Spray drying microencapsulation of purple cactus pear (Opuntia ficus indica) peel extract and storage stability of bioactive compounds

Purple cactus pear (Opuntia ficus indica) is a fruit found in Mexico that is mainly consumed fresh. The fruit has a peel, which is a non-usable by-product that can represent up to 52% of the fruit's total weight. This peel is rich in phenolic compounds (PC) and betalain pigments (betacyanins (BC) and betaxanthins (BX), with important antioxidant capacity (AC), making this waste product an interesting source to obtain extracts rich in bioactive compounds that can be utilized by food industry. Since extracts are liable to degradation, they require protection through techniques such as spray drying microencapsulation. Therefore, this study evaluated the retention of bioactive compounds during spray drying microencapsulation of purple cactus pear peel extract using 10, 15, and 20%w (weight percentage) of maltodextrin (MDX) and Gum Arabic (GA) solutions as encapsulating agents, under different drying conditions. Storage stability during 90 days was also studied for powders obtained at the best drying conditions with both encapsulating agents. The best drying conditions were 170-80 °C (inlet-outlet temperature), in which retention efficiencies for MDX were: 95.5 % (PC), 100.5% (BC), 103.5% (BX) using 20%w MDX, and 117.9% (AC) using 15%^w MDX; for GA retentions were 92.4% (PC) and 107% (AC) with 20%^w GA and 103.4% (BC) and 93.4% (BX) with 10%^w GA. Under storage for 90 days at 22-25 °C, 10%^w of encapsulating agent protected microcapsules in presence or absence of light, having the advantage of containing higher concentration of bioactive compounds per gram of dry solid.