Encapsulation of carotenoid-rich oil from Gac peel: optimisation of the encapsulating process using a spray drier and the storage stability of encapsulated powder

The carotenoid-rich oil recovered from Gac peel, a waste from Gac fruit processing, has been encapsulated with a mixture of whey protein concentrate and gum Arabic using a spray drier. A response surface methodology using Box-Behnken design was employed to investigate the effects of the ratio of oil to the wall material, inlet temperature and the emulsion feeding rate on the retention of total carotenoid and antioxidant capacity of the encapsulated powder. The encapsulated powder obtained under the optimal spray drying conditions has been stored at 5 °C and 20 °C for 6 months to evaluate the storage stability of the carotenoids. The results showed that the optimal conditions for the encapsulation process were 160 °C of inlet temperature and 180 mL/h of feeding rate for the emulsion of 24.5% total solids that contained a ratio of 3:10 of oil to wall material. Under the optimal conditions, 80% of carotenoids and 82% of antioxidant capacity were retained in the encapsulated powder compared to those in the infeed oil. During 6 months of storage, the encapsulated powder showed significant higher retention of carotenoids compared to the oil at both storage temperatures. The results suggest that carotenoids recovered from Gac peel should be encapsulated for better storage stability.