Identification Of Fermented Millet Strain And Its Effect On Starch Structure And Aging Properties

In order to study the effect of fermented millet starch structure and anti-aging properties,this paper selected from natural fermented millet modification plays a major role in the culture and the separation and purification.26 s r DNA and 16 s r DNA were used to identify the isolated strains,and the physiological and biochemical properties of the isolated strains were studied.the acid and amylase production ability of different strains were studied by liquid chromatography,calcium carbonate transparent circle,starch circle and other indicators.Fourier transform infrared spectroscopy(FTIR)and gel permeation chromatography(GPC)were used to study the starch structure of fermented millet.Study on starch gelatinization and aging properties after fermentation by fast viscosity analyzer and DSC differential thermal scanner;The changes of millet starch granules after fermentation were studied by scanning electron microscopy and polarizing cross microscopy.The aim of this study was to lay a foundation for the study of the mechanism of the modification of millet starch aging properties by fermentation strains and natural fermentation.The results show that:(1)The effects of different strains on organic acid content and starch structure-activity of fermentation broth were studied by pure strain fermentation.Selected from natural fermented liquid in the major strain of Lactobacillus plantarum,Pediococcus pentosaceus,Enterococcus faecium,Saccharomyces cerevisiae,Bacillus strain.The ability of producing acid of Lactobacillus plantarum > Lactobacillus plantarum > Enterococcus faecium.The yeast do not have the ability to produce acid but can decompose starch,Bacillus do not produced acid but has strong ability to degrade starch.The growth index of Lactobacillus plantarum and Streptococcus faecium,Enterococcus faecium increased at 12 h and 24 h after fermentation,and then the p H decreased rapidly.The colony number of Saccharomyces cerevisiae and bacillus at 36 h reached exponential stage,but p H declined.(2)The results of liquid chromatography show that the content of organic acid by pure fermentation of Pediococcus pentosaceus,Lactobacillus plantarum,Enterococcus faecium,Saccharomyces cerevisiae,Enterococcus faecium respectively that the content of lactic acid in the coccus was 1.82 g/L and 0.52 g/L acetic acid;Lactic acid and acetic acid producing ability of Lactobacillus plantarum was weaker than Enterococcus faecium,the content was 1.91 g/L and0.97 g/L;Pediococcus pentosaceus has the ability to produce lactic acid and acetic acid,and its content reaches 3.27 g/L and 1.16 g/L respectively;Saccharomyces cerevisiae can produce 3.82g/L ethanol and 0.04 g/L lactic acid and 0.02 g/L acetic acid after fermentation;the fermentation broth of Bacillus contains 0.34 g/L of lactic acid,0.2 g/L acetic acid and a small amount of ethanol.Polarized light microscopy showed that the fermentation did not change the polarized cross of starch.Scanning electron microscopy showed that the surface of millet starch has been erosion by fermentation of Lactobacillus plantarum,Pediococcus pentosaceus and Enterococcus faecium;after yeast and Bacillus fermentation,the surface erosion signs of starch granules became heavier,and the pores deepened and the number increased.According to Fourier transform infrared spectroscopy,Saccharomyces cerevisiae and Bacillus fermented millet starch functional area of the peak position has not changed,but the characteristic peak intensity.The starch fingerprint of millet was partially disappeared after fermentation by Lactobacillus plantarum,Streptococcus faecium and Enterococcus faecium.Gel permeation chromatography showed that the average molecular weight and molecular weight of I and II regions were lower after Lactobacillus plantarum fermentation,The weight average molecular weight of I region increased and the number average molecular weight decreased after the fermentation of S.cerevisiae,Enterococcus faecium and Saccharomyces cerevisiae,but the average molecular weight and average molecular weight of II decreased.After fermentation of Bacillus,the number average molecular weight of I region increased slightly,and the weight average molecular weight decreased slightly,but the average molecular weight and average molecular weight of II decreased.A rapid viscosity analyzer and a DSC differential scanning calorimeter were used to demonstrate the results that the gelatinization temperature,retrogradation value and final viscosity of the fermented starch were decreased after fermentation by Lactobacillus plantarum,Streptococcus faecium and Enterococcus faecium,while the enthalpy rise.The gelatinization temperature and retrogradation value of Saccharomyces cerevisiae decreased after fermentation,and the final viscosity and enthalpy increased.After acid-producing bacteria fermentation,there were more organic acids accumulated,so that starch granules were eroded,amylose molecular weight and proportion were relatively reduced,and retrogradation value was reduced.Bacillus sp.has the ability to produce extracellular amylase,and the amylopectin is broken and debranched by fermentation to produce part of amylose and small molecular substances,which leads to aslight increase in the retrogradation value compared with other strains,but is lower than that of unfermented millet starch.(3)The changes of starch structure-activity after fermentation were studied by using these strains to verify the effects of screened strains on starch structure-activity in natural fermentation.High performance liquid chromatography showed that the lactic acid and ethanol content in the fortified broth of Bacillus subtilis,Lactobacillus plantarum,Enterococcus faecium and Saccharomyces cerevisiae were 7.93 g/L and 1.65 g/L,respectively.The content of acetic acid was higher than that of natural fermentation,and the content of acetic acid was 0.59 g/L and 0.50g/L respectively.Polarized light microscopy showed that the fermentation did not change the polarized cross of starch.Scanning electron microscopy showed that the surface of millet starch was eroded after natural fermentation.After intensified fermentation,the surface erosion signs of starch granules became heavier,the pores deepened and the number increased.Fourier transform infrared spectroscopy showed that the peak position of functional groups of millet starch remained unchanged after natural fermentation.The fingerprint of starch was partially disappeared in fortified millet,and the characteristic peak intensity of millet starch decreased in natural fermentation and fortified fermentation.Gel permeation chromatography showed that the average molecular weight and average molecular weight of I increased after intensified fermentation.However,the average molecular weight and average molecular weight of natural fermentation decreased slightly,but the average molecular weight and average molecular weight of the two populations in II region decreased.Rapid viscosity analyzer and DSC differential scanning calorimeter showed that the retrogradation and final viscosity of starch decreased after natural fermentation and intensified fermentation.And the difference between the two strains was not significant,which indicated that the screened strains were one of the main strains which affected the starch structure activity of natural fermentation.In conclusion,the effects of different strains fermentation on the molecular weight,functional groups,gelatinization characteristics and aging characteristics of millet starch were studied by screening the strains in natural fermentation broth.The partial reasons for the changes of starch structure-activity caused by fermentation were determined,which led to the improvement of short-term anti-aging properties of starch.