Time-dependent extraction kinetics of infused components of different Indian black tea types using UV spectroscopy

Abstract

Time-dependent aqueous extraction of six tea types was carried out with leaf–water–ratio of 0.5 g/100 ml, temperature of extraction 90°C and time of extraction ranging from 1 to 10 min. UV–vis spectroscopic analysis in the range varying from 220 to 900 nm of the aqueous tea extracts showed a prominent peak at 273 nm in the ultraviolet region which can be associated with n → π* electronic transition of caffeine molecules. Parabolic diffusion, Power law, hyperbolic, Weibull’s and Elovich’s models were fitted to represent the aqueous soluble component extraction behaviour for time-dependent extraction of aqueous extractables. Parabolic diffusion model, Power law and Elovich’s model were a close fit to the experimental data for all the selected tea types with correlation coefficients (R2) ranging 0.8029–0.9953, whereas hyperbolic and Weibull’s models showed poor fitness to represent the extraction behaviour of fanning and AO leaf, LD, fanning and dust, respectively, with R2 < 0.8, for time-dependent aqueous soluble component extraction.

Keywords

• parabolic diffusion model
• power law model
• hyperbolic model
• weibull’s model
• elovich’s model