Revalorization of winery by-products as source of natural preservatives obtained by means of green extraction techniques

Abstract

Winemaking industry produces huge amounts of by-products such as grape seeds, pomace and stems with important remaining polyphenol content after vinification process. Extracts obtained from two green extraction techniques, accelerated solvent extraction (ASE) and ultrasound assisted extraction (UAE), were evaluated to inhibit the growth of bacteria implicated in alimentary pathologies and to avoid the oxidation reactions. Hydroalcoholic extracts obtained by UAE resulted to have higher antibacterial and antioxidant properties compared to aqueous extracts from ASE. Results confirmed differences in bacteria susceptibility to extracts. Among Gram-negative bacteria, E. coli were especially sensitive to the inactivation of grape seeds and pomace extracts (IC50 ranged between 0.33–0.12 mg mL−1), meanwhile stem extracts were particularly effective against S. aureus growth (IC50 = 0.09 mg mL−1). No significant correlation was found between antibacterial activity and the phenolic composition, suggesting that structure-function of phenolic extracts and the interspecific relationship among different bacteria strains have a great influence. On the other hand, strong correlations were found among antioxidant capacity of extracts and phenolic composition (DPPH, r = 0.778, P < 0.05; ABTS, r = 0.879, P < 0.01). Due to the high content of hidroxycinamic acid derivatives, flavonols, tannins, catechins and anthocyanins, winery by-products are postulated as a good source of natural preservatives whose antibacterial and antioxidant properties can be customize to satisfy the requirements of the diverse food industries.