Yeast Genetics?

Been doing a fair bit of reading about yeast characteristics and fermentation profiles and I've come across some interesting stories about different breweries and their yeasts. One comes to mind from a brewery, I believe in Portland, that claims to have repitched onto its Ringwood yeast over a thousand times.

I'm wondering if we can start to develop our own individualized brewery yeasts as homebrewers. Is too much viability lost from repitching or yeast washing to allow for enough change in the yeast's characteristics to give it a different character? Does anyone have any experience with this?

You won't see a lot of change in your original yeast except maybe a change in flocculation depending on whether you bottom crop (from the trub) or top crop (from the krausen). The bigger problem at the homebrew level is the lack sterile environment. Yeast and bacteria constantly float around in the air on dust and make their way into our beers no matter how much we try to stay sterile. Our systems are too exposed to keep everything out. So the most likely result is wild yeast and bacteria will start taking over and change the flavor, usually in a bad way. You can acid wash but that will generally only knock out bacteria and not wild yeast.

How do craft breweries keep their entire set-up sterile? Is it an issue of the volume they brew or the way the breweries themselves are constructed?

Tantalus said:

How do craft breweries keep their entire set-up sterile? Is it an issue of the volume they brew or the way the breweries themselves are constructed?

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Have you ever seen the old show Brew Masters? I was confused about this topic as well until I learned from the show that its very common for breweries to have an expert that deals with only yeast. They will often have labs dedicated to the preservation and preparation of their yeast strains. I didn't know this when I first started homebrewing.

Tantalus - craft breweries are not sterie, neither are the big breweries. Periodically the brewery likely acid washes the yeast (like every 5-10 generations, possibly less), and then on a less regular basis they will take some of the yeast and send it to the lab (in house or off-site) and have it isolate to a single yeast cell and then re-grow the culture from that single cell to use for subsequent batches. To do this on a homescale would be quite a multi-year project!

The problem of constantly repitching yeast on the homebrew scale is getting more than 6-7 generations without introducing an infection causing bacteria to the yeast. Acid washing works pretty well, though it can stress the yeast and won't kill all of the bacteria. Around me, there are a number of Ringwood breweries that have repitched their yeast for hundreds of generations. However, most of them have a portion of their yeast banked and will go back to the original strain if it becomes compromised. One of these breweries had a Ringwood yeast that went over a thousand generations... when they sent it to Whitelabs for testing, they found out it consisted of around 10% bacteria and rogue yeasts. Going back to the "original" strain was impossible, since so much of their beers character depended on all the new stuff growing in their yeast.

In the past, a lot of brewing yeasts (Europe especially) were mixed strain. This is practically unheard of with craftbrewers nowadays. Shame too, since mixed strain yeasts can produce some very complex tasting beers.

theredben said:

Tantalus - craft breweries are not sterie, neither are the big breweries. Periodically the brewery likely acid washes the yeast (like every 5-10 generations, possibly less), and then on a less regular basis they will take some of the yeast and send it to the lab (in house or off-site) and have it isolate to a single yeast cell and then re-grow the culture from that single cell to use for subsequent batches. To do this on a homescale would be quite a multi-year project!

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Years? Not really...yeast grow nice and fast. Assuming that you have all the right media and incubators, you could isolate a clone from a mixed culture, and grow up a starter-sized culture of that clone, within a week.

Maybe a bit slower using malt-based growth media and room temperature incubators, I've never done it that way.

jagec - the "years" was in reference to the 1000 generations comment posted by the OP.

What sort of materials are involved in an acid wash? Is it conceivable that someone could do the process at home?

For acid wash, a diluted solution of sulfuric acid (0.5% v/v) is employed.