Effect of the solvent on the extraction of polyphenols from distillery stillage and on their antioxidant activity

The increase in the costs of storage and disposal of post-production residues has resulted in the search for new directions for their recycling, which is closely related to the necessity of protecting the natural environment and promoting a circular economy. Moreover, the apparent interest shown by the food market in raw materials with high antioxidant activity implies an increasing use of by-products. The objective of the study was to determine the effect of the type and concentration of the solvent on the efficiency of extracting polyphenols from distillery stillage as well as their antioxidant activity by using several solvents: methanol:water (70:30 v/v), methanol:water (100:0 v/v), ethanol:water (70:30 v/v) or ethanol:water (100:0 v/v). The DPPH radical method was used to determine the antioxidant activity of the obtained extracts. The normalised variable (NV) and statistical measure (MS) were determined, based on which the effectiveness of the solvents was evaluated. The highest polyphenolic content and the antioxidant activity were obtained by using ethanol:water (70:30 v/v) as a solvent in the extraction of polyphenolic compounds from distillery stillage.