## 1 Introduction  
Wine is a complex solution containing abundant volatile compounds which contribute to wine aroma and flavour, and consequently impact wine quality and appreciation. Wine aromas are broadly categorised into three groups that reflect their source. Primary aromas are grape-derived volatiles that pass through fermentation often unchanged, and are largely responsible for \"varietal\" aromas. Secondary aromas, which are by far the greatest pool of volatile molecules, are produced through the winemaking process, with the great majority produced by yeast during alcoholic fermentation as metabolism byproducts [1; 2]. Tertiary aromas develop in finished wine through storage and maturation, and result from intermolecular chemical interactions and equilibrium effects as the wine matrix changes. The volatile composition of most wines, or styles of wine, is very similar, and the varietal differences that exist between wines made from different varieties of grapes are largely due to the relative ratios of the volatile compounds contained within [3]. The types of volatile compounds are diverse, and include esters, higher alcohols, aldehydes, ketones, lactones, acids, phenols, \(N\)-heterocycles, isoprenoids and sulfur compounds [1; 4]. Of these categories, higher alcohols represent the largest volatile pool in terms of concentration, but esters have the largest number of contributing molecules [5]. In this work the term _esters_ encompasses both ethyl and acetate esters, which have a significant effect on wine aroma by contributing fruity and floral characteristics [6; 7]. These esters are mainly produced by yeast metabolism through fatty acid acyl- and acetyl-Coenzyme A (CoA) pathways [7; 8]. CoA is a critical cofactor for a large number of metabolic pathways and is used to activate intermediates during the biosynthesis of medium chain fatty acids (MCFAs); the acyl-CoA intermediates formed are then esterified with ethanol by esterase and transferase enzymes, forming MCFA ethyl esters. Acetate esters, on the other hand, are produced through the condensation of yeast-derived higher alcohols with acetyl-CoA, again under the control of ester-forming enzymes [7; 8]. Ester production mainly occurs during fermentation when yeasts generate ample amounts of ethanol and higher alcohols via sugar and amino acid metabolism, respectively [9], so CoA may play a significant role in determining the ester content in wine [10]. For instance, it has been suggested that factors that regulate the production or consumption of acetyl-CoA will in turn alter the amount of esters produced by yeast, and there is evidence for the association of some specific amino acids with CoA biosynthesis [11; 12; 13]. However, there are no reports directly studying the effect of CoA-related amino acid composition (arising from the grapes) on CoA biosynthesis, and subsequently how a change in CoA concentration might influence ester levels in wine. Despite the role of acyl transferase enzymes in ester formation by yeast, [PERSON] _et al._[14] indicated that the level of gene expression is not the limiting factor for ester production, and that the availability of MCFA precursors has an important role. Moreover, grape chemical composition has been highlightedas being highly influential to the level of production of a suite of aroma compounds, and many grape components are known to be depleted and converted to alcohols and esters through fermentation [15]. It has been widely demonstrated that yeast can liberate volatile molecules from various grape-derived conjugates, such as glycosidically bound and cysteine- and glutathione-conjugated volatile compounds [16,17]. More recent investigations have sought to demonstrate the relationship between grape-derived precursors and wine volatile aromas, such as a study involving fermions in model grape juice medium spiked with varying amounts of natural grape juice to test the impact on wine aromas [18].