INTERACTION BETWEEN PROTEINS OF PLANT ORIGIN AND WINE COMPONENTS: MOLECULAR-BASED CHOICE OF PROTEIN FINING AGENTS FOR ORGANOLEPTIC IMPROVEMENT

Gelatine, casein, egg albumin, and, more recently, proteins from plant sources are commonly used in winemaking as fining agents to remove particles responsible for turbidity, to improve stability, and to control browning, over-oxidation, and bitterness during ageing (Spagna et al., 2000; Cosme et al., 2008). The formation of covalent and non-covalent interactions (hydrogen bonds and hydrophobic interactions) between the protein matrix and wine polyphenolics is the basis of the flocculation and of the consequent clarification which results in an overall improvement of wine quality parameters (Versari et al., 1999; Sarni-Machado et al., 1999). In accordance with the PhD thesis project, we studied the molecular basis of the interactions between selected plant proteins (soybean, pea, lentil and gluten proteins) and polyphenolic and aroma compounds by using spectrometric and mass spectrometry methodologies (LC-ESI MS, MALDI TOF MS). Protein surface hydrophobicity was investigated in a wine-like model system by spectrofluorimetric determination of changes in the binding properties of 1,8-anilinonaphthalenesulfonate (ANS), used as extrinsic fluorescent probe. Hydrophobic interactions between phenolic compounds and protein finings were evaluated by the study of competition of phenolic compounds with the ANS probe for the same binding sites. Structural characterization of phenolic compounds (polymer chain length and chemical structure and composition of individual chains), as well as their interactions with the plant proteins, essential for the definition of protein binding affinity, was performed by means of mass spectrometry techniques. Differences among interactions between polyphenols with the various protein matrices have been related with the quality parameters of the resulting wines.