Anthocyanins enhance yeast’s adsorption of Ochratoxin A during the alcoholic fermentation

Ochratoxin A (OTA) is a mycotoxin that can be present in food products and beverages such as wine, in which the European Union has regulated its maximum concentration. Since yeasts can adsorb OTA during the alcoholic fermentation (AF), we have analyzed whether anthocyanins influence the reduction of OTA in wine during AF carried out by two Saccharomyces cerevisiae strains. Laboratory experiments were conducted with one white must and two red musts that were obtained by adding to the white must two different concentrations of anthocyanins extract. Musts were supplemented with OTA and tested at two pHs. A reduction of OTA was observed in all wines, being higher in red wines. These data point that a chemical bond between anthocyanins and OTA is probably responsible for enhanced adsorption of OTA by yeast. On the other hand, the removal of OTA between the two inoculated yeast strains was different. This result cannot be only attributed to differences in the yeasts’ cell wall composition, because differences were not detected in white wines

Partial Dealcoholization of Red Wines by Membrane Contactor Technique: Effect on Sensory Characteristics and Volatile Composition

Recently, the European Union regulation has fixed the maximum permitted dealcoholization level at 2 %; however in some cases, higher dealcoholization levels could be necessary. It is assumed that higher levels of dealcoholization could negatively affect the organoleptic quality of wine, but little data on this item is available. In the present study, two red wines (cv. Aglianico) with different initial alcohol contents (15.37 and 13.28 % v/v), were partially dealcoholized at three levels (-2, -3, -5 % v/v), by a polypropylene hollow fibre membrane contactor apparatus. In order to evaluate if dealcoholized wines differed from the untreated ones, triangle sensory tests were performed. Both -2 % wines were not perceived as different from the standard wines, while both -5 % wines were different. Sensory profiles and overall quality ranking were obtained by a selected and trained panel. Dealcoholization caused a modification of the sensory profiles, and the greatest differences were found after a dealcoholization of 5 % v/v. The most decreased olfactory notes were those of "Red fruits", "Cherry" and "Spicy", which is very important for the sensory quality of red wine. Concerning taste, both -5 % dealcoholized wines were more astringent than the correspondent untreated ones. Slighter differences were found for the other degrees of dealcoholization. The analysis of the volatile compounds, both free and glycoconjugated was performed by solid-phase extraction and gas chromatography mass spectrography analysis. While the composition of the glycoconjugated volatile fraction was almost not affected, many free compounds were decreased, most of all esters and alcohols, with an increasing amounts as the level of dealcoholization raised