The effect of drying temperature on the physico-chemical characteristics of herbal tea preparation of red dragon fruit skin (Hylocereus polyrhizus) in whole form and powder form

Hylocereus polyrhizus skin, often discarded, is rich in antioxidants, making it a promising ingredient for herbal tea. This study evaluates the effect of drying temperature on the physicochemical characteristics of dragon fruit skin herbal tea in whole and powdered forms. The research employed a completely randomized design (CRD) with two factors—drying temperature (45°C, 50°C and 55°C) and formulation form (whole and powder), resulting in six treatments with four replications each. Data were analyzed using ANOVA, followed by DMRT at a 5% significance level. The results showed that the interaction between drying temperature and product form significantly affected yield, moisture content, pH, lightness (L*), total phenols, total flavonoids, total tannins, and antioxidant activity. A drying temperature of 50°C in the whole form was most effective in preserving total phenols (92.5±2.1 mg GAE/g) and total flavonoids (34.7±1.8 mg QE/g), while 55°C resulted in the highest antioxidant activity of 47.29±5.78 mmol Fe²⁺/g. However, temperatures beyond this may degrade heat-sensitive antioxidants due to oxidation. These findings suggest that 50°C is the optimal drying temperature for maintaining the nutritional quality of dragon fruit skin herbal tea.