Abstract
A new chemical pathway yielding A-type vitisins in red wines is proposed herein from the reaction between anthocyanins and oxaloacetic acid (OAA). This new chemical path is thought to occur in the first stages of the wine production even during the fermentation process. This is due to the revealed high reactivity of OAA with anthocyanins compared with the already known precursor (pyruvic acid, PA). In model solutions at wine pH (3.5), when malvidin-3-O-glucoside (mv-3-glc) is in contact with OAA and PA a decrease in the OAA concentration is observed along with the formation of A-type vitisin. Moreover, part of the OAA is also chemically converted into PA in model solutions. The reaction yields were also determined for OAA and PA using different mv-3-glc:organic acid molar ratios (1:0.5, 1:1, 1:5, 1:10; 1:50, and 1:100) and these values were always higher for OAA when compared to PA, even at the lowest molar ratio (1:0.5). The reaction yields were higher at pH 2.6 in comparison to pH 1.5 and 3.5, being less affected at pH 3.5 for OAA. These results support the idea that OAA can be at the origin of A-type vitisins in the first stages of wine production and PA in the subsequent ageing process.
Highlights
Color is an important characteristic that is directly associated with the quality of red wines.Anthocyanins, the compounds responsible for this color, are flavonoid pigments formed in berries from verasion onwards via the phenylpropanoid pathway [1]
A-type vitisins are one of the main pyranoanthocyanins found in red wines during ageing [6] and are described in the literature to be formed from the reaction of anthocyanins with pyruvic acid (PA)
The occurrence of A-type vitisins in red wines could be due to the reaction of mv-3-glc with PA, as already documented in the literature
Summary
Color is an important characteristic that is directly associated with the quality of red wines. Anthocyanins, the compounds responsible for this color, are flavonoid pigments formed in berries from verasion onwards via the phenylpropanoid pathway [1] These pigments are slowly extracted from grape skins during maceration/fermentation into the must and wine. This is due be low,lack its quantification in sensitive those matrices is not wellsimultaneous documented detection in the literature [20].keto-acids This is due to to the of a reliable and method for the of various and the of instability a reliable and sensitive method for the simultaneous duelack to the of OAA in severe reaction conditions [21].
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