Study On Gelatin/cmc Complex Coacervate Microencapsulation And New Crosslinking Agents

Complex coacervation has many advantages such as the high payloads achievable, the controlled release and sustained release possibilities, etc. The most commonly used microcapsule wall materials are gelatin & gum arabic, however, gum arabic is expensive and its quality is irregular. Usually adopted toxic crosslinking agent formaldehyde limited extensive application of microcapsule products. It is of great importance to develop low-cost coacervation wall materials and non-toxic crosslinking agents. Preparation method of spherical multinuclear microcapsules by gelatin/carboxymethyl cellulose (CMC) coacervation was investigated. Cross-linking parameters in the process of tea polyphenols-hardened microcapsules were optimized. Mechanism of polyphenols crosslinking proteins was also studied. The results were as follows:The optimal technical parameters for preparation of cinnamaldehyde microcapsules by coacervation of gelatin/CMC were as follows: gelatin/CMC ratio 9:1, pH4.6, wall material concentration 1%, core/wall ratio 2:1. Microcapsules made under these parameters have nice spherical shape and uniform particle size. The encapsulation yield and efficiency were 97.01% and 86.55%, respectively. The heat-stability of microcapsules was investigated, TGA curves showed that at 150°C, the release rate of cinnamaldehyde decreased dramatically after microencapsulation, which has direct ratio relations of the core/wall ratio.The hardening effectiveness was significantly affected by the change of the hardening pH, time and tea polyphenols concentration. The optimum hardening parameters were as follows: hardening pH 10.0, hardening time 12 h, tea polypenols concentration 0.1 g/g gelatin. The mechanism research showed that polyphenols can only react with proteins after they were oxidized to polyquinones, there were no specific reaction sites and almost all N-terminal amino acid participated in the crosslinking reaction.Properties of microcapsules made of different wall materials (gelatin/CMC and gelatin/gum arabic) and the hardening effect of different crosslinking agents (polypenols, formaldehyde and transglutaminase (TG)) were compared. Comparing with gelatin/gum arabic microcapsules, gelatin/CMC microcapsules have similar morphology, better embedding effect, thermal stability, and much lower cost. The result of 80℃water-bath and TGA showed that compared with formaldehyde and TG, tea polyphenols exhibited similar hardening effectiveness, and can replace them as crosslinking agent of coacervation microcapsules.Physical and chemical properties of sprydried microcapsules were studied. The moisture was 3.32% and fit for storage; the repose angle was 38.2°, and the fluid was good; The loading of microcapsules was 40.74%. The microstructure valued by scanning electron microscope showed that microcapsules were integral and the surface was not destroyed through sprydrying. TGA curves showed that microcapsules made by sprydrying have fine thermal stability.