Alcoholic fermentation of citrus flavedo and albedo with pure and mixed yeast strains: physicochemical characteristics and phytochemical profiles

The present study aimed to investigate the effects of alcoholic fermentation on the physicochemical and phytochemical characteristics of the tissues flavedo and albedo from five citrus fruits, namely grapefruit (Citrus paradisi), lemon (Citrus limon), and sweet oranges (Citrus sinensis) cvs. ‘Tarocco’, ‘Washington navel’, and ‘Moro’. The tissues were fermented with pure and mixed cultures of Saccharomyces cerevisiae, Brettanomyces bruxellensis, and Torulaspora delbrueckii. Flavedo and albedo increased the water holding capacity (WHC) and oil binding capacity (OBC) when subjected to fermentation. The treatment with B. bruxellensis resulted the most effective at enhancing WHC and OBC, e.g., lemon flavedo achieved the highest WHC (9.67 ± 0.15 g/g; P < 0.001). Concerning the phytochemicals, samples increased the total contents of phenolic compounds and carotenoids upon fermentation. The orange ‘Tarocco’ benefited markedly as regards phenolic compounds, e.g., the naringenin and hesperidin contents reached 244 ± 15.5 and 2900 ± 160 mg kg−1 DW, respectively, when the albedo was fermented with T. delbrueckii, with increases above 4-folds. Likewise, the total carotenoids were augmented (P < 0.001) when flavedo samples were treated with T. delbrueckii. Overall, the performed alcoholic fermentations ameliorated the physicochemical and phytochemical characteristics of the selected citrus tissues, and are recommended to expand their utilization in the nutraceutical sector.