Diastatic activity of German hop cultivars with respect to variety, crop year, and separated hop cone parts

Dry hopping of beer can result in unintended refermentation, also known as hop creep, because of intrinsic hop diastatic activity. The objective of the work described herein was to determine the enzymatic activity across 16 different hop cultivars grown in Germany in crop years 2019, 2020, and 2021. Optimized enzyme kit protocols were used to quantitate hop α-, β-amylase, amyloglucosidase, and limit dextrinase activities, while a recently published method measured hop diastatic activity. Clear varietal distinctions exist, and hops of harvests 2019, 2020, and 2021 were subsequently classified into three groups depending on their enzymatic activity. With respect to different harvest years, the results imply an annual influence on the amylolytic activity of hops in principle, but more monitoring is needed. Processing methods such as pelletization and storage under different conditions showed a minimal impact on enzymatic activity. Based on further sampling from hops of the harvest 2022, it was observed that differences among hop fractions are pronounced, with the vegetative material and strig exhibiting higher enzymatic activity compared to the lupulin fraction.