Ideal fermentation temperature

Question

I'm just finishing up a DIY fermentation chamber made from a chest freezer, reptile tank heater, and a temperature controller.

Now I just need to figure out what temperature to set!

Most yeast packets have a range of temperature listed. E.g.:

• Wyeast strains all have different ranges: generally 10-15 ˚F wide.
• Safale yeasts have a large range: 59 ˚F to 75 ˚F.

How do I know what to use for a fermentation temperature? Should I attempt to hit the middle of the recommended range? Or does it depend on the recipe?

Answer 1

I would suggest that for each recipe you put together, to do some googling to find out what temp ranges for a given yeast are going to work best for the flavor you are trying to get. Starting off in the middle of the yeast manufacturer's range is good, I know of several strains where the recommended range doesn't match what real home-brewers are reporting. For example, White Labs Hefeweizen yeasts are advertised to be best from mod 60's to low 70's, but in homebrewing circles, 59-63F is a widely-reported to be a better sweet spot for more balanced beers. Also, some specific ale yeasts get fruiter at lower temps, contrary to the general rule (US-05 gets 'peach' flavors when fermented in the low 60's, according to many folks).

So pick a recipe, including a yeast, and then do research to find the best temps for that particular strain. Include the manufacturers recommended range, but don't go by that alone.

Answer 2

The answer depends upon the qualities that you want from the yeast. In general, lower temperatures produce less characteristics from the yeast strain, while higher temperatures produce more. For example, ale yeasts tend to produce more fruitiness when fermented warmer, but cleaner tasting when fermented cooler.

The flavor characteristics vary from yeast strain to yeast strain, so best to read up to determine what you want from that yeast. If that's more than you have time for right now, you can play it safe and stick within the middle of the range until you get a feel for how the yeast performs and the flavors produced at that temperature.

Keep in mind that during vigorous fermentation, the wort temperature can be several degrees higher than the surroundings, so you can dial down the temperature by 5F initially, and raise as fermentation completes.

Answer 3

Generally cooler is better. For most ale yeasts 60-65 F ambient is pretty good (remember that internal fermentation temps can be as much as 5-8 degrees higher than ambient air temp). Stability of temperature is very important--so pick a temp and don't vary it if you can help it (which means leave the vessel in the chamber without messing with it).

An exception to cool temps would be something like Saison yeast which likes high temps--sometimes VERY high. Or certain specialty styles like California Common. In general, though, you will know when you need a higher fermenting temp.