Effect Of Soy Protein Isolate Hydrolyzates Obtained From Limited Enzymatic Hydrolysis On Noodles Quality:Investigation Of The Mechanisms

Noodle is one of the main food in China and its quality has attracted more and more attention in recent years.Lysine is lack in wheat flour but rich in soy protein,adding soy protein into wheat flour can achieve complementary amino acids.Soybean peptides could be easier to digest and uptake than soybean protein,and have various biological activities.Thus,effect of soy protein hydrolysates(SPH)on the noodles quality were studied systematiclly,and the affecting mechanisms was investigatedFirstly,the effects of SPH on noodles quality were discussed.Compared with control,the hardness,springnees,adhesiveness,chewiness,resilience and the breaking length decreased,breaking force were no significant difference;the cooking water absorption increased,and dry material loss and protein loss of noodles incrased dignificantly;the L*value decreased,a*and b*value increased;the noodle L*value decreased significantly,the noodle a*and b*value increased.The hardness,springness,adhesiveness,chewiness,resilience and the noodle L*value adding H7 were lower than the noodles adding H4,and the a*value,b*value,dry material loss and protein loss of noodles adding H7 were higher.Secondly,the effects of SPH on the rheological properties of dough were discussed.Compared with the original flour,the gluten yield,gluten index and sedimentation value of flours adding SPH(F-SPH)decreased;the peak viscosity,final viscosity,trough viscosity and breakdown value of F-SPH decreased significantly;the dough stability decreased and softening degree increased.The results of facets rupture test showed that the springness of noodle sheet was no significant,while the extensibility increasedThirdly,the research focused on affecting mechanism of SPH on noodles quality.The changes of noodles protein compotent showed that SPH hindered the formation of GMP,affecting the gluten network structure adversely.The molecular forces of noodles demonstrated that wheat-SPH interactions were both noncovalent and covalent.Hydrophobic bond and hydrogen bond between SPH and wheat interactions were the main non-covalent forces in the gluten network structure.The secondary structure of noodles proteins displayed significant difference,the increasing of ?-turns and random coil in noodles proteins adding SPH reflected that the hydrogen bonding between the protein chain were weakened.The result of SEM showed that the network of noodles structure become discontinuous,more starch granules was free from the network.The AFM pictures showed that the network was weakened after adding SPH.Based on the above study,a model explaining the interaction between SPH and gluten was established:small molecular weight polymer formed between SPH and gluten through disulfide bond,which not participate in the formation of gluten network structure.The interaction disrupted the polymerization of glutenin macropolyme(GMP),hindered gluten development,influenced noodles qualities.