Analytical Studies on Tara Tannins

Abstract

In this paper, an extract from fruits pods of Caesalpinia spinosa (tara) a native leguminosae widely distributed in Peru, known by its high tannin content is evaluated for its utilization in wood adhesives. Commercial pods of tara were extracted for 1 hour with water (1:4w/v) at 65°C. The extract was spray-dried to obtain tara tannin. Spectrophotometric and chromatographic analysis were performed before and after hydrolysis to quantify amounts of free and combined components. Gallic acid concentration in the extract reached up to 53% and these results encourage us to further develop a method to extract gallic acid from tara pods (25% yield). The thermal behaviour of tara tannin-formaldehyde reaction at different pH conditions were investigated by thermoanalytical methods (Borchardt-Daniels and ASTM E-698). Kinetic parameters obtained were compared with those obtained for gallic acid-formaldehyde reaction.