| Egg white powder(EWP) includes a wealth of protein resources and is well known for their favourable gelling and foaming, therefore, it is usually used as a kind of food additive. Noodle is one kind of oriental staple, the crowd which almost feed on noodle is enormous, especially in the north of China. EWP was added in noodle, it not noly could enhance nutrition, but also improve the quality of noodle. In this study, the effects of EWP on wheat flour, dough and quality of noodle were inverstigated. And the interactions between egg white proteins and wheat gluten proteins including gluten-, glutenin- and gliadin-rich fractions during heat-denaturing were further investigated.Firstly, with the rheological properties of wheat flour and dough as the indices, farinograph, extensograph, rapid viscosity analyzer and rheometer were used to study the effects of different amount of EWP on the quality of wheat flour and dough. Results showed that EWP not only increased the elastic modulus, but also decreased the viscous modulus, as a result, the processing characteristics of wheat flour was elevated; Meanwhile, the dough development time, gelatiniation viscosity and breakdown value were increased as the addition of EWP; However, the water absorption rate of dough was decreased with the increasement of EWP; When the added ratio of EWP was 3%, the values of wet gluten content and dough stability time were biggest, while the degree of softening was minimum. The results of effects of different amount of EWP on dough showed that significant increase was observed in resistance and maximum resistance of the dough as the increase of EWP, but, the effect of EWP on extension of dough was negligible; The elastic modulus of dough was increase and the viscous modulus was decrease when the addition ratio of EWP was 3%.Secondly, the effects of different amount of EWP on cooking characteristics, brightness, textural characteristics and sensory properties of noodle were studied. These results showed that EWP could extend the cooking time of noodle and increase the water absorption index; Meanwhile, the dry matter lossing and dissolution rate of protein were the least when the added ratio of EWP was 3%; At the same time, the breaking force of dry noodle, the tensile strength, hardness, gumminess and chewiness of cooked-noodle were raise as the incresement of EWP; However, adhesion of cooked-noodle was decrease with the increasement of EWP; When the addition ratio of EWP was 3%, resilience, cohesiveness of cooked-noodle, brightness of noodle pieces were maximum and the score of sensory evaluation was the highest, while the cooked-noodle elasticity was the worst.Thirdly, Based on the scanning electron microscope and confocal laser scanning microscope techniques, the microscopic structures of(cooked) noodle which included EWP(0%, 3%) were observed. The results showed, compared with noodle with no EWP, the microscopic structures of noodle(3%) appeared more compact, especially the cooked-noodle(3%).Finally, based on high-performance liquid chromatography, gel electrophoresis and thiol measurement methods, the interactions between egg white protein and wheat gluten protein including gluten-, glutenin- and gliadin-rich fractions during heat-denaturing were investigated. These results showed, during heating, proteins polymerization was observed in the mixtures of gluten-, glutenin-, gliadin-rich fractions and egg white protein, it was more obvious as the increase of temperature; But, this further suggested that interaction was more potent in glutenin-egg white protein than gliadin-egg white protein and gluten-egg white protein as the increase of temperature; Meanwhile, the result of thiol measurement presented that the cross-linking via disulfide bond in glutenin-egg white protein was more obvious than gliadin-egg white protein and gluten-egg white protein. This provided a molecular theory for that EWP could improve the quality of noodle. |
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