The Study On The Shrinkage Of Quick-Frozen Steamed Buns After Steaming

In this paper, the shrinkable steamed buns were selected as research objects to study the shrinkable phenomenon of quick-frozen steamed buns after steaming. The physical and chemical properties of shrinkable steamed buns were analyzed using texture analyzer, differential scanning calorimetry(DSC), rapid viscosity analyzer(RVA), SDS-PAGE and scanning electron microscope(SEM). The effects of thawing time, steaming time and stewing time after steaming on the shrink of quick-frozen steamed buns after steaming were also studied according to the product feature of quick-frozen steamed buns, The details of this research were as follows:The shrinkable steamed buns were selected as research objects, normal steamed buns were the control group, the relations between shrinkage degree and steamed buns quality were researched. The results showed that: with the aggravation of shrinkage level, the teamed bun’s specific volume, elastic, cohesiveness, resilience and viscosity characteristics were gradually decreased, which were lower than the normal steamed buns, and the shrinkage level with the test index of steamed buns were into a positive correlation; the hardness, gumminess and chewiness were higher than normal steamed buns, and becoming a negative correlation.The results of RVA showed that the peak viscosity, valley viscosity, final viscosity and setback value of shrinkable steamed buns were degraded as the shrinkage level aggravated, which lower than the normal steamed buns. The RVA index of grade I shrinkable steamed buns(the worst shrinkable steamed bread) showed significant difference compared with the control group(P<0.05).Other physical and chemical index of shrinkable steamed buns showed that in the shrinkable process of steamed buns, the protein and subunit content had no significant differences, and also having no protein aggregation and decomposition, the content of soluble amylase showed a trend of gradually increasing, and there was no phenomenon of starch aging, little change in water content and the p H value was gradually reduced with the shrinkage level aggravated.Scanning electron microscopy(SEM) showed that the destructed degree of gluten increased as the shrinkage level aggravated, which network structure fracture. Starch granules was deformed or fractured, the number of minute bubbles in steamed buns skin gradually increased and air-tightness enhanced.The results of steaming process showed that there’s a connection between the changes of thawing time and stewing time and the shrinkage of quick-frozen steamed buns. Steamed buns which storaged at-18 for 48 h thawed indoors for 1 min, which ℃under the condition of 20±2 ℃and 50-70% humidity, stewed for 1min followed by streaming for 8 min, which can get the least shrink ratio of steamed buns(1%), and the shrinkage was also slight.