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

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Parents
  • these questions overwhelm me due to how technical they are and the depth of detail required. Would you go into additives here like CMC or mannoproteins? What about electrodialysis? If so, how would you approach? How do you deal with RS in a question like this? I'd love to know how you'd approach in terms of bringing in specifics, but here's how I think I'd approach an initial intro and general topics. Also, very apparently need New World examples! 

     

    Stabilizing a wine refers to the removal of unstable elements to prevent spoilage, including unintentional re-fermentation and excess precipitation, from occurring post-bottling. There are several winemaking techniques that can be employed in order to stabilize a wine: decanting and racking; cold stabilizing; filtering; chemical additions; and aging pre-bottling. This essay will explore these methods and the reasons why they are implemented.

    • Decanting and racking
      • Decanting can be implemented at multiple stages throughout the winemaking process, allowing unstable elements, including lees, MOG, and precipitates, to naturally fall and settle at the bottom of a vessel. 
      • Racking refers to the process of running the clean wine from one vessel to another in order to remove the precipitates manually after the clean wine has been remove; often, the clean wine is then returned to the vessel.
      • Examples:
        • At La Mission Haut Brion, winemakers rack their barrel every 3 months, using gravity to run the wine out of barrel, specifically into a wine glass over a candle until the light shows that the liquid has become cloudy. At that time, they stop running the wine and filter the remaining sediment, reclaiming any additional wine. They prefer to remove sediment regularly, but they vary the frequency based on vintage and how much O2 the wine can take. (Also: they note this helps color stability)
        • Erni Loosen in the Mosel leaves his dry wines for 12 months on the lees without racking to preserve a reductive environment and stabilize his wines through exposure to the mannoproteins released by the yeast cells (e.g. longer lees contact leads to greater potassium bitartrate stability; see: cold stabilization)
    • Cold stabilization
      • Cold stabilization occurs when the wine in tank is dropped to freezing temperatures in order to induce the formation and dropping of tartrates, crystals which may form in the future due to tartaric acid precipitating in bottle at cooler cellar temperatures. The formation of these crystals is more common in higher pH wines. The process is done due to more aesthetic reasons and consumer concerns (look like pieces of glass).
      • How it’s done: Cool wine to -1 to -4 degrees Celsius for minimum 2 weeks; can add cream of tartar to speed the precipitation process, but it requires the recovery the crystals. Note as well the high cost of electricity in large quantities, which can account for up to 25% of a winery’s electricity costs.
      • Examples:
        • Widely practiced in traditional method sparkling wine production after blending and before the liqueur de tirage is added. (Multiple examples of grandes marques, etc.)
        • Bulk wine example?
    • Filtration
      • Filtration is the process by which large particles are removed from the wine by passing through a material, where a pad or a thin membrane. Often times, a fining agent like bentonite will be added to the wine first to cause invisible protein colloids to precipitate and thus be large enough to be removed.
      • Examples:
        • Quercetin precipitate from a grape low in anthocyanins from a hot vintage (Sangiovese and Nerello Mascalese – use a fining agent to cause the molecules to precipitate pre-bottling, then filter out
    • Chemical additions/SO2
      • SO2 additions in either gas or liquid form can bind to unwanted acetaldehyde aromas that may have formed during MLF (or be used to block it) and can help prevent oxidation during steps like racking and filtration. They can also kill off unwanted microbes in the wines, especially at the final step before bottling.
      • CMC? Mannoproteins?
    • Aging pre-bottling
      • Extended aging in cask before bottling will naturally allow for exposure to oxygen in small amounts; with more time the wine spends in wood, intentional aromas of oxidation may occur and will act like a preservative.
      • Examples:
        • Marco de Bartoli’s perpetual solera in which wine is added each year for the production of his Vecchio Samperi. The large oak casks are only half filled, causing intentional oxidation of the wines.
        • Madeira: canteiro — natural aging oxidative process where small barrels are placed in attics without temperature control, allowing the wines to concentrate over time.
        • Other fortified, white rioja, etc.
Reply
  • Hi . Good news and bad news. There's info in here that is out of the scope of the question. This means that you can free up some time to focus on the relevant topics in here!

    I'd break this question down into three 4 major categories - tartrate stability, protein stability, colloidal stability, and microbial stability. When I did this in the S1, I addressed the "why" in the introduction/conclusion, and focussed each paragraph on the different "hows".

    No need to include racking since that's more in the scope of P2. You've made an interesting point of about oxidation providing stability in fortified wines. I'd steer clear of that one too since it's not mentioned in the examiner's report.

    For cold stability - you can include some of your additions examples here. CMC and other gum products are used for cold stability but don't need to traditional cold to work. You can also include your ion exchange electrodialysis example in here so you've hit three methods. I bet you could find some diverse global examples for this as well - traditional cold in boutique Champagne vs ion exchange at larger facilities. 

    You mention proteins under filtration, but even a sterile filter won't filter out hazes - a giant colloid of protein is still much smaller than a bacteria. I'd address protein stability on its own with bentonite. I struggle to have a fleshed-out paragraph here since bentonite is still the main way that wines are proteins stabilized around the world.

    I'd include your SO2 addition info in a microbial stability paragraph with your filtration info.

Children
  • hey ya'll as i was cleaning my inbox, i got to a note from Kelli and I was reminded to check in here. I noticed something that i wanted to comment on briefly - Sabrina,  -usually with the phrasing "why and how" or something to that effect, you are usually expected to give similar weight to those questions. in fact, taking Jennifer's topics below, each one of them has their own "why" - cosmetic, consistency in product/long-distance shipping, financial implications, and qualitative (organoleptic) etc. addressing the why should happen more than just in intro/conclusion - otherwise it's just a descriptive essay, not analytical; also perhaps included is the assumption that you consider the efficacy of the methods to achieve various stability parameters.