Study On Extraction Of Rice Bran Protein And PH Or Ionic Strength Affect The Characteristics And Structure

Rice bran is the renewable agricultural with great development potential in our country, it’sprotein had high nutrition, low allergy unique nature, which was recognized as a quality plantprotein resource in the world. In order to increase the use of plant protein species and the valueof rice bran, this experiment used different methods to extract rice bran protein, and the bestextraction methods were optimized. In the viewpoint of physicochemical properties and structurecharacteristics, this study exclusively by Physical chemistry and spectroscopy methods to investigate theeffect of different pH and ionic strength on the functional properties and structure of rice branprotein, in order to provide theoretical basis for the deeper processing of rice bran protein. The main resultsare as follows:1. Analysised and compared different effects on the extraction rate and purity of rice branprotein among alkaline extraction, colloid milling assisted alkaline extraction, ultrasonic assistedalkaline extraction, colloid milling of ultrasonic assisted alkaline extraction. It was shown thatthe extraction rate of rice bran protein was significantly improved by the method of colloidmilling ultrasonic assisted alkaline and its purity was74.27%. With the method of ultrasonicpower, liquid material ratio, temperature and ultrasonic time as the response factor, and theextraction rate rice bran protein as the response values. Using Design Expert8.0.6software tocarry out response surface analysis. The optimum conditions of colloid mill and ultrasonicassisted alkaline extract rice bran protein were as follows:40mesh of rice bran, pH9, ultrasonicpower was69W, Working time was4s, pause time was2s, liquid material ratio (mL/g) was20:1,ultrasonic time was40min, treatment temperature was46℃. The theoretical extraction rate ofrice bran protein was92.14%. Furthermore, the actual extraction rate was90.84%, which was inaccordance with theoretical result. Colloid mill ultrasound assisted alkaline extraction woulddramatically enhance the extraction rate of rice bran protein in a short time, which laid a solidtheoretical foundation for further study of rice bran protein.2. Though the different pH treatment on rice bran protein, the solubility, emulsification,foaming of rice bran protein in alkaline environment were significantly better than acidic, andcomparision with solubility with solubility profile, emulsifying and foaming showed asignificant positive correlation with solubilitanty; The subunit compositon of rice bran proitein had no significant change in alkaline conditions, but acidic environment was that it waspartially cleaved macromolecule subunit into small molecular weight subunit, while the resultsof fluorescence spectra and infrared spectrum had been different trends of change in acidic andalkaline environments. These changes illustrate that the structure changes of rice bran proteincaused the change of physical and chemical properties.3. With0.05mol/L NaCl as a turning point, the solubility, emulsification emulsion stability,foaming foam stability of rice bran protein were increased first and then decreased with theincreased of concentration of NaCl. Compared with the sampale of rice bran protein which noneNaCl, the fluorescence intensity was increased with increasing ionic strength, the λmaxhappened red shift, leaded to the hydrophobic groups were exposed, surface hydrophobicity andthe content of free thiol groups increased, and significant negative correlation with solubilitanty;FTIR results showed that with0.05mol/L NaCl as a turning point, the secondary structurecontent had the trend of changes on both sides, especially the conten of β-sheet structurechanged the largest. This showed that changed in the content of β-sheet structure was the mainfactor that caused the change of physical and chemical properties.