The Dionysus integrated system: the advantages
The more and more widespread use of pesticides for the treatment of grapes in the vinyard and increasing atmospheric and environmental pollution are among the main causes of health and enological problems. The consumer is increasingly “health conscious” and demands information about the products purchased, and the governments are imposing stringent standards regulating the use of pesticides. In view of the need to produce wines of high quality, free of defects but also free of outside contamination, the growers are focusing on the subject of grape washing with the introduction of new technologies.
These could be included in an integrated system that allows the removal of the MOG (Material Other than Grapes like organic material, insects, stones, plastic….), their evacuation and a very accurate dripping of the grapes.
Washing the grapes prior to winemaking means drastically reducing the concentration of contaminants like pesticides (Fenhexamid, Dimetomorph, Fenamidone, Spiroxamine, etc.) and metals (Copper, Lead, Manganese, Iron), from the surface of the fruit (Fig. 1 e 2).
Fig. 1 and 2 – Concentration of Fenexamid (anti-botrytis fungicide) and Copper, expressed in mg per kg of grapes, found on the surface of unwashed grapes and grapes that have undergone a washing process.
The phenomenon translates into improved healthfulness of the product and better results in the alcoholic fermentation process. (The residues on the surface of the grapes are toxic for the yeast cell). Excessive quantities of copper are also detrimental to the quality of certain types of wine which base their characteristics on the aroma of volatile thiols (such as Sauvignon): it combines with those substances and precipitates, diminishing the "typical" aspect the product.
Washing the grapes also ensures a drastic reduction of the microbic load (up to 95%) which, in some cases, includes classes of microorganisms that affect the quality of the wine, like acetic bacteria, brettanomyces spp., Botrytis cinerea just to mention a few, but also has many advantages at the level of fermentation: reduction of fermentative arrests, quicker and more linear fermentions with the use of both LSA (active dry yeast) and indigenous yeasts, and thus a “cleaner” wine (Fig. 3 and 4).
The data shown in figures 3 and 4 confirm the improvement that can be obtained by washing the grapes at the beginning of the winemaking process. Fermentations are quicker, even when working with spontaneous fermentation, contrary to expectations. This is an interesting phenomenon, as one would logically assume that washing would “eliminate” the indigenous yeasts responsible for spontaneous fermentation from the surface of the grapes, and refuse to do it for that reason; however fermentation is actually propmoted thanks to the elimination of most of the substances that are toxic for yeasts.
Fig. 3 and 4 – Fermentation process (Accumulation of ethanol and reduction of sugars) of washed and unwashed grapes. Comparison between spontaneous fermentation with LSA (active dry yeast) inoculum).