Comparative study on properties of rice bran oil microcapsules prepared by spray drying and freeze drying

Microencapsulation of rice bran oil using Arabic gum and whey protein concentrate as wall material was studied through both spray drying and freeze drying methods. To this aim, oil -in- water emulsions containing 4 % rice bran oil in an aqueous solution including 20 or 25% of total wall material composition were produced with ultra- turrax homogenizer. The emulsion containing 100% Arabic Gum has a minimum droplet size of (0.36 µm) while the maximum droplets size of (0.96 µm) was obtained for the emulsion containing 100% whey protein concentrate and for other ratios of these wall materials the droplets have sizes ​​between these two amounts. Droplet size and viscosity measurements show that the stability of emulsions was influenced by the concentration and type of wall material. Also, the method of drying of emulsion, not only was effective on the size of the microcapsules, but also on the encapsulation efficiency and oil retention in the capsules. The results indicated that the maximum encapsulation efficiencies in the Arabic gum of 60% concentration for wall compound (the total of gum and whey protein concentrate) were 90% through spray drying and 68% through freeze-drying method. Of the two methods, microcapsules obtained from spray drying, while maintaining the regular spherical structures, showed more oil retention during six weeks storage.