Control of environmental parameters in postharvest partial dehydration of wine grapes reduces water stress

The hypothesis that a controlled environmental condition of postharvest partial dehydration of wine grapes may reduce berry water stress keeping a better grape quality, was verified on white wine grapes, var. ‘Pecorino’. Grapes were harvested at 21.5% solid soluble content (SSC) and kept at 15 °C, 60% relative humidity (RH), and 2.5 m s−1 or 1.2 m s−1 air speed (tunnel), with a vapor pressure deficit (VPD) of 7.5–8 mbar; control bunches were kept in an uncontrolled condition (VPD = 0.7–6.4 mbar). Samplings for chemical and biochemical analyses were performed on grapes with 10, 25, 35, and 45% mass loss (m.l.). Tunnel and control samples reached 31.5% (in 24-26 days) and 28.5% (in 28 days) SSC, respectively. Control grapes had higher CO2 production, alcohol dehydrogenase (ADH) and lipooxygenase (LOX) activities and proline content. Ethanol and acetaldehyde contents reflected ADH activity patterns. Control grape had higher percentage of branched alcohols than control ones. An activation of aerobic fermentation in control grapes is discussed with comment on related generation of specific volatile organic compounds (VOCs).