Relation between Antibacterial Activity against Food Transmitted Pathogens and Total Phenolic Compounds in Grape Pomace Extracts from Cabernet Sauvignon and Syrah Varieties

Grape pomace is the main by-product of wine production that concentrates bioactive metabolites of polyphenolic nature with antibacterial activity. Since grape pomace composition varied depending on grape variety, climate, vineyard location, and winemaking technology, it is important to study the composition and antibacterial activity of each variety separately. In this study, antibacterial activity against different food pathogens was evaluated and its relation with polyphenols content was determined. Grape pomace from Cabernet Sauvignon and Syrah varieties was extracted with methanol/HCl 1% (v/v), followed by sequential extractions with hexane, chloroform and ethyl acetate. Ethyl acetate fraction had the highest antibacterial activity determined through the microdilution method, reaching over 90% of inhibition at 500 μg∙ml−1 with the exception of Salmonella Typhi (70% of inhibition). Staphylococcus aureus and Escherichia coli were the most susceptible strains, exceeding 50% of inhibition at 62.5 μg∙ml−1. Ethyl acetate fraction contains the highest phenolic concentration in both Cabernet Sauvignon (132.2 mg of GAE g−1) and Syrah (102.6 mg of GAE g−1) pomace, as determined by the Folin-Ciocalteau method. Antibacterial activity present in grape pomace extracts is in direct relation to the polar phenolic content, in particular Corresponding author.