Boiling Fermentation of Berlin Weissbier
Schoenfeld — Wochenschrift f. Brauerei
Boiling fermentation, the foam of which, rising in the tank, does not stand, produces beers which will hold the foam very poorly. The typical properties of yeast will in part determine the production of kraeusen. Yeast of the Saaz type for instance, will not produce high and vigorous kraeusen. The quantity, age and quality of hops exercise an influence upon the production of kraeusen, liberally hopped beers having higher kraeusen than scantily hopped beers, and old hops producing heads inferior to those of fresh hops. Bottom-fermented beers will always produce kraeusen, either strong or weak, but in Berlin weissbier there may be no kraeusen at all. In this case the wort has too small a percentage of viscous matter, chiefly of albuminous substances. As weissbier-wort is not boiled, the diastatic and peptatic enzymes all remain effective when the yeast is added so that they are able to act upon the split-products of starch and albuminous matter when fermentation begins. But Berlin weissbier usually possesses excellent foaming qualities which must be caused by the presence of albuminous substances not split up to a great extent, and this circumstance justifies the assumption that the peptatic enzymes have either been considerably weakened in the pitching wort, or that fermentation makes them rapidly ineffective. The presence of more or less peptase depends largely upon the quality of the malt. A malt produced at low temperature and with short growth of acrospires will never carry the splitting up process so far as a malt produced at high temperature and with long acrospires. A short mash with high initial temperatures may succeed in improving a boiling fermentation, as it means less peptase, hence less splitting up, and more viscous substance, hence firmer kraeusen. But if a malt is slack and has therefore been split up to a greater extent by peptatic enzymes, there is hardly a possibility of improvement. The author mentions an instance where a wheat malt of forced growth which contained a great deal of diastatic and peptatic enzymes, and the albuminous matter of which was, consequently, split up to a great extent, caused a boiling fermentation and resulted in a beer of a flat taste and poor foam stability. The analysis of this malt showed more ready-formed sugar, extract soluble in cold water, and considerably more soluble albumen than a normal malt. It was found that more peptatic enzymes had been at work in the germination of the former malt than the latter. In order to avoid boiling fermentation, especially in making Berlin weissbier, only malts that have been grown cool and short ought to be used.