Differences in Thermal Process Conditions Affect Tannin Polymerization Reaction in Gambier (Uncaria gambier Roxb.) Extract

Gambier (Uncaria gambier Roxb.) is an agricultural commodity rich in tannin polymers with high potential for functional and industrial applications. However, the formation of stable condensed tannins is strongly influenced by heating temperature, which can affect the formation of tannin polymers. This study investigated the dynamics of tannin polymerization from gambier extract under four heating systems: direct heating without a condenser (DH-WOC), direct heating with a condenser (DH-WC), water bath without a condenser (WB-WOC), and water bath with a condenser (WB-WC). The powdered gambier extract was subjected to four controlled heating conditions at ۷۰ ± ۱ °C for ۲۴۰ min. The resulting powder was then analyzed for its characteristics using DSC, TGA, and morphological assessment. The results revealed that the WB-WOC heating system could produce the most advanced polymer structure, exhibiting the highest enthalpy stability, high transition temperature, balanced mass loss profile, and the darkest and densest powder morphology. In contrast, the direct heating system induced only partial polymerization, resulting in a brittle polymer with limited stability, while the WB–WC system suppressed oxidative crosslinking, resulting in a lighter and more brittle powder. Overall, this study conclusively shows that gradual heating in an open water bath is the most effective condition for promoting extensive tannin condensation and the formation of thermally stable, high-molecular-weight gambier tannin polymers.

کلیدواژه ها:

condensed tannins ، polymerization dynamics ، heating regime ، water-bath system ، Oxidative crosslinking