Preparation And Study Of Properties Of W/O/W Double Emulsion Of Microwave-treatment Rice Bran Protein

Rice bran is often used as feed,but it contains 12～22%protein.Essential amino acid composition of rice bran protein（RBP）is reasonable,and the hypoallergenic can serve as a good source of lysine supplements of special groups.Besides,it also has low allergenic.When RBP is used as particles to stabilize emulsion,its emulsification is still to be improved compared with whey protein,and there are few reports on RBP in emulsion,especially in double emulsion.In this study,RBP was used as hydrophilic emulsifier and PGPR was used as lipophilic emulsifier to prepare O/W and W/O/W emulsions.The EAI,ESI,AP of the protein and the viscosity,particle size,Zeta potential and microstructure of the emulsion were described,which combined with the main instability mechanism of the emulsion.On this basis,the emulsifying conditions of the emulsion were optimized.The effects of microwave treatment on the properties of RBP as emulsifier and the stability of the microwave treatment-RBP double emulsion were discussed and the stability of the double emulsion was characterized.The results showed that:（1）The concentration of RBP was taken as the variable,W_P/O/W,W/O/W_P,and W_P/O/W_P emulsions were prepared with RBP in the internal aqueous phase,the external aqueous phase,and both in the internal aqueous phase and external aqueous phase respectively beside the O/W_P emulsion.According to the results,W_P/O/W emulsion has higher EAI,ESI and AP than that of other emulsions.The particle size of W_P/O/W emulsion decreased with the increase of RBP content.Compared with O/W_P emulsion,the EAI,ESI and AP of RBP were increased by 76%,600%and31.41%,when the concentration of RBP was 1.5%.The viscosity of emulsion was 4times that of O/W_P emulsion,the absolute value of potential was larger,and the emulsion had good stability.（2）The emulsifying conditions of the double emulsion of RBP,such as the type of lipid,the amount of PGPR,the ratio of external water phase to primary emulsion was studied.In the double emulsion of RBP prepared from soybean lipid,0.5%PGPR was added and the ratio of primary emulsion to external water phase was 1:0.5,the protein had higher EAI and ESI,and AP reached about 99%.The viscosity of emulsion was obviously higher,the particle size distribution is more uniform and the droplet size is smaller.The absolute value of Zeta-potential was high,which means the emulsion could effectively stabilize the emulsion by electrostatic repulsion.The L^*of the emulsion was higher and apparent stability was the best.（3）The RBP was modified by microwave treatment.Compared with natural RBP,microwave treated RBP had smaller particle size,its absolute potential increased,its surface hydrophobicity increased by 13%,and the protein surface state changed from smooth spherical surface to fragment state,and there’s no change in the group.The ESI of RBP in W_mp/O/W emulsion was not significantly different from that of RBP treated with other parameters when the microwave power was 750W and the time was10min,but the EAI was the highest.The AP of protein reached to 99.5%.The W_mp/O/W emulsion prepared by microwave treatment of RBP was in the range of 33～40μm in particle size,and had good biocompatibility.When the microwave treatment power was 750W and the treatment time was 10 min,the absolute value of Zeta potential of the emulsion was the highest.The apparent stability of the emulsion was the best.（4）The effects of different freeze-thaw cycles,heat treatment cycles and UV irradiation cycles on the stability of RBP emulsion were characterized and compared.The W_mp/O/W emulsion prepared by the method studied above had good UV stability and thermal stability,the change of emulsion index was 0.00%.It was unstable in 1cycle of freeze-thaw and the change of emulsion index reached to 15.38%.When stored for 35d,coliform containing 64CFU/mL was detected.