Microencapsulation of turmeric oleoresin: complex coacervation and crosslinking strategies for improving encapsulation efficiency and stability in gastrointestinal simulated fluids

Turmeric oleoresin microcapsules were prepared by complex coacervation of gum arabic (GA) and chitosan (Ch) using genipin as a crosslinker. For this propose, the effect of pH and the biopolymer mass ratio (R-GA/(ChpH)) on the zeta-potential and coacervate yield and their viscoelastic properties were evaluated. A liquid-like behavior was found for all the samples in the small- and large-amplitude oscillatory shear regions, with sample R-5(4.5) having the highest viscoelastic properties. Samples R-6(3), R-5(4.5) and R-4(6) with the highest coacervate yield (similar to 98%) for each pH chosen to produce the microcapsules. Then, turmeric oleoresin-gum arabic emulsions were produced and characterized. The pH affected the droplet size and charge. At pH 3.0, the droplets were about 50 nm and had a negative charge. At pH 4.5 and 6.0, the droplets were larger but more negatively charged. These emulsions were coated with chitosan and crosslinked with genipin were lyophilized to make microcapsules, showing high encapsulation efficiency (>98%) and low surface oil content (4.5-9.0%). The crosslinked turmeric oleoresin microcapsules showed lower swelling and water uptake in gastrointestinal media than did the uncrosslinked powders. The results of this research will contribute to the knowledge of coacervate systems for nutraceutical applications.