Extraction Of Millet Prolamin And Effects Of Deamidation On Its Properties And Structure

Millet is a traditional crop in China and is widely consumed by people.As the main storage protein of millet,millet prolamin accounts for 60% of millet's total protein.Millet prolamin has strong hydrophobicity,poor solubility,and low digestibility,resulting in Low bioavailability of the protein.In this paper,millet was used as the raw material,and the response surface method was used to optimize the extraction process of millet prolamin,and the millet prolamin was modified by acid deamidation.The properties and structure of the small miol-soluble protein were analyzed from the aspects of solubility,surface hydrophobicity,denaturation temperature,microstructure,secondary structure,tertiary structure,etc.,in order to provide a theoretical basis for the application and product development of the later stage.A response surface method was used to optimize the extraction process of millet prolamin,and on the basis of single factor Box-Behnken response surface test,the optimized extraction conditions of millet prolamin were as follows:ethanol concentration 80%,solid-liquid ratio 1:8(g/mL),extraction time2.5 h and extraction temperature 40?.Under these conditions,the yield of millet prolamin was3.284%,which was very close to the predicted value of 3.174% and has a high consistency with the response surface model,indicating that the model can better predict the extraction conditions of millet prolamin and has high reliability.Different degrees of deamidation protein were prepared by 0.25 mol/L of hydrochloric acid to determine the physicochemical properties and peptic changes of different degrees of deamidation protein.Under pH 7.5 and pH 1.5 conditions,the solubility of millet prolamin increased first and then decreased with the increase of deacylation degree.The surface hydrophobicity decreased with the increase of deamidation.Deamidation has little effect on water retention and oil retention.The oil retention rate is maintained at about 2.793(g / g)and the water retention is maintained at about 2.374(g / g).The in vitro digestibility of millet prolamin indicated that the in vitro digestibility of millet prolamin after deamidation treatment increased from 71.46% to 82.31%.A study on the structural changes of deamidation proteins showed that the SEM showed that the deamidation prolamin were granular or spherical,with smooth surface and close intermolecular connections.And as the degree of deammonia increased,the prolamin showed loose porous structure.DSC indicated that the denaturation temperature of the prolamin increased after deammonia treatment.Fourier transform infrared spectroscopy showed that the millet prolamin ?-helix decreased and the ?-sheet content increased,the ?-helix / ?-sheet ratio decreased,and the molecular flexibility of millet prolamin increased.AFM showed that after deammonia treatment,the millet prolamin was spherical,and when the deamidation reached 40.25%,it was spherical and more fibrous.Endogenous fluorescence indicates that the fluorescence spectrum of the millet prolamin after deamidation modification is red-shifted,and the deamidation modification is beneficial to the conformation expansion of the millet prolamin,and the tertiary structure of the protein is greatly changed.There is a certain correlation between the physical and chemical properties and structural changes of deamidized millet prolamin.