Angiotensin-converting enzyme inhibitory activity of hydrolysates generated from whey protein fortified with salal fruits (Galtheria shallon) by enzymatic treatment with Pronase from Streptomyces griseus

Whey proteins mixed with salal fruits extract (0-20% w/w) were hydrolysed with Pronase E from Streptomyces griseus for a period of 8 h. The angiotensin-converting enzyme (ACE) inhibitory activity of the hydrolysates was highest (IC50: 0.087 mg mL(-1)) for samples fortified with the highest extract concentration (20%). Peptides (>7 amino acids) with documented ACE inhibitory activity (DAQSAPLRVY, ALPMHIR, DKVGINY, LHLPLPL, YPFPGPI, YPFPGPIPN, VYPFPGPIPN) were identified bv LC-MS/MS data analysis using a database search approach. Fluorescence spectra of the whey proteins mixed with salal fruits extract indicates fluorescence quenching for alpha-lactalbumin. SDS-PAGE analysis suggests that alpha-lactalbumin is less susceptible to proteolysis when the extract is included in the formula. Data indicate that alpha-lactalbumin may be interacting with phenolic compounds naturally present in salal fruits. These interactions and the formation of complexes between a-Lac and phenolic compounds may affect the hydrolysis pattern of whey protein and the release of peptides with ACE-inhibitory activity.