# Can Yeast Overheat?



## Saxman11290 (Jan 17, 2013)

Hi all,

I just started a primary fermentation of a WineXpert Eclipse Riesling on 1/15/13. Fermentation is going well, lots of CO2 coming out of the airlock, a light odor in the air of yeast / wine.

My questions pertains to the temperature of the yeast and their metabolic activity / what is the maximum allowance before degredation or detrimental decrease in activity.

I started my ferment at a liquid temperature of 75 degrees and have been monitering it at several points throughout each day. So far it has stayed within the 72 - 75 degree range, except for last night and this morning, it has started to peak to near 77 degrees or even a little higher.

I was wondering if this would really negatively affect the yeast that much. Should I make an effort to cool the bucket down a bit? Crack a window? I understand that during the normal metabolic activity of the yeast, they will produce their own heat, and that probably explains the slight rise in temperature, however, I'm not sure if the temperature is too high.

Any and all input, advice, recommendations etc are appreciated by this first time brewer!

Thank you in advance!


----------



## ckassotis (Jan 17, 2013)

Each yeast variety has an optimal range that it should be fermented at. If you see which yeast they sent you, you can do a google search for the name and should come up with an optimal range. That being said, you're probably fine until you go over 80, and might be fine well over that. The only caveat is that whites can really benefit from lower fermenting temps as it retains some of the pleasant compounds a bit better. I wouldn't be averse to cracking the window a bit, as long as it doesn't drop the temp too far. ~60-70 should work fine I'd think.


----------



## JohnT (Jan 17, 2013)

In a general sense, yes a yeast can overheat. But, this is very difficult to do when dealing with grape must.

To expand, it is very rare to have the conditions right for yeast to produce enough heat to kill itself. If your must is at a good starting temperature, this really would not happen. 

There are two schools of thought when it comes to fermentation at high temperatures, and at low temperatures. 

The choice of a high temperature fermentation is usually made when the winemaker wants to "burn off the fruit". In other words, higher temp fermentation tends to remove some of the more delecate fruit characteristics of the finished product. Instead of a "crisp and fruity" wine (like most rieslings), you can end up with a "deep and complex" wine (like most chardonnays). 

It is really a matter of your tastes an what you are trying to achieve.


----------



## TonyP (Jan 17, 2013)

It depends on the yeast and I believe your kit may have come with 1118, which tolerates temps. to approx. 80 degrees. My suggestion, though is to stay around 72 to 75 degrees.


----------



## Saxman11290 (Jan 17, 2013)

JohnT said:


> In other words, higher temp fermentation tends to remove some of the more delecate fruit characteristics of the finished product. Instead of a "crisp and fruity" wine (like most rieslings), you can end up with a "deep and complex" wine (like most chardonnays).



This is really intriguing. It almost makes me want to buy another of the same kit and ferment at 65 degrees to see what happens and if there is any discernible difference. It also makes me want to experiment with a different yeast rather than blindly following the one included in my kit ... I guess that will have to wait till further down the road.

I am a big fan of Rieslings, and have found them to be extremely versatile dependent on region grown and (apparently) decision made by the vinters. I have had almost-too-sweet Rieslings to rather dry and gravely Rieslings, and still like them both. Since I tend to appreciate all the different notes the grape can develop, I figured this wine might be a good place to start. This way, if I happen to alter one variable by mistake on my first try at wine making, perhaps the end result will still be enjoyable.

It's good to hear that I won't be letting my yeast kill themselves by letting them sit around 77 degrees or so.

Update: cracked the window and temp fell back to 75 region. Think I'll try to keep it around there, just for consistency.

Thanks again everyone, for your help in my understanding this stuff.


----------



## Brew and Wine Supply (Jan 17, 2013)

you won't kill yeast untill you get over 110* f but as said above the flavors wont be there


----------



## Saxman11290 (Jan 17, 2013)

Update #2: put on a small room fan aimed at the primary a few hours ago and the temperature dropped to around 73. Cracking a window in this weather in NY is a bad idea. Might lower the fermenter temp, but it is makes ME cold haha.

All's well for now, thanks again for the advice, everyone.


----------



## JohnT (Jan 18, 2013)

Saxman11290 said:


> Update #2: put on a small room fan aimed at the primary a few hours ago and the temperature dropped to around 73. Cracking a window in this weather in NY is a bad idea. Might lower the fermenter temp, but it is makes ME cold haha.
> 
> All's well for now, thanks again for the advice, everyone.


 

Another suggestion would be to fill empty 2 liter soda bottles with 2/3 water and stick them in the freezer. The can act as large "ice packs" to cool things down while fermentation is hot and heavy. simply chuck one in if the temp starts climbing. Also, please realize that the most important thing here is to keep the must at a proper temp to kick off fermentation, then keep it cool (as fermentation creates a lot of heat). But do not cool it too far down BEFORE fermentation has a chance to kick in.

Also, since you are doing a cold fermentation, this will have the effect of slowing the yeat's metabolic rate down. In other words, fermentation will take longer!


----------

