## 1 Introduction  
The presence of carotenoids in grape berries is well documented [1]. 5,6-epoxysamthophylls and their 5,8-epoxy isomers were identified together with the most common carotenes and xanthophylls (i.e., \(\beta\)-carotene and lutein), the content of which was established to decrease during grape ripening from veraison to harvest [2; 3; 4]. The grape variety and viticulture practices, but also climate conditions and geographic origin, can influence the qualitative and quantitative profile of carotenoids in berries [5; 6; 7].  
Structurally, carotenoids are C\({}_{40}\) tetraterpenoids with a long chromophore of conjugated double bonds; thus, they can confer from red to yellow coloration to fruit [8]. However, especially in red/black grapes, this function is ascribed to anthocyanins and polyphenols [9]. Instead, carotenoids are mainly known as precursors of volatile compounds (i.e., C\({}_{13}\)-norisoprenoids), with very low olfactory perception thresholds. Thus, they have a fundamental role in defining the varietal aroma of grapes and wines [10; 11]. C\({}_{13}\)-norisoprenoids form by the direct enzymatic oxidation of carotenoids, such as \(\beta\)-carotene, lutein, neoxanthin, and violaxanthin, followed by the acid hydrolysis of glycosylated intermediates [12].  
There is no standard extraction procedure of carotenoids from foodstuffs; generally, in the case of grapes, aprotic and poor-polarity organic solvents, such as acetone [2] or diethyl ether/hexane 1:1 [13], are employed to extract caroten and xanthophylls simultaneously. Reversed-phase HPLC coupled with various detection techniques (e.g., DAD and MS) is currently the method of choice for carotenoid analysis [14]. In particular, the C\({}_{30}\) stationary phase has the highest separation selectivity including structural and geometrical isomers [15].  
Currently, the vineyard application of elicitors (i.e., methyl jasmonate or yeast extracts) represents the most original strategy to activate the biosynthesis of secondary metabolites because it may stimulate an innate immune response in grapes [16; 17]. Generally, it works in the case of the phenolic and volatile composition of grapes [9; 18; 19], but recent research has demonstrated that treatment with methyl jasmonate and yeast extracts was also determinant for increasing lutein and \(\beta\)-carotene concentrations in Tempranillo, Graciano, and Garnacha [20]. Additionally, the enzymes involved in carotenoid biosynthesis and degradation are acknowledged to be stress-dependent [21; 22].  
A previous study conducted by our research group on carotenoid degradation during the grape ripening of four varieties (Chardonnay, Merlot, Primitivo, and Negro Amaro) in the Apulia region proposed a parameter (\(\Delta\)C) to distinguish grapes with higher C\({}_{13}\)-norisoprenoid aroma potentiality. \(\Delta\)C (\(\mu\)g/kg), calculated as the difference between the total carotenoid content at veraison and harvest, was lowest in the autochthonous Primitivo and Negro Amaro [7]. Considering the supposed effect of yeast extracts on carotenoids, their application to vineyards could be hypothesized to enhance \(\Delta\)C in grapes, although, to the best of our knowledge, no other reports exist in the literature about this property.  
Therefore, this work aimed to assess the effectiveness of pre-harvest treatment by inactivated yeast extracts (YE) in improving the C\({}_{13}\)-norisoprenoid aroma potentiality of Apulian Negro Amaro and Primitivo varieties, which are fundamental in the context of Italian wine production.