Water Soluble Antioxidant in Supernatant Fraction of Okara, a By-product of Tofu Manufacturing

Abstract

The water soluble antioxidant (partial by purified WSA: p-WSA) was partially purified from the supernatant fraction of okara, a by-product of tofu manufacturing. The contents of total phenolics, sugar and protein in p-WSA were 0.11%, 0.14% and 74.8%, respectively. The ninhydrin reaction was positive, and the ultraviolet absorption spectral λ max values were 264 nm and 280 nm. The antioxidant activity of p-WSA was determined by two different systems. The p-WSA showed remarkable antioxidant activity in a linoleic acid system and had the same effect as mixed tocopherols; however, it appeared weak in active oxygen method systems. The p-WSA showed a strong synergistic antioxidant effect with tocopherol but appeared weak with citric acid. The antioxidant activity was completely stable even after heating at 100°C for 1 h. Isolation and identification of the structure of p-WSA are currently under way.