Session Chair:
Monica Mandrutiu (Group Head of Quality, Asahi Europe & International, RO)
Better Knowledge of Dual Hops for a Better Utilization in Late and Dry Hopping
By Cécile Chenot and Sonia Collain, UC Louvain
Over the past few decades, new dual varieties have been produced, characterised by hop cones rich in both α-acids and essential oils. Dual hops generally showed an exceptional citrus-like potential explained by either monoterpenic alcohols (such as geraniol or linalool up to 109 mg/kg) or polyfunctional thiols (41 detected up to 117 μg/kg, including the sulfanylalkyl alcohols 3SPol, 3SHol and 3S4MPol, their corresponding acetates and some aldehydes). More recently, a substantial pool of non-odorant cysteinylated (Cys-) and glutathionylated (G-) conjugates was evidenced in dual hops (G-3SHol up to 118 mg/kg and G-3S4MPol up to 4 mg/kg in Polaris, G-3SPol up to 18 mg/kg in Citra). Some of these adducts were also found in the noble hop, Saaz. In addition to seeking efficient ways to release this huge aromatic potential, identifying the S-conjugates profile of each variety will help brewers anticipate the delicate citrus/exotic flavors expected when using these cultivars. A screening of various ale and lager yeasts allowed us to identify some strains as super producers of free thiols. Lager yeasts appeared as essential to get the best of Saaz S-conjugates in premium lagers.
Deepening our Understanding of the Diastatic Power of Hops from Agronomical and Industrial Perspectives
By Thomas Shellhammer et al., Oregon State University
A prevalent topic circulating the brewing industry is the diastatic power of hops, which refer to the enzymatic activity found naturally in hop cones. Dry-hopping is the act of adding hops late in fermentation, and hop-associated enzymes may result in a dry-hop-induced refermentation of previously unfermentable beer dextrins due to the hops’ diastatic power. This study examined agronomic factors that influence hops’ enzymatic activities revealing a varietal and plant maturity dependency. Regionally, no notable changes were identified based on growing location. Hop kilning temperature (the air-on drying temperature) also influenced the hops’ enzymatic activity; with higher kilning temperatures resulting in reductions in diastatic power. Brewers have attempted to predict and prevent hop creep. We examined acidification, exogenous enzyme additions, and pasteurization as enzyme reduction strategies for the brewer, and found that pasteurizing hops had a significant impact in inhibiting hop creep. These results offer both agronomical and industrial factors that inform how we think about controlling dry-hop-induced refermentation.
Valorisation of spent hops from dry-hopping: About the potential reutilisation in the brewhouse
By Florian Schrickel et al., VLB Berlin
For many years, dry hopped beers have seen increased consumer interest and sales. The resulting spent hop material from the dry hopping process is commonly regarded as waste and hence discarded. During dry hopping, transfer rates of hop bitter acids are negligible due to the limited solubility of humulones in beer. In this study, samples of spent hop material were collected, freeze-dried and analysed for bitter acid content by HPLC. The untreated spent hops were then used as the sole source of bitter acids in the wort kettle on a 5 hl scale. Resulting worts and beers were analysed for bitter acid composition by HPLC to evaluate the formation of iso-humulone. Sensory evaluation was performed on fresh and aged beers using descriptive analysis. Humulone concentrations in the spent hops ranged from 0.9 to 10.3 % dry matter and 0.1 to 2.4 % w/w as is. Calculated retention rates of humulone in spent hops varied from 28 to 94 %. In most beer samples, the targeted bitterness was achieved. Sensory analysis gave no indication on decreased quality of beers brewed with spent hops. In conclusion, brewers can reuse spent hops as a bittering ingredient in the kettle to increase sustainability.
Impact of dry hopping on beer aroma, bitterness, color and haze: key-role and fate of terpenoids, polyfunctional thiols, esters, humulinones and flavan-3-ols in Belgian dry-hopped beers over two years of storage
By Sonia Collin and Carlos Silva Ferreira, UC Louvain
Dry hopping imparts distinct aromas, but also non-volatile compounds suspected of causing flavor and physical instability in beer. In this work, aromas, bitter compounds and flavan-3-ols, along with color and chill haze, were monitored in Belgian dry-hopped beers over 24 months of storage at 20ºC. Among the volatiles, various terpenoids, esters and polyfunctional thiols were found above their sensory thresholds in fresh samples. Unfortunately, most hop odorants were degraded after two years (only 45-57% of geraniol/linalool and 9% of polyfunctional thiols still detected). In addition, hop esterases were shown to strongly degrade fermentation esters. Humulinones were detected as important bitter compounds only in dry-hopped beers (up to 13.3 mg/L). Their poor stability through storage (73% of degradation after two years), comparable to that of trans-isohumulones, led to unpleasant compounds. Flavan-3-ol monomers, dimers and trimers were detected at high levels in dry-hopped beers (up to 6.6, 14.1 and 10.2 mg/L, respectively). While monomers from early hopping impact the color after aging, oligomers from late and dry hopping were pointed as responsible of colloidal instability.