Direct determination of lactulose in heat-treated milk using diffuse reflectance infrared Fourier transform spectroscopy and partial least squares regression

Abstract

The aim of this work was the direct determination of lactulose (LCT) concentration in freeze-dried heat-treated milks using diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) without any chemical pretreatment of the milk. The 'actual' lactulose concentrations estimated by means of high-performance liquid chromatography (HPLC) were correlated with the spectral region 1286-754 cm-1 of DRIFTS spectra in the second-derivative form of the milk samples using partial least squares (PLS) regression. A linear relationship was established between the 'actual' and the concentrations recalculated using the built model. The proposed DRIFTS method is simple, rapid and low cost.