Prediction of glucose and sucrose values of black tea samples using NIR spectroscopy and chemometrics

Abstract

FT-NIR and chemometrics are considered one of the most important analytical tools for the quality control of tea. The present study focused on developing and validating a rapid quantification method for the quantification of sugar, specifically sucrose and glucose in black tea using FT-NIR spectroscopy. Calibration models were established by partial least squares (PLS) regression analysis. Fructose, glucose, and sucrose concentrations in black tea were analyzed using high-performance liquid chromatography. The spectral range and the number of PLS factors were optimized for the Residual Predictive Deviation (RPD) and correlation coefficient (r2) of determination. The NIR spectral region between 5878 and 3996 cm−1 (1701–2500 nm) was selected as the best range for predicting glucose, sucrose, and fructose concentrations in black tea. The calibration model developed for sucrose has high RPD (4.29) and r2 (0.95) indicating the potential for predicting the inherent sucrose content in black tea with high accuracy. The calibration model developed for glucose has RPD of 2.73 and r2 (0.87) showing the potential for predicting glucose content in black tea with reasonable accuracy. Both calibration models could be useful for quality assurance purposes in black tea, and easier and faster than the wet chemical HPLC method. FT-NIR spectroscopy coupled with chemometrics has been demonstrated for the first time to quantify the inherent glucose and sucrose concentrations in black tea. Calibration models could be used to determine adulteration of black tea with sucrose and glucose.