Studies On The Producing Process And Qualities Of Chinese Steamed Bread Of Defatted Wheat Germ

As Chinese traditional staple food, steamed bread plays an important role in people's life. Steamed bread made with a certain proportion of the defatted wheat germ powder, not only make full use of the defatted wheat germ resources, but also increase the nutritional value of the steamed bread. Firstly, by changing those factors such as dough mixing, rolling,proofing, the single factor and orthogonal test were conducted. Research in characteristics of defatted wheat germ steamed bread production process and the basic quality changing rules of steamed bread basic with different mixture powder proportion was performed to get more reasonable making process parameters. Then, on this basis, discuss the influence of defatted wheat germ addition on dough texture tensile properties and its impact on steamed bread characteristics and in vitro digestibility of TPA. In addition, NMR was used to observe the moisture distribution of dough with defatted wheat germ., comparing the differences in volatile compound between the defatted wheat germ steamed bread and ordinary steamed bread were tested by GC-MS analysis. The main conclusions are as follows:1.With the increase in the addition of defatted wheat germ, water absorption rate of mixed powder increased significantly. And the formation time, stability and Farinograph index decreased at different degrees. Weakening increased with the proportion of wheat germ powder. The dough extension area, maximum tensile resistance, tensile resistance, tensile ratio and maximum tensile ratio decreased, elongation characteristics increased first and then decreased. Overall, influence of granularity of mixed powder on tensile properties is less than the addition amount.2. In the technical study of steamed bread with defatted wheat germ, through the single factor experiment, the best production process of defatted wheat germ steamed bread were obtained as follows: defatted wheat germ size 60~80 meshes, the addition of defatted wheat germ 3%~4%, the time of dough mixing 15~20min, the amount of water 42%~44%, the water temperature of dough mixing 30 ?, the number of sheeting 15~35 times, roll gap width11~17mm, The amount of qiang mian 0%~1%, proofing time 25~30min, proofing temperature36~40?, proofing humidity 80%~85%. Under these experiment parameters, steamed bread shows low hardness, high whiteness, large volume and high sensory score. Through the orthogonal experiment, the best production process of defatted wheat germ steamed bread wasobtained as follows: particle size of 80 mesh, the addition 3%,the time of dough mixing15 min, the number of sheeting 25 times, roll gap width 14 mm, the amount of qiang mian0%,proofing time 25 min, proofing temperature 36?, proofing humidity 80%.3. According to the RSM results, during the extending, tolerable stress would be affected by the factors in the descending order as amount of water, time of dough mixing, addition of defatted wheat germ, defatted wheat germ size, while that of the extending distance as defatted wheat germ size, amount of water, time of dough mixing, addition of defatted wheat germ.4.According to the RSM results, the springiness of steamed bread would be affected by the factors in the descending order as time of dough mixing, amount of water,defatted wheat germ size, addition of defatted wheat germ, while that of the cohesiveness as amount of water,defatted wheat germ size, time of dough mixing, addition of defatted wheat germ.5. In vitro digestion test of skimmed wheat germ steamed bread showed that the content of reducing sugar had little change when the addition of wheat germ was less than 4%, which had little effect on the digestion of wheat germ steamed bread. However, when the content of wheat germ was higher than 4%, the content of reducing sugar changed greatly, which affected the digestion of steamed bread.6. The NMR experiment showed that the addition of defatted wheat germ promoted the conversion of free water to loosely bound water, loosely bound water to strongly bound water,the paste fluidity weakened, stability is enhanced; when the addition is excessive, the gluten structure is damaged, part of the loosely bound water converted to free water, leading to the flow of dough increased.7. GC-MS analysis results show that the defatted wheat germ and whole wheat germ will presented fragrance type of fruit or vegetable aroma to the steamed bread, but volatile components are different. Although the content of aldehydes, esters and aromatic compounds is low, it will give steamed bread flavor characteristics.