# Comparison of Three Approaches to Assess the Flavour Characteristics of Scotch Whisky Spirit
## 5 Conclusions  
The three methods compared in this study each provided different insights into the differences among whisky spirits. QDA gave quantitative data on the perceived intensity of flavour attributes, which could be presented in an easily interpreted graphical format and allowed statistical significance to be determined between spirits. However, this method was time-consuming, and required a pre-determined vocabulary of attributes and a trained and experienced panel. In comparison, Napping required only around one third of the time taken for QDA. With Napping panellists provided their own descriptions of sample differences, so no pre-selected vocabulary was needed. Although in this case the same panel was used, it is possible to carry out this approach using less experienced assessors. With Napping, differences between samples can be mapped out using PCA, but flavour profiles of individual samples cannot be produced. GC-MS provides information on the compositional differences between samples. The results of this analysis can be link to flavour differences based on previous knowledge of the sensory impacts of the measured congeners. A detailed summary of the advantages and disadvantages of the three techniques are summarised in Table 3.  
Overall, the study showed that the high ABV spirits contained relatively high concentrations of esters and certain alcohols which were linked to lighter flavour characteristics, such as _fruity, floral, solventy_, and _sweet_. The low ABV samples were richer in heavy flavour characteristics, such as _fruity, cereal, sour, oily_, and _sulphury_ and contained more aldehydes, than certain other alcohols. The medium ABV spirits were more variable in terms of flavour and composition. It was concluded that the nature of these spirits was likely to be due to other differences in metabolism between the yeast strains that were not directly correlated with the amount of alcohol that they produce. HMFA was used to statistically compare the three approaches. The results revealed that QDA showed a better resolution between the low ABV spirits, while GC-MS gave the best discrimination between the high ABV spirits. Napping showed the lowest resolution of the samples, though overall the product map was similar. When designing a study to determine the flavour characteristics of a set of food or drink samples, the researcher  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & **GC-MS** & **QDA** & **Napping** \\ \hline
**Nature of Analysis** & **Analytical** & **Sensory** & **Sensory** \\ \hline \multirow{4}{*}{Costs} & medium (after initial capital cost of the GC-MS): regular replacement of column, fibre, septa, no reuse of vials possible, internal standard & low: sensory glasses & low: sensory glasses, nappé possible, internal standard \\ \hline \multirow{4}{*}{Preparation time} & medium: diluting samples, preparing GC-MS (column, injector), runtime of the method & medium: diluting samples for each session, pre-select vocabulary & low: diluting samples \\ \hline \multirow{2}{*}{Sample volume required} & \multirow{2}{*}{1 to 5 mL at 20\% ABV} & 20 mL 20\% ABV multiplied by number of sessions & \multirow{2}{*}{20 mL at 20\% ABV} \\ \cline{1-1} \cline{2-2} \cline{4-4} \cline{5-5} \cline{1-1} \cline{2-2} \cline{  
must select a method that best matches both the information that they want to obtain and the resources that they have available. Overall, this research has shown that the best understanding of the flavour differences in whisky spirits will be obtained through using a combination of sensory and compositional analyses. Conceptualization, M.D. and F.J.; methodology, M.D., F.J. and I.B. ; formal analysis, M.D. and B.H. ; investigation, M.D. ; writing--original draft preparation, M.D. ; writing--review and editing, F.J., I.B., B.H., J.G. and G.W. ; supervision, F.J., J.G. and G.W. ; funding acquisition, F.J. and G.W. All authors have read and agreed to the published version of the manuscript.