Production of phenylalanine-reduced soymilk for phenylketonuria patients

Phenylketonuria (PKU) is a hereditary disease caused by the deficiency of phenylalanine (Phe) hydroxylase enzyme or its cofactor tetrahydrobiopterin. Treatment involves a Phe-restricted diet, although food options are limited. Soymilk, derived from soybeans, is a functional food with nutritional benefits. In this study, soymilk was produced and hydrolyzed with protease of Aspergillus oryzae and papain, and then activated carbon was used to remove Phe for PKU patients. The second-derivative spectrophotometry method was used to determine Phe content in soymilk. The results showed no significant difference in dry matter, fat, and crude fiber between soymilk and Phe-extracted soymilk with respect to the control group (P < 0.05). Soymilk’s protein content was calculated as 2.74% (w/w) and that of Phe-reduced soymilk as 1.94% (w/w). Similarly, consecutive Phe content was 40.53 mg/L and 5.09 mg/L. After hydrolization, the calculated Phe removal rate was 87.44% (w/w), and the protein content was reduced by 29.19% (w/w). The study demonstrates that Phe-reduced soymilk is suitable for PKU patients, thus reducing the need for imported products and offering new market opportunities.