Evaluation of the Antimicrobial Capacity of a White Grape Marc Extract Through Gastrointestinal Digestion

Polyphenols are extensively studied for their antimicrobial and prebiotic properties, but concerns about their stability persist. In order to elucidate the antimicrobial stability of such molecules in the gastrointestinal environment and their potential effect as antimicrobials and microbiota modulators, a white grape marc extract from the variety Albariño has been exposed to simulated digestions. In vitro digestions were performed following the INFOGEST protocol and samples were taken after each digestive phase and submitted to bacterial resazurin viability assays. The results reveal that the extract presents a potential antimicrobial effect against foodborne pathogens, such as Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Salmonella enterica, which is enhanced during the intestinal phase. Modulation of the bacterial growth at concentrations below 2% (v/v) of the extract against pathogenic bacteria was observed. Although gastrointestinal digestion reduces the extract’s polyphenolic content, with procyanidin and quercetin-3-glucoside identified as the most unstable compounds, cell viability assays confirmed that its antimicrobial efficacy is maintained. In conclusion, the Albariño marc extract demonstrates a promising microbial modulation capacity, which persists during the digestive process despite variations in the polyphenolic composition.