Preparation Of Oil-containing Microcapsules Based On Soybean Protein Isolate-sodium Dodecyl Sulfate By Complex Coacervation And Their Characterization

Soybean protein isolate (SPI) and sodium dodecyl sulfate (SDS) were chosen as wall material to form microcapsules by complex coacervation. Hexadecane, a simulacrum of insect sex pheromones, was used as the core material in the first step. Based on the primary results, insect sex pheromones species (dodecanol acetate and oleyl acetate) were encapsulated. The morphology of microcapsules and release of core material were characterized. Because three components were chosen as different core materials, this paper included 3 parts: (1) Preparation and characterization of SPI/SDS microcapsules used hexadecane as core material; (2) Preparation and characterization of SPI/SDS microcapsules used dodecanol acetate as core material; (3) Preparation and characterization of SPI/SDS microcapsules used oleyl acetate as core material.(1) Preparation and characterization of SPI-SDS microcapsules with hexadecane (HD) as core material. In a first step, isoelectronic point of SPI was found by several means. Then complex coacervation of SPI and SDS was optimized by varying experimental conditions. At the optimized coacervation condition, hexadecane was wrapped in wall material with different core/shell ratio and agitation rate. Appearance of microcapsules was measured by optical microscope, and drug loading of microcapsules was investigated by gas chromatography. Release of HD was measured at constant temperature and humidity (T=35oC,RH=50%). It was observed that a maximum complex coacervation yield of 85% was achieved with 0.6% of wall material concentration for SPI/SDS ratio of 5/1 at pH 3.5. Increasing core/shell ratio, the loading was increased, and the release rate was increased thereby. Release of HD from microcapsules showed a quick start in 3-5 days, then it remained at a constant rate until HD completely released.(2) Preparation and characterization of SPI-SDS microcapsules with dodecanol acetate (DA) as core material. Firstly, dodecanol acetate was synthesized by esterification between dodecanol and acetic acid in the presence of p-toluenesulfonic acid as catalyst. DA was encapsulated by complex coacervation between SPI and SDS. With the same wall material concentration, increasing core/shell ratio, the encapsulation rate was increased, while the loading was increased and so was the release rate. Release of DA was slower than HD at the same loading. In initial stages, quick release period of DA from microcapsules is shorter than HD distinctly. Constant release could reach nearly 80 days. Hereafter with the decrease of DA in capsules, release rate of DA clearly reduced until DA completely released.(3) Preparation and characterization of SPI-SDS microcapsules used oleyl acetate (OA) as core material. The optimized SPI/SDS system was used for the encapsulation of insect sex pheromone component OA, synthesized by esterification between oleyl alcohol and acetic anhydride in the presence of p-toluenesulfonic acid as catalyst. OA was encapsulated by the former method. Similar to the encapsulation of HD and DA, the encapsulation rate was increased when increasing core/shell ratio at the same wall material concentration, while the loading and release rate were both increased. Release of OA was evidently slower than that of HD and DA at the same drug loading, and the release curve seemed to get a transition period. Release of OA showed slightly quick start within 40 days, henceforth release of OA kept at relatively constant rate until OA completely released.