Tannin content of tea and coffee

✍ Scribed by H. Savolainen

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 308 KB
• Volume: 12
• Category: Article
• ISSN: 0260-437X
• DOI: 10.1002/jat.2550120307

✦ Synopsis

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 diffusionprotein precipitation technique and with a spectrophotometric method. The green beans contained 6.6 f 0.6 mg g-' weight tannic acid equivalents as found by protein precipitation ( n = 5, f SD) or 6.8 2 2.3 mg g-' by spectrophotometry.

The same figures for roasted beans were 18 2 1.7 and 17 rt 2.7 mg g-', respectively. Tea contained 37 2 2.6 mg g-' weight tannic acid equivalents as analysed by spectrophotometry and 24 2 2.8 mg g-' 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.