Mechanism of SPI,SPH and Their Mixed Products on Dough Properties and Noodle Quality

In order to improve the nutritional quality of flour products,wheat flour was fortified with soy protein isolate(SPI),soy protein hydrolyzates(SPH,hydrolysis degree:4.54%)and SPI and SPH compound products(SPI-SPH)respectively. The gluten and farinographic properties of composite powder,the dynamic rheological properties,the protein components,disulfide bonds and non-covalent bonds of composite dough,and the quality of noodles were observed. The result showed that addition of SPI resulted in an increase in wet gluten content,farinograph quality number,and reduction in dry gluten content,gluten index. The content of gliadin and glutenin increased,so the viscoelasticity and elastic ratio increased.The changes of gluten and dough properties with SPI-SPH were the same as those with SPI,and the farinograph quality number was increased. There was no gluten formed in flour fortified with SPH,and farinograph quality number increased;the salt soluble protein content of dough increased significantly(P<0.05)and the elastic ratio decreased. Furthermore,the disulfide bond number increased,hydrophobic interaction weakened and hydrogen bond strengthened in the dough fortified with soybean protein. The hardness of noodle fortified with SPI increased by 10.82%,the elasticity of noodle fortified with SPI-SPH and SPH decreased by 7.23% and 6.02% respectively,and the protein retention rate of noodle fortified with SPH decreased from 93.02% to 87.31% compared with wheat noodle. Overall,soybean protein and gluten protein interacted through disulfide bond and non-covalent bond,which impeded the formation of gluten network and disrupted the continuity of gluten network. Also,the combination of SPI and SPH weakened the effect of SPH on gluten to some extent.