EFFECT OF HOT-AIR DRYING TEMPERATURE ON BETACYANIN, POLYPHENOL CONTENTS, AND ANTIOXIDANT ACTIVITY OF RED-FLESHED DRAGON FRUIT PEEL (HYLOCEREUS COSTARICENSIS)

Abstract

Red-fleshed dragon fruit peel contains large amounts of betacyanins and bioactive compounds, which are unstable at high temperatures. This study aimed to investigate the effect of hot-air drying temperatures on betacyanin and polyphenol contents, and the antioxidant activity of this by-product. Samples were dried at 40°C (HD40), 50°C (HD50), and 60°C (HD60), and measured for moisture and CIE Lab* color space. Betacyanin (TBC), phenolic (TPC), and flavonoid (TFC) contents were analyzed using spectrophotometry and standard curves of quercetin and gallic acid. DPPH and reducing power assays were conducted to evaluate antioxidant capacity. Dried samples have acceptable values of moisture and color. HD50 and HD60 obtained similar values of TBC, TPC, TFC, and DPPH free radical scavenging capacity, and the values were higher than those of HD40. In the reducing power test, there were no statistically significant differences in the OD₇₀₀ values of the samples. Results suggest that red-fleshed dragon fruit peel dried at 50–60^oC could be applied to the production of food colorants and functional foods.