Chris White of White Labs is giving the next presentation, "Choosing the Right Yeast." I'm really looking forward to this, since Chris is an AMAZINGLY knowledgeable guy when it comes to all things yeast. I've learned a lot about yeast, propagation, esters, phenols, etc., just by reading past presentations and papers that he authored. I'm ready to get my learn on! Based on the contents, this is going to be another glorified bullet list, rather than a nicely written, well-thought out treatise. Sue me.

Chris and Jamil Zainasheff have a new book out called "Yeast." Based on some of the early info here, it sounds like a good book to pick up for any brewer who wants more info on yeast biochemistry.

Kingdom-Phylum-Class-Order-Family-Genus-Species. Strain is below that normal classification level. Thanks to yeast's ability to bud, they can spontaneously create new and different strains. Strains have a tendency to be pretty stable which is what allows them to be consistently used for beer.

Ale yeast: A big class with many strains. All those strains share some characteristics: Warmer temperatures, ferments clean to fruity, usually a "top cropper", stores well. Typically pitch 10 million cells per milliliter

Hefeweizen yeast: Produces a lot more banana and clove phenols, has low flocculation, low diacetyl, can produce sulfur, ferments very rapidly, but not a great cell count. Top cropping is the best way to collect a Hefeweizen slurry.

Belgian Yeast: Ferments with unusual wild-like character, has low flocculation, low diacetyl. Also ferments rapidly, can produce sulfur and can be very fruity.

Lager Yeast: A different species from standard Saccharomyces C. Ferments clean, will not drop out quickly, will produce diacetyl, will produce sulfur. Slow fermenter, that can't usually be top cropped. Typically pitched at 50 million cells per milliliter. Lagers definitely need a diacetyl/sulfur rest in order to drive off some of the volatile sulfur, and allow the yeast to consume some of the excess diacetyl.

Wild Yeast types: Mainly Brettanomyces used in beers. Necessary to really produce an authentic "English" character. Brett. is usually used in secondary fermentation, and in bottle conditioning. Brett. is sometimes referred to as "Dekkera", which is the asexual form of the yeast. What is unique about Brett. is the ability to produce B-glucosidase, which can break down wood sugar cellobiose. Cellobiose is produced when fire is used to toast the inside of barrels. Brett also produces isovaleric acid and guaiacol (4-ethyl guiaicol is common).

Bacteria: Most bacterias are undesirable, producing off flavors and acids like acetic acid. Lactobacillus, pediococcus are the lactic acid producing bacteria. They don't mind alcohol, low PH, and anearobic conditions of beer. Unlike most bacteria, these also reproduce very slowly. Acetobacter, Gluconobacter, Obesumbacterium, Rahnella are other examples of bacteria that can grow in beer. Very few Gram-positive bacteria can live with Hops (which blocks nutrient absorption).

Jamil's Strain Selection Process
Set goals (ABV, IBU, SRM)
Flavor concept (Malty, hoppy, other?)
Select likely candidates
Test batches

Key Requirements
Flavor (Bitterness, maltiness, sweetness, alcohols, esters)
Alcohol Tolerance
Attenuation
(Some other stuff that I couldn't type fast enough!)

End of session, end of notes. On to more beer!

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