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Title: Change in texture improvement of low-fat tofu by means of low-fat soymilk protein denaturation

item SHIN, WOO-KYOUNG - Korea University
item Yokoyama, Wallace - Wally
item KIM, WOOK - Korea University
item WICKER, LOUISE - University Of Georgia
item KIM, YOOKYUNG - Korea University

Submitted to: Journal of the Science of Food and Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/9/2015
Publication Date: 7/15/2014
Citation: Shin, W., Yokoyama, W.H., Kim, W., Wicker, L., Kim, Y. 2014. Change in texture improvement of low-fat tofu by means of low-fat soymilk protein denaturation. Journal of the Science of Food and Agriculture. 95:1000-1007. doi: 10.10002/jsfa.6780.

Interpretive Summary: Low fat tofu made by the conventional heating process has poor textural characteristics. By using a two-step heating process where the two major soy proteins are denatured separately, the texture is significantly improved and the product is more like typical fat tofu.

Technical Abstract: Low-fat tofu made as a byproduct of oil processing has nutritional benefit as well as an economic advantage. However, low-fat tofu has poor quality, especially weak texture. The quality of low-fat tofu was evaluated after a two-step heating process (heating at 75 oC, followed by holding at 95 oC). The decreased fat in low-fat soy flour resulted in increased denaturation enthalpy and higher denaturation temperature of ß-conglycinin and glycinin. The viscosity of low-fat soymilk and texture of low-fat tofu by the conventional one-step heating were weaker than full-fat soymilk and tofu. However, through selective thermal denaturation by the two-step heating process, free sulfhydryl group, total cysteine content and viscosity of low-fat soymilk increased to a value similar to the conventional heated full-fat soymilk. Syneresis of the low-fat tofu was improved about 30% by the two-step heated soymilk. The texture of low-fat tofu made by two-step heated soymilk had similar hardness and more chewiness to the full-fat tofu by the one-step process. The microstructure of low-fat tofu became finer, denser and more homogeneous through two-step heating soymilk. Two-step heating soymilk provided the improved texural qualities of low-fat tofu by more aggregation of denatured protein molecule though hydrophobic interactions.