Effect of Oak Wood Aging on Chemical Composition of Wheat Distillate

Traditionally, grain distillates are left to age in oak barrels. This process needs intensification, and this problem remains understudied despite numerous scientific publications. The study expands and clarifies the data on the chemical composition of grain distillates after a long-term contact with oak wood. The research featured samples of 60% immature grain distillate from wheat harvested in 2023 and model solutions prepared from immature grain distillate in industrial oak chips (1.0×0.5 cm, Ecochips, France) subjected to a weak, medium, and strong heat treatment modes and stored in the dark for 7, 14, 21, and 28 days. The study relied on a combination of gas chromatography, chromatography / mass spectrometry, and capillary electrophoresis. The thermal treatment mode and extraction time were variables. The authors developed a set of express methods to define the composition of volatile organic impurities and the ionic composition of grain distillates. Isoamylol, isobutanol, and 1-propanol were the most abundant higher alcohols (≤ 80% total volatile organic impurities). The variation ranges were 1 354.3–1 489.3 mg/dm3 for isoamylol, 235.0–261.9 mg/dm3 for isobutanol, and 119.6–134.9 mg/dm3 for 1-propanol. The Whiskey22 thematic spectral library provided a 90% identification accuracy. The aging affected not only the mass concentrations but also the list of ions. In the model solution with the highest degree of thermal treatment, the maximal concentrations belonged to acetates (67.3 mg/dm3), potassium (4.2 mg/dm3), phosphates (2.9 mg/dm3), lactates (2.4 mg/dm3), and chlorides (2.3 mg/dm3). The optimal ratios and ranges were as follows – isoamylol:isobutanol (5.7–5.9), isobutanol:1-propanol (1.9–2.0), ethyl caprate:ethyl laurate (2.1–2.3), and ethyl caprate:ethyl caprylate (2.9–3.2). The new methods proved effective in determining the chemical composition of grain distillates and can be recommended for commercial production of alcoholic beverages