Antioxidant activity and controlled release analysis of red ginger oleoresin (Zingiber officinale var rubrum) encapsulated in chitosan cross-linked by glutaraldehyde saturated toluene

The aim of this study was to determine encapsulation efficiency, particle size, and characterization of red ginger oleoresin microcapsules such as controlled release, morphology microcapsule and also determine the antioxidant activity of red ginger oleoresin microcapsules. The red ginger oleoresin was dispersed in chitosan and stirred to form an emulsion, then added to corn oil and stirred again to form a second emulsion. Glutaraldehyde saturated toluene (GST) as a crosslinking agent was added dropwise into the emulsion and continues to be stirred for the solidification process. Chitosan microspheres filled with red ginger oleoresin were washed using petroleum ether followed by hexane and then dried in the oven. Controlled release analysis was carried out in a phosphate buffer medium at pH 7.4. Red ginger oleoresin microcapsules produced the highest encapsulation efficiency was 82.54 ± 3.5 with a mean diameter ranging from 110.12 ± 12.2 to 161.42 ± 40.1 µm. Cumulative release of red ginger oleoresin from microcapsules reached the highest level was 61.69 ± 1.3% from 2% chitosan concentration and 5 ml GST, and the lowest level was 50.01 ± 1.8% from 4% chitosan concentration and 20 ml GST after they were immersed in phosphate buffer for 72 h. The value of antioxidant activity was between 38.28 ± 0.07% and 61.99 ± 0.33%. The release mechanism based on the Korsmeyer-Peppas model was Fickian diffusion with a diffusion coefficient value of 1.332 × 10^?11–4.576 × 10^?13 cm²/s.