Plastein Reaction Of Soy Protein And Casein Under Temperature Control And The Evaluation Of Its Characterization

In this research,soybean protein and casein act as raw material,using chymotrypsin catalyzed plastein reaction to soybean peptide(SP)in the introduction of casein non phosphopeptides(CNPP)formation of soybean protein-casein complexes(CNPSPC).Then the process of plastein reaction is optimized by using artificial neural network method.And the macroscopic kinetic equation of synthetic proteins is deduced.Finally,amino acid composition,structure characterization,the functional properties and nutritional properties of CNPSPC prepared by different temperature are analyzed.(1)Using artificial neural network to plastein reaction of soybean protein-casein to optimize process parameters,the artificial neural network model of reaction conditions and CNPSPC yield is established.The results show that:the addition amount of substrate proportion 4:1(CNPP:SP,w:w),the reaction temperature is 46.2?,the reaction pH is 4.97,the reaction time 10h,plastein yield reaches up to 87.0±0.10%.(2)Dynamic light scattering is used to determine the changes of the aggregation of different time periods of the plastein reaction.The equation of apparent kinetic equation is obtained as follows.(3)The secondary and morphology structure of SP,CNPP and CNPSPC are characterized by determination of thiol and carbonyl groups,SDS-PAGE electrophoresis,Raman spectroscopy,Fluorescence spectra,Circular dichroism,Infrared spectroscopy,Scanning electron microscope and Atomic force microscope analysis method,etc.Electrophoresis results show that:Compared with SP and CNPP,the molecular weight of CNPSPC appeares as the new band,which is the formation of new peptides.And with the increase of temperature,the content of aggregation peptides of CNPSPC is decreased,and the content of free hydrophobic group shows a downward trend;Raman spectroscopy shows that;the content of p-helix,?-sheet and random coil of CNPSPC are slightly decreased and then increased significantly.And the lowest at 40?,7.1%,9.3%and 0.1%,respectively.At the same time,the content of ?-sheet increased significantly after a slight decrease,and at 40?,the maximum value is 83.5%;The IR shows that:the quantitative value of Quantitative secondary structure of CNPSPC in the amide ? band and the amide ? band is different.Namely with the increase of temperature,content of(3-sheet showed a trend of increase firstly;Circular dichroism also indicated:content of a-helix and ?-sheet of CNPSPC decreased,showing a stronger surface hydrophobicity;Therefore,the results of Circular dichroism,Raman and IR spectra show that the structure of the ?-sheet structure of CNPSPC is changed to a major role in the reaction;Fluorescence spectrum results show that:at 20?40?,the maximum emission wavelength is decreased from 349.4nm to 348nm.at 40?60?,The fluorescence intensity increased sharply,and the maximum emission wavelength increases from 349.4nm to 348nm;Scanning electron microscopy and atomic force microscopy shows that the morphology and size of CNPSPC are changed.So hydrophobic interaction in the SP with the combination of CNPP has played a vital role.(4)The contents of amino acids,antioxidant,digestion and absorption of CNPP,SP and CNPSPC a re analyzed.The expperimental results show that:compared with the SP and CNPP,CNPSPC has good functional properties.However,temperature has a significant effect on functional properties of CNPSPC,good solubility and foaming ability can be shown at 50?.Compared with CNPP and SP,the functional characteristics and total amino acid contents of CNPSPC are significantly increased;scavenging capacity,reducing ability,DPPH scavenging ability of CNPSPC have been improved,and the ability of superoxide radical scavenging is decreased;In vitro digestion experiments show that:in both the stomach and small intestine,the higher the synthesis temperature,the greater the digestibility of CNPSPC.