Temperature

Temperature has a big influence on the rate of fermentation and the flavors in the final beer. By controlling temperature, you can produce a smooth tasting brew with any Mr. Beer recipe.

The Basics
Think of brewers’ yeast as a living organism (it is actually a fungus!). As it warms up, yeast gets very active – it produces lots of alcohol in a short period, eating up every fermentable sugar in short order. Fermentations between 76 and 90 °F proceed to completion very rapidly, often within just a few days.

When yeast is kept cool, it cannot ferment very quickly. In fact, at refrigerator temps, your yeast is basically inactive, sitting as a layer beneath the beer, as if in “suspended animation.” (It’ll take about six months for the yeast in your beer to actually die.)

The Paradox
So it might seem logical to ferment beer very warm – thus making for a quick and complete fermentation. But warm temps aren’t the answer! Fermentations at higher temperatures produce different yeast byproducts than at lower temperatures. At high temps, a family of “higher alcohols” is produced. Collectively called “fusel alcohols” or “fusel oils,’ these substances are believed to contribute to hangover headaches. “Hot,” “solventy,’ and “peppery” are three descriptions common to fusely beers.

When beers are fermented at cool temperatures, the yeast slowly produces ethyl alcohol (the ‘good’ alcohol), without the fusel oils. This is why true lagers (fermented at 40 to 55 °F) are so smooth tasting. Unfortunately, lagers require special cold tolerant yeast, cool fermentation conditions, and often several weeks to ferment.

The region between very warm and cool is the range of ale fermentation (65 to 76 °F). Since Mr. Beer yeast is an ale yeast, this is the temp range you want to be in. The ale temperature range is a compromise between the smoothness of the lager fermentation and the quickness of a hot fermentation. At these temperatures, the fermentation typically takes only a week or ten days, yet the taste is quite good.

Some fermentation related flavors and aromas that are produced during the ale fermentation include trace fruity qualities such as “orchard fruit” (apples, pears, apricots) and “berry fruit” (strawberry or blackberry). Your choice of Beer Mix, unhopped malt extract, and hops will also impact the overall flavor of the beer.

Cold conditioning of the beer after it is in the bottles and has carbonated will serve to refine the flavor of the beer. Even when cold, the yeast slowly chugs along, looking for anything to ferment. But since all the fermentable sugars in the finished beer have already been made into alcohol, the only thing the yeast can eat are left over flavor molecules. So, even though you produce a beer at ale temperatures, cold conditioning gives you some of the smoothness of a lager fermentation, but without the process of having to ferment at cold temperatures with a special strain of yeast.

So, what’s the best temperature for fermenting a Mr. Beer recipe? 70-76 °F is the general answer. But your yeast will ferment from the high 60’s to the mid 90’s. If you add very cold water to your fermenter when you are diluting the hot wort and ferment in the low seventies for 10 days or so, you should have a really tasty beer with a mellow and mature flavor.

 

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