Abstract
Carotenoids are important secondary metabolites in wine grapes and play a key role as potential precursors of aroma compounds (i.e., C13-norisoprenoids), which have a high sensorial impact in wines. There is scarce information about the influence of pre-harvest inactivated yeast treatment on the norisoprenoid aroma potential of grapes. Thus, this work aimed to study the effect of the foliar application of yeast extracts (YE) to Negro Amaro and Primitivo grapevines on the carotenoid content during grape ripening and the difference between the resulting véraison and maturity (ΔC). The results showed that β-carotene and (allE)-lutein were the most abundant carotenoids in all samples, ranging from 60% to 70% of total compounds. Their levels, as well as those of violaxanthin, (9′Z)-neoxanthin, and 5,6-epoxylutein, decreased during ripening. This was especially observed in treated grapes, with ΔC values from 2.6 to 4.2-fold higher than in untreated grapes. Besides this, a principal components analysis (PCA) demonstrated that lutein, β-carotene, and violaxanthin and (9′Z)-neoxanthin derivatives principally characterized Negro Amaro and Primitivo, respectively. Thereby, the YE treatment has proved to be effective in improving the C13-norisoprenoid aroma potentiality of Negro Amaro and Primitivo, which are fundamental cultivars in the context of Italian wine production.
Highlights
The presence of carotenoids in grape berries is well documented [1]. 5,6-epoxyxanthophylls and their 5,8-epoxy isomers were identified together with the most common carotenes and xanthophylls (i.e., β-carotene and lutein), the content of which was established to decrease during grape ripening from véraison to harvest [2,3,4]
It is worth noting that consistency in carotenoid attribution is very complex due to their structural diversity
The double bond-conjugated system is susceptible to heat, light, oxygen, and acids, giving rise to unwanted cis–trans isomerization
Summary
The presence of carotenoids in grape berries is well documented [1]. 5,6-epoxyxanthophylls and their 5,8-epoxy isomers were identified together with the most common carotenes and xanthophylls (i.e., β-carotene and lutein), the content of which was established to decrease during grape ripening from véraison to harvest [2,3,4]. The presence of carotenoids in grape berries is well documented [1]. The grape variety and viticulture practices, and climate conditions and geographic origin, can influence the qualitative and quantitative profile of carotenoids in berries [5,6,7]. Carotenoids are C40 tetraterpenoids with a long chromophore of conjugated double bonds; they can confer from red to yellow coloration to fruit [8]. Carotenoids are mainly known as precursors of volatile compounds (i.e., C13 -norisoprenoids), with very low olfactory perception thresholds. They have a fundamental role in defining the varietal aroma of grapes and wines [10,11]. C13 -norisoprenoids form by the direct enzymatic oxidation of carotenoids, such
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