Proteome-metabolite interactions in wine. Tracking down the X factor

Mestrado em Viticultura e Enologia - Instituto Superior de AgronomiaProtein haze formation is a recurrent problem in white and rosé wines. Formation of his type of haze is dependent on only for the protein content of the wine, but is strictly related to one or more non-proteinaceous wine components termed as X factor. A selected wine from the variety Moscatel of Alexandria was fractionated using a preparative RP-18 chromatography column in eight methanolic fractions that were subsequently subjected to heat stability test with wine isolated protein in model wine solution. The results obtained indicate that the X factor is not a single compound, but rather an interaction of several compounds with wine proteins. A heat stability test involving the combination of four of these fractions with an isomer of the major compound identified in the water soluble fraction, the erythritol, presented the higher haze formation. Nuclear magnetic resonance (NMR) and mass spectrometer (GCT) analysis allowed the identification of two compounds present in the methanolic fractions. As a whole, this work constitutes a step forward in the difficult process of purification and identification of the wine non-proteinaceous components that modulate the wine protein haze formation