Why do dark styles foam more during fermentation?

Question

Why do dark styles foam more during fermentation?

Frank van Wensveen

2021年5月26日 05:42

I have found that my stouts produce much more foam during fermentation than other beers do. On the Mr. Beer website it says: Plenty of foam, although messy, is not a bad thing as it indicates healthy yeast and a strong fermentation. Excess foaming is more likely to occur when using ale yeast with darker brews and higher fermentation temperatures. (Emphasis mine.)

This confirms my own experience. Question: why is it that ale yeasts fermenting dark styles are so prone to producing more foam in the fermenter?

Topic krausen foam stout yeast homebrew

Category Mac

Rasputin · Accepted Answer · 2021年5月26日 05:42

There are multiple reasons why you will have different levels of krausen in different beers. As @Frank van Wensveen pointed out, melanoidins are one source. These are produced by Maillard reactions during the malt kilning process (i.e. making dark malts) as well as during any similar heating process, such as a decoction mash (where a portion of the mash is removed and boiled in a step-mash process).

Other sources of high krausen include: using ale yeasts instead of lager yeasts (clearly a bottom fermenting yeast will produce less krausen than a top fermenting yeast), hop oils, proteins, vigorous yeast, and wort density, to name a few.

The mere fact that a beer has dark malt is not determinative of krausen level. By way of example, measure the krausen height of a dark ale you brew. Then make a simple blonde ale using K-97 kolsch yeast (a yeast with a notoriously thick, persistent krausen) and measure which is taller. Alternatively, you can view pictures of K-97 krausen for comparison here (or on any similar forum via a simple internet search): https://www.homebrewtalk.com/threads/safale-k-97-questions.586790/

At the end of the day, the amount of krausen is due to many factors, not simply malt lovibond.

Frank van Wensveen · Accepted Answer · 2020年12月1日 13:06

I have finally managed to discuss this with someone who has forgotten more about brewing than I have ever known, and he opines that the main cause of increased foaming in darker styles had mainly to do with the melanoidins that occur in greater quantities in darker malts. Melanoidins are foam-positive.

The combination of high levels of melanoidins and bittering hops also appears to be mutually enhancing, i.e. separately they produce a certain amount and type of foam, but combined they produce more than the sum of both separately.

It's a funny ol' world, innit?

Why do dark styles foam more during fermentation?

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