Identification of angiotensin converting enzyme inhibitory and antioxidant peptides in a whey protein concentrate hydrolysate produced at semi‐pilot scale

Summary Antioxidant and angiotensin converting enzyme (ACE) inhibitory peptides were identified in a 5 kDa ultrafiltration permeate of a whey protein hydrolysate generated at semi‐pilot scale. Further laboratory scale ultrafiltration of this 5 kDa permeate resulted in a 0.65 kDa permeate with antioxidant, (1.11 ± 0.074 μmol TE per mg dry weight, oxygen radical absorbance capacity, ORAC) and ACE inhibitory (ACE IC50 0.215 ± 0.043 mg mL−1) activities. Semi‐preparative (SP) reverse phase high‐performance liquid chromatography (RP‐HPLC) of the 0.65 kDa permeate resulted in a fraction (SP_F3) with a 4.4‐fold increase in ORAC activity (4.83 ± 0.45 μmol TE mg dry weight) and a 1.3‐fold increase in ACE inhibitory activity (84.35 ± 1.36% inhibition when assayed at 0.28 mg mL−1). Peptides within SP_F3 were identified using UPLC‐ESI‐MS/MS. Met‐Pro‐Ile had the highest ORAC activity (205.75 ± 12.08 μmol TE per mmol peptide) while Met‐Ala‐Ala and Val‐Ala‐Gly‐Thr had the highest ACE inhibitory activities (IC50:515.50 ± 1.11 and 610.30 ± 2.41 μm, respectively).