Preparation Of Controlled-release Emulsions Based On Interfacial Control Technique And Their Application Exploration

The aggregation rate between protein molecules during coagulation process determines the gel network structure to a great extent.A quick aggregation rate of protein molecules would lead to random aggregation and coarse gel microstructure with large pores and a low water holding capacity(WHC).Oppositely,ordered aggregation results in homogeneous structure with a high WHC value,which is beneficial for improving the quality of food based on protein gels.Take the bittern tofu as example,the preparation of emulsion system based on interfacial control technique was considered to control the release of coagulant MgCl2,in order to solve its quick coagulation problem and to further induce the formation of an ordered gel structure.Water-in-oil(W/O)and water-in-oil-in-water(W/O/W)emulsion system were used to encapsulate and control the release of MgCl2.Main research and conclusions were as follows:1.The addition of MgCl2 and protein(WPI,BSA)contributed to the stability of W/O emulsions.The improving effect was more significant when MgCl2 concentration was lower than 1.2 M.The presence of MgCl2 significantly reduced the interfacial tension between water/oil phases and prevented the Ostwald ripening of emulsion droplets.In addition,the addition proteins improved the stability of W/O emulsions as they can decrease the particle size and interfacial tension value of W/O emulsion and increase emulsions’ viscosity.It was possible that the addition of BSA and WPI could partially replace PGPR molecules.2.The interfacial dilational rheology was used to investigate the effect of protein,MgCl2 and PGPR on the interfacial viscoelastic properties of oil/water interface.The results showed that,with the increase in PGPR concentration,the interfacial tension of oil/water system decresed,and reached equilibrium when the PGPR concentration was 1.0%.The interfacial dilational viscoelastic modulus tended to increase and then exhibited a decreasing trend.At 1.0%PGPR,the irreversible adsorption of BSA and WPI could inhibit the exchange/diffusion of PGPR molecules at the interface,thus increasing the strength of interface.The presence of MgCl2 could increase the adsorption of PGPR molecules at the interface,therefore increasing the dilational viscoelastic modulus of PGPR and PGPR/protein mixture.3.The addtion of magneisum salt in the inner aqueous phase could drive the water transfer between the two aqueous compartments and a final breakdown of emulsion droplets.The concentration of encapsulated MgCl2 affected the long-term stability of W/O/W double emulsions.The change in the particle size and viscosity of double emulsion during storage could reflect the water transfer rate and direction.The main release mechanism was "swell-breakdown".The addition of protein such as gelatin and BSA enhanced the stability of W/O/W emulsion and retarded the release of Mg2+ from emulsions.4.Both W/O and W/O/W emulsion coagulants could significantly improve the yield,WHC and texture of tofu.The release rate of Mg2+ could be controlled by adjusting the concentration of protein and MgCl2 in the inner aqueous phase,and thus controlling the quality of tofu gel.The decrease in MgCl2 concentration reduced the reaction rate between soy protein molecules and magnesiμm ions,thus decreasing tofu yield,increasing the hardness of tofu.With the increase in WPI concentration,the release rate of Mg2+ from W/O emulsion decreased and this could retard the aggregation rate of protein molecules,improving the quality of tofu.In addition,with the increase in BSA concentration,the prepared W/O/W double emulsion could increase the tofu yield and quality of tofu.The color became whiter and the hardness of tofu decreased.5.During tofu coagulation process,the amount of the total water and free water decreased while the amount of bound water increased,which demonstrated that the free degree of water had decreased.With prolonged time,the soy gel structure became denser and the network pores became smaller,and this resulted in a higher content of free water.The prepared soy gel network structure induced by MgCl2 alone exhibited a coarse and unordered structure.The gel structure of tofu prepared with W/O and W/O/W double emulsion coagulants was more homogeneous and ordered.In addition,the protein aggregates were dense with smaller network pores.