The Study On Protein Degradation During Sourdough Fermentation

Sourdough fermentation play an important roles infoods,The sourdough fermentation has a number of beneficial effects that include prolonged shelf life, accelerated volume gain, delayed staling, improvedbread flavor, and good nutritional value. In the present study, sourdough, yeast fermented dough and Lactobacillus fermented dough were prepared by wheat flour, yeast and Lactobacillusplantarum M616.Sourdough fermented using yeast, or Lactobacillus plantarum M616 alone, was used as the control sample.Changes of total protein, soluble protein, gliadian, gluten and peptides during the fermentation were determined to explore the pattern of protein degradation. Additionally, the change of p H, TTA, gas production rate and growth curve were also detected to find the influence of physicochemical property and Rheological properties by Lactobacillus plantarum M616 fermentation, So that, we could know the degradation of protein from molecular.The result showed that growth of Lactobacillus plantarum M616 had an obvious inhibition on yeast. the yeast has a high growth rate in yeast fermented dough compared with sourdough fermentation and the cell counts in yeast fermented dough reached 8.82 log cfu/g, while that only 7.91 log cfu/g in sourdough at the stationary phase.Compared with yeast, Lactobacillus plantarum M616 has an low growth rate but a long log phase in sourdough than Lactobacillus plantarum M616 fermented dough. In other hands, Lactobacillus plantarum M616 played amain role in the changes of p H and TTA. The p H was 3.73 at the end of fermentation and the low p H may inhibit the growth of mounds.In addition, both yeast and Lactobacillus plantarum M616 have an ability on the degradation of starch; the Lactobacillus plantarum M616 could increase the content of reducing sugar, but the content of reducing sugar always keep low during the fermentation. The increase of reducing sugarcould increase sweet taste of sourdough and improve the growth rate of yeast.The degradation of proteins and formation of peptides were determined by SDSPAGE and HPLC and the contents of soluble proteins, gliadins and glutenins were detected by Bradford. The result showed that yeast has no effect on the degradation of proteins; Lactobacillus plantarum M616 play a key role in protein degraded and the contents of proteins were declining during fermentation. The major degradation was in 4-10 h, a further analysis combine with the growth curve found that 4-10 h was the log phase of Lactobacillus plantarum M616. Because the metabolism was vigorous and major organics was need for the growth and reproduction, proteins and other organics in dough were degraded quickly. Additionally, the low p H could also increase the solution of proteins which could improve the degradation of proteins. The main degradation was on soluble proteins and middle molecular weight. What more, content of gliadins increases first and then decreases during 0-10 h. The analysis of peptides indicted that Lactobacillus plantarum M616 could increase the concentration of peptides which would increase the nutritive value of dough.During the study on Fermentation characteristics, fermentation properties and Rheological properties were detected by F3 Rheo-fermentometer and Blow Bubble Instrument. The result showed thatgrowth of Lactobacillus plantarum M616 could not only improve the dough viscosity and dough thews, but also relieve the decrease of dough tenacity.Additionally, the viscosity and thews was two folds in sourdough than yeast fermented dough. Additionally, Lactobacillus plantarum M616 could degrade the protein and result to caving in of the net structure of protein.