Physicochemical, functional, and digestive characteristics of tea seed cake protein obtained by ultrafiltration

To make full use of tea seed cake protein (TSCP), this study investigated the physicochemical and functional properties of TSCP, including the TSCP extract and three ultrafiltration fractions TSCP-1 (Mw > 10 kDa), TSCP-2 (3.5 kDa < Mw < 10 kDa), and TSCP-3 (Mw < 3.5 kDa). After ultrafiltration, the content, thermal stability, and surface hydrophobicity of TSCP were increased, and the molecular weight distribution and structure of TSCP showed significant differences. In terms of functionality, each fraction showed its advantages. Specifically, compared with the others, TSCP had better solubility and foaming properties, and TSCP-1 had significantly higher oil absorption capacity, and TSCP-2 had better water absorption capacity and emulsifying properties, and TSCP-3 can flow more easily (p < 0.05). In terms of nutritional value, the content of essential amino acids in all samples was sufficient. The degree of hydrolysis of TSCP was highest (80.98 ± 1.50%), and ultrafiltration decreased digestibility. These results indicated that ultrafiltration effectively improved the structure and functional properties of TSCP, and the obtained fractions can be applied to different scenarios. Practical Application: Tea seed cakes are rich in protein and usually regarded as byproducts during oil processing. Because of its good functional properties, tea seed cake proteins obtained by ultrafiltration have the potential to be used as ingredients for food.