Yeast Question

[Shifty]

Hi there,

Just wondering - what happens to yeast cells after all available sugar is converted in a mash? Does the yeast die, or does it go into a dormant state?

Thanks!
Shifty

[linw]

It would be nice to think that they just went to sleep but I fear many have gone to the next life!

I think the real answer is that a lot die and a lot are still viable as re-using the left-overs is done by people who are a. tight or b., want to generate their own strain.

[The Chemist]

Most die, but many go dormant. That's why, with beer, you can bottle with a little extra sugar and get carbonation--still some live yeast.

[Shifty]

So how do pitchable yeasts (i.e. White Labs) "store" the yeast cells in the tubes? I guess I figured they were dormant yeast cells that were "multiplied" with a small amount of convertable sugar.

Shifty.

[ricki]

Places like white labs actually "plate out" yeast, pick a single, healthy looking colony, then grow them under perfect conditions to a certain yeast count and deep freeze (-70C). Yeast cells handled this way will be viable in a frozen state for a long time--they use this as a stock when someone orders they will scrape some off their stock and grow them up (under perfect conditions to maintain viability) package and ship. By the time we, the consumer, gets them, they are typically 95%+ viable. If you have perfect growing conditions (not typical for the homebrewer) you'll be able to maintain high viability through several pitches, but usually a number of them die off. One thing to be aware of, if you over-pitch or under-pitch, bad stuff happens to the yeast--they starve and start eating each other or they mutate. It's always better to over-pitch than under. Also make sure you have the nutrients they need; if not, they build up certain off-flavor compounds, ie acetaldehyde, and taint the beer or spirit.
Hope it helps.

[Pieterpost]

better over-pitch then under-pitch? So what happens to yeast cells that are underpitched? Don't they just ferment until no sugar is available? Is the age of a yeast cell related to the amount of off-flavours they produce?

[Fourway]

It's always better to over-pitch than under.

And in distilling it is completely reasonable (commercially this is typical) to over pitch massively by comparison to what you would pitch for brewing beer or wine and then distill in under four days.

[Pieterpost]

I guess this has only has something to do with speed fourway?

[Virginia Gentleman]

I think the real answer is that a lot die and a lot are still viable as re-using the left-overs is done by people who are a. tight or b., want to generate their own strain.

Or c. making sour mash (which encompasses b.)!