EFFECT OF OXIDATION ON LOW MOLECULAR WEIGHT PHENOLIC FRACTION, SALIVARY PROTEINS PRECIPITATION AND ASTRINGENCY SUBQUALITIES OF RED WINES
Changes in the low molecular weight phenolic fraction, obtained by liquid-liquid microextraction technique, were studied after controlled oxidation of two typologies of Sangiovese wines (Brunello di Montalcino and Chianti Classico) belonging to two vintages (2017 and 2018). The fractions were characterized by LC-MS and quantified by HPLC. The most abundant extracted compounds were the phenolic acids. The effect of oxidation, vintage, and wine typology was stated by a three-ways ANOVA. Gallic and syringic acids significantly increased after oxidation while (–)-epicatechin decreased the most. The interaction and precipitation with salivary proteins, mechanism at the basis of astringency, was carried out at three phenolic concentrations (3.0–5.0–7.5 g/L). The amount of salivary proteins and phenolic compounds were in turn analysed by HPLC. Only the caftaric, cis- and trans-coutaric acids, and procyanidin dimer B7 showed a significant precipitation with salivary proteins. The oxidated wine fractions showed a high interaction and more precipitation with salivary proteins than the not oxidated ones. However, the high precipitation of the low molecular weight phenolics was not correlated with the sensory astringency of wines. Control wines were characterized by unripe astringency felt with acidity, described as greenness subquality, due to the high content of (+)-catechin, (–)-epicatechin, caftaric acid and myricetin-3-O-glucoronide in the fractions. The decrease of such phenolic compounds by oxidation was correlated with the corresponding increase of silkiness and velvety sensation in the oxidated wines.
Issue: OENO Macrowine 2023
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oxidation, astringency, subquality, greenness