Process optimization of subcritical water extraction for the recovery of antioxidant compounds from white wine lees

Abstract

Subcritical water extraction (SWE) represents a highly efficient green alternative to conventional organic solvents such as methanol, ethanol, or acetonitrile for the recovery of bioactive compounds from white wine lees, leading to more than a threefold increase in the antiradical activity of the extracts [1]. Using a Doehlert experimental design combined with response surface methodology (RSM), the extraction process was optimized by varying temperature, extraction time, and stirring speed [1]. Temperature was identified as the key parameter driving the enhancement of antioxidant capacity as evaluated by DPPH (antiradical activity), FRAP (ferric reducing antioxidant power), and oxygen consumption rate (OCR) assays. Optimal conditions were achieved at 240 °C for 15 min and 550 rpm, yielding extracts with high antioxidant activity [1]. Chemical analysis by LC-HRMS of the extracts obtained under optimal conditions revealed a high total sulfhydryl (TSH) content. A strong positive correlation was observed between TSH levels and antioxidant capacity, whereas glutathione (GSH) showed no such correlation [1, 2]. These results suggest that the antioxidant activity mainly originates from sulfhydryl-containing compounds derived from the protein and lipid fractions of wine lees. High SWE temperatures promote hydrolysis and the release of these compounds from yeast cell walls, resulting in extracts in which elevated sulfhydryl content is directly associated with enhanced antioxidant capacity [1, 2]. The antioxidant capacity of extracts was further evaluated in wine, where they exhibited a strong ability to reduce oxygen consumption through their antiradical activity, thereby slowing chain oxidation reactions [1].

References

Poulain, B.; Winstel, D.; Massot, A.; Moine, V.; Nioi, C. (2024). Valorisation of white wine lees: optimisation of subcritical water extraction of antioxidant compounds. OENO One, 58(3), 1-12.

Garcia, L.; Poulain, B.; Douliez, A.; Naud, E.; Valls-Fonayet, J.; Nioi, C. (2025). White wine lees as a source of antioxidants: Insights into their chemical profile. Food Chemistry, 494, 146118.