Evaluation of the maillard reaction in infant formulas by means of front-face fluorescence

Foods are complex mixtures of macro- and micronutrients, which interact, leading to oxidation, glycation, and hydrolysis upon heating (e.g., sterilization, cooking) and storage. Their nutritional quality and safety are consequently affected, justifying the need for accurate monitoring of the evolution of the food composition during processing and shelf life. Classical chromatographic analysis as well as newly proposed rapid methods based on fluorescence spectrometry analyses were applied on whey powder-based models and commercial samples (in powdered form and ultrahigh temperature [UHT] sterilized), some of which had been previously submitted to protein hydrolysis. These samples were incubated for 48 h at 60 degrees C to mimic accelerated storage. Fluorescence fingerprints addressing modifications in the product composition during processing were recorded and analyzed by chemometric methods. Carboxymethyllysine (Nepsilon-[carboxymethyl]lysine; CML) was measured using an ELISA method. Fluorescence, recorded in a front-face mode on intact samples, is very sensitive to pertinent physicochemical changes induced by heat treatment, formulation (the moisture level in powders, presence of vitamin C and iron), and storage. Similar trends were observed between powders' fluorescence and CML-for example, a strong effect of protein hydrolysis and increasing water content. Addition of vitamin C was associated with an antioxidant effect despite the presence of iron. Good calibration models were obtained for predicting CML from fluorescence spectra both in food models and in commercial samples, although more work is needed to obtain accurate and robust calibration models. Results show the potential of nondestructively applied fluorescence spectrometry for measuring CML in formulas, a rapid, simple, and cost-effective method to monitor formula quality.