Interest and impact of PVP/PVI (Polyvinylpyrrolidone/ Polyvinylimidazole) on winemaking and final quality of wines

Abstract

Consumers’ health and security force authorities to limit, in wine as in others food industry products, the concentration in « dangerous » molecules. Therefore the legal limit in heavy metals keeps on decreasing. As per proof EU regulation just decrease the stain concentration in wine from 0,2 to 0,15 mg/l. Certain changes , such as sodium arsenite treatment in vines, disappearance of brass in wineries to the benefit of stainless steel, limit even more the concentration of heavy metals in wines. But the use of copper derivates in vines treatments is difficult to replace. In the case of wine and its elaboration, the problem is even more complex. Indeed, regulation forces the wine producers to control the concentration of certain heavy metals in final wines. But most of the time the measured concentration is largely under legal limit (copper < 1 mg/l) with an average of 0 à 0,2 mg/l of CU, this has the consequence to let consider the wine producers that they have no problem. Unfortunately they are wrong ! This lecture will demonstrate that a major part of musts contain a copper concentration over 0,5 mg/l. The gap between must and wine is majorly do to the alcoholic fermentation that eliminate partially copper. This high concentration has a direct impact on winemaking and final wines quality. Copper is a known antiseptic, and it can have some toxic effects on micro-organisms (this effect is strain / species dependant). This leads to fermentations problems from slugglish to suck AF or difficult MLF. In addition heavy metals have an impact that can cause over 50% of “destruction” of certain aromatic compounds of grapes such as free thiols. Copper is also taking an active part in oxidation mechanisms that forms quinones and conduct to an increase of yellow length in wines colour. It increases bitterness of wines and also limit SO2 action ( copper is trapping free fraction). As for conclude this lecture will demonstrate the interest and impact PVP/PVI (only or in formulation) during winemaking as a solution to heavy metal presence such as copper.