Application of a hop by-product in brewing: reduction in the level of haze-active prolamines and improved antioxidant properties of the beer

摘要

After supercritical CO_2 extraction of hops or formation of lupulin-enriched pellets (type 45), polyphenol-rich by-products remain. These have some industrial and agricultural applications (preparation of polyphenol extracts and in the production of low-bitterness beers). In this work, both materials were used in pilot-scale brewing experiments for the production of beer enriched with polyphenols. Samples of beer made from these residues underwent analyses for haze-active prolamines, total polyphenols, phenolic monomers, antioxidant capacity, bitterness and colour. An almost identical decrease in the content (from hopped wort to final beer) of the prolamines of approximately 30% was detected in standard beer as well as in the beer prepared from the hop residue (HR 1) after supercritical CO_2 extraction. In contrast, the level of prolamines was reduced by more than 50% in the beer following addition of the hop residue (HR 2) after production of lupulin enriched pellets. Both hop materials contributed to an increase in the antioxidant capacity of the final beer by 21.5 and 11.9%, respectively. Another part of this work was aimed at the investigation of colour and bitterness changes in beers made using hop by-products. Addition of the material HR 2 into the wort caused an increase in colour and in bitterness of the matured beer by 20 and 11% rel., respectively.