Proteins and Odors. New Frontiers for Food Quality Assessment

The quality of cow's milk is a critical parameter for human nutrition, making essential the development of rapid, sensitive, and cost-effective methods for monitoring them. Volatile Organic Compounds (VOCs) are odorant molecules that represent key indicators of milk quality since they reflect important factors such as, to name a few of them, animal metabolism, animal diet, and farming practices. In this work we present the biophysical characterization of the porcine odorant-binding protein (pOBP) and the bovine odorant-binding protein (bOBP) as studied by fluorescence spectroscopy and the design of an innovative fluorescence biosensor based on the use of these two proteins to detect the presence odorant molecules in: a) milk produced by in-tensive livestock farming and b) milk produced by extensive livestock farming. The biosensor employs an “impinger” system to capture the odorant molecules from milk, which are then transferred to a liquid phase for quantitative and qualitative analyses. The binding of the odorant molecules to the OBPs triggers a Förster Resonance Energy Transfer (FRET) signal, allowing for a real-time VOC quantification. The performance of the assays was evaluated by Head Space Solid-Phase Microextraction coupled with Gas Chromatography-Mass Spectrometry (HS-SPME/GC-MS) experiments. The obtained results are presented and discussed.