Exploring new horizons for wine grapes: modulating functional effects by varying harvest timing and solar exposure

Abstract

Grenache (GN) and Cabernet Sauvignon (CS) are two traditional red grape varieties widely cultivated in the Mediterranean area and both late-ripening cultivars, which makes them less sensitive to global warming conditions and more stable to harvest timing. Although different studies have evaluated the final antioxidant properties of grapes and pomaces, few studies have explored the effect of sun exposure and harvest on the nutritional and antioxidant properties of these products. This study investigates the control of sunlight and ripening as tools to tailor nutritional and antioxidant properties of grape juices (GJ) and their byproducts (pomace GP). The compositional analysis showed no significant (p ≥ 0.05) differences associated to either harvesting timing or exposure to sunlight for either of the two studied varieties. However, differences (p ≤ 0.05) were observed between varieties of protein and total dietary fibre (TDF). CS protein content ranged from 0.52 to 3.88 (g 100 g−1) in GJ and from 1.0 to 1.32 (g 100 g−1) in GP; meanwhile, GN had higher protein values in GJ (from 2.11 to 4.77 g 100 g−1) and GP (from 5.11 to 6.75 g 100 g−1). The opposite behaviour was observed in TDF; CS grape had higher values for juice (from 11.43 to 19.53 g 100 g−1) and pomace (from 42.20 to 65.80 g 100 g−1) than GN (from 11.43 to 17.22 g 100 g−1 in juice and from 25.90 to 54.0 g 100 g−1 in pomace). The total phenolic content (TP) in GP was 100 times higher than in the juices and showed a much less pronounced evolution compared to the GJ during the harvesting time. GN TP values ranged from 5835 to 8772 mg GAE 100 g−1; meanwhile, CS values ranged from 7637 to 9040 mg GAE 100 g−1. A significant (p ≤ 0.05) correlation between the TP total antioxidant capacity (TAC) results was observed, regardless of variety, harvesting time, and sunlight exposure. These findings show how the control of different factors can contribute to obtain modified grape-derived products from conventional varieties beyond the wine market.