Wednesday, February 19, 2014

More Yeast!

The subjects keep getting more in depth. I almost forgot to write my blog post today since I've been studying so much ever since class ended for the day. It got pretty intense talking about all the different ways that yeast produces ethanol and how yeast flocculates. One thing that I hadn't realized was that when yeast creates esters, it then will break down esters into alcohol. It was especially interesting to talk about the different secondary metabolites of yeast today since I began to make connections to how fermentation effects distilling. After talking about ester production, I began to understand a lot better why a distiller makes cuts the way they do.

For example, ethyl acetate is the main ester produced by brewer's yeast. Ethanol is the main primary metabolite of yeast and is the main thing that a distiller wants to collect from their still. Ethyl acetate evaporates at a very close temperature to alcohol and it creates a solvent like flavor. If anyone has ever seen a distillation and tasted heads, the main thing that is getting collected in the first bit of collection is ethyl acetate. So, if you can control the production of ethyl acetate in fermentation, than your "heads" will be less volume, leaving you more "hearts" or pure ethanol to collect. This same thing applies to production of "higher alcohols" (alcohols that burn your throat). These alcohols have a higher evaporation temperature, so they come out in the tails of distillation.

After the interesting discussion of yeast flavors, the class lecture began to be extremely difficult to follow. It is starting to make sense now after studying for several hours, but it was a real struggle in class trying to make sense of why Stoke's Law doesn't apply to yeast and trying to make sense of the different forces that affect the ability of yeast to settle in the fermenter.

I believe it is time for a beer.

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