Preparation Of Microcapsules And Their Simulated Release Characteristics In Vitro

Vitamins, peptides and proteins of bioactive substances are important functional components of food. In recent years, the use of microencapsulation technology to protect the active ingredients of food has become a very important and the most promising approach, especially in the preparation of a sustained-release microcapsules or microcapsules.In this study, the vitamin, peptides or bovine serum albumin microcapsules were prepared by coacervation, emulsion method and spray drying with some common wall materials. The encapsulation efficiency of core materials in the microcapsules and in vitro release behavior of the corresponding were determined. The major findings are as follows:1. Alginate–chitosan microcapsules were prepared in this study by coacervation basing on Ca2+ single or dual crosslinking treatment, with tyrosine, vitamin B1 and bovine serum albumin as core materials and the selected conditions of the ratio of core material to wall material of 1:10 and pH 5.0. The encapsulation efficiency of core materials in the microcapsules prepared was evaluated, and the releasing behaviors of core materials in the simulated gastrointestinal conditions were also determined. The results showed that the encapsulation efficiency of bovine serum albumin was the highest and up to 83%. It was found that core materials in the microcapsules released slowly in simulated gastric fluid than in simulated intestinal fluid, and the releasing rate was related to the molecular weights of core materials. Meanwhile, it was also shown that core materials in dual crosslinked microcapsules released more slowly than that in Ca2+ single crosslinked microcapsules in simulated gastric fluid, for the amount of core materials released from dual crosslinked microcapsules was less than 50% in 30 min duration. The results indicated that dual crosslinked microcapsules could release core materials in a limited behavior in acidic medium, but in a rapidly behavior in mild alkali medium.2. Alginate-coated gelatin microcapsules were produced to encapsulate vitamin B1 with the objective of enhancing resistibility during exposure to the adverse conditions of the gastro-intestinal tract. Gelatin microcapsules were cross-linked with the non-cytotoxic genipin and coated with alginate cross-linked by Ca2+ from external or internal sources. The results showed that core materials in the microcapsules released slowly in simulated gastric fluid than in simulated intestinal fluid, and core materials in the alginate coat microcapsules released more slowly than that in uncoated gelatin microcapsules in simulated gastric fluid. The alginate coat prevented degradation of the gelatin microcapsules in simulated gastric juice, and the accumulated release of core materials is 70%, 60% by the internal and external Ca2+-source methods, respectively. The results indicated that the alginate coat microcapsules protects core materials during exposure to adverse environmental conditions.3. Gelatin was cross-linked by ferulic acid and genipin, and whose cross-linking degree was 10.4% and 54.7%, respectively. In degradation study in vitro, free amino content of raw gelatin and modified gelatin were nearly unchanged when they were put in a simulated gastric fluid for 60 min, which indicated they were degraded a little or not degraded. In simulated intestinal fluid, raw gelatin and modified gelatin were both degraded and modified gelatin was degraded slower than raw gelatin.4. Microcapsules containing vitamin B1, ACE inhibitory peptides or bovine serum albumin were prepared by the spray-drying technique using EudragitⅡand Surelease as coating materials at the selected conditions of the ratio of core material to wall material 1:10. The appearances, encapsulation efficiencies of the microcapsules, together with their release behaviors in the simulated gastrointestinal condition, were studied. The results showed that the encapsulation efficiencies of the microcapsules prepared were more than 98%. The microcapsules prepared with EudragitⅡshowed smooth surface, while the microcapsules prepared with Surelease were depressed microcapsules. The accumulated release of core materials from the microcapsules prepared by EudragitⅡwas less than 10% after 120 min in simulated gastric fluid, but near to 100% after 1 h in simulated intestinal fluid. At same time, the accumulated release of core materials from the microcapsules prepared by Surelease was more than 70% after 120 min in the simulated gastric fluid or intestinal fluid. The result indicated that the accumulated release of the core materials from the microcapsules prepared by EudragitⅡis small in simulated gastric fluid.5. From above experiment, the core materials from the microcapsules prepared by EudragitⅡrelease the slowest in simulated gastric fluid, but it can release fast in in simulated intestinal fluid. The result indicated that microcapsules prepared by EudragitⅡcould release core materials in a controlled release behavior in gastrointestinal conditions.