Innovative red winemaking strategy: biosurfactant-assisted extraction and stabilization of phenolic compounds

In the present study, a biosurfactant extract obtained from a fermented residual stream of agri-food waste from corn industry, named corn steep liquor (CSL), has been used during winemaking to improve the colour features of red wines. Therefore, the first aim of this study was to evaluate the effectiveness of CSL biosurfactant to increase the release and preservation of anthocyanins during skin simulated macerations, and to compare its effect with four treatments based on exogenous tannin additions (grape seeds, grape skins, quebracho, and acacia tannins), considering two red winegrape varieties (‘Cabernet sauvignon’ and ‘Aglianico’). Then, the pre-fermentative addition of CSL biosurfactant was evaluated through nano-vinifications of ‘Merlot’ winegrapes, during spontaneous or inoculated fermentations with commercial Saccharomyces cerevisiae yeasts. Technological parameters, colour characteristics, and phenolic composition were determined, as well as the fermentation dynamics. For the simulated maceration trial, the results obtained showed that the addition of the CSL biosurfactant increased colour intensity from the beginning of maceration with respect to untreated control, particularly for ‘Cabernet sauvignon’. During ‘Merlot’ grapes nano-vinifications, the inoculated samples confirmed higher values of colour intensity with the addition of CSL biosurfactant and, at the end of alcoholic fermentation, a higher percentage of large polymeric pigments was also observed. After malolactic fermentation, the colour of CSL biosurfactant-added wines was also darker.