P-02 - Mechanism Underlying Winter-type Gushing in Beer: A Study on Chemical Reactions During Storage

The phenomenon of gushing, or overfoaming, negatively affects beer sales and has been a persistent problem in the brewing industry. Gushing is mainly classified into two types: summer and winter. Summer-type gushing can be observed immediately after packaging. By contrast, winter-type gushing has been reported to appear after 1 to 2 months of storage at 25°C, reaching its maximum potential after 3 to 4 months. Because the gushing takes several months to evaluate, the cause is not well known. To prevent gushing, we investigated the mechanisms underlying winter-type gushing. To date, our findings suggest that catechins in hops increase the potential for winter-type gushing. It has also been confirmed that gushing activity can occur without storage through the polymerization of catechins. This suggests that the polymerization reaction of catechins during storage may trigger winter-type gushing. We suspect that a chemical reaction occurs during storage.

Since the relationship between the temperature and reaction rate in chemical reactions is known to be expressed by an Arrhenius equation, we investigated winter-type gushing in beer stored for various durations at different temperatures to determine whether it follows an Arrhenius equation. By determining the reaction rate at each temperature and creating an Arrhenius plot, we found that it is indeed governed by an Arrhenius equation. This finding indicates that winter-type gushing is caused by components gradually formed through chemical reactions during storage.