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 5kDa ultrafiltration permeate of a whey protein hydrolysate generated at semi-pilot scale. Further laboratory scale ultrafiltration of this 5kDa permeate resulted in a 0.65kDa permeate with antioxidant, (1.11 +/- 0.074 mu mol 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 mu mol 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 mu mol 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 mu m, respectively).