The Optimization Of The Re-proofed Frozen Steam Bread And Researching The Effects Of Croprotectants

The paper was aimed at to researching the effects of the freezing technology and thawing process on frozen steam bread’ specific volume, sensory quality and texture characteristics by the process of pre-proofed frozen dough techniques, and using the response surface analysis to determining the best process parameters. And on this basis, adding cryoprotectants to study its impact on fermenting power, volume, sensory and textural quality of re-proofed frozen steam bread during the frozen storage. Rearching the impact of cryoprotectants on moisture status of the re-proofed frozen steam bread’s.The mainly experimental results are as follows:(1)The freezing time, freezing temperature and thawing time were determined by studying the freezing technology and thawing process of pre-proofed frozen steam bread.The results show: when the freezing time was 31.24 minutes, freezing temperature was-35.36℃ and the thawing time was 61.12 minutes, the frozen steam bread had the best volume, sensory evaluation and hardness values. Combined the verification test and the feasibility of practical operation, the best parameter conditions: the freezing time was 30 minutes, freezing temperature was-35℃, thawing time was 60 minutes.(2)With the increase of frozen storage time, the fermentation activity and the finished volume were both decreased, the sensory quality and texture quality of the frozen steam bread were worse. Independently adding the right amount of cryoprotectants including trehalose, transglutaminase and glycerol could improve the yeast fermentation activity during the freezing and frozen storage, increasing the volume and the sensory quality of the finished product of frozen steam bread. And to some extent, the cryoprotectants could improve the phenomenon of quality deteriorated of the frozen steam bread during the frozen storage.(3)Studying the influence of adding different cryoprotectants on the moisture status of the re-proofed frozen steam bread by nuclear magnetic resonance techniques. The results showed that in the test three different free energy of water were detected including T2 l, T22 and T23. In the course of frozen storage, it was indicate that the water retention of protein, starch and other macromolecules were decreased and the water molecules bound from a free state to migrate with the T2 were increased.(4)With the increase of frozen storage time, the water loss rate of the frozen steam bread was improved. Compared with the blank sample, after adding trehalose, transglutaminase and glycerin, the water loss rate of the sample was significantly reduced. This showed that, adding trehalose, transglutaminase and glycerin in frozen dough could inhibit the loss of water moisture in the dough during the frozen storage and keep the water retention in the system of re-proofed frozen steam bread.