Kinetics and equilibria of tea infusion. Part 10—The composition and structure of tea scum
1994; Elsevier BV; Volume: 49; Issue: 4 Linguagem: Inglês
10.1016/0308-8146(94)90004-3
ISSN1873-7072
Autores Tópico(s)Analytical Chemistry and Chromatography
ResumoA simple technique is described for collecting the film of tea scum, which forms on the surface of tea brewed in hard water. Powder diffractometry showed the scum to be amorphous. Scanning electron micrographs revealed the existence on the scum of islands of calcium carbonate which could be removed with dilute hydrochloric acid (the underlying polymeric scum dissolved only in highly concentrated hydroxide solution). Inorganic carbonate was confirmed by solid state 13C-NMR and by FTIR measurements: these techniques also pointed to the presence of hydroxyl groups, carbonyls and some unsaturated organic linkages. Molar masses of the order of 103 g were obtained by the MALDI method for both the original and the HCl-treated scums. Chemical microanalysis showed that the percentage of calcium rose from 3 to 7 wt% as the scum developed. The calcium, as well as smaller amounts of magnesium, manganese and sodium which were present, were all removed by the HCl treatment. The empirical formula of the organic scum matrix contained c. 45 carbon atoms.
Referência(s)