D. J. COOK (1), K. Westwood (2), R. S. Linforth (1);
(1) University of Nottingham, Loughborough, U.K.; (2) Barth Innovations Ltd., Paddock Wood, U.K.
Technical Session 11 - Flavor and Product Stability II
Wednesday, June 17
Fining agents are used in the clarification of beers to reduce the time required to sediment suspended yeast cells and ensure the colloidal stability of beer. Here we describe the production and characterization of a novel fining agent extracted from hops—a natural ingredient used in the brewing process. This can be used in brewing instead of isinglass, with the advantages that it is kosher and vegan friendly. Not only does it flocculate yeast efficiently, it also takes out chill-haze. The objective was to demonstrate the feasibility of extracting and preparing a fining agent from hops and to characterize its performance. A rapid assay to appraise the yeast-fining activity of hop extracts was developed and used to screen extracts of both native hop cones and spent hops (from commercial extraction with either CO2 or ethanol). Several commercially significant hop varieties were screened. The influence of extraction solvent and conditions such as time, temperature, and pH were also investigated. Following optimization of the extraction process hop extracts were compared to a commercial isinglass preparation for their fining activity and effectiveness in reducing chill-haze in both ale and lager style products. The results showed the active material could be extracted from both intact hops and spent hop material and was present in all eight spent hop samples investigated (Galena, Summit, Zeus, Target, Magnum, Hallertauer Magnum, Hallertauer Herkules, and Hallertauer Taurus). Extraction using 70% acetone (aq) generated the purest, most active form of product with an indicative dose rate to fine beer of 16 mL/L at 4°C, as compared with 12 mL/L of commercially sourced isinglass. Approximately 20 g of spent hops generated sufficient extract to treat 1 hL of beer, on which basis there are more than enough spent hops produced annually to meet global demands for fining agents in brewing. The active component is a proanthocyanidin. These polyphenolic compounds occur in many plant types, are known to stick to yeast cells, and are associated with antioxidant activity. The proanthocyanidins extracted from hops are of sufficient size to be potent yeast-flocculating agents, effecting rapid fining of suspended cells. Moreover, within the optimal dose range, hop extracts were active against chill haze and matched the action of isinglass in this regard in the beers tested. When used to treat beer in maturation, or under cask conditions, the finings formed a compact sediment which was not easily disturbed and should ensure that beer losses are minimized. The feasibility of preparing a novel fining agent from hops has been demonstrated. Preliminary data indicate that addition of the finings at an optimal dose rate has minimal impact on the organoleptic properties of beer. Brewing trials to determine the potential impacts on the properties and stability of beer in-pack are ongoing and will be reported at this meeting.
David Cook is an associate professor in brewing science at the University of Nottingham, U.K. David holds a B.S. (honors) degree in chemistry and food science (Reading) and a Ph.D. degree in flavor technology (Nottingham). David has 20 years of experience conducting research and teaching related to brewing, analytical food chemistry, and flavor technology. He is the course director for the innovative e-learning–based master’s degree courses in brewing science at Nottingham. His group is engaged in collaborative research with industry across the malting and brewing sectors, with current projects focused on malting science and technology, beer flavor quality and stability, and the reduction of primary energy usage in malting and brewing.