Influence of the residual enzymatic power of hops added during fermentation and/or maturation on beer stability

Details

Supervisors

Collin, Sonia ; Willemart, Guillaume

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en chimie et bioindustries, à finalité spécialisée

Abstract

In the production of hop-forward India Pale Ales (IPA), the “hop creep” phenomenon resulting in beer over attenuation, out-of-specification alcohol content, excessive carbon dioxide and off-flavors is a major issue in breweries worldwide. For this reason, numerous studies have focused on the problem and have provided new insights into its causes. The origin of the problem lies in the presence of amylolytic enzymes within hops capable of producing fermentable sugars from dextrins of fully attenuated beer. In addition, the existence of an esterase enzyme capable of hydrolyzing fermentation esters has also been demonstrated. The present work aimed to evaluate how different factors, such as hop contact time, temperature, ethanol content, hop heat treatment, hop variety and conditioning, could affect the enzymatic activities of hops. To this end, various hop varieties were incubated in beer under different conditions of temperature and ethanol content over a three-week period. Samples were periodically collected to analyze changes in fermentable sugars and fermentation esters over time via HPLC-RID and GC-HS-MS, respectively. First, results highlighted that longer contact times significantly promoted enzymatic activities involved in glucose production, maltose degradation and isoamyl acetate hydrolysis. The same observations were evidenced at higher temperatures. Then, it was noted that a dry heat treatment of hops prior to incubation revealed to reduce the release of glucose and the hydrolysis of isoamyl acetate. Surprisingly, only a high dosage of 10% v/v ethanol in beer resulted in inhibition of amylolytic enzymes. For this dosage, esterase activity remained intact. Concerning the influence of hop variety, only amylolytic enzymes of Simcoe hops exhibited pronounced activities compared to other varieties. Finally, cryo pellets exhibited lower enzymatic activities compared to T90 pellets and whole cones, which indicates that enzymes could be mainly found in vegetative material.