Effect of Post-harvest Handling Conditions on Polyphenol Content and Ferric Reducing Antioxidant Properties of Selected Ugandan Sweet Potato Varieties

Abstract

Sweet potatoes are rich in nutrients, including bioactive compounds like carotenoids and polyphenols. This study provided information on the effect of postharvest handling conditions; curing (direct sunshine) and ambient storage on the total carotenoids, total polyphenols and antioxidant activity of five Ugandan sweet potato varieties. The total carotenoid content was determined following Rodriguez and Kimura's method, while total polyphenol content and antioxidant activity were assessed using Folin-Ciocalteu’s reagent and the FRAP assay, respectively. Findings showed significant variation in total carotenoids, total polyphenol content and antioxidant activity of the different sweet potato varieties. There was an increase in total carotenoids in both cured (322 to 391 µg/100g) and non-cured roots (325 to 366 µg/100g), on average during storage. The total polyphenol content declined from 1.04 mg GAE/g (at harvest) to (0.42 and 0.47 mg GAE/g) in cured and non-cured roots, respectively, on average. The antioxidant activity was reduced from 8.74 µmol/g (at harvest), to 3.40 and 3.73 µmol/g in cured and non-cured roots respectively, on average. This study concluded that curing under direct sunshine decreases the polyphenols and antioxidant activities in all varieties but increases total carotenoid content, suggesting careful consideration of postharvest handling procedure before storage, for nutrient maximization.