Effects of pretreatments and air drying temperatures on the carotenoid composition and antioxidant capacity of dried gac peel

Gac fruit contains a high level of carotenoids in the seed membrane (aril), pulp, and peel. However, only the aril is commercially processed and the peel is currently discarded. This study investigated different pretreatments and drying temperatures on the colour, content of carotenoids and antioxidant activity of air-dried Gac peel. The results showed that pre-treatments of Gac peel prior to drying and the drying temperature significantly affected the colour, carotenoid content and antioxidant capacity of the dried peel. Peel treated with ascorbic acid and dried at 70°C retained the highest levels of carotenoids and ABTS antioxidant capacity. These results suggest that the pre-treatment with ascorbic acid solution can be applied to prevent the loss of carotenoids and antioxidant capacity caused by drying of Gac peel. Practical applications: Gac peel contains high levels of carotenoids but thousands tons of the peel are currently discarded as waste of the Gac processing industry. The results of this study showed that the combination of the pre-treatment of Gac peel with ascorbic acid solution with air drying at 70°C is an effective way to preserve carotenoids and antioxidant capacity of dried Gac peel, which can be utilised as a material for extraction of carotenoids.