Haruhito Kato, Hiroko Wake, Masaru Kato
Winter-type gushing refers to the spontaneous overflow of beer upon opening, due to rapid carbon dioxide release. While previous research has focused primarily on the roles of proteins and proteases in gushing, the impact of hops has not been studied extensively. In this study, the influence of malt and hops on winter-type gushing was investigated, with particular attention on the chemical components and mechanisms involved. Beers brewed with higher hopping rates exhibited significantly greater overfoaming, with malt playing an important role in inducing gushing. Fractionation of hop extract revealed that catechins are candidate compounds for promoting gushing. Chemical analyses demonstrated that catechins and procyanidins derived from hops increased the amount of overfoaming beer. Comparative analyses of polyphenols from malt and hops revealed that hop-derived catechins showed a higher gushing potential. Observations of chemical changes during storage suggest that the formation of oxidatively coupled multi-bridge oligomeric structures of catechin may contribute to gushing activity. The findings provide insights into the importance of malt- and hop-derived polyphenols in winter-type gushing and offer new insights into the underlying mechanisms.