OPTIMIZATION OF DRYING TEMPERATURE OF DRAGON FRUIT (Hylocereus undatus) PEEL TEA INFUSION

Abstract

Dragon fruit peel tea infusion is a functional drink containing phenolic compounds with antioxidant activity. The aim of this study was to optimize the drying temperature on the bioactive compounds of dried dragon fruit peels. A part of dragon fruit peel was maintained in the fresh form in refrigerator until chemical analysis and the remaining part were chopped in 2.5 cm lengthwise and dried at 50°C, 60°C and 70°C till the moisture content reached 5%. The dried peels were grinded into powder form and sieved through 40 mesh size to a fine consistency. Proximate analysis and bioactive components were determined for fresh samples. Total phenolic content, total flavonoid content, betacyanin content and antioxidant activity were determined for the dried samples. The tea was prepared by infusing 1.5g of dried dragon fruit peels in 50ml of hot water (90°C) and leaving it to stand for 5 min. After that, sensory analysis of tea infusion was carried out using 9-point hedonic scale rating. The findings indicated that drying dragon peel at higher temperatures resulted in significant losses in bioactive components. The optimum drying temperature of dragon fruit peel was found to be 50°C having TPC, TFC, betacyanin content and antioxidant activity of 64.92 mg GAE/100g, 56.34 mg QE/100g, 52.34 mg/100g and 77.37% respectively. Increase in temperature decreased the bioactive components, i.e. at 70°C the total phenolic content, antioxidant activity and betacyanin content were found to be reduced significantly (p<0.05). All the analyzed samples showed that low temperature drying method is the best method for better retention of higher bioactive components. According to sensory analysis, tea infusion at 50°C was found to be the best among other samples.