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 R2 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.