yogurt is a happy culture

mac invited me to help host tonight's diybio meeting, which was an informal chat about making yogurt, why we might prefer mixed cultures over monocultures (on which, more soon), and other issues pertaining to folk microbiology. i brought some yogurt culture to share, to guard against the day when i accidentally eat the last of it. i got the original culture from the google kitchens back in 2008, and that in turn came from harold mcgee's very old indian strain (referenced here).

the mixed culture and fermentation method i use produces a thick, pleasantly-tangy yogurt without the complications (and equipment) involved in maintaining a constant incubation temperature for many hours. i just wrap a bunch of towels around the warm containers to slow down the cooling rate and leave them undisturbed for 6-9 hours. since the culture probably contains multiple types of bacteria with different temperature and ph preferences, fermenting at a range of different temperatures as the containers cool down might even be preferable to fermenting at just one constant temperature over time (which would probably be great for a pure monoculture). some work using genetic algorithms to optimize yogurt culturing seems to support this hypothesis.

and for those of you who were at diybio tonight, here's a more comprehensive, printer-friendly yogurt culturing protocol.