Effect of modified soy protein isolate on dough rheological properties and noodle qualities

Abstract

Soy protein isolate, soy protein hydrolysate (SPH), and texturized soy protein (TSP) were used to fortify flour nutrition, and the rheological properties of dough and qualities of noodles were determined. Soy proteins increased the peak viscosity of flour paste. Dough fortified with TSP also exhibited more solid-like behavior with the highest storage modulus, while dough fortified with SPH showed the lowest storage modulus. Soy proteins increased the cooking loss of noodles. The protein loss of SPH-W noodles was up to 32.0%, much higher than wheat noodles, 13.3%, while the protein loss of TSP-W noodles was only 14.3%. Three types of soy proteins weakened the gluten network on different levels. The larger protein molecules in TSP linked with glutenin and formed the higher molecular polymers, counterbalancing the weakening effects deriving from the interfering with the glutenin–glutenin linkages. Therefore, TSP is more suitable to utilize in noodles. Practical applications Wheat flour noodles are widely consumed in most countries, so the protein quality in noodles is critical to consumer health. The essential amino acid, lysine, is relatively deficient in wheat proteins. Soy protein is rich in lysine and could be used to fortify the nutrition of flour products. However, some negative effects of soy protein on the qualities of flour products have been observed. Therefore, we modified Soy protein isolate (SPI), hoping to increase the interaction between soy protein and wheat protein, and reduce the negative impacts of soy protein on qualities of noodles. Results showed texturized soy protein exhibited fewer negative effects on noodle qualities than SPI and soy protein hydrolysate. The results presented in this study provided us with some useful information about how to select soy proteins to fortify noodle nutrition.