Covalent modification of soy protein hydrolysates by EGCG: Improves the emulsifying and antioxidant properties

Tianyi Wu; Ling Lin; Xinyi Zhang; Xinyue Wang; Jian Ding

doi:10.1016/j.foodres.2022.112317

Covalent modification of soy protein hydrolysates by EGCG: Improves the emulsifying and antioxidant properties

Food Res Int. 2023 Feb:164:112317. doi: 10.1016/j.foodres.2022.112317. Epub 2022 Dec 9.

Authors

Tianyi Wu¹, Ling Lin¹, Xinyi Zhang¹, Xinyue Wang¹, Jian Ding²

Affiliations

¹ College of Food Science and Engineering, Nanjing University of Finance and Economics/Collaborative Innovation Center for Modern Grain Circulation and Safety, Nanjing 210023, China.
² College of Food Science and Engineering, Nanjing University of Finance and Economics/Collaborative Innovation Center for Modern Grain Circulation and Safety, Nanjing 210023, China. Electronic address: dingjian@nufe.edu.cn.

PMID: 36737910
DOI: 10.1016/j.foodres.2022.112317

Abstract

In this study, the effect of EGCG conjugation on the emulsifying and antioxidant properties of SPHs was investigated to improve the functional characteristic of soy protein hydrolysates (SPHs) and develop a novel hydrolysates/peptides-EGCG conjugates. Enzymatic hydrolyzed SPHs (DH 5%, 8%, 10%) covalent with 1% EGCG to prepare conjugates at pH 9.0. The free amino group and tryptophan content of SPHs-EGCG conjugates significantly decreased, indicating the successful preparation of SPHs-EGCG conjugates. Additionally, 5% SPHs-EGCG conjugates showed the highest EGCG binding capacity. EGCG conjugation increased the particle sizes and charge of SPHs. Compared with non-covalent SPHs, the covalent modification of EGCG increased the emulsifying and antioxidant capacity, especially for 5% SPHs-EGCG, it exhibited much higher surface hydrophobicity, ESI (emulsifying stability index), EAI (emulsifying activity index), and antioxidant activity than others. This result revealed that SPHs and EGCG played a synergistic effect in improving the emulsifying and antioxidant capacity. Fluorescence spectroscopy analysis showed that the combination of EGCG conjugation significantly decreased the fluorescence intensity and caused maximum emission red-shift. The formation of a covalent bond between SPHs and EGCG was verified through Fourier transform infrared spectroscopy (FTIR), and the results also showed a significant increase in the α-helix and random coil contents of the conjugation, and a significant decrease in the β-sheet and β-turn contents. These results indicate that EGCG conjugation with SPHs induced the unfolding and stretching of protein flexibility. Overall, SPHs-EGCG conjugates can be applied as a promising emulsifier to fabricate emulsion systems and would be helpful in designing functional beverages containing polyphenols and peptides with enhanced functional nutritional properties.

Keywords: Antioxidant; Covalent conjugation; EGCG; Emulsifying property; Soybean protein hydrolysates.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Antioxidants* / chemistry
Antioxidants* / pharmacology
Emulsions / chemistry
Peptides
Protein Hydrolysates* / chemistry
Soybean Proteins / chemistry

Substances

Antioxidants
Protein Hydrolysates
Soybean Proteins
Emulsions
Peptides