Study On The Mechanism Of How Added Insoluble Dietary Fiber Influence Bread Quality

In recent years,the daily dietary fiber(DF)intake of residents in China is 10.8 g,much lower than the recommended daily intake,which is 30 g.The lack of DF is one of the main causes of chronic diseases.Therefore,it is of great practical significance to increase the intake of DF in daily diet.DF is widely found in cereals,beans,fruits and vegetables,and contains a lot of insoluble dietary fiber(IDF).Due to its unique physicochemical properties and physiological functions,IDF is widely used in baked food.However,the addition of IDF will inevitably affect the original quality of the food.Bread was used as a carrier of IDF,and this paper aimed at analyzing the effects of IDF addition on the quality of bread and dough characteristics,establishing the relationship between dough characteristics and bread quality,and exploring the interaction between IDF and the gluten,wheat starch in wheat flour,so as to give some guidance on the reasonable application of adding IDF in bread.First of all,six kinds of IDF were selected from cereals,beans,fruits and vegetables.Then,based on the measurement of composition and physicochemical properties,the effects of different IDF on the quality of bread were investigated,including specific volume,color and texture,changes in moisture content and texture characteristics of bread during storage within 1 week.The results indicated that there were significant differences in chemical composition of IDF from different sources,which directly affected physicochemical properties of IDF.The addition of 10% IDF had negative effects on the overall quality of bread,while the specific volume was reduced,the bread became harder and the structure became larger and sparser.The qualities of breads with IDF from different sources were compared,and the property of bread with wheat fiber was the closest to the blank group,while the specific volume decreased by 0.59 mL/g,and the hardness increased by 219.13 g.Meanwhile,the quality of citrus fiber is the worst,while the specific volume decreased by 1.55 mL/ g,and the hardness increased by 513.73 g.Moreover,the changes of bread core hardness and moisture during storage showed that the addition of IDF could delay the deterioration of bread quality.The hardening rate of breads with IDF from citrus and apple was relatively low,and the rate of water reduction in those breads was the slowest.According to the results,the physicochemical properties of IDF were related to the quality of bread.Secondly,in order to build up the relationship among the characteristics of IDF,the properties of dough and the quality of bread,the effects of the addition of IDF on the farinograph characteristics,gelatinization properties,extenograph,fermentation and texture properties were investigated.The results showed that the addition of IDF increased the water absorption rate of wheat flour,the formation time and weakening degree of dough,while it reduced the stabilization time,extenograph properties and fermentation characteristics of the dough.What's more,the changes between groups of dough added with different IDFs tended to be consistent with the bread quality.For instance,the content of wet gluten of dough added with IDF from citrus was 24.95%,and the stabilization time was only 5 minutes,which suggested the worst gluten dilution.Meanwhile,the bread added with IDF from citrus showed the worst quality,which indicated that the properties of dough were affected by physiological properties of the raw materials,and would have an impact on the quality of the bread.Finally,the gluten and wheat starch in wheat flour were extracted to investigate the interaction between IDF and gluten protein,and the interaction between IDF and wheat starch.The results showed that the high water absorption and expansion ratio of IDF resulted in a significant decrease in the disulfide bond content in gluten.The content of disulfide bond in gluten added with IDF from citrus was 19.64%,which was 7.21% lower than the blank.This destroyed the network structure in gluten and resulted in a large difference in bread and dough properties.The results indicated that the effect of IDF on gluten was the key factor that affected the rheological properties of dough.However,the correlation between the basic characteristics of IDF and starch was not obvious.