Determination of lactulose and furosine in milk using front-face fluorescence spectroscopy

A novel rapid and non-destructive front-face fluorescence method to quantify furosine and lactulose in heat-treated milk has been developed. The emission fluorescence spectra (305 - 450 nm) of tryptophans of proteins, and emission and excitation fluorescence spectra of fluorescent Maillard-reaction products were recorded directly on milk samples. Principal component analysis (PCA) and principal component regression (PCR) were applied to process the spectra obtained. The front-face fluorescence method can give valuable information on the quality of heat-treated milk because it allows the evaluation of furosine and lactulose content simultaneously. The results were well correlated with those of the reference methods. The front-face fluorescence technique is relatively low-cost, rapid and non-destructive and it could replace existing conventional analytical techniques practiced for lactulose and furosine evaluation in dairy products.