Volume 12, Issue 3 p. 191-192
Article

Tannin content of tea and coffee

H. Savolainen

H. Savolainen

Institute of Occupational Health Sciences, University of Lausanne, Rue Bugnon 19, CH-1005 Lausanne, Switzerland

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First published: June 1992
Citations: 47

Abstract

The tannin content of over-the-counter Indian tea, of green coffee beans and of the roasted coffee beans prepared from the same green beans was determined with a radial diffusion - protein precipitation technique and with a spectrophotometric method. The green beans contained 6.6 ± 0.6 mg g−1 weight tannic acid equivalents as found by protein precipitation (n = 5, ± SD) or 6.8 ± 2.3 mg g−1 by spectrophotometry. The same figures for roasted beans were 18 ± 1.7 and 17 ± 2.7 mg g−1, respectively. Tea contained 37 ± 2.6 mg g−1 weight tannic acid equivalents as analysed by spectrophotometry and 24 ± 2.8 mg g−1 by the protein precipitation technique. The latter finding may show that the biological reactivity of tannins is variable, although no major changes in the tannin-precipitated albumin occurred as shown by electrophoretic analysis. Both methods provide an easy analysis of the reportedly carcinogenic plant tannins.