The Analyse On The Phenomenon Of Steamed Bread Shrinking

At first, this study investigated and analysed the phenomenon of steamed bread shrinking on the spot, then conclued the main factors which affected steamed bread shrinking, and this study primarily definited and classified the phenomenon of steamed bread shrinking. This study did a single factor experiment analysis on the flour quality and producing process of steamed bread in two ways. Through statistics and analysis in laboratory experiments,this study researched the impacts of gluten quality, gluten content, falling number, damaged starch content on the steamed bread shrinking; Through the combination of laboratory experiments and large-scale production in the workshops, this study researched the changes of stir conditions, fermentation conditions and steam conditions on the steamed bread shrinking to find the main factor of the steamed bread shrinking, and researched it on various quality traits of steamed bread. Finally, we proposed some corresponding measures, which might prevent the shrinkage of steamed bread.Main conclusions of this paper was as follows:1. Consumers pay more attention to appearance and texture requirements of steamed bread. In the actual production of steamed bread, shrinkage is widespread, and it is generally considered that: the shrinking of steamed bread dues to excessive dough proofing.2. In order to facilitate statistical analysis of experiments, this study divides shrinkage into the following four categories according to different degrees of shrinking: severe shrinking type, moderate shrinking type, mildly shrinking type, and partial collapse type.3. We cound not find their correlation between shrinking and each quality indicator about six different way flour, but found that it is related to steamed bread volume to some exent. When gluten quality is too high, severe shrinking types appear much more times, whlie too low, mild shrinking and partial collapse type are majority. The changes of falling number and damaged starch content are certainly correlative with steamed bread shrinking, but the changes of gluten content and other quality such as moisture, ash content, it is no significant correlation between them.4. The changes of yeast addition, old dough addition, water hardness, water addition, stir time, proofing period and steaming pressure have a certain relevance to shrinking, this study found that the pre-fermentation time of paste and the proofing period of bread blanks affact on shrinking more apparently, when the time of fermentation exceeds a certain critical time(60 min), as the time proofing period to extend, the shrinking extent and number of shrinked steamed bread will amplify and increase rapidly. Therefore, the researches that the respective sensory indicators are went on regarding the time of fermentation as the main remarkable factor.5. With the prolonging time of fermentation of the steamed bread, the variation circumstances of the respective quality indicators are as follows: Sensory evaluation shows the steamed bread in 40min fermentation has the best quality. The specific volume is increased and then decreased. The whiteness of the epidermis, pulp and inner, the ratio of height and diameter and the gelatinization degree are decreased gradually. The internal hole and water content was increased.6. To prevent steamed bread from shrinking,we should start with staple materials, and work on the process. At first, controlling a good job of flour quality and making appropriate choice of flour for steamed breasd. And then kneading properly grasp the extent of the dough system and acquiring a good degree of proofing dough.