Complex Coacervation Of Gelatin And Sodium Carboxymethyl Cellulose And Preparation Of Microcapsules

Complex coacervation microcapsules have many advantages such as the high payloads achievable,and the controlled release,etc.The combination of gelatin and gum Arabic is the most common system used in studies of complex coacervation,however,gum Arabic is expensive with unstable properties.Sodium carboxymethyl cellulose(CMC)with wide source and low-price,which expected to replace the gum Arabic so as to reduce the cost of microcapsules by complex coacervation method.However,due to the large number of classes and properties parameters,the key characteristic of CMC and gelatin suitable for the microencapsulation by complex coacervation should be determined,which is of great significance for the development of microencapsulation.In this thesis,the effects of CMC viscosity and gel strength of gelatin on the formation of and properties of complex coacervates were investigated.The complex coacervation behavior of preferred gelatin/CMC was discussed.On this basis,the preparation parameters of cinnamaldehyde microcapsule by complex coacervation were optimized.The effects of CMC viscolity and gel strength of gelatin on the formation of complex coacevates and interfacial properties were investigated.The result showed that coacervates with better morphology,good size distribution and highest yield were observed with gelatin at different gel strength to CMC with differnet viscolity at mass mixing ratio of 9:1 and pH 4.50.High emulsifying activity and low interfacial tension was observed with gelatin(200,Bloom g)/CMC(FL9),in which the formation of spherical multinuclear microcapsules were observed with the yeild and efficiency were 87.56% and 91.03%,respectively.By changing total concentration,mixing ratio and mixing order,the phase boundaries of gelatin/CMC/water three system were determined,then the phase diagram of gelatin/CMC complex coacervation system were conducted.The complex coacervation behavior of between gelatin and CMC was investigated.It was found that pH had an important effect on the phase separation behavior of gelatin/CMC system.Compared with the three-phase diagram at pH 4.50,the phase separation region at pH 3.50 was greater than that at pH 3.50,which indicating that phase separation could occur at higher charge density.The critical pH(pH?1)corresponding to the beginning of the formation of the insoluble comple of gelatin/CMC system were determined by turbidity titration curve at mixing ratio of1:5,1:3,1:1,3:1,5:1,9:1(w/w),while the critical pH(pH?1)were 2.97,3.10,3.76,4.23,4.71,4.80,respectively.The formation process of gelatin/CMC complex coacervates was analyzed by soft particle theory,Fourier transform infrared spectroscopy and circular dichroism spectroscopy.The results showed that the absolute value of gelatin was equal to that of CMC in the formation of insoluble complex at pH?1 of different ratio of gelatin to CMC.The evaluation of coacervates formation behavior revealed that there was no chemical bond between gelatin and CMC.The gelatin molecules experienced a conformational change in its secondary structure from a flexible pattern to an ordered PPII helix.The cinnamaldehyde microcapsules was prepared by gelatin/CMC complex coacervation system.The morphology and encapsulation capability of the cinnamaldehyde microcapsules were evaluated under different pH,wall material concentration,emulsifying conditions andstirring rate.The optimal conditions were as follows: pH 4.50,wall material concentration 1%(w/v),mass ratio of gelatin and CMC was 9:1,the high-speed dispersion rate was 10000 r/min,dispersion time was 2 min,stirring rate 400 r/min,Under these conditions,the yield and efficiency were 88.92% and 92.13%,respectively.The thermal stability and high saltion stability of cinnamaldehyde microcapsules were investigated at different core material concentration.The thermal stability and high saltion stability of microcapsules were better when the core material concentration was 1.0%.Hence,the cinnamaldehyde microcapsules prepared at the core material concentration were applied to tobacco.The result showed that transfer rate of cinnamaldehyde in the mainstream flue gas was improved by microencapsulation,and the loss rate of cinnamaldehyde in the process of drying was reduced.