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

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).