Hop Science - November 2025

More insights into hop creep

Dry hopping in beer production can unintentionally trigger refermentation, known as hop creep, due to the natural diastatic enzymes present in hops. This study aimed to assess the enzymatic activity in 16 German hop varieties from the 2019, 2020, and 2021 harvests. Using optimised enzyme kit procedures, the activities of hop α- and β-amylase, amyloglucosidase, and limit dextrinase were measured, alongside an updated method for evaluating overall diastatic activity. The results revealed distinct differences between hop varieties. The hops from each harvest year were grouped into three categories based on their enzymatic profiles. The findings suggest that the year of harvest may influence the amylolytic activity of hops, though more comprehensive monitoring is required. Additionally, processing steps like pelletising and varying storage conditions were found to have little effect on enzymatic activity. Further analysis of hops from the 2022 harvest showed that notable differences exist between hop fractions, with vegetative parts and the strig demonstrating higher enzyme activity than other components. Knowing this, the usage of enriched hop pellets or, of course, of hop extracts will limit the hop creep phenomenon.

Philip C. Wietstock, Daniel Michalek, Till Treetzen, Mariana Barreto Carvalhal Pinto, Martin Biendl, and Brian Gibson; Diastatic Activity of German Hop Cultivars with Respect to Variety, Crop Year, and Separated Hop Cone Parts ACS Food Science & Technology 2025 5 (6), 2408-241, https://pubs.acs.org/doi/abs/10.1021/acsfoodscitech.5c00217

Thiols – just not easy to release…

Fermented beverages, including both wine and beer, contain a variety of precursors that can give rise to volatile sulphur compounds (VSCs), which contribute significantly to the beverage aroma. This also includes thiols, which can impart complex tropical notes to beer. Carbon−sulphur (CS) lyases are enzymes essential for releasing aromatic thiols from their respective precursors. These enzymes are naturally produced by a range of organisms, most notably yeasts and bacteria, which participate actively in the fermentation process during the production of beer and wine. Wine researchers have now investigated this in more detail. Despite their presence, only a limited proportion of thiol precursors are typically transformed into volatile sulphur compounds during fermentation. To address this, one method aiming to boost aroma involves the addition of external CS lyases at specific points throughout the fermentation process. In the study at hand, researchers selected and recombinantly expressed three wild-type variants of CS lyases alongside two mutated forms, subsequently examining their capacity to convert thiol precursors under a range of laboratory conditions. These included variations in pH and the presence of certain amino acids, which could potentially inhibit enzyme activity. Furthermore, the team assessed the impact of introducing purified CS lyases during pilot-scale production runs of ale, lager, and Sauvignon Blanc wine. Despite these interventions, the results did not demonstrate a marked increase in the concentration of volatile sulphur compounds. One explanation might be that as we know, the far larger amount of thiols is bound in gluthathion, which firstly needs to be degraded so that lyase enzyme can do a further degradation.

Luigi Clérat, Carolina Conter, Alessandra Astegno, Rémi Schneider, Florine Cavelier, and Eric Vivès, Exploring Carbon–Sulfur (CS) Lyase Enzymes across Microbial Diversity for Enhanced Thiol Release in Beer and Wine Journal of Agricultural and Food Chemistry 2025 73 (37), 23560-23569, https://pubs.acs.org/doi/10.1021/acs.jafc.5c07932?ref=PDFDOI: 10.1021/acs.jafc.5c07932

Please meet my cousins

Hops (Humulus lupulus) are regarded as one of the most important ingredients in brewing worldwide, providing essential resins and oils crucial for beer production. The majority of hops used in the industry are bred from European and American genetic backgrounds, and these origins are often the focus of research aimed at developing new, beer-optimised varieties. In this study, we analysed the chemical makeup of 76 different commercial hop varieties using gas chromatography-mass spectrometry (GC-MS) in combination with metabolomics. Statistical methods showed that hops tend to cluster according to whether they originate from North American or European lines. By employing molecular networking, we identified 26 metabolites that helped distinguish between these two groups. Hops with American ancestry were found to contain more mono- and sesquiterpenoids, ketones, and esters, while those of European descent showed higher levels of α- and β-selinene, trans-α-bergamotene, humulene epoxide II, neophytadiene, and tocopherols. The results reinforce the idea that selinenes can serve as markers for European hops, and highlight trans-α-bergamotene as a significant chemical indicator in these cultivars. Overall, GC-MS-based metabolomic profiles of numerous commercial hop cultivars have revealed clear chemical distinctions between American and European lineages, improving our knowledge of hop chemical diversity in relation to their ancestry and offering a scientific foundation for classifying and tracing hop varieties.

Guilherme Silva Dias, Marília Elias Gallon, and Leonardo Gobbo-Neto, Mapping Metabolomic Relationships of Hop Cultivars in an Ancestral Lineage Context ACS Omega 2025 10 (40), 47281-47291, DOI: 10.1021/acsomega.5c06162 https://pubs.acs.org/doi/10.1021/acsomega.5c06162?fig=abs1&ref=pdf