Vanillin-HCl method for condensed tannins: Effect of organic solvents used for extraction of tannins
- 1k Downloads
Tannins are generally extracted using aqueous organic solvents, mainly methanol and acetone. The presence of various concentrations of methanol in the sample containing catechin or tannins did not alter the kinetics of their reaction, but the absorbance depended on the amount of methanol in the sample; the higher the methanol, the higher was the absorbance. Acetone reacted with acidified vanillin to produce a chromogen with λmax at 548 nm, which produce a substantial error in the determination of condensed tannins. In the presence of acetone, the time courses of the reaction for catechin and tannins were different, which depended on the acetone concentration and the reaction temperature. Reaction conditions for catechin and tannins that enable their measurement in the presence of acetone are presented.
Key WordsCondensed tannins catechin vanillin-HCl method organic solvents methanol acetone
Unable to display preview. Download preview PDF.
- Broadhurst, R.B., andJones, W.T. 1978. Analysis of condensed tannins using acidified vanillin.J. Sci. Food Agric. 29:788–794.Google Scholar
- Deshpande, S.S., Cheryan, M., andSalunkhe, D.K. 1986. Tannin analysis of food products.CRC Crit. Rev. Food Sci. Nutr. 24:401–449.Google Scholar
- Cork, S.J., andKrockenberger, A.K. 1991. Methods and pitfalls of extracting condensed tannins and other phenolics from plants: Insight from investigations onEucalyptus leaves.J. Chem. Ecol. 17:123–134.Google Scholar
- Hagerman, A.E. 1988. Extraction of tannins from fresh and preserved leaves.J. Chem. Ecol. 14:453–461.Google Scholar
- Makkar, H.P.S., Singh, B., andNegi, S.S. 1990. Tannin levels and their degree of polymerisation and specific activity in some agroindustrial byproducts.Biol. Wastes 31:137–144.Google Scholar
- Makkar, H.P.S., Singh, B., andDawra, R.K. 1991. Tannin levels in the leaves of some oak species at different stages of maturity.J. Sci. Food Agric. 54:513–517.Google Scholar
- Price, M.L., Scoyoc, S.V., andButler, L.G. 1978. A critical evaluation of the vanillin reaction as an assay for tannin in sorghum grain.J. Agric. Food Chem. 26:1214–1218.Google Scholar
- Strumeyer, D.M., andMalin, M.J. 1975. Condensed tannins in grain sorghum: Isolation, fractionation, and characterization.J. Agric. Food Chem. 23:909–914.Google Scholar