Wine Yeast Mythbusting

I listened to an episode of The Brewing Network's Sunday Session yesterday which featured an extended talk with Shea Comfort, a consulting winemaker who has adopted the moniker of "The Yeast Whisperer." (For those of you who listen to the BN regularly, there's a brief snippet where JP launches into a Caesar Milan impersonation where he's ranting about how "The yeast need to know that you are in control. You most be dominant over your yeast..." etc which had me rolling!)

Shea knows yeast. He presented a ton of useful information about yeast in general and wine yeast applications in beer in particular. There's a whole separate portion of his talk about using wine yeasts in beer in order to get some very distinct flavors. I'll save that for a separate post since I'm now pretty interested in doing some experiments with it.

He also cleared up some of the misconceptions that seem to be held pretty commonly amongst brewers about wine yeasts.

• Wine yeasts fall into one of three categories: Killer, Neutral, or Susceptible. Yeast, being a living organism with a desire to reproduce, have evolved over time. Some strains within Saccharomyces Cerevisiae (wine and ale) have developed the ability to produce and release a protein which literally stops other susceptible strains of yeast from fermenting. Many of the wine strains fall into this category. All (or most) of the beer strains are susceptible. As such, pitching Champagne yeast into an active beer fermentation will eradicate your beer yeast within about 12 hours.
• Wine yeasts are bad at breaking down maltotriose and other higher-order dextrins produced by mashing malted barley. Beer yeasts are also a little lazy and will start by eating glucose and maltose before moving on to maltotriose. If you're scratching your head, here's the practical application: Pitching Champagne yeast into a stuck fermentation likely will not "dry out" your beer and take it down to the final gravity you're looking for. If you have a stuck fermentation, your beer yeast has probably chewed through most of the lower-order sugars and is getting lazy about eating the higher order sugars. The wine yeast can't eat them and it'll kill your beer yeast once you pitch it. So you'll just have another layer of flocculated yeast in your fermenter at the same gravity. The only situation where this will actually help you is if you've handled your beer yeast poorly and it crapped out for a different reason. (Lack of nutrients, oxygenation, temperature stress, etc.)
• So in the case of a stuck fermentation, Shea recommended using enzymes which replicate the process which takes place in your mash. (He recommended using Convertase.) There are commercial enzymes which exist for use in brewing and distillation which will break down higher order dextrins into more easily fermentable compounds. Dosing stuck fermentations with a very small amount of these enzymes will help your lazy yeast out, and if done properly will help you nail your target final gravity without completely fermenting out. (The enzymes are essentially a protein which gets denatured and has limited capacity to convert higher order sugars, so they will run out of steam after a certain amount of activity.)

I have yet to try any of the techniques he mentioned, but you can be damn sure I will be running some experiments...