Impact of Contact Time, Temperature, and Ethanol Content on Hop Creep-Related Enzymatic Activities in Beer

In the production of hop-forward India Pale Ales (IPA), the "hop creep" phenomenon, resulting from hop enzyme activities (combined with yeast fermentation), is a major issue in breweries worldwide. In order to improve our knowledge of the parameters that can modulate these enzymatic activities, the present work aimed to assess to what extent hop contact time, incubation temperature, and beer ethanol content can affect the enzymatic activities of hops. To this end, various hop varieties were incubated in beer over a three-week period under different conditions of temperature and ethanol content. Samples were periodically collected to monitor changes in fermentable sugar and fermentation ester concentrations over time. A longer contact time favored α-glucosidase and esterase activities, leading to a higher glucose concentration and lower maltose and isoamyl acetate concentrations. An assay at 50 °C allows predicting this phenomenon more quickly. As expected, dry heat pre-treatment of hop was found to delay glucose release and isoamyl acetate hydrolysis. Ethanol at 10% v/v was required to inhibit hop amylolytic enzymes in beer, but had no effect on hop esterases.