Influence of emulsification methods and use of colloidal silicon dioxide on the microencapsulation by spray drying of turmeric oleoresin in gelatin-starch matrices
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Microencapsulated turmeric oleoresin can present improved curcumin stability and be easily applied in hydrophilic systems. Most of the microencapsulation techniques rely on the initial emulsification of the core material in the wall biopolymers and this step affects the encapsulation efficiency and properties of the resulting microcapsules. The objective of this work was to evaluate the effects of different emulsification methods, the use of colloidal silicon dioxide and Tween 80 as additives, and the rheological behaviour of the encapsulating gelatin-starch dispersions on the emulsion stability, encapsulation efficiency, and yield of turmeric oleoresin microcapsules produced by spray-drying. The encapsulating matrices were prepared with varied concentrations of modified starch (from 0.22–0.317 g/g (22–31.7 wt%), dry basis) and gelatin (0–0.06 g/g (0–6 wt%), dry basis). The microstructure of the emulsions was evaluated through optical microscopy and small amplitude oscillatory shear rheology. The emulsification of turmeric oleoresin was performed by the following methods: high-shear mixing, using a rotor-stator homogenizer, with and without addition of Tween 80 as a surfactant; and by ultrasound homogenizer with and without the colloidal silicon dioxide (Aerosil 200). The homogenization method presented considerable influence on the emulsion stability and on the average droplet sizes in the emulsion. The concentration of gelatin directly affected the emulsion and microcapsule properties. Ultrasound homogenization and the use of colloidal silicon dioxide resulted in the highest encapsulation efficiency of turmeric oleoresin in the low total-solid formulations.