When do yeast produce esters?

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NWMushroom

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Currently fermenting an English pale ale and don't want much in the way of esters. Using yeast with recommended temp range of 64 to 72. I noticed that I let the temperature climb to 70 for the first 48 hours of fermentation. Will this produce esters?

Generally speaking, when do yeast produce esters? When you go over the temperature range, or when you hit the higher end inside the recommended temperature range?
 
It's usually when you hit the high end of the yeast's temp range. But this one's is only 72F,so? Ime,it's usually around 75-78F when esters start coming out. You could try keeping it at 66F till it finishes & cleans up.
 
Yeast will produce the fruitier esters that you said you wanted to avoid at the higher end of it's temp range. This will depend on the strain you're fermenting with. What is it? With the high end of the temp range being 72, I'd guess you'll start getting fruity esters (totally appropriate in an English pale) at temps over 68-69 degrees. But again, totally depends on the yeast strain.
To avoid the higher temp flavors/esters, try pitching at the low end of recommended temps, keep your carboy in a room/container that is below the high end of the yeasts range and let fermentation raise to this temp. That should cut down on the amount of esters and other flavors such as diacetyl that you're trying to avoid.
Hope my long winded rambling helps. Good luck.
 
It's usually when you hit the high end of the yeast's temp range. But this one's is only 72F,so? Ime,it's usually around 75-78F when esters start coming out. You could try keeping it at 66F till it finishes & cleans up.

That's not so at all! Some strains are "estery" strains even at a cool temperature. You may very well get a ton of esters from an English strain at 66-68 degrees. You WILL get fusels and other nasty stuff at 75-78 degrees, and possibly more esters.

Yeast tend to produce more esters at the beginning of fermentation, often during the reproductive phase. But it's always good to keep the temperature down if you wish to minimize them at every phase.
 
I was speaking from personal experience. It does it like I said,I was there. But,of course,there are yeasts I haven't tried yet. But ale yeast can produce these things at the temps I mentioned. Been there,done that. But his going to 72F as an upper range temp,I'd think wouldn't produce an ester that is as prominent as,say,a hefe yeast,or coopers.
I'll have to pick this up tomorrow,time to start the bbq pit.:mug:
 
Yeast tend to produce more esters at the beginning of fermentation, often during the reproductive phase. But it's always good to keep the temperature down if you wish to minimize them at every phase.

This is sort of on track. During the fermentation process, esters are produced during the multiplication or aerobic phase (generally the first 2 days of fermentation). However, the bulk of esters are produced during the anaerobic fermentation when the yeast start eating up the glucose to produce carbon dioxide and ethanol.

As far as ester production being dependent on temperature, you are correct. The esters people smell and taste are predominantely large chain molecules. The higher the temperature, the more readily available energy is to produce these long chain esters. Depending on your yeast strain, you likely did not produce too many esters during the aerobic phase. I'd suggest dropping the temperature down towards the optimal temperature range for your strain and you should be able to minimize the ester production.

Sources:
Performed academic research on the production of volatiles in wine.

Side Note:
Esters (such as Ethyl heptanoate) are the product of a carboxylic acid (heptanoic acid) and an alcohol (ethanol). This particular ester results in a sweet, fruity smell similar to diluted brandy or grapes. In general, the early fermentation process has very little ethanol being produced, so there is very little alcohol to produce esters.
 
Well,there is one thing I forgot to mention. Kinda strange really. The dry Cooper's ale yeast,wne I open it,smaells much like white grapes. Makes me wonder where they get it,or how it's produced?...
 
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