Abstract
Ozone, a powerful oxidative stressor, has been recently used in wine industry as sanitizing agent to reduce spoilage microflora on grapes. In this study, we evaluated ozone-induced metabolic and molecular responses during postharvest grape dehydration. Ozone increased the contents of total volatile organic compounds (VOCs), which have a great impact on the organoleptic properties of grapes and wines. Among terpenes, responsible for floral and fruity aroma, linalool, geraniol and nerol were the major aromatic markers of Moscato bianco grapes. They were significantly affected by the long-term ozone treatment, increasing their concentration in the last phases of dehydration (>20% weight loss). At molecular level, our results demonstrated that both postharvest dehydration and ozone exposure induce the biosynthesis of monoterpenes via methylerythritol phosphate (MEP) pathway and of aldehydes from lipoxygenase-hydroperoxide lyase (LOX-HPL) pathway. Therefore, transcriptional changes occurred and promoted the over-production of many important volatile compounds for the quality of white grapes.
Highlights
In grapevine (Vitis vinifera L.), several classes of secondary metabolites are synthetized in berries, which determine the characteristics and the quality of each cultivar and of the wines produced
A significant effect of ozone treatment was observed on glucose, fructose and glycerol when berries were dehydrated until reaching 10 and 20% of weight loss (P10 and P20, respectively), increasing their contents in relation to air-treated grapes
The contents of glucose and fructose increased for both air and ozone treatments
Summary
In grapevine (Vitis vinifera L.), several classes of secondary metabolites are synthetized in berries, which determine the characteristics and the quality of each cultivar and of the wines produced Among these metabolites, many volatile organic compounds (VOCs) are present in grape berries and some of them play a key role in the aromatic quality of white wines[1]. C6-compounds are produced by oxidative cleavage of polyunsaturated fatty acids (PUFAs), in particular linoleic and linolenic acids This process occurs through the lipoxygenase–hydroperoxide lyase (LOX– HPL) pathway, in which lipoxygenase (LOX), hydroperoxide lyase (HPL) and alcohol dehydrogenases (ADHs) are the major enzymes involved[9,10,11,12]. It has been reported that volatile isoprenoids can mitigate the effects of oxidative stress, including the one caused by ROS production in plant cells[20]
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