Study On The Effect Of Curdlan On Frozen Steamed Bread Dough Quality

Steamed bread is one of the traditional staple foods in China.With the development of economy and society,steamed bread processing has gradually turned to industrial large-scale production.However,steamed bread has high moisture content,fast starch staling,and short shelf life,which seriously affects the industrialization and commercialization of steamed bread.Freezing steamed dough technology solved the problems of vulnerable contamination and short shelf life of steamed bread.Freezing steamed bread dough technology reduced labor costs and the waste of resources.However,the quality of frozen steamed bread dough in the process of frozen storage gradually declined,the gluten structure was damaged,and the yeast activity was reduced,resulting in the deterioration of the texture and sensory quality of steamed bread.How to improve the quality of frozen steamed bread dough has become one of the research focuses.Curdlan has good freeze-thaw stabilities and strong water holding capacity.The study of curdlan on the improvement of frozen steamed bread dough has certain practical significance.In this paper,the effect of curdlan on the quality of steamed bread was studied from three aspects.The effect of curdlan on the quality of frozen steamed bread dough,the effect of curdlan on the quality of frozen steamed bread,the effect of curdlan on the structure and properties of frozen gluten protein were investigated,respectively.The main research results were as follows:Firstly,the effect of curdlan on the quality of frozen steamed bread dough was studied.The results showed that with the amount of the curdlan addition increased,the water absorption of dough increased,the dough formation time prolonged,and the dough stability time first increased and then decreased.The water absorption and formation time of the dough with 0.9%curdlan reached the maximum value.The tensile energy and extensibility reach the maximum value when 0.5%curdlan was added.As the amount of curdlan increased,the pasting temperature increased.When 0.9%of curdlan was added,the pasting temperature was the highest（70.80℃）.The peak viscosity and final viscosity first increased and then decreased with the increased amount of curdlan.The breakdown value and setback value first decreased and then increased with the amount of curdlan increased.Adding 0.5%of curdlan significantly improved the gelatinization characteristics of starch.The dynamic rheological properties of dough were significantly affected by the addition of curdlan.The viscosity modulus and elastic modulus of dough with curdlan were higher than those of the control group,indicating that the addition of curdlan had better viscoelasticity.The results of the quality changes of frozen dough during freezing storage with curdlan showed that with the prolongation of freezing time,the freezable water content of the dough increased,and the relaxation times T₂₂ and T₂₃gradually decreased.After adding curdlan,the moisture change of the dough was minimal.Therefore,it was believed that curdlan could enhance the water retention of the dough.Scanning electron microscope showed that the gluten protein network structure of frozen steamed bread dough was damaged during freezing storage.The gluten structure had collapsed.The starch granules were broken and exposed.The gluten structure of the dough with 0.5%curdlan was more complete,and the starch granules were less damaged.The results of fermentation characteristics showed that the gas holding capacity of frozen steamed bread dough decreased during freezing storage.The gas production of yeast and fermentation height Hm decreased with the extension of freezing storage time.The specific volume and sensory score of frozen dough steamed bread gradually decreased with the extension of the frozen storage time of the dough.The hardness,chewiness and stickiness of steamed bread gradually increased,and the elasticity and resilience gradually decreased.The addition of curdlan could slow down the quality deterioration of frozen dough steamed bread.Secondly,the effect of curdlan on the quality of frozen steamed bread during frozen storage was studied.The results showed that with the extension of freezing storage time,the moisture content in frozen steamed bread gradually decreased,the relaxation time T₂₁ and T₂₂became larger,and the peak areas A₂₁ and A₂₂ decreased,indicating that the water fluidity of steamed bread increased.The strong bound water changed into weak bound water,but the peak area A₂₁ of steamed bread added with curdlan changed slightly,indicating that curdlan reduced the content of freezing water in frozen steamed bread.The XRD patterns of steamed bread showed that the crystallinity of starch gradually increased with the prolongation of freezing storage time,indicating that the starch staling was aggravated in freezing.In the process of frozen storage.The crystallinity of steamed bread with curdlan was lower than that of the control group.When curdlan was added at 0.5%,the change of starch crystallinity was the smallest,which was consistent with the results of curdlan on starch gelatinization properties.With the extension of frozen storage time,the specific volume of steamed bread gradually decreased,the hardness,chewiness and stickiness gradually increased,and the elasticity,resilience and sensory scores gradually decreased.Compared with the control,the quality deterioration of frozen steamed bread was slowed down by the addition of curdlan,and the optimal addition amount was 0.5%.Finally,the effect of curdlan on the structure and properties of frozen gluten protein during freezing storage was studied.The results showed that the increased degree of GMP depolymerization and the content of disulfide bonds in frozen gluten gradually decreased,while the content of free sulfhydryl groups and surface hydrophobicity gradually increased with the prolongation of frozen storage time;The secondary structure of frozen gluten protein was significantly influenced by curdlan.After 90 days of frozen storage,the concentration of gluten protein in the control groupβ-sheets content decreased from 44.22%to 40.08%,and the gluten protein in the experimental groupβ-sheets content decreased from 43.42%to41.28%.The results of scanning electron microscopy showed that the surface of unfrozen gluten protein was smooth and the structure of gluten protein collapsed after freezing.The gluten structure of the experimental group was smoother than that of the control group,and the gluten pores were denser,indicating that the curdlan could reduce the formation and growth of ice crystals and damage the structure of gluten protein.XRD diffraction patterns showed that with the prolongation of freezing time,the crystallinity peak of gluten protein decreased,and the crystallinity of gluten protein with curdlan was lower than the control group.The curdlan significantly improved the water holding capacity of unfrozen gluten proteins,with little impact on oil holding capacity.After freezing storage treatment,the water holding capacity of gluten protein decreased and the oil holding capacity increased.Compared with the control group,the addition of curdlan can reduce the changes in water and oil holding capacity of frozen gluten protein during freezing storage.