Effect On Protein And Edible Quality Of Steamed Bread By Steaming

As the Chinese traditional food, steamed bread is the staple food for people in northern China, currently, household production is the main mode of production of steamed bread, and many problems are prensent in industrial production.Effect on component content、molecular weight distribution、secondary structure of protein are studied during steaming process, at the same time, influence on edible quality caused by change of content of protein is studied. Providing technical guidance for the industrial production of steamed bread.The Kjeldahl method and Bradford experiments showed that in the first 15 min, the content of albumin、globulin、glutein and gliadins were decreased, the residual protein was increased; In the 15 min-30 min, the change of component content of protein is not obvious. In the process of steamed, the rule protein content remained unchanged, and it is equal to the toal of the each component content of protein.The composition changes of protein were analysised by SDS-PAGE, the resultes showed that in the first 15 min, number of bands in the whole protein、soluble proteins and glutenin gel electrophoresis profiles were reduced, The content of the whole soluble protein which molecular weight greater than 90 k Da and lower than 50 k Da both were reduced, it indicated that the high molecular were degradaed; the content of albumin and globulin which molecular weight greater than 50 KDa was decreased; the bands of glutenin which molecular weight greater than 90 k Da were disappeared, and the content of glutenin which molecular weight is from 30 KDa to 50 KDa were induced. The changes of composition of protein are coincide with the changes of content of proteins.The results of secondary structure of protein analysised by Ellman‘s method and FTIR showed that in the first 20 min, the content of α-helix was decreased, both of β-angle and β-sheet were increased, the ratio of α-helix and β-sheet bacame lower; The disulfide bond content was increased, sulfhydryl content was decreased. The results indicated that the spatial structure of protein became more tightly, rigidity of protein was decreased, and flexibility was increased.The change of peptides which were from degradation of protein component was studied by HPLC. The results showed that during the fermentation, the peptides were synthesized by yeast; in the first 20 min, just little of peptides were disappeared, most of peptides were changed little, and the results indicated that the steaming has little effect on peptides.The correlation between indexes of TPA and parameters of sensory evaluation was analysised, the results showed that the relationship between indexes of TPA and parameters of sensory evaluation was not one correspondence, parameters of sensory evaluation was the comprehensive reflection, surface structure、luster and stickiness and taste of steamed bread are significantly positive correlated with their indexes of TPA, internal structure is negative correlated with springness, elastic toughness is negative correlated with hardness、gumminess and chewiness.The correlation between protein content and edible quality showed that, the increases of contents of albumin 、globulin and gliadins have negative effect on ediable quality of steamed bread, the cohesiveness and resilience were decreased, while the hardness was increased; the increases of contents of glutenin and residual protein have positive effect on ediable quality of steamed bread, the gumminess and hardness were increased, while springness and resilience were increased.