tell me about yeast mutation

Yeast can undergo different changes, which can affect fermentation, in response to their environment. They can undergo physiological changes and they can undergo mutational or genoimic changes.

Researchers consider any change that undergoes the yeast population after about 20 generations to be a physiiological change. That is the yeast are still the same strain, they just have turned on different genes and re doing differnet things. As a winemaker you cannot really do anythign about that...but these fchanges are minor and not a big problem.

Changes that undergo a yeast population after about 200 generations are considered to be mutational, that is the yeasts DNA has changes and they have become a different strain. These changes can have significant effects on the fermentation or they may be benign.

Now two things, first wine yeast are pretty much optimized to work in wine, so there is no real change to adapt to. So they do not need to change so much. (although they still do change, but that is a differnt issue called genetic drift). Second, yeast manufactures produce yeast from stocks that are created froma progenitor cell. So they are in theory identical from batch to batch. So if you jsut use fresh yeast, you will be using the same yeast every time. This issue is only really a concern for people that culture their own yeast, or those that seed their vines with yeast (from pomace) and let their wine undergo spontaneous fermentaion.

wow, how complicated!

Yeah, you have to go to school for 20 years to really understand it.

does yeast ever mutate to the point that it stops making ethanol and makes harmful things?

Yeast can mutate so much that they cannaot survive in the condition encountered in a must or wine but that isn't something you will ever encounter if you are following normal winemaking procedures. Yeast are distant relatives of humans and many things that would make humans sick would also kill yeast. Yeast won't make anything that will kill you unless you are foolish and drink too much.

Warren Place

well I wonder about that because, as I've stated publicly here, I've been using the same yeast for over a year, and it seems to still be working. in fact, I've got excess yeast in the process and I mix that with flour for bread or just throw it out.

but now I'm wondering if the yeast I started with a year ago is the same as the yeast I have now???

to allay this fear, I've spent the whopping total of 2 dollars and 25 cents on new yeast and a package of yeast nutrient to add to the mix on the theory that the nutrient will allow the yeast to remain in its current form for a while.

who knows? lord knows I don't.