Effect Of Lactic Acid Bacteria Fermentation On Cadmium Binding Protein In Rice

In recent years,with the rapid development of China's industry and mining industry,the environment has also been increasingly destroyed,and a large amount of harmful substances are discharged thereby polluting water bodies and soil.Among these harmful substances,heavy metals have occupied the top spot in soil hazards because of their enrichment and refractory properties.Cadmium is a heavy metal that is easy to accumulate in rice.Eating cadmium exceeding the standard will cause bone pain in the human body.It will also damage the kidney,cardiovascular,immune system,nervous system,etc.,and long-term intake of high cadmium rice can also cause cancer.China is the country with the largest rice production and consumption.Solving the problem of exceeding the standard of cadmium rice is a major event for the national economy and the people's livelihood.At present,many researchs have done a lot of research on the storage and transport of cadmium in crops such as rice.Many scholars have also shown that protein plays a vital role in the storage and metabolism of cadmium in crops.This provides a certain theoretical basis for the research of this topic,and also provides an important reference basis for the research methods.However,predecessors have focused more on how to process rice that contain cadmium or the cadmium distribution of rice,and there still lack the in-depth study of the species,structure and functional properties of cadmium-binding proteins in rice storage proteins.Therefore,this study uses three kinds of glutinous rice with different cadmium content as raw materials,which fermented by lactic acid bacteria to reduce cadmium,and the rice before and after cadmium is extracted by Osborne method to extract four kinds of storage proteins,namely albumin,globulin,prolamin and valley protein.The structure and functional properties of these four storage proteins before and after cadmium reduction were studied by different analytical methods.The purpose of this study was to study the mechanism of cadmium reduction in cadmium rice.Finally,the acid method was used to reduce cadmium in rice,and the dynamic equation between cadmium and its nutrients in rice was explored to further verify the principle of cadmium reduction in cadmium rice.The main conclusions of this study are as follows:1.Using the Osborne method to extract and extract four kinds of storage proteins from rice,it is found that the binding ability of cadmium in rice and four kinds of storage proteins from large to small is globulin,albumin,gluten,prolamine,and the relative molecular weight of cadmium binding proteins were 16 kDa,32 kDa.2.The raw rice was fermented by lactic acid bacteria to reduce cadmium.After extracting four kinds of rice cadmium proteins,the secondary structure was analyzed by fourier transform infrared spectroscopy.It was found that the rice proteins were both mainly ?-folded and not after cadmium reduction or cadmium reduction.The regular curl content was mostly.After cadmium reduction by lactic acid bacteria,the content of a-helix decreased slightly,and the content of ?-sheet decreased significantly.It may be because the fermentation process of lactic acid bacteria produced a large amount of acid substances,which made the structure of rice protein more ductile.3.The raw rice were fermented by lactic acid bacteria to reduce cadmium.After extracting four kinds of rice cadmium proteins,the secondary structure was analyzed by circular dichroism.It was found that the content of ?-sheet of rice proteins decreased after cadmium reduction by lactic acid bacteria,which also indicated that the acidic condition would make the rice proteins peptide chain more extended.After cadmium reduction,thea-helix content decreased,and the irregular curl content increased,indicating that the rice proteins tends to disorderly development.This result is consistent with the fourier infrared analysis results.4.The four rice proteins before and after cadmium reduction were extracted,and their functional properties such as water holding capacity,oil holding property,foaming property,foam stability,emulsifying property and emulsion stability were measured.The results showed that the higher the cadmium content,the worse of the water retention,oil retention,foaming and foam stability,the emulsification and emulsio stability.After fermentation of the lactic acid bacteria the water retention and oil retention of rice protein,foaming property and foam stability,emulsifying properties and emulsion stability are increased.5.Soaking cadmium-containing rice with different kinds of organic acids,immersed at different concentrations,time,temperature,material-to-liquid ratio and at a speed of 150 r/min,the results showed that the best soaking acid was malic acid,the best time was 2.5 h.The optimum concentration is 0.4 mol/L,and the optimum temperature is 35?.The optimum ratio of material to liquid is 1:4.And with the removal of cadmium in rice,the protein content of rice gradually decreased.When the cadmium reduction effect was the best,the dissolution of rice protein was 20%.6.The quality of the rice before and after the acid leaching was analyzed.The microstructure observation results showed that the rice flour became loose after acid leaching,and the pore size between the starch molecules increased,which may be caused by the dissolution of the protein.Thermodynamic properties results showed that the gelatinization temperature of rice flour decreased after acid leaching,the gelatinization temperature decreased from 73.19? to 72.35?,and the endothermic enthalpy increased from 11.08 J/g to 11.33 J/g.The results of paste properties showed that the gelatinization temperature of rice flour decreased after acid leaching,the final viscosity decreased,the retrogradation value decreased,and the gelatinization temperature decreased.This indicates that acid leaching improved the taste quality of rice flour to some extent.The results of FTIR showed that malic acid soaked rice flour had little destructive effect on the crystal configuration of rice starch,and no strong chemical changes occurred during acid leaching to produce new chemical bonds or groups.