Some molecular and colloidal aspects of tea cream formation

Abstract

The formation of tea cream for a range of black tea materials was studied by turbidity measurements, time-resolved light scattering, gravimetric measurements and High Performance Liquid Chromatography (HPLC). These techniques demonstrate that, in the absence of caffeine and/or gallate esters the solubility of tea solids in black tea infusions is enhanced compared with the ‘standard’ black tea material. All the tea system show an increase in cream-point, amount of tea cream and particle size with increasing tea solids concentration. Decaffeination has a larger impact on enhancing the solubility of tea colloids than degallation. HPLC studies indicate that theaflavins have a preference for the cream phase, whereas ie. catechin C is preferentially partitioned into the aqueous supernatant phase. Caffeine is preferentially partitioned into the cream phase, albeit less favourably than theaflavins and other relatively high-molecular mass polyphenols. Comparison between ‘standard’ and decaffeinated black tea shows that in the absence of caffeine, epigallocatechin gallate (EGCG) is preferentially partitioned into the cream phase.