Study On The Behavior Of Dough Components And The Improvement Of Whole Wheat Bread Quality By Co-fermentation Of Lactobacillus Plantarum LB-1 And Yeast

Whole wheat bread is rich in minerals,vitamins and dietary fiber.Regular consumption of whole wheat bread can effectively prevent high cholesterol,hypertension and other related diseases.However,the wheat bran can easily lead to sensory quality deterioration and shelf life shortening of whole wheat bread.The synergetic fermentation of lactic acid bacteria and yeast has a broad application prospect in the improvement of whole wheat bread quality,but its internal improvement mechanism is lack of in-depth research.Therefore,this study aims to screen a kind of lactic acid bacteria with antifungal activity,and apply it to the preparation of whole wheat bread for improving the sensory quality of whole wheat bread and extending the shelf life of whole wheat bread.This study will contribute to provide a theoretical basis for the development of high-quality lactic acid bacteria that can be applied to the preparation of whole wheat bread.The main contents and results of this study are as follows:1.The antifungal effect of 20 kinds of lactic acid bacteria against 6 kinds of wheat molds(Penicillium,Aspergillus niger,Aspergillus flavus,Aspergillus ochraceus,Aspergillus fumigatus and Fusarium graminearum)was analyzed by antifungal experiment.Three kinds of lactic acid bacteria with good antifungal activity were screened out,including F-50,F-3 and LB-1.The three kinds of lactic acid bacteria were identified as Lactobacillus plantarum by 16S r DNA sequencing.The morphological observation and physicochemical properties of the three Lactobacillus plantarum strains were analyzed.The results showed that the three Lactobacillus plantarum strains were Gram-positive.Lactobacillus plantarum LB-1 not only possessed good antifungal ability and acid production ability,but also possessed excellent sugar fermentation ability.Therefore,Lactobacillus plantarum LB-1 was selected as the optimal fermentation model strain in this study.2.Lactobacillus plantarum LB-1 and yeast were used to co-ferment dough,and the behavior changes of gluten and starch were analyzed.The results showed that the contents of globulin,gliadin and glutenin in dough decreased with the increasing of albumin content during fermentation process.The particle size of GMP decreased,the ratio of?-helix and?-sheet of ordered secondary structure increased,and the high molecular weight GMP components were hydrolyzed to low molecular weight components.In addition,the number-average molecular weight and weight-average molecular weight of starch in co-fermented dough decreased,and the content of short chains including A_fp,A_crystaland B_fp-chains in amylopectin and?-restricted dextrin and?-restricted dextrin increased.The crystallinity of starch increased,while the thicknesses of amorphous regions and long period distance decreased.SEM analysis showed that starch granules became rougher,and the solubility and swelling degree of starch increased.The more ordered and compact network structure formed by gluten and starch improved the viscoelasticity and gas holding capacity of dough.3.The co-fermentation of Lactobacillus plantarum LB-1 and yeast can improve the viscoelasticity,tensile resistance and ductility of whole wheat dough,increase the bound water content in whole wheat dough,and improve the gluten network structure.In addition,the hardness,viscosity and chewiness of the whole wheat bread made from the co-fermented dough decreased significantly,while the elasticity and cohesion increased significantly,indicating that the whole wheat bread taste was softer and more palatable.The flavor characteristics of the co-fermented whole wheat bread were enhanced,and the acetic acid content increased significantly.The co-fermented whole wheat bread could significantly inhibit the growth of mold,compared with the control group,the shelf life was extended by three days.These results showed that the co-fermentation of Lactobacillus plantarum LB-1 and yeast could be effectively used in the preparation of whole wheat bread,and improve the edible quality and storage characteristics of whole wheat bread.