Identification of Volatile Compounds Contributory to Mango and Tropical-Type Aroma in Whisky

Figures & data

Table 1. The production region and additional properties of the investigated single malt whisky products. Production regions are defined using nomenclature of territorial units for statistics (NUTS) descriptors^[32] or Scotch whisky producing regions as described by the Scotch whisky regulations 2009.^[33]

Whisky	Production region	Alcohol (% ABV)	Product age (years)	Additional properties
1	Ireland (Dublin)	55	14	Bourbon cask, non-chill filtered, cask strength
2	Ireland (Dublin)	60	14	Bourbon cask, non-chill filtered, cask strength
3	Ireland (Dublin)	40	NAS	Bourbon cask
4	Ireland (Dublin)	43	12	Bourbon cask
5	Ireland (Mid-East)	40	NAS	Peated malt
6	Northern Ireland	40	10	Bourbon and sherry cask
7	Scotland (Highland)	40	10	Bourbon cask
8	Scotland (Speyside)	40	12	–
9	Scotland (Highland)	40	12	–
10	Scotland (Highland)	40	12	Predominantly sherry cask
11	Scotland (Speyside)	55	15	Bourbon cask, non-chill filtered, cask strength
12	Scotland (Highland)	46	10	Bourbon cask, non-chill filtered
13	Ireland (Mid-East)	43	NAS	Bourbon cask
14	Scotland (Highland)	46	10	Non-chill filtered, no color adjustment

NAS: Non-age statement.

Figure 1. PCA plot displaying the aroma characteristics of 14 whisky samples assessed using sensory evaluation by eight trained panellists (PC1 and PC2 70.16%).

Table 2. The average sensory scores of 16 lexicon terms in 14 commercial whiskies as determined by an industry panel. Traits scored on a scale of 0–100.

Whisky	Alcohol	Apple	Banana	Caramel	Cereal	Cream	Floral	Green	Mango	Oily	Orange	Peach	Smoky	Sulphury	Tropical	Woody
1	40.3 ^a	45.4 ^ab	39.1 ^a	28.9 ^a	28.9 ^a	29.3 ^a	44.0 ^a	54.0 ^a	46.4 ^ab	27.9 ^a	32.3 ^a	42.3 ^ab	18.8 ^c	28.7 ^b	47.0 ^ab	26.8 ^a
2	33.2 ^a	54.8 ^a	43.8 ^a	27.4 ^a	25.8 ^a	32.0 ^a	43.8 ^a	32.2 ^b	54.7 ^a	27.5 ^a	35.7 ^a	58.5 ^a	14.7 ^c	30.0 ^b	55.7 ^a	25.8 ^a
3	39.5 ^a	42.4 ^ab	34.2 ^a	20.5 ^a	30.3 ^a	25.1 ^a	40.8 ^a	46.0 ^ab	33.0 ^abc	29.1 ^a	27.8 ^a	41.0 ^ab	20.2 ^c	28.2 ^b	36.4 ^ab	27.8 ^a
4	38.7 ^a	49.6 ^a	40.2 ^a	35.8 ^a	26.3 ^a	35.8 ^a	43.1 ^a	38.2 ^ab	30.3 ^abc	33.8 ^a	30.9 ^a	43.8 ^ab	16.0 ^c	27.9 ^b	35.8 ^ab	37.4 ^a
5	38.7 ^a	27.0 ^b	26.8 ^a	28.4 ^a	38.7 ^a	36.1 ^a	27.2 ^a	26.3 ^b	21.6 ^c	39.3 ^a	24.4 ^a	27.3 ^b	82.1 ^a	40.3 ^ab	25.5 ^b	28.7 ^a
6	32.3 ^a	46.0 ^ab	36.0 ^a	29.0 ^a	32.0 ^a	37.0 ^a	39.5 ^a	31.1 ^b	32.7 ^abc	33.5 ^a	33.3 ^a	41.4 ^ab	30.4 ^c	36.9 ^ab	33.2 ^ab	31.0 ^a
7	37.4 ^a	45.2 ^ab	36.3 ^a	33.8 ^a	34.0 ^a	42.8 ^a	31.7 ^a	38.9 ^ab	34.8 ^abc	34.6 ^a	28.6 ^a	41.0 ^ab	14.8 ^c	39.3 ^ab	37.2 ^ab	27.1 ^a
8	36.6 ^a	44.0 ^ab	35.2 ^a	35.8 ^a	35.5 ^a	39.9 ^a	39.9 ^a	37.8 ^ab	39.1 ^abc	34.6 ^a	30.7 ^a	42.2 ^ab	17.7 ^c	31.9 ^b	39.4 ^ab	25.1 ^a
9	41.1 ^a	37.6 ^ab	36.5 ^a	32.6 ^a	35.0 ^a	36.6 ^a	32.3 ^a	31.2 ^b	27.3 ^bc	40.0 ^a	26.0 ^a	35.1 ^ab	24.3 ^c	44.9 ^ab	31.6 ^b	28.8 ^a
10	40.6 ^a	33.5 ^ab	29.0 ^a	35.0 ^a	36.2 ^a	35.7 ^a	31.3 ^a	33.0 ^ab	28.9 ^bc	43.8 ^a	25.7 ^a	31.1 ^b	51.1 ^b	59.1 ^a	28.3 ^b	29.6 ^a
11	35.3 ^a	47.3 ^ab	40.9 ^a	36.0 ^a	27.3 ^a	42.5 ^a	37.8 ^a	34.4 ^ab	36.8 ^abc	33.2 ^a	34.2 ^a	49.3 ^ab	19.6 ^c	27.0 ^b	38.6 ^ab	27.1 ^a
12	33.5 ^a	53.8 ^a	41.2 ^a	30.3 ^a	29.4 ^a	36.3 ^a	47.3 ^a	38.9 ^ab	41.2 ^abc	37.3 ^a	33.6 ^a	45.7 ^ab	15.8 ^c	30.3 ^b	39.3 ^ab	28.5 ^a
13	41.4 ^a	47.2 ^ab	41.7 ^a	28.2 ^a	26.6 ^a	30.3 ^a	40.1 ^a	39.9 ^ab	29.9 ^bc	34.7 ^a	27.5 ^a	39.9 ^ab	17.8 ^c	34.4 ^b	29.6 ^b	25.5 ^a
14	28.0 ^a	43.2 ^ab	42.8 ^a	28.2 ^a	29.8 ^a	32.3 ^a	42.6 ^a	41.0 ^ab	47.0 ^ab	30.5 ^a	31.3 ^a	46.1 ^ab	18.4 ^c	35.1 ^b	48.5 ^ab	25.3 ^a

Superscript letters signify post-hoc significance groups as determined by Tukey’s HSD.

Table 3. Pearson’s correlation assessing the relationship between sensory evaluation score by eight panellists (of 14 commercial whiskies) and peak area of whisky component compounds measured using GC-MS.

Sensory trait	Isoamyl decanoate	Isoamyl octanoate	Isovaleraldehyde diethyl acetal	Isobutyraldehyde diethyl acetal	2-Heptanol	1,1,3-Triethoxy- propane	Acetaldehyde diethyl acetal	4-Methyl-3- penten-2-one	2-Heptanone	Ethyl decanoate
Alcohol	−0.592*	−0.479	−0.338	−0.108	−0.025	−0.199	−0.570*	0.122	0.084	−0.532*
Apple	0.623*	0.680*	0.312	0.423	0.436	0.322	0.144	0.222	0.352	0.116
Banana	0.716*	0.779*	0.502	0.404	0.356	0.334	0.340	0.244	0.235	0.207
Caramel	−0.058	0.100	−0.116	−0.321	−0.335	−0.253	0.046	−0.201	−0.282	−0.217
Cereal	−0.636*	−0.619*	−0.430	−0.503	−0.455	−0.394	−0.203	−0.299	−0.420	−0.088
Cream	−0.032	0.147	−0.293	−0.426	−0.384	−0.271	−0.001	−0.396	−0.441	−0.126
Floral	0.587*	0.532	0.368	0.392	0.357	0.276	0.160	0.349	0.346	0.245
Green	0.095	0.182	0.047	0.261	0.376	−0.009	−0.188	0.559*	0.382	−0.090
Mango	0.767*	0.723*	0.709*	0.694*	0.658*	0.650*	0.584*	0.566*	0.554*	0.536*
Oily	−0.429	−0.450	−0.484	−0.674*	−0.717*	−0.512	−0.350	−0.538*	−0.621*	−0.245
Orange	0.761*	0.716*	0.449	0.461	0.441	0.494	0.388	0.352	0.339	0.293
Peach	0.791*	0.817*	0.556*	0.604*	0.574*	0.559*	0.455	0.281	0.504	0.326
Smoky	−0.396	−0.590*	−0.165	−0.252	−0.331	−0.043	0.004	−0.173	−0.293	0.159
Sulphury	−0.441	−0.553	−0.195	−0.354	−0.394	−0.267	−0.088	−0.369	−0.281	−0.341
Tropical	0.729*	0.721*	0.737*	0.745*	0.719*	0.666*	0.647*	0.567*	0.637*	0.545*
Woody	−0.312	−0.358	−0.253	−0.162	−0.158	−0.261	−0.123	−0.206	0.012	−0.265

* Correlation significant at p < 0.05 (two-tailed)

Table 4. The concentration of compounds identified to correlate positively with mango aroma (with three associated aldehydes) in 14 whisky samples. Results are presented as the mean of triplicate analyses ± standard deviation.

	Whisky
Compound	1	2	3	4	5	6	7	8	9	10	11	12	13	14
Aldehydes
Acetaldehyde (mg/LAA)	84 ± 19 ^bcd	83 ± 7 ^bcd	52 ± 13 ^d	106 ± 7 ^bc	84 ± 4 ^bcd	93 ± 8 ^bcd	71 ± 9 ^bcd	87 ± 11 ^bcd	89 ± 16 ^bcd	115 ± 47 ^b	62 ± 3 ^cd	58 ± 2 ^cd	61 ± 4 ^cd	557 ± 34 ^a
Isobutyraldehyde (mg/LAA)	14.2 ± 3.0 ^a	13.0 ± 0.2 ^ab	12.6 ± 1.7 ^ab	10.1 ± 0.5 ^bc	4.5 ± 1.1 ^e	8.1 ± 1.8 ^cd	3.2 ± 0.2 ^e	5.6 ± 0.5 ^de	4.9 ± 0.2 ^de	5.1 ± 1.8 ^de	3.1 ± 0.2 ^e	3.3 ± 0.4 ^e	5.8 ± 0.1 ^de	6.6 ± 0.4 ^cde
Isovaleraldehyde (mg/LAA)	2.49 ± 0.22 ^ab	2.64 ± 0.07 ^a	1.41 ± 0.10 ^fgh	2.34 ± 0.10 ^abc	1.59 ± 0.18 ^efg	1.38 ± 0.05 ^fgh	1.94 ± 0.13 ^cde	1.93 ± 0.07 ^cde	1.70 ± 0.15 ^def	2.14 ± 0.44 ^bcd	1.09 ± 0.05 ^h	1.18 ± 0.01 ^gh	1.84 ± 0.06 ^def	2.64 ± 0.09 ^a
Acetals
Acetaldehyde diethyl acetal (mg/LAA)	36.4 ± 0.7 ^c	57.6 ± 2.9 ^a	10.9 ± 0.9 ^h	30.7 ± 0.9 ^cde	26.5 ± 1.1 ^def	26.1 ± 1.1 ^ef	21.1 ± 1.8 ^fg	26.6 ± 1.8 ^def	26.6 ± 4.7 ^def	33.4 ± 5.6 ^cd	27.7 ± 1.9 ^def	18.1 ± 0.9 ^g	18.7 ± 0.3 ^g	50.3 ± 1.2 ^b
Isobutyraldehyde diethyl acetal (mg/LAA)	4.23 ± 0.11 ^b	6.13 ± 0.12 ^a	2.03 ± 0.03 ^c	1.86 ± 0.02 ^c	0.91 ± 0.18 ^ef	1.40 ± 0.34 ^d	0.64 ± 0.02 ^f	1.09 ± 0.04 ^de	0.90 ± 0.03 ^ef	0.78 ± 0.10 ^ef	0.96 ± 0.05 ^ef	0.67 ± 0.08 ^f	1.07 ± 0.02 ^de	1.35 ± 0.04 ^d
Isovaleraldehyde diethyl acetal (mg/LAA)	1.10 ± 0.05 ^b	1.42 ± 0.10 ^a	0.27 ± 0.02 ^f	0.45 ± 0.03 ^cd	0.32 ± 0.04 ^ef	0.26 ± 0.02 ^f	0.33 ± 0.02 ^ef	0.36 ± 0.03 ^def	0.26 ± 0.03 ^f	0.32 ± 0.02 ^ef	0.35 ± 0.02 ^def	0.25 ± 0.00 ^f	0.39 ± 0.02 ^de	0.55 ± 0.01 ^c
Alcohol/Ketone
2-Heptanol (mg/LAA)	0.389 ± 0.010 ^b	0.413 ± 0.012 ^a	ND ^c	ND ^c	ND ^c	ND ^c	ND ^c	ND ^c	ND ^c	ND ^c	ND ^c	ND ^c	ND ^c	ND ^c
2-Heptanone (mg/LAA)	0.608 ± 0.008 ^b	0.652 ± 0.010 ^a	0.444 ± 0.019 ^c	0.284 ± 0.005 ^d	ND ^e	ND ^e	ND ^e	ND ^e	ND ^e	ND ^e	ND ^e	ND ^e	ND ^e	ND ^e
4-Methyl-3-penten-2-one (mg/LAA)	1.359 ± 0.060 ^a	0.535 ± 0.023 ^b	ND ^c	ND ^c	ND ^c	ND ^c	ND ^c	ND ^c	ND ^c	ND ^c	ND ^c	ND ^c	ND ^c	ND ^c
Fatty acid esters
Ethyl decanoate (mg/LAA)	40.2 ± 0.9 ^de	60.2 ± 8.3 ^ab	26.3 ± 13.9 ^ef	44.3 ± 3.9 ^cd	17.4 ± 2.1 ^f	31.6 ± 3.3 ^def	18.6 ± 1.5 ^f	21.0 ± 0.1 ^f	23.1 ± 0.9 ^f	39.2 ± 8.1 ^de	66.1 ± 0.7 ^ab	57.2 ± 1.2 ^bc	16.6 ± 1.4 ^f	72.3 ± 0.5 ^a
Isoamyl octanoate (mg/LAA)	0.812 ± 0.090 ^b	0.932 ± 0.016 ^a	0.486 ± 0.017 ^d	0.642 ± 0.047 ^c	0.271 ± 0.033 ^e	0.415 ± 0.043 ^d	0.224 ± 0.011 ^ef	0.123 ± 0.074 ^f	0.169 ± 0.038 ^ef	0.235 ± 0.004 ^ef	0.671 ± 0.023 ^c	0.632 ± 0.040 ^c	0.410 ± 0.044 ^d	0.643 ± 0.033 ^c
Isoamyl decanoate (mg/LAA)	2.63 ± 0.33 ^b	3.42 ± 0.09 ^a	1.02 ± 0.08 ^cd	1.31 ± 0.08 ^c	0.48 ± 0.13 ^ef	0.69 ± 0.12 ^de	0.44 ± 0.03 ^ef	0.23 ± 0.02 ^f	0.34 ± 0.05 ^ef	0.36 ± 0.01 ^ef	2.34 ± 0.15 ^b	2.37 ± 0.07 ^b	1.21 ± 0.10 ^c	2.31 ± 0.03 ^b

Superscript letters signify post-hoc significance groups as determined by Tukey’s HSD. ND = not detected.

Table 5. Odour activity values (OAV) for whisky components. Values are based on previously reported aroma thresholds and compound concentration in Whisky 2 at 20% ABV.

Compound	Threshold (mg/L)	OAVs
Isobutyraldehyde	0.0059^a	442
Isovaleraldehyde	0.0028^a	189
Acetaldehyde diethyl acetal	0.719^a	16
Isobutyraldehyde diethyl acetal (No FG available)	0.1^b	12
Ethyl decanoate	1.1 ^d	11
Isovaleraldehyde diethyl acetal	0.05^b	6
2-Heptanol	0.25^c	0.33
Isoamyl octanoate	0.6^d	0.31
2-Heptanone	2^c	0.07
Isoamyl decanoate	5^d	0.05

^{a [28]} (threshold determined in whisky),

^{b [34]} (whisky),

^{c [35]} (beer),

^{d [36]} (imitation whisky)

Table 6. Impact of spiking five candidate compounds on reporting of fruit-type aroma descriptors in mature whisky product. Results are presented as the average scores of 16 panellists across two duplicate sensory sessions.

Whisky	Combination additive	Mango	Peach	Orange	Apple
2	None	51.7 ^a	42.4 ^a	33.3 ^a	33.9 ^a
13	+ IBA, IVA, ACD, IVD, 2HN	48.6 ^ab	43.1 ^a	25.9 ^a	40.8 ^a
13	+ IBA, IVA, ACD, IVD	46.9 ^abc	42.9 ^a	26.5 ^a	33.8 ^a
13	+ IBA, IVA, ACD	47.0 ^abc	41.5 ^a	25.0 ^a	40.3 ^a
13	+ IBA, IVA	48.8 ^ab	36.4 ^a	24.0 ^a	37.7 ^a
13	+ IBA	34.4 ^bc	45.2 ^a	20.7 ^a	37.3 ^a
13	None	32.3 ^c	37.5 ^a	22.5 ^a	40.1 ^a

Superscript letters signify post-hoc significance groups as determined by Tukey’s HSD. Traits scored on a scale of 0-100.

IBA: isobutyraldehyde; IVA: isovaleraldehyde; ACD: acetaldehyde diethyl acetal; IVD: isovaleraldehyde diethyl acetal; 2HN: 2-heptanol.

Table 7. Impact of spiking isobutyraldehyde, isovaleraldehyde, and isovaleraldehyde diethyl acetal on reporting of fruit-type aroma descriptors in mature whisky product. Results are presented as the average scores of 16 panellists across two duplicate sensory sessions.

Whisky	Combination additive	Mango	Peach	Orange	Apple
13	+ IBA, IVA, IVD	53.3 ^a	45.0 ^a	32.1 ^a	37.7 ^a
13	+ IBA, IVA	47.3 ^ab	47.0 ^a	23.6 ^a	43.7 ^a
13	+ IVA, IVD	45.2 ^ab	51.5 ^a	33.2 ^a	41.9 ^a
13	+ IBA	44.9 ^ab	45.0 ^a	32.2 ^a	43.3 ^a
13	+ IVD	43.8 ^ab	51.4 ^a	30.4 ^a	48.4 ^a
13	+ IVA	38.7 ^ab	47.3 ^a	27.3 ^a	44.3 ^a
13	None	34.0 ^b	46.4 ^a	30.7 ^a	45.1 ^a

Superscript letters signify post-hoc significance groups as determined by Tukey’s HSD. Traits scored on a scale of 0-100.

IBA: isobutyraldehyde; IVA: isovaleraldehyde; IVD: isovaleraldehyde diethyl acetal.

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