The effect of hopping regime, cultivar and β-glucosidase activity on monoterpene alcohol concentrations in wort and beer

Abstract

Previous studies show that the complexity of hop aroma in beer can be partly attributed to the hydrolysis of glycosidically bound monoterpene alcohols extracted from hops during the brewing process to release volatile aglycones. However, fundamental studies that examine the extraction of glycosides during brewing and their subsequent hydrolysis by yeast have not been performed. Furthermore, extraction of other hop-derived compounds into beer shows a strong dependency on the hop cultivar being used and the point at which it is added. This study focused on the extent of glycoside extraction owing to hopping regime and cultivar, and their hydrolysis by yeast β-glucosidase activity. Glycoside concentrations of wort made with three different hopping regimes and three cultivars were measured by the difference in volatile aglycone concentrations between samples treated with purified β-glucosidase and untreated samples. Aglycone concentrations were measured by solid-phase microextraction gas chromatography–mass spectrometry. Additionally, β-glucosidase activities for 80 different yeast strains and their effect on aglycone concentration in wort were determined. Results showed that yeast have a wide range of abilities to hydrolyse glycosides with a maximum hydrolysis occurring after 3 days of fermentation regardless of yeast activity. Although it was shown that yeast are capable of glycoside hydrolysis, glycoside concentrations in wort are low and make small contributions to hop aroma. These results help explain the extent to which different brewing yeasts and hopping regimes contribute to hoppy beer aroma through the hydrolysis of non-volatile hop-derived compounds. Copyright © 2017 The Institute of Brewing & Distilling.