Abstract
This study was conducted in vitro to investigate the antioxidative properties of soymilk whey, which was made from soymilk by adjusting to pH 4.5 and removing of soy protein by centrifugation, and its fractions (soymilk whey recovery, 100%; of which fraction A, 88%; fraction B, 12%; fraction C, 9%; and fraction D, 3%). Soymilk whey and its fractions suppressed lipid peroxidation in rat liver microsomes and a rat brain homogenate. In particular, the antioxidative activity of soymilk whey and fraction A toward rat liver microsomes was similar to that of ascorbic acid. All samples were found to possess Fe 2+-chelating and DPPH radical-scavenging activities. There was a significant inverse correlation between these two activities of soymilk whey and its fractions (r=-0.98). The chelating and radical scavenging activities of soymilk whey and its fractions appeared to depend mainly on their respective content of phytic acid and phenolic compounds. These results suggest that the antioxidative activity of soymilk whey and its fractions might depend on the interaction among different substances present in the samples, and that these samples could be used as natural antioxidants.
