Preparation of angiotensin I-converting enzyme (ACE) inhibitory peptides from Tie Guanyin tea residue protein using two-step enzymatic hydrolysis

Abstract In this study, we attempted to prepare novel angiotensin I-converting enzyme inhibitory (ACEI) peptides from Tie Guanyin tea residue protein (TTRP). Different proteases were used to hydrolyze TTRP to prepare ACEI peptides, neutral protease and alkaline protease hydrolysates exhibited higher ACEI activity and was chosen in further hydrolysis treatment. Response surface methodology (RSM) was used to optimize the enzymatic condition, and the results indicated that the optimal conditions of enzymatic hydrolysis were: 4% (w/v) of TTRP in water was hydrolyzed with 3500 U/g neutral protease at 50 °C and pH 6.5 for 2.5 h in the first step and then with 5000 U/g alkaline protease at 50 °C and pH 10.0 for 3 h in the second step. Under the optimum condition, the ACE inhibitory rate of the final products was 88.45% ± 0.45% at the concentration of 1.0 mg/mL. Moreover, ACEI peptides derived from TTRP showed good stability under different temperatures, pHs, metal ions and gastrointestinal digestion. These results indicated that the TTRP has potential to be used for preparing ACEI peptides.