Optimization of the Extraction of Bioactive Compounds from Cabernet Sauvignon Grape Pomace from Querétaro, Mexico, Using MSPD

Red wine contains polyphenols which are extracted during the winemaking process. However, winemaking is not an extraction; therefore, the resulting byproducts still have a substantial polyphenol content. The aim of this study was to compare two methods for the extraction of phenolic compounds: maceration and matrix solid-phase dispersion (MSPD). Grape pomace (Vitis vinifera var. Cabernet Sauvignon) from a winery in Querétaro, Mexico was used. The optimal conditions for both methods were identified. Phenolic compounds and antioxidant activity were the response variables. A central composite design was used (Minitab 17) for the extraction by maceration. The maceration time (1, 4, 12, 20, and 24 h) and the ratio of ethanol (50 to 80%) acidified with 1% HCl were the two factors studied. For the MSPD extraction, sea sand was used as a dispersant, and a 22 factorial design was employed for the evaluation, with the elution volume and the ratio of sample/dispersant being the two factors analyzed. The optimal extraction method was MSPD with 96 mL (acidified ethanol) as the elution volume and a 1:2 ratio of sample/dispersant. Using these conditions, 14.01 ± 0.19 mMol TEAC/100 g db (Trolox equivalent of antioxidant capacity) of grape pomace was obtained, whereas the total phenolic content was 2836.73 ± 41.90 mg GAE/100 g db. These values are greater than those obtained by maceration. These conditions are close to those predicted by the model (analysis of variance (ANOVA) with a level of significance of 5% (p < 0.05) and a Tukey comparison test for determining significant differences in the comparison of results).