Wednesday, January 30, 2013

Wild Yeast Culture Experiments - Intro and Mixed Culture Method

Brewing (and drinking) sour, funky, "wild" beers is a passion of mine. I always have at least a few microbe-laden brews fermenting. I focus much of my reading and researching on topics surrounding sour beer. For me, brewing with brett and bacteria is a perfect combination of science and alchemy. I am basically the bugs' assistant brewer; preparing the equipment and materials so they can make the magic.

My most successful sour projects have all been fermented with a cocktail of flora, harvested from dregs of my favorite commercial sour beers. Maintaining and fermenting with this mixed culture has yielded significantly more depth and complexity than commercial  yeast/bacteria blends.

A double batch of Flanders Red, split and fermented with Wyeast Roselare (left) and my mixed wild culture (right). The mixed culture portion showed significantly higher levels of acidity and brett character.

I do not have the resources to plate and bank yeast, so I am limited to a macro-scale mixed culture. In the past, it has been as simple as a 1-gallon growler with 2-3 quarts of low gravity wort. The initial pitch is normally either a pack of commercial yeast blend or dregs from a few bottles of young, lower-gravity commercial sours. Prior to pitching the dregs into the starter, I will conduct a small step up with a few ounces of wort in the bottle. This gives the dregs a fighting chance in the mixed culture, and it is a decent test for both contamination and yeast health. The main culture is routinely decanted and fed fresh wort every 3 months or so.

My method is a primitive one, giving up even more control of the finished product to the yeast. However, I have been able to use the culture over a period of 2-3 years, all the while creating beers with strikingly similar  flavor profiles and levels of acidity and attenuation. The most significant differences stem from the additional depth contributed from introducing new species into the culture over time. I have yet to find the "expiration date" of a mixed culture; I have used all of the slurry before noticing any undesirable changes.

This series of posts aims to compare different methods of maintaining wild yeast cultures on a 'macro' level. More to come!

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