Broken Rice Protein-Saccharide Graft Prepared By Ultrasonic And Wet Heating Method

Broken rice protein had low solubility,which resulted from high surface hydrophobicity and excess disulfide bond.The above physicochemical properties limited the application of broken rice protein in food industry.The glycosylation of protein was simple to operate,without any chemical additives,and which could improve the functional properties of protein.In the paper,the effect of ultrasonication on the wet heating way was studied systematically.We chose broken rice protein as material to grafted with lactose and carrageenan and optimized the process conditions,then studied grafts' functional and structure.The present work aimed to develop a fast and efficient method for protein modification.A grafting modification of broken rice protein with lactose and carrageenan under the condition of ultrasonic assisted.The effects ultrasonic time,ultrasonic power,protein concentration on degree of graft and browning degree were studied.The rate of grafting reaction raised greatly compared with traditional wet heating method.The time of graft reaction was shorted and the browning degree of grafts was lighten when achieved the same degree of graft.The NSI improved 8-10 times in neutral pH water.At the same time,the isoelectric point of broken rice protein moved from pH5 to pH4 after its grated with Saccharide Under the conditions of ultrasonic power 300 w,ultrasonic time 30min,protein concentration12 mg/mL,we obtained broken rice protein-lactose grafts with a graft degree at 42.89%.Under the conditions of ultrasonic power 400 w,ultrasonic time 50min,protein concentration 10 mg/mL,we obtained broken rice protein-carrageenan grafts with a graft degree at 37.12%.Compared with the broken rice protein under the same ultrasonic treatment,The solubility of grafts was significantly improved at pH levels rangihg from 3-10;The grafts maintain the NSI at 32%and trend stability;emulsion ability increased significantly;foam ability improved not obvious;surface hydrophobicity lowed compared with broken rice protein.Protein-lactose graft' ability of removing radicals to its maximum Under the conditions of ultrasonic time 30min and Protein-carrageenan graft' ability of removing radicals to its maximum Under the conditions of ultrasonic time 60min.We investigated the amino acid content,particle size distribution,secondary structure,denaturation temperature,surface hydrophobicity,fluorescence feature,chemical shift and microstructure and its grafts using the methods of amino acid analyzer,Laser light particle size analyzer,ANS fluorescent probe,Fourier infrared spectrometer,differential scanning calorimeter,NMR equipment and scanning electron microscope.The results showed that lysine and arginine contents decreased most significantly.The particle size distribution revealed that grafts' particle size was smaller than broken rice protein.However,the content of nonregular coil structure of grafts' protein were gradually increased.The surface hydrophobicity decreased,furthermore,the denaturation temperature maintained at 48.65?.The result of fluorescence spectrum showed that grafts possessed the characteristic of Maillard reaction and grafts'fluorescence intensity changed.According to 13C-NMR spectra analysis,the Ci,C2 and C3 of the lactose were involved in forming chemical bond.Moreover,the images of SEM revealed that the surface structure of broken rice protein was different from grafts.More details,the steel disc structure of broken rice protein disappeared,while whose grafts became loose.