Characterization and biological activity of ultrafiltrate goat whey protein concentrate over the in vitro digestion

This study aimed to characterize the peptide profile of a goat whey protein concentrate subjected to in vitro gastrointestinal digestion using pepsin and pancreatin enzymes and evaluate the resulting hydrolysates' antioxidant and antimicrobial properties. The whey protein concentrate was obtained through ultrafiltration and analyzed across three stages: undigested (ND), gastric digested (GD), and gastrointestinal digested (GID). Molecular size and protein composition were assessed using SDS-PAGE/Tricine electrophoresis. Hydrophobicity was evaluated via column chromatography, and free amino acid profiles were determined. Antioxidant activity was measured using DPPH-+ and ABTS(-+) assays. In contrast, antimicrobial activity was assessed by determining the minimum inhibitory concentration (MIC) and minimum bactericidal/fungicidal concentration against foodborne pathogens, spoilage bacteria and yeast. The results revealed that alpha-lactoalbumin was degraded in the GD phase, whereas beta-lactoglobulin showed significant degradation after pancreatin action in the GID phase. High molecular weight (>52 kDa) whey proteins formed diffuse bands after enzymatic action. Chromatographic analysis showed peptide release in the GID phase and a reduction of peaks in goat whey (3.42 ND to 0.34 GID). The GID phase exhibited a significant increase (p < 0.05) in the release of essential (56%-80.9%) and branched chain (6%-15%) amino acids. GID peptides showed the highest antioxidant activities with 64.68% (ABTS(-+)) and 47.95% (DPPH-+) inhibition and the strongest activity against Escherichia coli and Listeria innocua. These findings underscore the bioactive potential of goat whey protein hydrolysates following simulated gastrointestinal digestion, highlighting their promise as functional ingredients with antioxidant and antimicrobial properties.