RAPID DETERMINATION OF SUGARS IN COMMERCIAL FRUIT YOGURTS AND YOGURT DRINKS USING FOURIER TRANSFORM INFRARED SPECTROSCOPY AND MULTIVARIATE ANALYSIS

A chemometric study for the quantification of sugars in commercial fruit yogurts and yogurt drink samples was carried out using fourier transform infrared spectrophotometery (FTIR), attenuated total reflectance (ATR), and partial least squares regression (PLS). The calibration set consisted of 43 mixtures of five sugars namely sucrose, glucose, galactose, lactose, and fructose. Different PLS models using raw, first, and second derivative spectra were tested in order to evaluate their prediction ability for the validation set. The second derivative transformation plot over a range of 1500 to 900 cm(-1) was found to highlight the variations among sugar mixtures and was further applied onto commercial fruit yogurt and yogurt drink samples for quantification of sugars. Results indicated that FTIR-ATR coupled with multivariate analysis could quantify total sugar contents of commercial fruit yogurts and yogurt drinks within minutes, without the need for any kind of sample preparation.