δ 18O/16O ratio changes due to innovative wine dealcoholization approaches

In wine production is now increasingly common to have high ethanol contents mainly due to the climatic trend of the lasts vintages that brought this problem also in temperate regions. Moreover the need to have well ripe grape leads to an excessive sugar content in musts and, consequently, of ethanol in wine. The high ethanol level is a serious issue for the quality of the product and for health of the consumer. To overcome this problem, the EU has permitted the wine dealcoholization of up to 2% v/v by mean of physical methods. On the other hand, in the US, the high ethanol issue is resolved by adding water to musts with high sugar content (higher than 22° Brix), restoring the water lost due to dehydration of the berries before harvest. Many studies have been performed on the effects of the dealcoholization on wine quality and on consumer preference. Up to date the possible modifications of the stable isotopes composition induced by dealcoholization techniques have not been taken into account. Even if irrelevant on the perceived quality, this aspect is fundamental in the traceability process and for the assessment of the origin and genuineness of the product. Firsts experiences with dealcoholization membrane, performed at different ethanol removal intensity (up to -8% v/v) both on fermenting must and still wine, showed a modification on the δ 18O/16O ratio from +1.14 to -1.83. The treatment performed during fermentation showed similar results. Industrial dealcoholizations, performed in order to lower the ethanol content of about 2% v/v, with the membrane directly in the wine, or with combined membrane techniques on a fraction of wine, showed a modification on the isotopic ratio (δ 18O/16O ) from +2.88 to +2.01 and +2.27 with membrane in the wine and with combined techniques (nanofiltration + contactor), respectively. It will be reported detailed studies on experiences performed in order to accurately evaluate the principles that manage these modifications and the parameters that influence these ratios. Finally some solutions to overcome these problems will be reported