New insights into betalactoglobulin - polyphenol interactions: towards wine astringency reduction applications

IGNACIO CABEZUDO; CARLOS BOSCHETTI; PAULA JAUREGI; DIANA ROMANINI

Salamanca

Congreso; BIOIBEROAMÉRICA 2016; 2016

Redwine is one of the most polyphenol-rich beverages, which have demonstrated tohave many health benefits due to several biological activities. The tannins,however, are responsible for some undesired sensorial properties, like astringency.Some proteins, such as casein, gelatine, egg albumin, and isinglass are knownto interact with phenolic compounds, in a process called wine fining. Inprevious 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 knowledgestudying protein interactions towards relevant wine phenolics. The isothermaltitration calorimetry (ITC) study of wine tannins and their interactions withproteins was used to better understand how fining with these proteins work andto insure that polyphenols with antioxidant properties are not ?finned? from wine.Alow molecular weight (LW) fraction and a high molecular weight (HW) fraction ofwine polyphenols were purified. Their interaction with the proteins ofinterest, BLG and gelatine were assessed by ITC. The phenolic fractions werepurified by Sephadex LH-20 from dry grape pomace. Then, they were characterizedby HPLC, and some polyphenols could be identified in the mixtures by the use ofstandards. ITC thermograms corresponding to the titration of gelatine and BLGwith purified tannins, in the presence and absence of salt were obtained. Appreciableinteractions for HW could be detected, for both proteins, which indicated ahigh binding affinity. The addition of salt (NaCl 200 mM) produced inhibition ofinteractions between the gelatine and HW, denoting a mainly electrostaticcharacter. On the other hand, the interactions of HW with BLG, were not affectedby the presence of NaCl. Finally, the interactions of the proteins studied weremeasured with LW, and this time interactions were negligible, indicating a lowbinding affinity. Weprogressed to obtain a more thorough study on the selectivity of BLG -aglobular compact protein- towards red wine phenolics and its comparison withgelatine -a random-coil protein- used in the clarification of wine.