Shin Woo-kyoung, Yokoyama Wallace H, Kim Wook, Wicker Louise, Kim Yookyung
Department of Human Ecology, Graduate School, Korea University, Seoul, Korea 136-701.
J Sci Food Agric. 2015 Mar 30;95(5):1000-7. doi: 10.1002/jsfa.6780. Epub 2014 Jul 15.
Tofu made from low-fat soy flour is a nutritional food for consumers and economically benefits the food processor. However, low-fat tofu has poor textural quality, especially insufficient firmness. Stepwise heating (heating at 75 °C, followed by holding at 95 °C) of full-fat soymilk increases gel properties. Therefore we evaluated the two-step heating of low-fat soymilk to improve tofu texture.
The denaturation enthalpy and temperature of β-conglycinin and glycinin were higher in low-fat tofu compared to high-fat tofu. The viscosity of low-fat soymilk and texture of tofu by one-step heating were weaker than full-fat soymilk and tofu. However, the two-step heating increased free sulfhydryl groups and viscosity of low-fat soymilk to a value higher or similar to conventional soymilk. The syneresis of low-fat tofu was reduced about 30% and hardness was higher (131.0 N) by the two-step process compared to one-step heating of full-fat tofu (101.4 N) by the one-step process. The microstructure of low-fat tofu became finer, denser and more homogeneous by the two-step heat process.
Low-fat tofu produced by denaturing the two major soy proteins separately had improved textural qualities similar to full-fat tofu as a result of increased hydrophobic interactions between denatured protein molecules.
由低脂大豆粉制成的豆腐对消费者而言是一种营养食品，对食品加工商也具有经济效益。然而，低脂豆腐的质地较差，尤其是硬度不足。全脂豆浆分步加热（先在75℃加热，然后在95℃保温）可提高凝胶特性。因此，我们评估了低脂豆浆的两步加热法对豆腐质地的改善情况。
与高脂豆腐相比，低脂豆腐中β-伴大豆球蛋白和大豆球蛋白的变性焓和温度更高。一步加热法制备的低脂豆浆的粘度和豆腐的质地比全脂豆浆和豆腐弱。然而，两步加热增加了低脂豆浆的游离巯基和粘度，使其达到或接近传统豆浆的水平。与全脂豆腐一步加热法（101.4 N）相比，两步加热法使低脂豆腐的脱水收缩减少了约30%，硬度更高（131.0 N）。两步加热法使低脂豆腐的微观结构变得更细、更致密且更均匀。
通过分别使两种主要大豆蛋白变性制备的低脂豆腐，由于变性蛋白分子之间疏水相互作用增加，其质地质量得到改善，与全脂豆腐相似。
