The effects of product and preparation variables on the in-cup chemical composition of tea extracts is of interest because the appearance and taste characteristics and the possible health effects of a tea liquor arise from the chemical components extracted from the leaf during tea preparation. A comprehensive study was therefore undertaken to determine the contributions of product and preparation variables on the total soluble solids, caffeine, and polyphenol contents of tea extracts. The results of this study show that the variety, growing environment, manufacturing conditions, and grade (particle size) of the tea leaves each influence the tea leaf and final infusion compositions. In addition, the composition of the tea infusion was shown to be influenced by whether the tea was contained in a teabag and, if so, the size and material of construction of the bag. Finally, the preparation method, including the amounts of tea and water used, infusion time, and amount of agitation, was shown to be a major determinant of the component concentrations of tea beverages as consumed. An illustration of the variation introduced by these product and preparation factors is provided by comparing solids, caffeine, and polyphenol contents of green and black tea infusions when commercial products are prepared according to the instructions given on their packaging.

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Aluminium() complexes of theaflavin (LH) were studied by potentiometric, UV-Vis, NMR and FTIR spectroscopic methods. The stoichiometries of the main species formed in the aluminium()-theaflavin systems areAlL, AlL 2 and AlL 3 correspond to complexes formed between Al() and the benzotropolone ring of one, two and three theaflavins, respectively. The species [AlL 3 H Ϫ1 ] and [AlL 3 H Ϫ2 ] could be accounted for by deprotonation of free phenol groups in the complexed theaflavin. 1 H NMR and HMQC experiments provided structural information on the complexes and allowed the determination of the metal coordination site. FTIR analysis of model aluminium complexes together with the aluminium theaflavin complexation corroborated the coordination site and allowed further spectral analysis of the aluminiumtheaflavin system. The following complex stability constants have been evaluated from potentiometric analysis; log β AlL = 7.80 (± 0.07), log β AlL 2 = 15.00 (± 0.12), log β AlL 3 = 22.46 (± 0.13), log β AlL 3 H Ϫ1 = 16.98 (± 0.1), log β AlLH Ϫ2 = 10.19 (± 0.1). UV-Vis spectroscopy confirmed in part the stoichiometric coordination of the aluminium theaflavin complex. The complexation of Mn() with theaflavin was also investigated potentiometrically. The stoichiometry of the major complex formed in the manganese()-theaflavin system is [MnLH Ϫ1 ] and the equilibrium constant has been evaluated as log β MnL = 4.80 (± 0.03).

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