Postharvest Wine Grape Dehydration: ethanol dissipation from grape and biochemical changes

Background: During postharvest dehydration, grapes are subject to metabolic changes including ethanol anabolism and catabolism. These changes affect the quality of the final product and ethanol production is a key step. Ethanol dissipation has never been measured during postharvest wine grape dehydration thus the present study aimed: i) to monitor ethanol dissipation; ii) to study chemical-biochemical changes in berries during dehydration. Results: Ethanol dissipation from Raboso grapes was measured, under controlled postharvest dehydration up to 36 % weight loss (w.l.). Moreover, the activity of enzymes involved in the anaerobic metabolism of grapes was studied. Ethanol dissipation was highly correlated with grape weight loss (R2 = 0.989). Alcohol dehydrogenase (ADH) activity, responsible for the reduction of ethanol to acetaldehyde, declined significantly with the w.l. Similarly, pyruvate decarboxylase (PDC) and lactate dehydrogenase (LDH) reduced their activity. High lipoxygenase activity (LOX) was measured at 27 % w.l., while polyphenol oxidation (PPO) was constant and declined in the last sampling. Conclusion: Ethanol dissipation during postharvest dehydration allows for reducing anaerobic metabolism and promotes oxidative metabolism. The sensor used can be a useful commercial tool to monitor the berry metabolism. This article is protected by copyright. All rights reserved.