FT-NIR spectroscopy for caffeine estimation in instant green tea powder and granules

The feasibility of measuring caffeine content in instant green tea and granules was investigated by Fourier Transform Near-Infrared (FT-NIR) spectroscopic technique. A calibration model was developed using pure caffeine standards of varying concentrations in the near-infrared region (4000-12000 cm(-1)). The developed model was validated using test validation technique. FT-NIR spectroscopy with chemometrics, using the PLS-first derivative plus straight line subtraction method could predict the caffeine content in tea samples accurately up to an R-2 value greater than 0.98 and a standard error of prediction (SEP) value less than 2.0 with 6 factors in the prediction model. The developed model was applied to predict caffeine content in tea samples within 2-5 min. The developed procedure was further validated by recovery studies by comparing with UV spectroscopic method of caffeine determination. (c) 2008 Elsevier Ltd. All rights reserved.