Use of sourdough lactobacillus plantarum (ATCC 43332) to improve the quality and shelf life of toast soy bread

Soy ingredients that have unique functional and nutritional properties have found wide application in bakery products .During storage of bread, several different physical and microbiological changes occur, lowering the quality of bread. The bread crumb becomes hard, the bread crust changes from crispy to leathery and the characteristic and favorable bread flavor disappears. Addition of sourdough in the bread recipe can be used to retard the staling process of the bread. Sourdough addition is the most promising procedure to preserve bread from spoilage, since it is in agreement with the consumer (demand for natural and additive free food) products. In this research, defatted soybean flour in 3, 5 and 10 % was mixed with wheat flour. For sourdough preparation, fresh microbial cells were collected by centrifugation from LAB primary cultures, and with wheat flour and tap water and 0.25% (w/w) active dry yeast extract, containing Saccharomyces cerevisiae were mixed, then sourdough Lactobacillus Plantarum (ATCC43332) was added to each of soy and wheat flour mixture in amount of 25% of flour weight. Specific volume, sensory characteristics, molds spoilage and firmness of bread, were measured in the period of 0,24,48 and72 hours after baking bread. In comparison with control bread, Specific volume in all of blends decreased. Results showed that by adding 25% sourdough, the rate of molds spoilage of bread decreased. During the storage of breads, increase in firmness was suppressed by adding soy flour and sourdough. The results showed that sourdough had significant effect (p<0.05) on shelf life of soy bread in comparison with control sample. Finally the results of sensory evaluation showed that toast bread which contains 5% soybean flour and sourdough, has the most acceptability regarding to the other samples.