| Microencapsulation is the process of preparing semi-permeable or sealed capsules using natural or synthetic macromolecule materials to embed solid particles, liquid drops or gas. Choosing the suitable wall-materials and effective methods to prepare stable microcapsules (MCs) have been the key target to researchers in the pharmaceutical and food industries. Fish oil is full of co-3 fatty acids such as EPA and DHA, which are functional ingredients to consumer. However, fish oil has poor solubility in water and is sensitive to light, heat and oxygen, which limits its application in food industries. Chitosan (CS) is a kind of natural alkalescency polysaccharides with polycation; and gum acacia (GA) is a kind of natural gel with carboxyl groups on molecular structure. Both CS and GA are absolutely safe to consumer as food materials, and have abundant sources. So it's a significant task for us to prepare fish oil MCs using CS and GA as wall materials by complex coacervation through electrostatic interaction.The low molecular weight chitosan samples were prepared by the method of acid degradation in the HCl+Ethanol mixtures. Preliminary investigations indicated that the different molecular weights of chitosan were 1080kDa,450kDa and 230kDa, and the DD were 87.8%,88.1%,87.6% respectively. The FTIR spectroscopic studies showed the stability of different Mw CS(1080kDa and 230kDa) prepared by degradation and appearance of well-defined characteristic peaks of saccharide chains and the primary amino group structures.The influences of different factors on CS/GA complex coacervation were investigated. The results of experiments indicated that the yield of coacervation and transmittancy of equilibrium phase could be affected by the mass ratio of CS to GA, total concentration of CS/GA, pH value and ionic strength. The higher yield of coacervation could be obtained at the following experimental conditions:the mass ratio of CS:GA was 1:6-1:8, the concentration of CS/GA was 3-6%, pH was 3.5-5, and low ionic strength.The results indicated the reaction temperature had miner infection on CS/GA coacervation, because the coacervation yields were continuously above 85% with the increase of the reaction temperature from 20 to 60℃. The results also showed that the least reaction time of CS/GA coacervation were 30 minutes to ensure complete reaction. The FTIR spectroscopic studies showed absence of the characteristic peaks of-NH2 and-CH-NH2 in the coacervation samples, which could be suggested the electrostatic interaction performed between the amino group of CS and carboxyl of GA in the formation of coacervates.Under the experimental conditions of obtaining high coacervates yield, the better preparing processes of wet CS/GA fish oil MCs were determined and the physicochemical properties of MCs were tested. The results of experiments showed that the molecular weight of CS performed an important role in coacervation. The CS (Mw1080kDa) was easy to agglomerate with GA and hard to coacervate. The MCs prepared by CS (Mw450kDa)/GA were anomalous and reliable to conglutinate each other. The MCs prepared by CS (Mw230kDa)/GA were spherical shape with satisfactory structural integrity and no conglutination. The results of experiments showed the CS (Mw 230kDa) was suitable experimental sample as the wall material of MCs.The conditions of fish oil MCs prepared by CS (230kDa)/GA complex coacervation were the followings:the concentration of CS/GA was 3-5%, the mass ratio of CS:GA was 1:6-1:8, pH 4.0-5.0, the temperature was 20℃, and the reaction time was 30 min. The MCs prepared by coacervation were investigated by light microscopy. The results showed that the MCs were spherical shape with regular structural integrity and uniformity, no conglutination and higher yield of MCs in the following experimental conditions:the total concentration of CS/GA was 5%, the mass ratio of CS/GA was 1:7, pH 4.5, the temperature was 20℃, and the reaction time was 30 min. The mean particles size of MCs prepared under such condition was 16.3μm, the entrapment efficiency of fish oil and the availability of wall materials was 75.33%,81.01% respectively.Wet CS/GA fish oil MCs were prepared through the determined laboratory processes; then dried MCs were obtained by freeze drying. The SEM photographs showed that dried MCs were generally porous spheres, and part of them had break walls. Dried MCs could comeback their original shapes by rehydration. The mean yield, efficiency of microencapsulation, and the oil loading rate of the dried MCs were calculated by measuring the content of surface oil, total oil and moisture. The experimental results were 72.63%,67.53%,31.59% respectively.During the process of preparing dried CS/GA fish oil MCs, the POV of fish oil has been increased, while the oxidation of fish oil could be inhibited by adding antioxidant TBHQ (250mg/kg fish oil).More systematical experiment of the CS/GA fish oil MCs, such as the drying technologies and the protective functions of dried CS/GA MCs to fish oil, will be performed in future. v... |
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