Encapsulation of colour from peels of eggplant in calcium alginate matrix

Microencapsulation of a natural food colourant (enriched in anthocyanins) extracted from peels of eggplants ( Solanum melongena L .) was carried out in a calcium alginate matrix to improve its shelf life and portability. Encapsulation parameters were optimised using response surface methodology. Stable beads with a maximum encapsulation efficiency of 73.56% and the best combination of phytochemical properties were obtained using 43.50 g/l sodium alginate, 20.0 g/l calcium chloride and 12.50 g/l colour concentration. The morphology of the encapsulated beads was determined from scanning electron microscopy photographs, while their physicochemical properties such as antioxidant activity, total anthocyanin content and total phenolic content were determined by biochemical assays. A storage study established that encapsulation of colour extract enhanced its shelf-life 16-fold, compared to the un-encapsulated colour extract. The release profiles of the colour from encapsulated beads were found to follow first-order anomalous transport kinetics. Food application in jelly crystals was also designed wherein these encapsulated beads were successfully used as a natural colourant.