Effects Of Protein Oxidation On Structure,Physicochemical Properties And Function Of Chickpea Protein Isolate

Chickpea protein isolates(CPI),as the main component of chickpea,may have a negative impact on the nutritional quality of CPI during drying,cooking and storage,thus affecting the structure,physicochemical and functional properties of CPI.In this paper,three kinds of simulated oxidation systems were established and applied to CPI to explore the structural changes of oxidized proteins and their effects on functionality.It can provide theoretical and practical reference for the control and application of CPI products in the food industry,and expand its application.The research contents and results of this paper are as follows:1.The effect of thermal degradation of 2,2 '-azodiisobutylamine dihydrochloride(AAPH)into peroxy radicals(ROO·)on the structure and functionality of CPI was studied.With the increase of CPI oxidation degree,protein carbonyl content,dimer tyrosine content,free mercaptan content and total mercaptan content were determined to determine the degree of protein oxidation.Surface hydrophobicity,endogenous fluorescence intensity(tryptophan content),FTIR,SDS-PAGE and amino acid content were used to evaluate the structural changes of oxidized protein.Moderate oxidation(0.04 mm AAPH)can form flexible soluble protein,which can improve the foaming ability of protein.Over oxidation(25 mm AAPH)has better foaming ability,but the foaming stability is reduced due to the formation of insoluble aggregates.Moderate AAPH induced ROO· oxidation results in the increase of soluble protein,resulting in the increase of emulsification and in vitro digestibility.However,excessive AAPH induced ROO· oxidation results in the increase of insoluble protein,which leads to the decrease of emulsifying property and in vitro digestibility.2.The 13-hydroperoxyoctadecadienoic acid generated by lipoxygenase acting on linoleic acid oxidized CPI,and the structure,thermal stability,solubility,foaming,emulsification characteristics,and in vitro digestibility of the oxidized CPI were investigated.The degree of oxidation was determined by the content of carbonyl and free sulfhydryl groups.The effect of oxidation on CPI structure was evaluated by intrinsic fluorescence,FTIR,SDS-PAGE and surface hydrophobicity.Compared with linoleic acid content of 0 mm,with the increase of oxidation degree,soluble protein increased,resulting in the formation of small molecular weight protein,and then protein solubility decreased,resulting in the increase of protein molecular weight.The change of protein molecular weight results in the decrease of oxidized protein denaturation temperature at first and then increase.However,the addition of linoleic acid increases the enthalpy of protein,and then the enthalpy gradually decreases due to the increase in the degree of oxidation.The protein structure induced by moderate linoleic acid content was expanded,which could promote the foaming properties,the emulsion properties and the in vitro digestibility of CPI.Over oxidation results in the increase of disordered structure and aggregation of proteins,which reduces the functional properties of proteins.3.The effect of acrolein on the structure and functionality of CPI was studied.The extent of protein oxidation was determined by the content of carbonyl,dimeric tyrosine,free sulfhydryl,and total sulfhydryl contents,and the effects of oxidation on CPI structure and protein nutritional value were determined by amino acid fraction determination,FTIR,endogenous fluorescence,SDS-PAGE,and surface hydrophobicity.With the increase of acrolein concentration,protein forms aggregates composed of disulfide bonds and covalent cross-linking,resulting in the decrease of protein solubility.Protein changes from soluble protein to insoluble protein,thus reducing the foaming and emulsifying properties of protein.And the in vitro elimination of protein increases first and then decreases.