Valorization of distillery stillage by polyphenol recovery using microwave-assisted, ultrasound-assisted and conventional extractions

• Published in: Journal of environmental management 2022-11, Vol.322, p.116150-116150, Article 116150
• Main Authors: Mikucka, Wioleta, Zielińska, Magdalena, Bułkowska, Katarzyna, Witońska, Izabela
• Format: Article
• Language: English
• Subjects: Distillery by-products; Hansen solubility parameters; Phenolic antioxidants; Principal component analysis
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2022.116150

An increasing understanding of the negative environmental effects of waste discharges has made valorization of distillery by-products to recover added-value compounds a sound option for distillery stillage management. In this study, the recovery of bioactive compounds, i.e. polyphenols, from distillery stillage was performed by microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE) and conventional solid-liquid extraction (CSLE) to investigate the effects of extraction time, the concentration of ethyl acetate (EA) in a solvent mixture with ethanol and water, and solid-to-solvent ratio on the recovery yield and antioxidant activity of the extracts. The highest yields of total polyphenol content (TPC) (3.73 mg gallic acid equivalent/g) and phenolic acid content (2.51 μg/g) were obtained with 8-min MAE with 70% EA. MAE provided 1.2- and 1.4-times higher yield of phenolic acids and 1.2- and 1.6-times higher antioxidant activity than UAE and CSLE, respectively. Due to the approximately 3-times higher rate of extraction, the ratio between energy consumption and extraction yield was better in MAE than in UAE. Principal component analysis (PCA) showed that the antioxidant activity of the extracts was positively correlated with TPC and phenolic acid content. Six phenolic acids that were identified were present mainly in their free forms (up to 95% of the total), with a predominance of ferulic (up to 0.80 μg/g) and p-coumaric (up to 0.72 μg/g) acids. [Display omitted] •Distillery stillage is a source of high-value bioactive compounds.•Six phenolic acids were recovered; ferulic acid and p-coumaric acid predominated.•Recovered phenolic acids were present mainly in the free form.•Phenolic acid recovery rate 3-times higher with microwaves than with ultrasounds.•Antioxidant activity of the extracts correlated with the phenolic acid content.