Effects Of Degreasing On Structure And Functional Properties Of Rice Dreg Protein And The Interaction Between Gluten And Linoleic Acid

Nowadays,rice dreg's application in industry has got more and more attention because of its advantages concluding about high protein content,reasonable balance of rice protein amino acid composition,mild taste,hypoallergenic and others.However,the quality and shelf life of rice dreg protein products is impacted because of the high fat content in protein,which is unfavorable to the further processing of rice dreg.So the degreasing treatment will be necessary to rice dreg.Rice dreg degreasing process mainly includes: alkaline degreasing,lipase degreasing and organic solvent degreasing method.Up to now,there are rarely reports about whether the different degreasing process will affect the structure and functional properties of rice dreg protein.In addition,some studies found that lipid would interact with protein in rice dreg,but the interaction of lipid and protein in rice dregs is not clear.In this study,three kinds of degreasing processes were used to degrease rice dreg,and the structure and function of rice dreg protein before and after degreasing were compared.The effects of different degreasing techniques on rice dreg protein were studied.At the same time,selecting linoleic acid and gluten as the representative object to study the interaction between proteins and lipid will provide a theoretical basis for further preparation to produce plant protein with high purity protein content and improving the added value and utilization of the protein product.The optimum conditions of the degreasing processes of rice dreg by alkaline method,lipase method and ethanol method were studied.The optimum conditions of alkaline degreasing were as follows: p H 9.5,reaction time 2.5 h,temperature 50 ?,degreasing rate under this condition was 77.35%;optimal degreasing conditions of lipase method: temperature 45 ?,p H 9.0,the amount of enzyme added of the rice dreg protein content was 3.0%,degreasing rate under this condition was 81.29%;The optimum conditions of the ethanol soaking degreasing were as follows: ethanol concentration: 85%,temperature: 30 ?,time: 2 h,the liquid content of the material ratio was: 1: 10,degreasing rate was 95.66% under these conditions.Results showed that: degreasing rate of three methods is: ethanol soaking method> lipase method> alkaline method.The structural and functional properties of defatted rice dreg protein,obtained by degreasing process including alkaline,lipase and ethanol soaking of rice dreg protein,were determined.Results showed that the degreasing methods had no significant effect on the primary and secondary structure of rice dreg protein,and the tertiary structure and surface microstructure of rice dreg protein was changed;The solubility of the rice dreg protein is reduced after the degreasing process,and the foaming property,foaming stability,emulsifying property and emulsifying stability have different degrees of improvement.Finally,the composition of fat and protein in rice dreg and the interaction between gluten and linoleic acid was studied.The contents of four protein components were as follows: albumin 7.81%,globulin 9.26%,glutelin 80.97%,gliadin 1.86%,the gluten content is the highest;the fatty acid composition of rice residue protein was: Linoleic acid 33%,oleic acid 26%,palmitic acid 18%,which linoleic acid content is the highest,so selected gluten and linoleic acid as a follow-up protein and fat interaction research objectives.The interaction between gluten and linoleic acid was studied by fluorescence,UV-visible and CD spectroscopy in gluten and linoleic acid.The results showed that linoleic acid could bind to gluten spontaneously,the fluorescence quenching mechanism of linoleic acid to gluten was static quenching,the tertiary structure and secondary structure of gluten changed after the interaction with linoleic acid,the content of ?-helix was increased and the stability of protein was enhanced,and the main interaction between linoleic acid and gluten was hydrophobic interaction.Further,the results of the Discovery Studio molecular simulation showed that linoleic acid binds to the surface hydrophobic residues in the hydrophobic cavity of gluten and the main interaction is hydrophobic interaction,and the results can verify previous experiments.