crowded marketplace – 60k SKUs in USA alone
    • Consumers expect brilliant clarity in most wines

    HOW

    Tartrate

    • Refrigeration
      • Wine is chilled to close to freezing and held at temperature for 2 weeks. Potassium tartrate is less soluble at colder temperature, will precipitate out of the wine. Process can be sped up with “contact process” of added potassium bitartrate powder which provides a nucleation point for crystal formation.
      • This process is more common at smaller wineries because it only requires glycol chilling. Energy intensive but doesn’t require the investment in new technology. This process does not guarantee stability.
      • Example: (thanks Anne) The Wine Group in Madera, USA uses traditional chilling for cold stabilization.
    • Ion exchange
      • Wine is passed through a resin column where potassium ions are swapped for sodium or hydrogen ions. Potassium tartrate cannot form because potassium is not present in wine.
      • This process guarantees stability but may impact sensory – sodium may have a soapy impact. Hydrogen may be overly acidic.
      • Example: 14 Hands in Prosser, WA, USA uses STARS electrodialysis on all wines. It is faster and less expensive than cold for their high volume products.
    • Crystal growth inhibitors
      • Block potassium bitartrate crystal nucleation and growth by binding to one of the crystal faces, therefore preventing further growth and precipitation of visible crystals.
      • Less impact on wine pH/TA than cold or ion exchange. Labor and time savings. Lower energy that traditional refrigeration.
      • Metatartaric acid – polymer of tartaric acid formed by heating. Wine should be protein stable before adding. Most effective at preventing precipitation in many wines (Eric Wilkes, AWRI). Product example: Laffort POLYTARTRYL®
      • Carboxymethylcellulose (CMC) gum – polymer of cellulose with carboxymethyl groups. Cannot be used on red wines or wines that are not protein stable, will form haze. Can cause color precipitation. Are not effective for calcium tartrate stability. Product example: Laffort CELSTAB®
      • Yeast mannoproteins – derived from yeast cell walls. Contributes to both tartaric and colloidal (tannin/color) stability of wines. Product example: Laffort MANNOFEEL®
      • Example: College Cellars in Walla Walla, WA, USA uses CMC gum on a Muscat wine which turns from harvest to bottle in one month. Small school/winery does not have time for traditional cold or money for ion exchange.

    Protein

    • Protein hazes form when proteins denature (change shape). The denatured proteins aggregate and form a haze.
    • Protein hazes are formed by grape derived proteins. Proteins derived from yeasts (lees contact etc) do not contribute to haze formation.
    • Bentonite addition
      • Bentonite is made from weathered volcanic ash. When hydrated, it “opens” to expose positively charged layers of ions which bind to negatively charged proteins.
      • Disadvantage: large amount of wine loss in “lees”, potential flavor stripping
    • Enzyme addition
      • Addition of enzyme which breaks down haze-causing proteins in conjunction with flash pasteurization. Enzyme has been approved for winemaking in Australia and New Zealand.

    Microbial

    • A wine should have a low microbial load before bulk transport or bottling.
    • The majority of the worlds wines by volume are transported in bulk and bottled in port. Change in temperature due to equatorial transport can lead to microbial bloom if wines have not been rough filtered down to a low level, and do not have sufficient preservatives including free sulfur dioxide.
    • Additionally, wines will need to be very close to microbially stable before attempting sterile filtration at bottling. Excessive microbial load will foul a 0.45 micron nominal filter. To achieve a low microbial level, wines can be sequentially filtered through filters of increasing tightness including diatomaceous earth filters, pad filters, and cross flow filters.
    • Other options for microbial stability include use of dimethyldicarbonate ("velcorin"). However, this is more common at bottling and out of the scope of the question.

    Additional stability concerns

    • Phenolic stability is a relevant issue too. Quercetin instabilities can occur when quercetin levels become excessive. This has become an issue is some Sangiovese based wines from Central Italy. According to Dr. Steve Price, ETS Laboratories, these instabilities can be mitigated by blending with high anthocyanin wines. If the quercetin colloid becomes too large and precipitates out, the wine can simple by racked off of the sediment and filtered.
    • Metal stability – more common in wines with high levels of copper sulfate from vineyard or use of copper fining in winery. 0.2 mg/L of Cu will likely throw a haze (according to Gordon Burns, ETS Laboratories). Metal haze or “casse” of metal salt looks like blue sludge.


    Further reading: Cold Stability, CMCs and other crystal inhibitors. Dr. Eric Wilkes, Australian Wine Research Institute.

Reply
  • Hi all

    Here are my notes for these questions. To keep things manageable, I tried to focus on the "how" since this is explicitly called for in both questions. I didn't put these notes together in an hour. So keep in mind that this is probably too much information for an essay.

    Stability definition: the removal of components from wine to ensure that no undesirable physical or sensory properties develop for a given period of time under a given set of conditions.

    Cold stability definition: the ability of a wine to resist the precipitation of tartrates (Dr. Eric Wilkes, AWRI)

    Protein stability definition: the ability of a wine to resist the denaturation and aggregation of grape proteins

    Microbial stability definition: the removal or inhibition of microbes in wine to avoid refermentation

    WHY

    • Removal of calcium and potassium tartrate which can precipitate in bottle
    • Removal of proteins which can form haze in bottle
    • Removal of microbes (or microbial nutrients) to avoid refermentation in bottle
    • Crowded marketplace – 60k SKUs in USA alone
    • Consumers expect brilliant clarity in most wines

    HOW

    Tartrate

    • Refrigeration
      • Wine is chilled to close to freezing and held at temperature for 2 weeks. Potassium tartrate is less soluble at colder temperature, will precipitate out of the wine. Process can be sped up with “contact process” of added potassium bitartrate powder which provides a nucleation point for crystal formation.
      • This process is more common at smaller wineries because it only requires glycol chilling. Energy intensive but doesn’t require the investment in new technology. This process does not guarantee stability.
      • Example: (thanks Anne) The Wine Group in Madera, USA uses traditional chilling for cold stabilization.
    • Ion exchange
      • Wine is passed through a resin column where potassium ions are swapped for sodium or hydrogen ions. Potassium tartrate cannot form because potassium is not present in wine.
      • This process guarantees stability but may impact sensory – sodium may have a soapy impact. Hydrogen may be overly acidic.
      • Example: 14 Hands in Prosser, WA, USA uses STARS electrodialysis on all wines. It is faster and less expensive than cold for their high volume products.
    • Crystal growth inhibitors
      • Block potassium bitartrate crystal nucleation and growth by binding to one of the crystal faces, therefore preventing further growth and precipitation of visible crystals.
      • Less impact on wine pH/TA than cold or ion exchange. Labor and time savings. Lower energy that traditional refrigeration.
      • Metatartaric acid – polymer of tartaric acid formed by heating. Wine should be protein stable before adding. Most effective at preventing precipitation in many wines (Eric Wilkes, AWRI). Product example: Laffort POLYTARTRYL®
      • Carboxymethylcellulose (CMC) gum – polymer of cellulose with carboxymethyl groups. Cannot be used on red wines or wines that are not protein stable, will form haze. Can cause color precipitation. Are not effective for calcium tartrate stability. Product example: Laffort CELSTAB®
      • Yeast mannoproteins – derived from yeast cell walls. Contributes to both tartaric and colloidal (tannin/color) stability of wines. Product example: Laffort MANNOFEEL®
      • Example: College Cellars in Walla Walla, WA, USA uses CMC gum on a Muscat wine which turns from harvest to bottle in one month. Small school/winery does not have time for traditional cold or money for ion exchange.

    Protein

    • Protein hazes form when proteins denature (change shape). The denatured proteins aggregate and form a haze.
    • Protein hazes are formed by grape derived proteins. Proteins derived from yeasts (lees contact etc) do not contribute to haze formation.
    • Bentonite addition
      • Bentonite is made from weathered volcanic ash. When hydrated, it “opens” to expose positively charged layers of ions which bind to negatively charged proteins.
      • Disadvantage: large amount of wine loss in “lees”, potential flavor stripping
    • Enzyme addition
      • Addition of enzyme which breaks down haze-causing proteins in conjunction with flash pasteurization. Enzyme has been approved for winemaking in Australia and New Zealand.

    Microbial

    • A wine should have a low microbial load before bulk transport or bottling.
    • The majority of the worlds wines by volume are transported in bulk and bottled in port. Change in temperature due to equatorial transport can lead to microbial bloom if wines have not been rough filtered down to a low level, and do not have sufficient preservatives including free sulfur dioxide.
    • Additionally, wines will need to be very close to microbially stable before attempting sterile filtration at bottling. Excessive microbial load will foul a 0.45 micron nominal filter. To achieve a low microbial level, wines can be sequentially filtered through filters of increasing tightness including diatomaceous earth filters, pad filters, and cross flow filters.
    • Other options for microbial stability include use of dimethyldicarbonate ("velcorin"). However, this is more common at bottling and out of the scope of the question.

    Additional stability concerns

    • Phenolic stability is a relevant issue too. Quercetin instabilities can occur when quercetin levels become excessive. This has become an issue is some Sangiovese based wines from Central Italy. According to Dr. Steve Price, ETS Laboratories, these instabilities can be mitigated by blending with high anthocyanin wines. If the quercetin colloid becomes too large and precipitates out, the wine can simple by racked off of the sediment and filtered.
    • Metal stability – more common in wines with high levels of copper sulfate from vineyard or use of copper fining in winery. 0.2 mg/L of Cu will likely throw a haze (according to Gordon Burns, ETS Laboratories). Metal haze or “casse” of metal salt looks like blue sludge.


    Further reading: Cold Stability, CMCs and other crystal inhibitors. Dr. Eric Wilkes, Australian Wine Research Institute.

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