Postharvest Dehydration Temperature Modulates the Transcriptomic Programme and Flavonoid Profile of Grape Berries

Area of Science:

• Plant Physiology
• Food Science
• Biochemistry

Background:

• Raisins, a popular snack, are made by dehydrating grapes at high temperatures (HT).
• The metabolic and transcriptomic responses of white grape varieties to dehydration temperatures are not fully understood.
• Understanding these responses is crucial for optimizing raisin quality and nutritional value.

Purpose of the Study:

• To investigate the effects of different dehydration temperatures (30°C, 40°C, 50°C) on the transcriptomic and metabolic profiles of 'Xiangfei' white grape berries.
• To identify the optimal temperature for accumulating beneficial compounds like polyphenols in raisins.
• To elucidate the molecular mechanisms underlying grape berry response to dehydration stress.

Main Methods:

• Dehydration of 'Xiangfei' grape berries at 30°C, 40°C, and 50°C.
• Transcriptomic analysis to study gene expression patterns.
• Metabolite profiling to quantify key compounds like sugars, organic acids, and polyphenols.

Main Results:

• Postharvest dehydration increased soluble sugars and organic acids.
• 40°C was optimal for accumulating flavonoids and proanthocyanidins.
• Gallic acid accumulation was linked to increased expression of biosynthesis genes and regulation of NADP+/NADPH.
• Dehydration at 40°C accelerated gene transcription, particularly genes involved in heat stress response and redox homeostasis.

Conclusions:

• Selecting an appropriate dehydration temperature is critical for producing raisins rich in beneficial polyphenols.
• 40°C appears to be an optimal temperature for enhancing the accumulation of specific health-promoting compounds in raisins.
• The study provides insights into the molecular mechanisms governing grape berry response to dehydration, informing future raisin processing strategies.