*Article* **Hemp (***Cannabis sativa* **L.) Seed Protein–EGCG Conjugates: Covalent Bonding and Functional Research**

**Xin-Hui Pang 1, Yang Yang 1, Xin Bian 1, Bing Wang 1, Li-Kun Ren 1, Lin-Lin Liu 1, De-Hui Yu 1, Jing Yang 1, Jing-Chun Guo 2, Lei Wang 2, Xiu-Min Zhang 3, Han-Song Yu 4,5,\* and Na Zhang 1,\***


**Abstract:** In order to make HPI have a wide application prospect in the food industry, we used EGCG to modify HPI. In this study, we prepared different concentrations (1, 2, 3, 4, and 5 mM) of (−)-epigallocatechin gallate (EGCG) covalently linked to HPI and use methods such as particle size analysis, circular dichroism (CD), and three-dimensional fluorescence spectroscopy to study the changes in the structure and functional properties of HPI after being covalently combined with EGCG. The particle size data indicated that the covalent HPI-EGCG complex was larger than native HPI, and the particle size was mainly distributed at about 200 μm. CD and three-dimensional fluorescence spectroscopy analyses showed that the conformation of the protein was changed by conjugation with EGCG. The β-sheet content decreased from 82.79% to 66.67% after EGCG bound to the protein, and the hydrophobic groups inside the protein were exposed, which increased the hydrophobicity of the protein and changed its conformation. After HPI and 1 mM of EGCG were covalently bonded, the solubility and emulsifying properties of the covalent complex were improved compared with native HPI. These results indicated that HPI-EGCG conjugates can be added in some foods.

**Keywords:** hemp protein isolate; (−)-epigallocatechin gallate; covalent binding; structural changes; emulsifying properties
