Study On The Improvement Of Solubility And Stability Of Rice Glutelin And Its Application

Rice protein is a rare high-quality non allergenic protein.However,the solubility of the most abundant glutelin component（80%dry basis）in rice protein is very poor near neutral pH,which seriously limits the functional properties of rice protein and the development of related products.Therefore,improving the solubility and stability of rice glutelin is the necessary premise to promote the full utilization of rice glutelin.Based on this,the purpose of this study was to develop a plant protein beverage with rice glutelin.This study explored the effect of heat treatment on the structure and solubility of rice glutelin under alkaline conditions.The electrostatic interaction between carboxymethyl cellulose（CMC）and glutelin was used to further improve the stability of rice glutelin under neutral and weak acid conditions,and the effect of typical heat sterilization on the stability and structure of their electrostatic composite solution was investigated.The shelf life and stability were evaluated by tracking and predicting the physicochemical properties.The main results are as follows:1.Effect of alkali-heat treatment on structure and properties of rice glutelinRice glutelin was heat treated at different temperatures（60℃,80℃,100℃）for30,60 min in alkaline solution（pH12）.The results showed that compared with natural protein,the solubility of glutelin in pH7 solution increased by about 3 times,the foaming power increased by about 2 times and had good foam stability after heating at 100℃for 60min.In addition,heat treatment reduced the average particle size of glutelin from 325 nm to 225 nm（100℃,60 min）,changed the surface net potential to-25 mV,increased the hydrophobicity and decreased the content of disulfide bond.The secondary and tertiary conformations of glutelin had changed and the structural flexibility was enhanced.2.Carboxymethylcellulose improving the stability of rice glutelin via electrostatic interactionTurbidity method was used to explore the effects of glutelin-CMC mass ratio,CMC substitution degree and pH value on the formation of rice glutelin-CMC electrostatic complex.It was found that CMC1.2 with higher substitution degree showed better stability than CMC0.7 with lower substitution degree.When the glutelin-CMC1.2 mass ratio was 10:1,the complex solution showed better stability in the range of pH5.5～7.The effects of typical sterilization conditions（80℃and 100℃）on the structure,physical and chemical properties and stability of glutelin-CMC1.2composite solution were further investigated.Dynamic light scattering and laser confocal imaging observations showed that the average size distribution of the complex solution became more uniform after 80℃,the surface potential changed from-20 mV to-45 mV,and the secondary structure of solution became more orderly.In addition,the rheological data showed that the complex solution had a certain viscoelasticity,and after heat treatment,the viscoelasticity was higher,and the system was easier to maintain a stable state.3.Quality change of rice protein plant beverage during storage and establishment of shelf life modelThe rice protein compound beverage（pH5,6）was prepared by glutelin-CMC1.2（6:1 mass ratio and 10 mg/mL of glutelin concentration）.The changes of physical and chemical properties and bacterial colony number of the beverage during storage were tracked at 4℃,25℃and 40℃.The results showed that the average size of beverage increased,which resulted in the precipitation of apparent form,and the color and smell changed with the extension of storage time.The beverage with pH6 had stable morphology,smaller average particle size and stronger sweet and sour taste after sterilization at 80℃.Based on this,the microbial shelf-life model of rice protein plant beverage was established by measuring the total number of colonies in the storage period:A=9424e^0.0664t.The shelf life of rice protein plant beverage is 25 days at room temperature（20℃）.The results showed that the combination of alkali treatment and heat treatment could improve the properties of rice glutelin,and the electrostatic binding of CMC with rice glutelin could improve the stability of rice glutelin,so as to prepare the plant protein beverage which was not easy to precipitate.