Study On The Characteristics Of Oat Globulin Gel

Oat protein is considered comparable with animal protein as a source of plant protein.With sufficient production and abundant nutrition value,oat protein had increasingly attracted people's interest and attention.In this paper,oat globulin was used as raw material to prepare acidic,alkaline and neutral gel.Characterization from macro and micro as well as the mechanism of oat globulin gel were discussed.Oat globulin was fractionated by Osborne fractions.The Box-Behnken was used to optimize the extraction method on the basis of single factor experiment.Analysis of ANOVO showed that concentration of NaCl,ratio of liquid to solid and extraction time had significant effect on oat globulin yield.The optimum conditions obtained by response surface methodology were as follows:concentration of NaCl 8.81%,ratio of liquid to solid 17.08,extraction time 75.33 min.The resulted extraction rate and purity of oat globulin was 51.95%and 88.23%.The results of UV and fluorescence spectrophotometry suggested that heat treatment in acidic and alkaline solution could induce exposure of hydrophobic group of oat globulin.Experimental evidences showed that the formation of oat globulin gel was related to various conditions such as pH,protein content,heating temperature and time.The proper condition for preparing acidic and alkaline gel was obtained by changing the factors mentioned above.Reducing the pH,improving globulin concentration,the heating temperature and heating time were proved to be beneficial for the formation of gel by LF-NMR and rheology,meanwhile,viscoelasticity and network of globulin gel was enhanced.Ultrasonic treatment could significantly improve the solubility of oat globulin.UV and fluorescence spectrophotometry indicated that ultrasound led to the exposure of hydrophobic amino acid.The neutral gel of oat globulin was prepared in 100 ? with ultrasonic treatment,which below the denaturation temperature.LF-NMR and rheology measurements showed that ultrasonic power,ultrasonic time,heating temperature and time facilitated gel formation.SDS-PAGE was performed to analyse the effects of different treatments on protein structure of oat globulin.Two main bands which belong to basic and acidic polypeptides were degraded with acid and alkaline treatment,while ultrasonic treatment had little effect on the polypeptides.Circular dichroism determined the secondary structure of native and treated oat globulin,which proved that a-helix structure transformed to ?-sheet with acid treatment and ?-sheet structure transformed to a-helix with acid treatment.The result of ultrasound was consistent with acid treatment.The three-dimensional network of acidic,alkaline and neutral gel was observed by scanning electron microscope.Acidic gel looked like "fishing net" consisted with linear aggregation.Alkaline gel had"honeycomb-like" and "chess-like" microstructure under different pH.The network of neutral gel was composed of pearl polymerization.Atomic force microscopy and dynamic light scattering characterized the change of particle size in acidic,alkaline and ultrasonic treatment.An increase of particle size of globulin subunit was observed in acidic and alkaline solution,while there was little change of particle size of ultrasound-treated globulin compared to the control.