Effects of Steaming and Drying Temperature of Gambir Leaves (Uncaria gambir Roxb.) on Catechin Content, Antioxidant Activity, and Sensory Acceptance of Herbal Tea as a Functional Food Typical of West Sumatra

Abstract

Gambir (Uncaria gambir Roxb.) is a West Sumatran commodity rich in catechins, yet the quality of gambir leaf tea varies due to unstandardized postharvest handling. This study determined the effects of steaming and oven-drying temperature on moisture content, total catechins, total polyphenols, antioxidant activity (DPPH IC50), brew color, and sensory acceptance of gambir leaf tea. A factorial Completely Randomized Design was used: steaming (none and 85 °C for 3 min) and oven temperature (40, 50, and 60 °C for 24 h) with three replicates; data were analyzed by two-way ANOVA and Duncan’s test at 5%. Steaming was the dominant factor affecting catechins, polyphenols, antioxidant activity, and color. Steaming plus 50 °C oven drying (K-50) gave the highest total catechins (44.8 mg CE/g) and total polyphenols (98.0 mg GAE/g), the lowest IC50 (34.0 µg/mL), the lightest brew (L* 55.0), and the highest overall acceptance (4.1). Drying at 60 °C reduced catechins and color, while omitting steaming halved catechin content. K-50 is recommended for functional gambir leaf tea production