Quantification of Isoflavones in Soymilk and Tofu from South East Asia

The concentration and distribution of isoflavones in commonly used soybean foods were evaluated by high-performance liquid chromatography. The different forms of isoflavone glucoside esters were converted to their corresponding glucosides by a mild saponification of the extracts. Isoflavone levels were reported as microgram aglycone equivalents per gram of soy food. The total isoflavone concentrations in soymilk and tofu ranged from 76 to 199 µg/g and 162 to 312 µg/g respectively, on a wet weight basis. A comparison of isoflavone levels in soymilk and tofu, prepared by a standard procedure with the commercially available packaged soymilk and tofu samples were also carried out. Even though different types of tofu had different isoflavones concentrations, each type had similar values compared to those produced by the standard procedure.