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Feasibility Study using a Novel Desorption/Absorption Process for Transferring Hop Volatiles to Beer
P. C. Wietstock, F. Gtz, R. Klie, F.-J. Methner and H. Scheuren

Specialty beers with distinct hop flavour profiles are becoming increasingly popular. To impart a ?hoppy? aroma, hops are commonly added as whole hops or as pellets during fermentation or maturation which can result in filtration/clarification problems. A separation of the aroma extraction process from the aroma insertion process is therefore advantageous. In this study, a novel hopping technique with sequenced desorption and absorption process was used to transfer hop volatiles into beer. Hop volatile desorption from a hop-water-mixture is forced by a stripping gas with following transfer in the gas stream to an absorption medium. The system operates in a closed loop. The process was tested with water, a buffered model solution (pH?4.3, 5?%?(v./v.) EtOH) and lager beer (11.8??P, 4.8?%?(v./v.)?EtOH) as absorption media. The experimental data were furthermore compared to thermodynamically calculated data. Outcomes from the study demonstrate that the process works and a maximum transfer was achieved after 24?hours desorption/absorption. The linalool transfer rate to beer was about 65?%. The thermodynamic approximation was deficient when working with water as absorption medium and was closer but still showed deviations to the experimental data when working in a beer system. Further terms are needed to optimize the model. This novel method features an easy-to-implement and cost-effective method for transferring hop aroma compounds into beer without directly bringing the beer in contact with hop solids that e.g. may yield filtration/clarification problems.

Descriptors: linalool, hop aroma, beer, desorption, absorption, hopping, dry hopping, stripping

BrewingScience Monatsschrift fr Brauwissenschaft, 68 (January/February 2015), pp. 1-7