Sunday, May 3, 2015

Learning Yeast Secrets Will Make Beer Better

The April 20, 2015, issue of Chemical & Engineering News (C&EN) carried an interesting article about Yeast.  The publication is normally only read by scientists, but I was able to acquire a free copy and read the article.  Most, if not all, of the information in this post comes from that article, entitled Tapping Yeast's Genome by Matt Davenport.  The article features the Colorado brewmasters Keith Villa (of Blue Moon Brewing) and Max Filter (of Renegade Brewing Co.).

Davenport tells us that "Yeast are perhaps the best understood organisms on the planet." Scientists have studied yeast for years, and with DNA sequencing equipment coming down in price, they are gaining even more knowledge about it.  If you're reading this blog, you know that yeast are the main workhorse ingredient in home brewing.  Yeast consume the sugars in beer (and some of the fatty acids from hops!), and give off alcohol, carbon dioxide, and a few esters that can improve the beer's flavor.
Scientists think humans stumbled onto the fact that yeast produce alcohol by accident, perhaps eating a fruit that fell off a tree and naturally fermented, or grain that got wet and fermented in a jar.  Since then, brewers have spent their time learning what makes yeast healthy and productive.  In the process, they began selectively breeding yeast to develop strains that delivered the flavors and qualities they wanted for beer and wine.

Avery Brewing Co. produces about 30 different kinds of beer, many of which use different yeast strains, in the same equipment.  There is a concern that a yeast strain from one beer (like a Belgian wit or a German hefeweizen) might not be completely cleaned out of the fermentation tanks when a different beer (which uses a different yeast) is brewed in the same vessel. This could result in the beer having an "off" flavor (e.g., an IPA with banana and clove flavors), and might require Avery to dump the entire batch.  They'd prefer not to have this happen.

One way they're doing this is to work with the university to uniquely identify all their yeast strains.  These "fingerprints" will be used to help the brewery determine if an IPA contains yeast from another beer style (hopefully before the contamination ruins the batch).

Something else scientists are doing is using biochemical tricks to block each gene in the yeast in order to figure out its function in the organism.  This will eventually enable them to begin producing "designer yeasts".  They've already managed one modified yeast that produces significant amounts of a banana flavored ester.  The brewer who tried using a batch of it said that it created a beer that tasted like a banana milkshake.  However, given that many people are averse to eating genetically modified food products, they don't plan to make the yeast available for use at this time.  It's being cryogenically stored for the future.

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