Impact of Conventional and Organic Cultivation Methods on Fermentation Efficiency and Volatile Composition of Rye Distillates

The effect of conditions of rye cultivation (conventional and organic) and method of mash preparation and fermentation, as well as supportive enzyme and yeast strains on the alcoholic fermentation efficiency and chemical composition of the obtained distillates was assessed. The conditions of rye cultivation did not affect the chemical composition of the tested rye grain; however the differences in the fermentation efficiency were observed. The supplementation of mashes from both conventional and organic rye grain with protease had a positive effect on ethanol biosynthesis. The rye distillates contained low concentrations of acetaldehyde (from 22.25 to 34.07 mg/L of 100% v/v alcohol and met the recommendations for agricultural distillates (<100 mg acetaldehyde/L of 100% v/v alcohol) in Polish distilleries. The samples obtained from both conventional and organic rye grain, pretreated by the thermal-pressure method, were found to contain higher concentrations of methanol than those obtained by the pressureless method of starch liberation. The concentrations of methanol in all distillates remained below the limit specified in EU Regulation 2019/787 for ethyl alcohol of agricultural origin (i.e., rectified spirit) (≤30 g/hL of 100% v/v alcohol). The distillates from organic rye grain subjected to pressureless pretreatment contained significantly lower concentrations of 2-methylbutanol and 3-methylbutanol than analogous distillates from conventional rye grain. The digestion of mashes with a protease preparation has been shown to increase the concentrations of 3-methyl-butyl acetate and 2-methyl-butyl acetate in distillates, irrespective of the rye grain type, the processing method, and the yeast strain employed for fermentation.