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Postharvest wine grape dehydration: ethanol dissipation from grape and biochemical changes.
Alessandro Bianchi1, Stefano Pettinelli1, Gregorio Santini1
1Department of Agriculture, Food and Environment (DAFE), University of Pisa, Pisa, Italy.
Journal of the Science of Food and Agriculture
|October 11, 2023
Summary
Postharvest dehydration of wine grapes significantly reduces ethanol levels, correlating with weight loss and decreased anaerobic enzyme activity. This shift promotes oxidative metabolism, crucial for grape quality during drying.
Area of Science:
- Agricultural Science
- Biochemistry
- Food Science
Background:
- Grapes undergo metabolic shifts during postharvest dehydration, impacting final product quality.
- Ethanol production is a critical metabolic step in grape dehydration.
- Ethanol dissipation dynamics during wine grape dehydration remain unquantified.
Purpose of the Study:
- To quantify ethanol dissipation during postharvest dehydration of Raboso grapes.
- To investigate associated chemical-biochemical alterations in the berries.
Main Methods:
- Controlled postharvest dehydration of Raboso grapes.
- Monitoring of ethanol dissipation and weight loss.
- Enzymatic activity assays for anaerobic metabolism indicators (alcohol dehydrogenase, pyruvate decarboxylase, lactate dehydrogenase).
- Measurement of lipoxygenase activity and polyphenol oxidation.
Main Results:
- Ethanol dissipation accounted for up to 36% of weight loss.
- A strong correlation (r² = 0.989) was observed between ethanol dissipation and grape weight loss.
- Activities of alcohol dehydrogenase, pyruvate decarboxylase, and lactate dehydrogenase significantly decreased with dehydration.
- Lipoxygenase activity peaked at 27% weight loss; polyphenol oxidation remained stable then declined.
Conclusions:
- Ethanol dissipation during dehydration shifts grape metabolism from anaerobic to oxidative pathways.
- This metabolic transition is linked to reduced anaerobic enzyme activity and weight loss.
- The study suggests a sensor for monitoring berry metabolism during dehydration could be a valuable commercial tool.
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