In this study, milk was hydrolyzed using protease (Asperigillus oryzae), trypsin, pepsin, or papain at concentrations of 0.001, 0.005, or 0.01 g/100 g milk for 30 or 60 min to produce angiotensin-converting enzyme inhibitory and antioxidant peptides. Results showed that the proteolysis, antioxidant, and ACE-I activity gradually increased with the increase in the enzyme concentration and hydrolysis time. The protease-treated milk had the highest proteolytic and ACE-I activity, while the papain-treated milk had the lowest. The papain-treated milk exhibited the greatest Fe 2+ chelating activity. The use of trypsin at concentration of 0.001 g/100 g milk for 60 min produced ACE-I and antioxidant activity without changes in the technological properties of milk.

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The effect of functional fermented milk rich in bioactive peptides on blood pressure, lipid profile, antioxidant status and some organ's in hypertensive-induced rats was studied. Functional fermented milk produced from skimmed milk fortified with 2% SMP:WPC (1:1) and partially proteolyzed by trypsin (2.5 mg/100 g milk for 20 min) before fermintation by using mixed starter culture of Lb. rhamnosus B-1445, O-114, YC-X11 and Lb. helveticusLh-B 02 with a 3:2:1:1 ratio, respectively. The main obtained results showed that the daily administration of functional fermented milk (group 4) for 4 weeks lowered the systolic blood pressure (SBP) and diastolic blood pressure (DBP) by 43 and 9 mmHg, respectively compared with a negative control group which administered saline (group 1). Plasma triglycerides, total cholesterol, atherogenic index and cardiac risk factor reduced in group 4 compared to group 1, while low-density lipoprotein, high-density lipoprotein, antithrombotic activity and antioxidant markers did not differ significantly among all groups. Histologically, there were no significant changes in the liver, kidney, heart and aorta tissues of rats in groups 1 and 4. In contrast, there were histopathological changes in these tissues of rats in group 2 which received daily 2 mg captopril /100 g BW. MATERIALS AND METHODS Materials Fresh skimmed cow milk was prepared after collecting from the Technology Center of Agricultural Production, Faculty of Agriculture, Cairo University. Spray dried Skimmed milk powder (SMP, 1. 5% fat and 5% moisture) was brought from Dina For Agriculture Industries Co. (Dina farms, Egypt). Whey protein concentrate (WPC, 53%) was supplied by CP Kelco, a Huber Company (Georgia, USA). Bovine trypsin (EC: 3.4.21.4) with activity ≥ 250 Units/mg protein was purchased from Sigma-Aldrich (Egyptian International Centre for Import, Cairo, Egypt). The DVI commercial starters of high viscosity yogurt culture YC-X11, O-114 and Lb. helveticus Lh-B 02 were obtained from Chr Hansen laboratories, Hoersholm, Denmark and Lb. rhamnosus B-1445 were procured from NRRL, USA. Triglycerides (TGs), total cholesterol (TC), high-density lipoproteins-cholesterol (HDL-C) and low-density lipoproteins-cholesterol (LDL-C) Spectrum kits were purchased from Egyptian Company for Biotechnology (Spectrum, Cairo, Egypt). Plasma total antioxidant capacity (TAC), superoxide dismutase (SOD) and glutathione peroxidase (GPx) Biodiagnostic Kits were obtained from Biodiagnostic Company, Giza, Egypt. Leptin enzyme-linked immunosorbent assay (ELISA) kit sandwich was purchased from DRG Instruments GmbH Company, Germany. Mixed starter preparation The activated starters of Lb. rhamnosus B-1445, O-114, YC-X11 and Lb. helveticusLh-B 02 was mixed at ratio of 3:2:1:1, respectively to avoid the predominant of strains each others. Fermented milk preparation Based on our findings in previous study (El-Kashef, 2017), two treatments of non-fat stirred fermented milk were manufactured at laboratory scale.