Effects of processing treatments on phenolic content, antioxidant capacity, and anthocyanin levels and antimicrobial activity in fruit pomace fractions

Fruit pomace is a source of phenolics and antioxidants, but processing conditions influence compound recovery and stability. This study evaluated the effects of pH, enzyme addition, and processing time on bioactive compounds in liquid fractions derived from grape, apple, cranberry, and lowbush blueberry pomace. The total phenolic content, anthocyanin concentration, phenolic composition, and antioxidant capacity were assessed. The antimicrobial activity of selected phenolic-enriched fractions was evaluated against food-relevant bacteria, including Escherichia coli, Salmonella enterica serovars, and Enterococcus isolates. The processing pH had the greatest influence on the phenolic content, antioxidant capacity, and anthocyanin levels, with acidic conditions (pH 3.0–3.5) consistently yielding higher values. Enzyme addition provided limited benefits under acidic conditions. The selected fractions exhibited inhibitory activity against all the bacterial groups tested, with the grape pomace extracts generally showing the greatest activity. Low-pH processing offers a simple, enzyme-free strategy for producing phenolic-enriched fractions from fruit pomace for value-added food applications.