Study on the Composition of Hop Terpenes and Terpenoids by Steam Distillation and Effects on Beer Flavor by an Ale Yeast

Abstract

Model systems of adding three distillates (hop oil, water-soluble aqueous, and residual aqueous) in model wort (buffer) and wort were used to produce model beers and special beers, respectively (with an ale yeast and fermentation at 18 °C). The attributes of hoppy flavor and organoleptic quality were comprised of sustained, surged, generated, or diminished oxygenated compounds and hydrocarbons by yeast biosynthesis in hop essential oil and non-volatile precursors. The matrix of content and instrumental composition of oxygenated terpenoids and hydrocarbons (terpenes and sesquiterpenes) and sensorial profile of model systems was directionally correlated to the matrix and sensory of the early hopped, late hopped, and dry hopped beers. The occurrence of hop aroma profile of the residual aqueous is reminiscent to traditional early kettle hopped beer. The water-soluble volatile components added beer were remarkably close to the distinctive odor profile of late hopped beer. However, dry hopped beer was seemingly a coupling of the hop oil and the water soluble aqueous added beers, but its perception was closer to the latter. The mechanism of the growth of nerol, citronellol, and methyl geranate via a reversed biosynthesis of free linalool by ale yeast and fermentation at 18 °C is contrary to a pathway via geraniol from the hop oil or the water-soluble aqueous. Free linalool was sustained after yeast hydrolysis of linalyl glycoside and related to metabolites in the residual aqueous due to sluggish yeast activity in the model wort (buffer) but not in the wort.