Investigation into Diurnal Changes in Hop Starch and Amylase Activity and Their Relationship to Hop Creep Potential

Following the discovery of starch in hop cone bracts, this study investigated the extent and change of diurnal starch concentration, amylase activity, and hop creep potential. Three hop varieties were hand-harvested over two separate days at 4 h intervals across a 24 h period in Prosser, Washington. Samples were dried, vacuum-sealed, and analyzed for starch concentration, α- and β-amylase activity, and alcohol increase following dry hopping in finished beer. Starch concentration ranged from 0.5–4.6 g/100 g and was significantly affected by variety, sampling time, and the variety × sampling time interaction. Alcohol increase from dry-hopped fermentations ranged from 0.48–0.83% ABV and was driven primarily by variety rather than sampling time. Starch concentration and α-amylase activity did not significantly predict alcohol increase, while β-amylase activity showed a positive association with alcohol increase but explained only part of the observed variation. These findings indicate that hop cones are metabolically dynamic across the diurnal cycle, with starch showing the clearest time-dependent response. However, hop creep potential was more strongly associated with variety than harvest time, supporting a more multifactorial model of hop creep involving further complexities.