Abstract

Gac oil was encapsulated in the hydrogel bead using alginate as carrying material by dripping method. Different parameters of all three stages of the encapsulation process were investigated: alginate concentration (emulsification stage), nozzle height, extruded pressure (bead formation stage) and calcium flow rate (bead stabilisation stage). Gac oil emulsion was characterised through the droplet’s size and emulsion stability. Bead’s morphology including size and shape was evaluated by image analysis using ImageJ software. Encapsulation efficiency was evaluated through encapsulated Gac oil and beta-carotene stability during storage at room temperature during 8 weeks. The beta-carotene content was determined through spectrometric absorbance in n-hexane at 452 nm. Results show that alginate is suitable to use as carrying material for Gac oil encapsulation with a moderate encapsulation efficiency of 62.5 ± 0.8 %. Gac oil emulsion had a droplet’s size in range 1-2 m and showed a good stability at low alginate concentration. The bead’s morphology was highly affected by the height of nozzle and the extruded pressure while the flow rate of gelling solution expressed no influence of the bead’s morphology. The most spherical bead and the biggest bead’s diameter were obtained with the lowest distance at 150 mm and the lowest pressure at 2 MPa. A smaller size but more irregular shape can be obtained with the higher distances and higher pressures. A progressive decrease in beta-carotene content during storage was observed for both bead’s surficial and total level. The degradation of beta-carotene in Gac oil bead fitted the first-order reaction with degradation rate constant k of 0.0020 day-1 and a hafl-life t1/2 equal to 347 days which show a good stabiltity of Gac oil in alginate bead.