Quality Improvement Of Whole Wheat Chinese Steamed Bread With Compound Enzyme

The nutrition and health benefits of whole grains have been widely recognized. Whole wheat bread is becoming more and more popular in western countries. Chinese steamed bread(CSB) is an important traditional staple food in China, which accounts for a large proportion in the dietary structures of residents. It can be assumed that with the development of whole wheat steamed bread, the health level of people might be improved, and the low-valued bran would be also effectively utilized. However, the modified technology and mechanism of CSB prepared from whole wheat flour have been poorly studied.This can be own to the presence of bran, which makes the whole wheat products extremely difficult to be accepted by the consumers due to the coarse or stringy texture. In this research, three kinds of commercial enzymes, as have been widely used to improve the quality of whole wheat bread and common flour products, were applied to improve the quality of whole wheat CSB. The types and addition levels of enzymes, bran partial size, as well as wheat varieties were all evaluated. The results might provide technical and theoretical supports for the development of whole grains industry in China.By use of whole wheat flour from the market, the effects of glucose oxidase(Gox)、pentosanase(Pn) and cellulose(Ce) on the texture and sensory characteristics of the whole wheat CSB were evaluated. Based on one single factor test, the optimal adding levels of Gox、Pn、Ce were 40 mg/kg、60 mg/kg and 30 mg/kg, respectively. The result of orthogonal experiment showed that with the combined use of three enzymes(Gox 40 mg/kg,Pn 40 mg/kg,Ce 30 mg/kg), the sensory score of whole wheat CSB can reach more than 90.The influence of enzymes on the properties of whole wheat dough was also investigated. The results indicated that Gox can improve the time of dough formation and stable, enhance the stability of gluten network, modify the dough resistance and extensibility, and increase the gas-holding capacity;although the dough stable time was decreased with the addition of Pn and Ce, the extensibility and gas-holding capacity were both significantly increased. A complex of three enzymes made the properties of dough close to that prepared from specificity steamed bread flour. The results obtained from rheological properties analyses of dough during fermentation showed that the complex enzymes could significantly increase the expansion properties of dough, improve the amount of gas released, and increase the specific volume of the steamed bread.The impact of bran particle size on the properties of whole wheat CSB was studied. Three kinds of whole wheat flour with different bran size(D50 value: 285.0、186.7、75.7 μm) were prepared through adding of bran to wheat flour. The results demonstrated that the quality of whole wheat CSB in the presence of medium bran size was the best compared with those containing large and small bran size for both of blank and modified samples. Large bran size caused coarse textured of steamed bread. However,if the bran size was too small, the water absorption of dough was highly increased, and dough stability time and degree of softening were decreased. Moreover, the CSB had a strong branny taste while the bran size was too small.JN17, APH, and JQ5 were selected from 10 wheat varieties to evaluate their processing suitability though properties analysis and cluster statistic. The result showed that the properties of whole wheat CSB prepared from three wheat varieties were significantly different. For the blank and modified samples, the sensory score from high to low was APH>JQ5>JN17, respectively. The modified degree of whole wheat CSB with enzymes were also different among the three wheat varieties.In conclusion, the quality difference between whole wheat CSB were mainly related with the strength of gluten networks, dough expansion capabilities, P/L values and gas-release abilities of dough.The quality improvement of whole wheat CSB with enzymes used in the present study were mainly can be attributed to their effects on these properties.