Removing alcohol from a starter

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mkj

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Maybe this is a crazy idea, but bear with me.

Is there any enzyme or similar that can break down alcohol? Wondering if you could put that in a high gravity starter (1.60 OG?) and then you'd end up growing a lot more yeast, but it would stay healthy since the alcohol levels haven't gone too high. Then you wouldn't require as large a volume of starter, and mightn't need to step it.
 
To make alcohol free beer I believe they boil off the alcohol which would kill the yeast.

If there was an enzyme or some other method I think it would be well known to make non alcohol beers more easily
 
Yes there is an enzyme (or more properly a series of enzymes that degrade alcohol) the first one is alcohol dehydrogenase, Found in the livers of mammals so you probably have some handy :)
Mark
 
mkj - you need to read up on the Crabtree Effect too much glucose (any sugar really) and the yeast makes alcohol rather than yeast.
There aren't any simple ways to build biomass without stressing the hell out of your yeast other than the standard 1:10 step-up into well aerated low gravity worts (<1.040). There are some complex ways but they require lots of money and high-end equipment - full industrial setups.
If you want a large amount of yeast, do more steps (i.e. 100ml >1L >10L...), cool the starter and separate the liquor from the yeast and pitch the yeast, there are even real advantages to letting the yeast go through the full fermentation cycle, slower I know, but you end up with more of healthier yeast.
Other option is to plan your brewing, do a smaller related beer say a mild, use the yeast cake for a bigger beer say a biggish porter, use the yeast cake for a monster like an Imperial OTT Porter.
Mark
 
Aha, thanks Mark for pointing out the Crabtree Effect. I suppose you could feed the starter with some more sugar after it's done a first ferment, but that isn't much easier than just stepping it.

Moad I reckon the problem for low alcohol beer would be byproducts of using alcohol dehydrogenase - acetaldehyde or acetic acid, yum :) At least with a starter you could decant them off.
 
Not really, unless you cam keep the sugar content very low (less than 2%) and make sure the yeast never runs out of any other nutrients including Oxygen.
Unless the yeast has everything it needs and not too much of some of its nutrients it will switch back and forth between aerobic an anaerobic (making yeast and making alcohol) this will harm the yeast as it depletes some of the internal reserves stored in the cells, you may end up with lots of yeast that has what is called a very low vitality (sick).

You best results come from doing it the old way (stepping up in 10X volumes), or spending $20K+ on a bioreactor that can monitor and adjust pH, wort supply, temperature, alcohol, dissolved Oxygen... even then there is a pretty sharp upper limit of about 300 million cells/mL.
That is under ideal propagation limits, in a home environment with a stir-plate and Oxygen its more like 100^6/mL, maybe (on a good day) 60-80^6/mL with just stirring and air.

Have a look at what Braukaiser built, it looks like a fairly simple and not too expensive a setup to get about as much healthy yeast as you are likely to at home.
Mark
 
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