Degradation Of Glutenin Macropolymer During Sourdough Fermentation

As an important component of sourdough,protein plays an important role in the formation and quality.Protein degradation in fermentation process is the most important factor affecting sourdough flavor and quality.The wheat flour,it is the main raw material of sourdough and the most complex structure of glutenin macropolymer(GMP)in the fermentation process,there is no report at home and abroad.the contents,free amino acids,molecular weight distribution and structure of GMP in five different types of sourdough(acid control group,blank control group,yeast fermentation group,lactic acid bacteria fermentation group and mixed fermentation group)were analyzed.The results show that with the fermentation time,lactic acid bacteria fermented dough in GMP degradation is very strong,but compared with the mixed degradation effect on GMP fermented dough and yeast fermentation in dough is not very obvious,it can be seen that the lactic acid bacteria in the dough fermentation process plays a leading main.The content of FAA extract in the dough fermentation process in GMP is lower in 4h were 74.681mg/100 ml,66.307mg/100 ml,173.849mg/100 ml,117.579mg/100 ml,101.882mg/100 ml,and 12 h fermentation to 78.808mg/100 ml,169.212mg/100 ml,89.654mg/100 ml,indicating that the main product of fermentation with peptide based;These four types of GMP fermentation extracted with Glu and Val,the content of free amino acids in liquid acid,the control group in these two kinds of amino acid content percentages were 10.87% and 5.62%,the percentage of lactic acid bacteria fermented dough in 10.92% and 5.64%,compared to 10.84% and 11.8%in yeast fermentation in dough,mixed fermented dough in the content two kinds of free amino acids reached 10.51% and 7.23%.By means of SDS-PAGE gel electrophoresis study found,the total amount of the subunits of high molecular weight glutenin in the dough of lactic acid bacteria decreased from 23.1% to 20.1%,while that of low molecular weight glutenin subunits increased by about 29.3%;the dough yeast fermentation,the protein content did not happen too much volatility,the percentage of high molecular weight glutenin subunitsin the basic 23.1%,low molecular weight glutenin subunits remain at 38.7%,mixed fermented dough,high molecular weight protein subunits of 111.4 KDa and 84.6 KDa appear obvious degradation.Through the analysis of four kinds of dough by HPLC size exclusion chromatogram found that the variation of spectral changes and the molecular weight of SDS-PAGE in dough GMP’s consistent,in lactic acid bacteria fermented dough have significant degradation effect,although mixed dough degradation appears,but in the late fermentation stage appeared obvious stagnation,it is also possible that the yeast growth was inhibited,while the opposite group of yeast fermentation were small,again proved that in the degradation process of GMP in the fermentation of lactic acid bacteria dough plays a decisive role.The changes of GMP,Fourier transform infrared spectra under different fermentation conditions were determined.The results showed that the fermentation changed the two level structure of GMP,and the emergence of a regular change,and provide a theoretical basis for the study of GMP two level structure and functional properties of further contact.Through the further analysis of five different types of GMP in the SEM,Lactic acid bacteria fermented dough and mixed fermentation dough these two kinds of dough under the action of microorganisms,will destroy the network structure of glutenin polymers,resulting in the collapse of the structure of the two.It is obvious that the fermentation changed the structure of the GMP in the dough,which affected the physical and chemical properties of the dough and changed the processing quality of the dough.