Study on Functional Properties of Alkaline Protein Extract from Tea Residue

Tea residue contains high amount of protein, which can be cost-effectively extracted by alkali. However, the application of tea protein in food industry was limited due to its reaction with polyphenols or sugars. In this study, the physicochemical properties and bio-functionalities of the protein extract obtained from green tea residue were determined, and the emulsifying, foaming and antioxidant properties were improved by enzymatic method. The results showed that the protein content of the extract was 52%, and its isoelectric point (PI) was 3.6. The solubility, dispersibility, foaming and emulsifying properties of tea residue protein were positively correlated with the pH value of the solution; when the concentration of protein extract was 80 mg/mL, the inhibition of psychrophilic bacteria and Pseudomonas were 98% and 93% respectively. After pepsin treatment, the foaming ability of protein extract was 58.3 mL/g twice as that of the untreated sample, and the emulsifying ability was 100.0 mL/g four times as that of the untreated sample. After treatment with Viscozyme R L, the foaming ability of tea residue protein increased to 52.4 mL/g, the emulsifying ability decreased to 12.0 mL/g, while the antioxidant activity increased by about 50% . The results showed that the protein extracts from tea residue and their enzymatic hydrolysates had good functional properties and potential for the application in food industry. © 2022 Chinese Institute of Food Science and Technology. All rights reserved.