Influence of Prefermentation Clarification on Heavy Metal Lability in Garnacha Must and Rosé Wine Using Differential Pulse Anodic Stripping Voltammetry

Resumen

A desirable must clarification process should improve the quality of the wine, remove substances that produce unwanted flavors, favor the fermentation to dryness, and increase the fermentation rate. Among the factors that affect the quality of wine, the cationic content and the form in which the cations exist in the must are important since they play a relevant part in the fermentative process. Differential pulse anodic stripping voltammetry (DPASV) is a precise and inexpensive technique for metal analysis, has excellent sensitivity due to preconcentration of metal ions in the mercury drop or film, and offers the potential of discriminating between certain electroactive and electroinactive metal forms. The aim of this study was to observe the influence of two prefermentation clarification treatments, static sedimentation and vacuum filtration, on total, acid-displaceable, and labile heavy metal content. The results demonstrate that vacuum filtration of the must decreases Zn and Cu, as much for total metal as well as labile species and those displaced by acid. In filtered must, the percentage of labile Zn and Cu increased with respect to its total metal content. However, sedimentation did not eliminate metal species displaced at pH 2. Cadmium and lead, with elevated toxicity, were greatly eliminated by clarification; what remained in the must formed highly stable complexes that cannot be measured with DPASV.