preliminary evidence of enhanced condensed tannin formation in gambir (uncaria gambir roxb.) under different heating treatments

Thermal processing can induce structural modifications in polyphenol-rich extracts; yet, its role in condensed tannin formation in gambir (uncaria gambir roxb.) remains underexplored. in this preliminary study, gambir samples were subjected to different heating regimes, including direct heating and water-bath systems with or without condensers, to evaluate changes in color, acidity, viscosity, and condensed tannin content. visual observations revealed progressive darkening under all treatments, with the most intense color change occurring in the water bath without a condenser. water-bath treatments also increased ph values and viscosity compared to direct heating, suggesting enhanced polymerization of catechins into condensed tannins. spectrophotometric analysis using the vanillin–hcl method confirmed that wb–nc samples displayed the highest absorbance at 500 nm, indicating greater reactivity and enrichment of condensed tannins. these findings demonstrate that indirect thermalization promotes more extensive tannin condensation than direct heating, highlighting the importance of heating mode and system openness in modulating polyphenol reactivity. as a preliminary investigation, this work provides foundational evidence to guide future molecular-level studies of tannin polymerization pathways and supports the potential for optimizing gambir processing for industrial applications in the food, pharmaceutical, and nutraceutical sectors.