title: Creaming in black tea.
abstract: Tea cream is the precipitate formed as tea cools. Its formation has been studied by X-ray scattering, and it is shown that a higher tea concentration leads to earlier onset of creaming and larger particles and that addition of theaflavin and calcium promotes creaming. Association constants between the major components of black tea have been obtained using NMR and show that calcium and glucose enhance the self-association of caffeine, polyphenols, and theaflavin but have little effect on hetero-association. Glycosylation of a polyphenol reduced self-association and reduced binding to caffeine. We conclude that theaflavin is important for the initiation of creaming, forming nanoclusters of typically 3 nm diameter, whereas caffeine acts more to fill in the gaps within the clusters and thus adds to the bulk of tea cream without being necessary for its initiation. Tea creaming may be reduced by increasing the solubility of the polyphenols (i.e., by glycosylation) or by removing calcium. Tea cream; theaflavin; caffeine; small-angle X-ray scattering; NMR; colloid.
authors.affiliation: Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, United Kingdom.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Jöbstl
authors.forename: J Patrick A
authors.initials: JP
authors.lastname: Fairclough
authors.forename: Alan P
authors.initials: AP
authors.lastname: Davies
authors.forename: Michael P
authors.initials: MP
authors.lastname: Williamson
mesh_terms: D044946:Biflavonoids / Q000008:administration & dosage / Q000737:chemistry; D002110:Caffeine / Q000737:chemistry; D002118:Calcium / Q000008:administration & dosage; D002392:Catechin / Q000008:administration & dosage / Q000737:chemistry; D011232:Chemical Precipitation; D003080:Cold Temperature; D005419:Flavonoids / Q000737:chemistry; D005947:Glucose / Q000494:pharmacology; D006031:Glycosylation; D006358:Hot Temperature; D009682:Magnetic Resonance Spectroscopy; D010316:Particle Size; D010636:Phenols / Q000737:chemistry; D059808:Polyphenols; D012542:Scattering, Radiation; D012995:Solubility; D013662:Tea / Q000737:chemistry*; D014965:X-Rays
chemical_list: D044946:Biflavonoids; D005419:Flavonoids; D010636:Phenols; D059808:Polyphenols; D013662:Tea; C056068:theaflavin; D002110:Caffeine; D002392:Catechin; D005947:Glucose; D002118:Calcium