| Dripping method appl ied for microcapsules preparation has been focused by many reseachers and producers. Drops be extruded are usually gelled or solidified by some chemical reagent in existing preparation procedure. Chemical residue will be existed in microcapsules prepared by this procedure. It is unfavorable for food application.Based on gelation properties of agar, a new procedure was investigated. Core material was mixed with wall material (agar is a main polymer), and emulsified. After that, the resulting emulsion was dripped into cool ing bath, the wall material would be cooled and gelled. Microcapsules prepared by this procedure than were dessicated by suitable way. In this study, research was focus on:(1) viscosity and gelation properties of the main. wall material-agar; (2)establishment and optimization of a procedure for microcapsules preparation based on agar by dripping method; (3)the properties of ultrasound treated starch, and the properties of composite of the treated starch and agar as wall material; (4) the properties of composite based on maltodextrin-agar as wall material; (5)quality characteritics of the microcapsules prepared by the optimized procedure.This study is aimed at the establishment of a new procedure for microencapsulation based on agar by dripping method, producing final microcapluses free from chemical residuces or abnormal favor and the application for oil or oil soluble substances.Achievement and conclusion as following:(1)Viscosity of agar solution was greatly effected by its concentration, temperature and the solvent water hardness. It was ordered as following: concentration>water hardness>temperature, at the range of 5-8, pH has no significant effects on viscosity. The factor affecting gel strength from strong to weak was ordered as following:concentration>gelation temperature>water hardness. (2) It is favorable for encapsulation based on agar by the preparation procedure estblished in this study. The optimized procedure was detailed as following: emulsion composited with 3% agar,0.3% Tween 80 and 4% oil; cooling medium temperature is set at 5℃and cooling bath depth is 30cm; Dried under vacuum at 35℃.(3) After treated by ultrasound, the viscosity of the starch paste was dramatically decreased, and the solubility was increased significantly. The properties of the resulting film made by the treated starch paste also were improved. Great improvement in oil loading and encapsulation efficiency was achieved based on this treated starch and agar.(4) Significant change in viscosity was revealed when the solutions is mixed agar and maltodextrin with different hydrolyzation degree. Effctive encapsulation was achived when the emulsion prepared from DE5 maltodextrin and agar, but if the concentration of the maltodextrin in emulsion was incresed to 10%, tailed microcapsules would be formed. It was hard to achive an high efficient encapsultion if the DE18 was mix in the emulsion.(5) Uniform particles with intact appearance will be achieved if it was prepared by optimized procedure and improved emulsion composition. Highest oil loading was found in USAG, minor in AG and MAG. Good oxygen insulation for all microcapsules was revealed and the oil peroxidaton was also significant decreased. Above melt temperature of agar, oil in capsules would be released in a short time. Below melt temperature of agar, oil would be released continuously in a low rate, oil releasing rate from fast to slow is MAG,AG and USAG.
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