Re- hydration of yeast .

[nannaandmike]

My question is I read warm a cup of water to 90-105 degrees Fahrenheit I thought over 80deg would kill the yeast can someone explain the high temperature please. My second question is I added two separate yeasts to my brew was I wrong to do that. Mike

 

[gyurmaember]

Please respect others, who might reply, by using °C, because most of us in the UK and we have to use Google to change Fahrenheit to Celsius, and the most of us will not bother to do that.
Back to the question, most of the dry yeasts not require rehydration, which one say in the packaging, I just simply pitch it halfway during the transfer to the fermenter.
I never tried co-fermentation, if the 2 yeasts are similar, you should be ok with that.

 

[Agentgonzo]

Cofermentation (using two different yeasts) is fine. You'll get a mix of the characteristics from each one.

Some commercial strains are blends of yeast. One of the MJ dried yeasts (it might be the Belgian trippel) has two colours of grains when you tip it out of the sachet.

 

[Agentgonzo]

Yeast can easily tolerate up to about 30-40 degrees C. It'll give you different flavours (normally undesirable) if you ferment it that high though.

 

[obscure]

People often talk about the optimum temperature for yeast being around 18-22°C or so however it would be more accurate to say it’s the optimum temperature for a particular strain to ferment beer without unwanted by products producing off flavours. You can actually ferment a batch of beer with S-04 for example at 40°C one unexpected heat wave a few years back had a batch do just that, it fermented out in about a day. Now the beer itself was undrinkable but as far as the yeast was concerned 30°C+ was probably pretty optimum. Basically rehydrating your yeast at 30-40°C or so will not kill the yeast (I actually googled it out of curiosity and you would need to hit about 48°C 120°F before the yeast starts to die off).

 

[peebee]

If using dried yeast, I used to sprinkle on the wort or rehydrate at 18-20C ... like you, worried that the recommended rehydration temperature wouldn't do the yeast much good.

But now. I started following the instructions and rehydrate at 30-35C. The fermentation starts much, much quicker. The yeast is visibly happier! Just be careful not to shock the yeast on pitching (30c -> 20C, but I understand 5C difference isn't excessive stress?).

 

[Agentgonzo]

Just be careful not to shock the yeast on pitching (30c -> 20C, but I understand 5C difference isn't excessive stress?).

What happens if you do "shock" the yeast?

 

[starseeker]

What happens if you do "shock" the yeast?

It might need a bit of therapy :)

 

[peebee]

What happens if you do "shock" the yeast?

Good point! I'm doing what I criticise others of doing: Repeating "popularist" phrases written by others, with no good reason to be believing them. But dropping yeast happily bathing in a 30-35C bath into a 20C bath can't do it any good? Kill it even? I guess it has to be true 'cos I wouldn't like it. Yeah, that's it ...

... (Eh?).

You know ... I don't actually know.

Okay ... scratch that "shock" phrase.

 

[dad_of_jon]

What happens if you do "shock" the yeast?

I've found that the smaller amount of liquid used when re-hydrating at 30-35 loses temperature quicker than 20L litres of wort so am always withing 5c of the wort come pitching time - you have to re-hydrated a little ahead of time of pitching about 30 mins I recall.