top fermentation

from the GNU version of the Collaborative International Dictionary of English.

• An alcoholic fermentation during which the yeast cells are carried to the top of the fermenting liquid. It proceeds with some violence and requires a temperature of 14-30° C. (58-86° F.). It is used in the production of ale, porter, etc., and of wines high in alcohol, and in distilling.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a violent kind of alcoholic fermentation at a temperature high enough to carry the yeast cells to the top of the fermenting liquid; used in the production of ale