UC Davis

Despite years of research, hop creep remains largely enigmatic to brewers and academics alike. This study adds a new dimension to this complex story with the discovery and quantification of starch within the bract of hop cones. Although glycosyl hydrolase enzymes from hops, are considered the main drivers of hop creep by breaking down complex sugars into fermentable ones, it was previously thought that these enzymes only acted on dextrins derived from malt during the mash. However, this study herein reveals that starch from the hop bract itself provides a previously unconsidered substrate, significantly impacting hop creep by contributing potential additional fermentable sugars. To confirm the presence of starch, hop products were stained with iodine. In addition, starch content and the monosaccharides involved in starch synthesis were quantified by high performance liquid chromatography. Starch was identified in hop bracts (mesophyll and stomatal guard cells) with visual confirmation using microscopy with the bracts stained with iodine. In addition, total starch (<0.5 to 1.6 g/100 g) and monosaccharide sugars (sucrose, glucose and fructose) were quantified in the bracts. The presence of starch provides unequivocal evidence that the enzymes responsible for hop creep are from the hop cone. This research emphasizes the potential additional role of starch in understanding the mechanisms underlying hop creep, contributing new additional insights to hops.