In John Palmer’s How To Brew, he recommends pitching around 400 billion yeast cells for a 5-gallon batch of high-gravity beer. (He does not, thankfully, recommend counting them out one by one.) On a per-bottle basis, that means more than 7 billion yeast helped make that 12-ounce bottle of imperial stout—equivalent to the world’s human population.
VIVA LA RESISTANCE?
Unlike their wild counterparts, many cultured strains evolved to have redundant sets of chromosomes. While more resistant to genetic mutation, the tradeoff is that they now reproduce asexually instead of the more fun way.
In 1995, Dr. Raul Cano of California Polytechnic State University reportedly extracted and revived dormant yeast cells from a 45-million-year-old piece of Burmese amber, knocking the laboratory-grade socks off the scientific community. Today, this ancient yeast is used to create beers in the Fossil Fuels Brewing Company lineup, currently brewed by Kelley Bros. Brewing in Manteca, CA.
Though typically only a few micrometers across, yeast in actively fermenting beers can generate a thick foam upwards of a foot high. While this might not seem particularly Herculean, it’s the scale equivalent of seeing an anthill a hundred stories tall.
There comes a certain point when one needs to throw in the microscopic towel. After a yeast cell dies, it will often go through a process called autolysis during which it releases enzymes that break down its cellular structures: dispersing nutrients and minerals and, in turn, helping to feed its neighbors.
Ken Weaver is a beer writer, fiction writer, and technical editor based in Santa Rosa, CA. His first book, The Northern California Craft Beer Guide with photographer Anneliese Schmidt, will be published by Cameron + Company in Spring 2012.