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 IC 50 0.215 ± 0.043 mg mL −1 ) activities. Semi‐preparative ( SP ) reverse phase high‐performance liquid chromatography ( RP ‐ HPLC ) of the 0.65 kD a 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 ( IC 50 :515.50 ± 1.11 and 610.30 ± 2.41 μ m , respectively).