Influence of hop seeds on the analytical properties and sensory quality of beer

Abstract

The EU certification system distinguishes between seedless and seeded hops. The vast majority of hops produced within the EU belong to the category of hops without seeds, which allows a maximum seed content of 2 % (w/w). However, with increasingly restrictive herbicide regulations and the resulting growing difficulty of controlling male plants, compliance with this limit may become challenging in the future. Hop seeds are generally regarded as undesirable in brewing because of their high fat content, which promotes oxidative degradation and may impair beer foam stability. Previous studies on the influence of hop seeds on beer quality have produced contradictory results. In this work, the impact of hop seeds on beer quality was assessed through brewing trials. Lager beers were produced with additions of 50 and 70 g/hl hop seeds during wort boiling and after primary fermentation. The addition of hop seeds showed no measurable effects on foam stability or sensory properties. Even in long-term storage tests (6 months at 30 °C), no differences in quality were detected between beers brewed with and without seeds. The only noticeable change was a slightly increased alcohol content, likely resulting from amylolytic enzyme activity in the seeds. Seed proportions above the EU limit of 2 % therefore do not appear to negatively affect beer quality. Nevertheless, hop seeds do not contain relevant amounts of bitter compounds and thus offer no technological value in brewing. Instead, they merely contribute additional weight, increasing costs for harvest and subsequent processing steps such as pellet production. Moreover, seed formation raises the plant’s nutrient demand during cultivation. Taken together, a high seed content is incompatible with economically and environmentally sustainable hop production.