New insights into β-lactoglobulin and wine polyphenol interactions

CABEZUDO, IGNACIO; JAUREGI, PAULA; BOSCHETTI, CARLOS E.; ROMANINI, DIANA

Salamanca

Congreso; BIO-IBEROAMERICA; 2016

BiBalVi

Red wine is one of the most polyphenol-rich beverages, which have demonstrated to have manyhealth benefits due to several biological activities. The tannins, however, are responsible forsome undesired sensorial properties, like astringency. Some proteins, such as casein, gelatine,egg albumin, and isinglass are known to interact with phenolic compounds, in a process calledwine fining. In previous work, we assessed the fining capacity in red wine of B-lactoglobulin(BLG), a milk whey protein. The aim of this work was to deepen the knowledge studying proteininteractions towards relevant wine phenolics. The isothermal titration calorimetry (ITC) study ofwine tannins and their interactions with proteins was used to better understand how fining withthese proteins work and to insure that polyphenols with antioxidant properties are not ?finned?from wine.A low molecular weight (LW) fraction and a high molecular weight (HW) fraction of winepolyphenols were purified. Their interaction with the proteins of interest, BLG and gelatine wereassessed by ITC. The phenolic fractions were purified by Sephadex LH-20 from dry grape pomace.Then, they were characterized by HPLC, and some polyphenols could be identified in themixtures by the use of standards. ITC thermograms corresponding to the titration of gelatine andBLG with purified tannins, in the presence and absence of salt were obtained. Appreciable interactions for HW could be detected, for both proteins, which indicated a high binding affinity.The addition of salt (NaCl 200 mM) produced inhibition of interactions between the gelatine and HW, denoting a mainly electrostatic character. On the other hand, the interactions of HW with BLG, were not affected by the presence of NaCl. Finally, the interactions of the proteins studied were measured with LW, and this time interactions were negligible, indicating a low binding affinity. We progressed to obtain a more thorough study on the selectivity of BLG -a globular compact protein- towards red wine phenolics and its comparison with gelatine -a random-coil proteinused in the clarification of wine .