Authors: Arnbjørn Stokholm and Thomas H. Shellhammer, Oregon State University, Corvallis, Oregon
There is evidence that hops have amylolytic enzymes in or on them that biochemically modify beer during dry-hopping, leading to degradation of long-chain, unfermentable dextrins into fermentable sugars. This increase in fermentable sugars can, in the presence of yeast, give rise to a slow secondary fermentation, which is referred to as ‘hop creep.’ Hop creep requires three conditions for it to appear: (1) some amount of unfermentable real extract in the wort or beer prior to dry-hopping; (2) live yeast in suspension; and (3) the addition of hops to fermenting or fermented beer. The main consequences of hop creep result in beer being out of specification in terms of alcohol, diacetyl and CO2 (Table 1). It is particularly concerning when it occurs post-packaging because of the consumer safety risk related to package over-pressurization. Methods for controlling hop creep, to either accentuate or reduce it, involve manipulating wort composition, yeast strain selection and suspended cell concentration during dry-hopping, and dry-hop form, timing, contact time and temperature.