Preparation of Antioxidant Peptides from Tea Residue and Its Antioxidant Activity

The antioxidant peptides were extracted by enzymatic hydrolysis of tea residues protein. Taking the reducing power and degree of hydrolysis of antioxidant peptides as the indicators, the single factor test and response surface methodology were used together to optimize the enzymatic hydrolysis conditions for preparing tea residue protein antioxidant peptides. Besides, this hydrolysate was fractionated by the ultrafiltration. Then, the effects of temperature, pH, metal ions, food additives and digestion environment in vitro on the reducing power stability of tea residue protein antioxidant peptides with molecular weight less than 3 kDa were investigated. The response surface methodology showed that the reducing power was 0.316 under the optimum conditions (substrate concentration of 2%, the time of 3 h, the temperature of 51 ^oC, the pH of 8.0, and the enzyme/substrate of 3034 U/g). When the molecular weight was less than 3 kDa, the reducing power of the antioxidant peptide was 0.412, which was 30.77% higher than before purification and had better vitality and stability. When the temperature rose from 30 ^oC to 90 ^oC, the reducing power decreased from 0.410 to 0.360. The peptides can still maintain good reducing power in the environment of acid and alkali and food additives. The reducing power decreased from 0.412 to 0.327 after 8 h in simulated digestion environment.