## 2 Results and Discussion
### Amino Acids Involved in CoA Biosynthesis
#### 2.2.2 \(\beta\)-Alanine Concentrations in Grapes are Sufficient to Stimulate Ester Production  
The previous experiment demonstrated that additions of 50 and 100 mg\(\cdot\)L\({}^{-1}\)\(\beta\)-alanine could increase ester concentrations in model fermentations, but cysteine, arginine and valine did not have a significant effect. The concentrations of \(\beta\)-alanine added to the must were above the maximum reported in the literature for _V. vinifera_ (33 mg\(\cdot\)L\({}^{-1}\); [39]) or _Vitis labruscana_ (13 mg\(\cdot\)L\({}^{-1}\); [41]). A collection of 50 Cabernet Sauvignon grape parcels obtained from eight growing regions across two vintages was analysed for \(\beta\)-alanine content to confirm that similar concentrations would be found in Australian-grown fruit. The concentration of \(\beta\)-alanine in these samples ranged from 14 to 66 mg\(\cdot\)L\({}^{-1}\) with no apparent pattern based on vintage or growing region. Given that some of these values were below the lowest concentration of \(\beta\)-alanine tested in the experiment above (50 mg\(\cdot\)L\({}^{-1}\)), lower concentrations of \(\beta\)-alanine were assessed for their ability to stimulate ester production. The results indicated that a significant stimulation of ethyl hexanoate production was achieved with the addition of 1 mg\(\cdot\)L\({}^{-1}\)\(\beta\)-alanine to the model must, and any further increase did not significantly increase ethyl ester production further (Figure 7A). This result was the same for ethyl octanoate and ethyl decanoate production (data not shown). Hexanoic acid, octanoic acid and decanoic acid also accumulated to higher concentrations in the wines produced after the addition of 1 mg\(\cdot\)L\({}^{-1}\) or more \(\beta\)-alanine--data is shown for hexanoic acid (Figure 7B). Similarly, ethyl acetate was present in higher concentrations in wines produced after any \(\beta\)-alanine addition compared to the control treatment (Figure 7C), although the accumulation of phenylethyl acetate and isoamyl acetate was not significantly different from the control treatments for some of the low \(\beta\)-alanine concentrations (data not shown). This suggests that 1 mg\(\cdot\)L\({}^{-1}\) or less of \(\beta\)-alanine is sufficient to stimulate the production of greater amounts of MCFAs and their corresponding ethyl esters, but the addition of more \(\beta\)-alanine does not significantly increase this production further. It is possible that 1 mg\(\cdot\)L\({}^{-1}\) of \(\beta\)-alanine is enough to account for the requirements of the yeast for maximum fatty acid anabolism and any extra is utilised for other forms of nitrogen metabolism. The effect of \(\beta\)-alanine additions on acetate ester production is probably complicated by the limitation of the alcohol moiety of the ester in the case of isoamyl acetate and phenylethyl acetate; in the case of ethyl acetate, where the alcohol is not limiting, the accumulation is similar to that seen for the ethyl esters (Figure 7). 2.2.3 \(\beta\)-Alanine or Pantothenate Supplementation Have a Similar Effect on Ester Production  
To test whether the effect of \(\beta\)-alanine addition to the model must had a similar effect as adding pantothenate, another set of fermentations was prepared with either no additions, addition of 100 mg\(\cdot\)L\({}^{-1}\)\(\beta\)-alanine (1.12 mM), addition of 267 mg\(\cdot\)L\({}^{-1}\) pantothhenate (1.12 mM), and addition of both \(\beta\)-alanine and pantothenate (same concentration as above). Figure 7: The concentration of (**A**) ethyl hexanoate, (**B**) hexanoic acid and (**C**) ethyl acetate in model wines produced after the addition of increasing amounts of \(\beta\)-alanine as indicated on the x-axis. Histograms represent the mean values (n = 3) and error bars show standard errors. Different letters (e.g., a, b) denote significant differences between treatments at \(p<0.05\) using ANOVA followed by [PERSON]’s _post hoc_ test.