Rice Storage Protein Oxidation And Its Effects On Pasting Properties In The Process Of Storage

This paper was based on Suqian 5# rice produced in 2014 as experimental material.Firstly,the preparation methods of two kinds of storage protein gliadin and glutelin were determined by comparing the different extraction methods.,then analyzed the oxidation change rule of the two storage proteins in PAPG superoxide anion oxidation system and lipoxygenase-linoleic acid oxidation system,finally studied the oxidation regulation of the two dfferent types of storage proteins and the influence of pasting properties in the process of rice storage.This study not only provided the theoretical basis for rice aging mechanism research,but also put the protein oxidation indexes as the new evaluation indexes of rice quality.The contents and results were as follows:1.The selection of rice storage protein(gliadin and glutelin)extraction methodIn order to determine the more convenient and effective extraction technology of rice gliadin and glutelin,this study used different methods to classification extract with content and SDS-page electrophoresis analysis.Results showed that the optimal extraction method was that phosphate buffer solution removed albumin and globulin first,55% n-propanol extracted to prepare gliadin extract,then gluelin extract was prepared with 0.05 M NaOH and adjusted pH to 4.8 to precipitate after removing the first three proteins.The content of the two rice proteins extract were 6.98% and 77.1% respectively,and the molecular weight range of gliadin was about 13 k Da and 16 k Da,glutelin was about 14.4k Da,20 k Da,32-34 k Da and 54 k Da.2.The establishment of PAPG superoxide anion oxidation systemSuperoxide anion oxidation simulation systemwas established.The changes of carbonyl,active sulfhydryl,total sulfhydryl,and surface hydrophobicity of two storage protein were investigate in the simulation system with different concentrations of PAPG(0-50mmol/L).The results showed that PAPG autoxidation reaction of superoxide anion(O2-)increased gradually,its effect on the strength of the rice storage protein(gliadin and glutelin)would gradually strengthen.These effectleaded to the physical and chemical properties of proteins changed regularly.Carbonyl compounds content of glutelin was obviously higher than that of gliadin,and all tended to rise.Active sulphur content of gliadin first increased and then decreased final rose again.Glutelin rose slightly at 30mmol/L and then declined.The total sulphur content of gliadin and glutelin was also different: the gliadin was on the rise as a whole and the curve was relatively flat.The change was not obvious.However,the gluten was first increased and then decreased and the change was bigger.The surface hydrophobic of gliadin and glutelin were increased along with the increase of PAPG concentration,changing trend was similar to carbonyl compounds.3.The establishment of lipoxygenase-linoleic acid oxidation systemIn the oxidation with linoleic acid catalyzed by lipoxygenase simulation system,the changes of carbonyl value,total sulfhydryl and active sulfhydryl and surface hydrophobicity of two storage protein were also studied.The results showed that with the increase of concentration of linoleic acid(0-0.856 mmol/m L),oxidation intensity of gliadin and glutelin increased gradually in the lipoxygenase-linoleic acid oxidation system.Lipid free radicals or part of the intermediate produced made the carbonyl contents of gliadin and glutelin also tended to rise.The active sulphur content of gliadin presented upward trend after fall first.Glutelin rose first in the 0.428mmol/m L,and then present downward trend as a whole.Total sulphur of gliadin also fell slightly.The change trend of the glutelin and the active sulphur are basically the same.The change of surface hydrophobicity also tended to rise.4.The influence of glutelin and gliadin on the pasting properties of riceProteins oxidation indexes and the pasting properties of freeze-dried residue after preparation for gliadin and glutelin rapidly from rice with high temperature and high humidity storage quickly were measured.The correlation of the effects of protein of gelatinization properties index and oxygen indexes were also analyzed.The results showed that oxidation of these two storage proteins gliadin and glutelin occurred significantly in the process of rice storage(P < 0.05).It was inferred that protein oxidation may be occurred by lipid stress effect,which resulted in changes of protein structure properties was combined with the front two oxidation system.Protein oxidation had a significant impact on pasting properties in the storage of rice.For glutelin,the structure and function changes in the process of rice storage had a significant impact on the five rice pasting property indexes,including,PV,HS,BD,FV,SB etc.(P<0.05).of all had a Especially the content of carbonyl compound,active sulphur,and surface hydrophobicity of glutelin had significant correlation with the rice pasting property indexes(P<0.05).However,gliadin only had significant effect on the three indexes,including PV,HS and FV(P<0.05).Thus the carbonyl compound,active sulphur,surface hydrophobicity of glutelin could be as sensitive indexes for the change of rice quality evaluation.