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​Unexpected Effects of Commercial β-Glucosidase Addition to Mash and Fermenting Beers​​

Abstract

Enzyme additives are widely used in both brewing and winemaking to improve color, ease of handling, flavor, and stability. β-Glucosidase has been featured in several commercial preparations with the intent of liberating flavorful terpene alcohols from their hop glycosides. In testing this principle on a Belgian-style farmhouse test brew with a phenolic off-flavor (POF)(+) yeast strain, we added the enzyme preparation 3 days into the fermentation stage, as recommended by the manufacturer. We noted few major changes in terpene alcohols in this modestly hopped beer using gas chromatography/mass spectrometry (GC/MS) but found a large increase in 4-vinyl guaiacol (4VG), a ferulic acid (FA) derivative. An olfactory triangle test showed high statistical significance (P = 0.001) in 4VG aroma versus the otherwise identical control. Because 4VG is considered an off-flavor in some beer styles, we sought to determine the source. Although FA β-glucosides exist, they have not been reported in significant amounts in barley, wheat, or hops, and they are unlikely to be the source. Using enzyme assays and test brews, we showed that this particular β-glucosidase preparation, ABV Aromazyme^TM (AZ), derived from Aspergillus niger, contains significant ferulic acid esterase (FAE) activity established by two different FAE enzyme substrates. Test brews with POF(–) strains of yeast did not show an increase in 4VG regardless of style but did demonstrate added FA release. In laboratory mashing trials, AZ released significantly higher levels of FA than controls (2–4×). Increases occurred at both 65 and 45°C. We found that tested barley malts released more FA than did wheat malt and significantly more than did oats. This additional enzyme activity need not be a sensory issue as long a​s POF(–) yeast strains are used.

Keywords: enzymes, ferulic acid, feruloyl esterase, β​-glucosidase, 4-vinylguaiacol, 4VG, VOC​