Preparation and characterization of low-phenylalanine polypeptides from whey protein

Low-Phe protein-based substances are an important clinical requirement for the development of medical foods. Herein, a combination method of two-step enzymatic hydrolysis with activated carbon adsorption removal was applied to prepare low-Phe whey protein polypeptides (LWPs). The two-step enzymatic hydrolysis was affected by enzyme/casein mass ratios and times. The activated carbon adsorption removal was affected by activated carbon addition amounts, pH, temperature, and time. The LWPs had similar secondary structure percentages to whey protein polypeptides. The LWPs had lower molecular weights (the large molecular weight part of 10,272-11,727 Da: 16.88 % - 20.78 % vs. 26.79 %) and Phe contents (1.92 % - 1.22 % vs.2.58 %) compared with whey protein. Compared with whey protein polypeptides, LWPs had higher foaming properties, lower fat-binding capacities, higher emulsifying activity indexes, lower emulsifying stability indexes, higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging capacity, higher reducing capacity, and lower Fe²⁺-chelating capacity. These results provided basic knowledge for the understanding of the relationship between the structure and function of low-Phe polypeptides.