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.)
(Kelli White, Sarah Bray)
I just read the new examiner's report for the stage 1 assessment and the examiners now believe that microbial stability is within the scope of the question.
Sabrina Lueck 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.
When I did this for the S1, I did quickly mention electro dialysis, CMC and mannoproteins. For the RS aspect I mentioned the need to sterile filter and gave the SO2 levels but style. A bulk example of a producer that does cold stabilization and not CMC, even though it would be cheaper, is The Wine Group in CA. For another domestic example, Ch. Ste Michele uses electrodialysis on all their whites.
Also, save yourself time on this by being really clear on where paper 3 starts and ends: Racking is Paper 2. Paper 3 starts with cold stabilization, or whatever methods are used for tartrate stabilization. The only filtration is the final filtration pre-bottling. I think this is confused when we go back to early questions before the paper boundries were so solid.
Stabilization before bottling I understand as tartrate, microbial, and metal stability (essentailly chemically and biologically stable and fault free.)
I am emailing you both my other outline because the formatting gets destroyed when I try to copy it in her.
Great point about P2 v. P3 Anne Cox. See? Up to my neck in weeds. The Wine Group is great; much appreciated. I’ll check out your outline as well (I know; I’ve had to reformat so many times on these threads!!)
Hi Sarah Bray. 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.
Good point on the metal stability - I'd include that in a paragraph on other instabilities (like color). And thank you for the Wine Group example!
Hi all, I just wanted to add a few thoughts. I'm not an MW student so I may be including technical details that are beyond what the MW is looking for.
Perhaps this is evident, but I wanted to mention a few high-level concepts on why wines may become unstable in bottle.
For each type of instability, there are tests that a winemaker can perform to determine whether it is necessary to treat the wine. For protein stabilization, the test is referred to as "heat stability", for microbial stability, winemakers often run "Scorpions" (PCR-based genetic tests that give cell counts for different common wine yeast and bacteria).
This is a great summary. Thanks Jennifer.
Hi allHere 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
Additional stability concerns
Further reading: Cold Stability, CMCs and other crystal inhibitors. Dr. Eric Wilkes, Australian Wine Research Institute.