Study On The Development And Quality Improvement Of Nutritional Bread

Whole grain nutritious foods are rich in dietary fiber,vitamins,minerals and polyphenols.Long-term consumption of whole grain foods can reduce the incidence of many chronic diseases including diabetes,cardiovascular disease and obesity.However,due to the high content of dietary fiber,whole grain bread has some problems such as small specific volume,hard texture and rough taste,which seriously restricts its promotion and application.Therefore,developing the methods for improving the baking quality of whole grain bread is important not only for theoretical significance but also for practical application.In present study,we first studied the effect of quinoa flour(QF)on baking performance,antioxidant properties and digestibility of wheat bread(WB).Then,the methods for improving baking quality and the nutritional evaluation of whole wheat bread were studied,aiming to provide some reference and theoretical basis for the promotion and application of whole grain bread.The main findings are as follows:(1)The addition of quinoa flour significantly affects the specific volume,porosity and texture of the wheat bread.The results indicated that with an addition of a small amount of QF(5%)would not affect the baking performance of WB,while higher amounts of QF(10% and 15%)resulted in smaller specific volume,increased hardness and coarse porosity,since QF changed gluten secondary structure and disrupted gluten network.However,sensory evaluation showed that the flavor of WB enhanced significantly with increasing QF addition.More importantly,WB containing QF exhibited improved antioxidant activity and reduced in vitro digestibility with lower estimated glycemic index(eGI),which could be due to the abundant fiber and polyphenols in quinoa flour.(2)The specific volume was used as optimization criterions,and the amount of composite improver on the specific volume of whole wheat bread(WWB0)was optimized through single factor experiment.The optimized proportions of different improvers are as follows: 7% of gluten,110 mg/kg of glucose oxidase,80 mg/kg of amylase,50 mg/kg of pentosanase.The resulted whole wheat bread(WWB1)has a specific volume of 4.39 mL/g.On the basis of this,the improved process of fermented sourdough using Lactobacillus plantarum on whole wheat bread was further optimized.The amount of Lactobacillus plantarum is 1%;the fermentation time is 12 h;and the amount of whole wheat sourdough is 10%.The specific volume of resulted whole wheat sourdough bread(WWB2)is 4.48 mL/g,increasing nearly 1.6 times compared with WWB0(2.73 mL/g).(3)The comprehensive evaluation of the baking quality of whole wheat bread before and after improvement was carried out from four aspects: specific volume,texture,porosity and sensory evaluation.The results indicated that the specific volume of WWB2 is significantly increased,and the pore structure is significantly improved.The TPA results suggested that the hardness,chewiness and gumminess of WWB2 were significantly reduced,while the springiness,cohesiveness and resilience were significantly increased.The texture indexes of WWB2 were not significantly different from ordinary white bread(WB).The sensory score of WWB2 was not significantly different from WB,and its flavor score(7.5 points)was significantly higher than the latter(5.5 points).In addition,the contents of wet gluten and SEM images showed that the insufficient content of gluten protein and the damage of gluten network structure were the inherent reasons for the poor quality of whole wheat bread.The content of wet gluten in whole wheat dough was improved significantly after modification,and the density of gluten network was remarkably improved.(4)We have systematically evaluated the antioxidant properties,digestibility and staling characteristics of whole wheat before and after the improvement.The results indicated that the total polyphenol content of whole wheat bread was higher than WB,and consequently showed stronger DPPH,ABTS and OH scavenging ability than WB.Overall,the antioxidant properties of bread samples followed the order: WBB2 >WWB1?WBB0 >WB.In terms of digestibility,the quality of WWB0,WWB1 and WWB2 is significantly better than WB,and the quality of WWB2 is the best,which exhibits lowest eGI values(63.56).In addition,the staling rate of WWB2 is significantly slower than WB,showing a lower bread crumb hardening rate,starch recrystallization rate and water migration rate.