Reprecussions of slightly out of band temps?

[blitzgp]

I was just curious about what would happen if temps rose above 70F? Is it going to affect flavor, time to finish, effectiveness of the yeast? All of the above? Im just curious because the place where I intend on storing my carboys is pretty tight and climate control in the summer, doesnt get too hot, but will probably get to 74ish. Also the reverse, if the bottom band is 60F and my temps get to 55, can I just let it ferment longer?

I just ask cause I see a lot of discussions on maintaining temps and not what happens or how tight the actual band is.

 

[a10t2]

Flavor: Yes. Generally the higher the temperature, the more esters the yeast will produce (banana and other fruity flavors). You can also get more fusel alcohols, which have solventy tastes.

Time: Yes. Generally shorter fermentations at higher temperatures.

Effectiveness: Not really. Yeast really like to ferment at >90°F (just think of yeast infections). But at those temperatures the result might not taste great, or even good. At the other extreme, below a certain temperature the yeast will simply go dormant and settle out. Exactly what that temperature is will be a little different for each strain.

Remember fermentation is exothermic too, so if the air temperature is 74°F then at the peak of active fermentation the beer could be around 80°F.

I think (and this is just me guessing) that the temperature ranges the yeast companies give are intended mostly for their commercial clients. Since the hydrostatic pressure in a large conical will suppress some ester production, to get the same ester profile in a bucket or carboy you probably need to subtract a few degrees.

 

[Duffer]

Each yeast pack will list a recommended temp range. Keep in mind, that is the wort temp which will be higher than room temp once the yeasties are going full blast.

Colder temps will slow fermentation, but give 'cleaner' tastes and aromas. Too cold and the yeast goes nighty-nite.

Warmer temps ferment harder/faster and create more 'off' flavors and aromas. These deviations may be desired depending on the style of beer.

You can still make great brews with wandering temps, but you can't reproduce those great brews without some kind of temp control.