Determination of the energetic value of fruit and milk-based beverages through partial-least-squares attenuated total reflectance-Fourier transform infrared spectrometry Original Research Article

The estimation of important nutritional parameters, such as carbohydrates content and energetic value (calories) in commercially available fruit juice and flavour milk shakes has been made by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) using a partial-least-square (PLS) calibration approach. A highly heterogeneous population of 65 samples obtained from the Spanish market, covering fruit juices, flavour milk shakes and milk-added fruit juices was used. The spectral range and the size of the calibration set for building the PLS model have been evaluated. Considering a calibration set comprised of 27 samples, selected via hierarchical cluster analysis, and a validation data set of 38 samples, the absolute mean difference (dx–y) and standard deviation of mean differences (sx–y) of the total carbohydrate content were 0.06 and 0.66 g/100 mL, respectively. The reproducibility of this determination established as the mean standard deviation of each triplicate analysis was 0.05 g/100 mL. In the case of energetic value, the dx–y and sx–y were 2.8 and 18 kJ/100 mL, respectively. The reproducibility of this determination corresponded to a standard deviation of 2.4 kJ/100 mL, for three replicate analyses. The root-mean-square error of prediction (RMSEP) was 18.4 kJ/100 mL and 0.72 g/100 mL for energetic value and total carbohydrates, respectively. The developed methodology favourably compares with that reported in previous works in much restricted sample composition and provided figures of merit which agree with the US-FDA statuary tolerance values.