Characterization and comparison of key aroma-active compounds of cocoa liquors from five different areas

Figures & data

Table 1. Sensory reference standards.

Descriptor	Definition
Roast	Roasted associated with pyrazines
Caramel	Caramel associated with Furaneol^TM [2,5-dimethyl-4-hydroxy-3(2H)-furanone]
Milky	The aromatic associated with 2,3-butanedione
Floral	The aromatic associated with a mixture of fresh cut flowers. A reference for floral is the aroma of linalool
Sour	The aromatic associated with acetic acid
Overall	Overall aroma intensity of the product

Figure 1. Sensory evaluation of five cocoa liquors (The scores of aroma were 0, 1, 2, 3, 4, and 5, which represent intensities of none, very weak, weak, middle, strong, and very strong, respectively).

Table 2. Sensory evaluation of five cocoa liquors.

Odor	Papua New Guinea	Ivory Coast	Indonesia	Ghana	Cameroon
Roast	3.8 ± 0.43d	3.0 ± 0.24c	1.2 ± 0.28a	2.6 ± 0.26bc	2.2 ± 0.18b
Caramel	3.2 ± 0.14d	2.9 ± 0.30c	0.9 ± 0.17a	2.6 ± 0.15bc	2.1 ± 0.22b
Milky	2.0 ± 0.45bc	1.5 ± 0.10ab	1.0 ± 0.10a	2.6 ± 0.34c	2.5 ± 0.26c
Floral	3.0 ± 0.19c	2.5 ± 0.36b	0.8 ± 0.08a	2.2 ± 0.39b	2.0 ± 0.13b
Sour	4.2 ± 0.18c	3.2 ± 0.34b	1.2 ± 0.20a	3.4 ± 0.37b	3.0 ± 0.36b
Overall	4.4 ± 0.45b	3.9 ± 0.52ab	2.8 ± 0.29a	3.8 ± 0.52ab	3.2 ± 0.17ab

Results stated as the mean ± SD (n = 10), results with different letters (a–e) were significantly different on the scores at p ≤ 0.05 by Turky’s test.

Table 3. Aroma-active compounds in the volatile extracts of five cocoa liquors obtained by DSE-SAFE.

Number	Compound	LRI^a		Odor property^b	Method of identification^c	Log3FD-factor^d
		DB-WAX	DB-5MS			Papua New Guinea	Ivory Coast	Indonesia	Ghana	Cameroon
	Alcohols
1	Linalool	1550	1101	Floral	MS,LRI,O	3	2	2	2	nd
2	β-Phenylethyl alcohol	1917	1118	Rosy	MS,LRI,O	2	3	1	3	3
	Aldehydes
3	3-Methylbutanal	938	<700	Malty	MS,LRI,O	5	5	5	4	4
6	Benzaldehyde	1527	972	Almond	MS,LRI,O	2	2	2	1	3
7	Benzeneacetaldehyde	1647	1049	Rosy	MS,LRI,O	2	2	1	2	4
	Esters
11	3-Methylbutyl acetate	1126	886	Fruity	MS,LRI,O	3	1	2	nd	3
13	Ethyl octylate		1196	Floral	MS,LRI,O	3	4	1	2	2
15	β-Phenylethyl acetate	1821	1259	Honey, sweet	MS,LRI,O	4	4	3	4	4
16	3-Methylbutyl benzoate	1846	1398	Sweet, cocoa	MS,LRI,O	2	3	2	2	3
	Pyrazines
21	2,5-Dimethylpyrazine	1330	919	Fried potato	MS,LRI,O	3	3	2	2	3
22	2,6-Dimethylpyrazine	1336	919	Fried potato	MS,LRI,O	3	3	2	2	3
23	Ethylpyrazine	1340	920	Popcorn	MS,LRI,O	5	5	4	4	4
24	2,3-Dimethylpyrazine	1355	938	Roasted, cocoa	MS,LRI,O	1	2	3	2	2
25	Trimethylpyrazine	1417	1006	Roasted, cocoa	MS,LRI,O	2	5	3	1	1
26	2-Ethyl-3,5-dimethylpyrazine	1472	1083	Potato chip	MS,LRI,O	nd	3	nd	2	3
27	3-Ethyl-2,5-dimethylpyrazine	1452	1080	Roasted, nutty	MS,LRI,O	5	nd	4	nd	3
28	Tetramethylpyrazine	1483	1089	Coffee, burnt	MS,LRI,O	3	3	4	3	3
29	3,5-Diethyl-2-methylpyrazine	1524	1159	Cocoa, chocolate	MS, LRI O	4	nd	4	nd	3
	Furans
31	Furfural	1463		Potato	MS,LRI,O	3	nd	3	nd	3
32	Linalool oxide	1477	1077	Floral	MS,LRI,O	3	2	1	2	1
	Acids
36	Acetic acid	1428	<700	Sour	MS,LRI,O	4	3	3	3	4
37	3-Methylbutanoic acid	1669	898	Stink	MS,LRI,O	5	5	5	4	3
	Sulfur compounds
38	Dimethyl trisulfide	1385	975	Onion, cabbage	MS,LRI,O	5	5	5	4	3
	Pyrroles
39	1H-pyrrole-2-carboxaldehyde	2041		Caramel, cocoa	MS,O	nd	3	nd	3	4
	Others
41	Massoia lactone	2017	1271	Floral	MS,O	1	3	2	3	3

^aLinear retention index (LRI) for the odors in DB-WAX and DB-5MS columns.

^bOdor descriptors are those used by all assessors, with most frequently used terms cited first.

^cMethod of identification as compound responsible for odor: MS, LRI, O, mass spectrum, linear retention index, and description of odor agree with reference compound in literature, which has been stated.

^dFlavor dilution factor determined by AEDA on capillary DB-WAX. Serial dilutions (1:3, 1:9, 1:27, etc.) in dichloromethane, the Log₃FD were 1, 2, 3, etc., respectively.

nd: not detected.

Table 4. Relative concentrations of predominant aroma-active compounds in five cocoa liquors measured by the P&T extraction followed by GC-O-MS.

			Relative contention (ng/g)^c
Number	Compound^a	LRI(DB-5MS)	Papua New Guinea	Ivory Coast	Indonesia	Ghana	Cameroon
	Alcohols
1	Linalool	1101	61.94 ± 1.69c	29.83 ± 1.15b	19.29 ± 0.81a	30.14 ± 1.53b	34.86 ± 2.29c
2	β-Phenylethyl alcohol	1118	22.91 ± 2.19b	31.61 ± 0.85c	6.66 ± 0.6a	63.53 ± 1.08e	47.26 ± 1.15d
	Aldehydes
3	2-Methylpropanal	<700	254.72 ± 4.14d	255.85 ± 6.27d	141.17 ± 5.24a	166.01 ± 4.84b	210.79 ± 3.92c
4	3-Methylbutanal	<700	1055.68 ± 20.85e	786.48 ± 4.93d	165.7 ± 4.9a	494.91 ± 6.85b	660.16 ± 5.4c
6	Benzaldehyde	972	147.56 ± 1.90e	106.91 ± 2.47c	39.65 ± 2.55a	78.71 ± 3.05b	122.51 ± 2.05d
7	Benzeneacetaldehyde	1049	tr^d	tr	tr	8.36 ± 0.98a	29.37 ± 2.85b
	Esters
7	3-Methylbutyl acetate	886	241.28 ± 2.71e	62.66 ± 2.56b	36.49 ± 1.49a	120.73 ± 2.51d	92.18 ± 1.67c
9	β-Phenylethyl acetate	1259	52.43 ± 1.69d	17.6 ± 1.10b	5.75 ± 0.38a	39.52 ± 1.11c	21.16 ± 1.33b
10	3-Methylbutyl benzoate	1398	15.95 ± 0.91cd	13.45 ± 1.06bc	4.90 ± 0.18a	16.14 ± 0.8d	11.57 ± 0.78b
	Pyrazines
11	Methylpyrazine	833	82.48 ± 1.65d	70.92 ± 2.35c	19.58 ± 0.97a	73.01 ± 2.44c	54.07 ± 1.73b
12	2,5-Dimethylpyrazine	919	59.53 ± 1.10c	75.09 ± 2.27d	20.51 ± 1.39a	63.33 ± 2.04c	50.97 ± 1.87b
13	2,6-Dimethylpyrazine	919	53.15 ± 1.43d	40.82 ± 1.84c	12.71 ± 1.51a	55.28 ± 2.27d	35.17 ± 1.21b
14	Ethylpyrazine	920	42.75 ± 1.68c	59.94 ± 1.72d	15.63 ± 1.01a	40.76 ± 2.60c	32.18 ± 1.46b
15	2,3-Dimethylpyrazine	938	50.54 ± 2.21c	48.18 ± 2.15c	12.38 ± 1.11a	46.15 ± 1.76c	29.93 ± 1.82b
16	Trimethylpyrazine	1006	127.65 ± 2.4d	100.47 ± 2.03c	11.19 ± 0.92a	95.9 ± 3.25c	62.13 ± 2.36b
17	2-Ethyl-3,5-dimethylpyrazine	1083	62.29 ± 1.60c	47.02 ± 2.24b	tr	42.13 ± 2.17a	28.21 ± 1.21c
18	Tetramethylpyrazine	1089	532.37 ± 4.91e	254.66 ± 2.92d	33.05 ± 1.37a	196.34 ± 6.36c	141.65 ± 2.66b
19	3,5-Diethyl-2-methylpyrazine	1159	45.02 ± 5.28	tr	tr	tr	tr
	Furans
20	2-Pentylfuran		24.36 ± 1.22ab	35.01 ± 7.16b	20.92 ± 0.74a	48.55 ± 1.81c	24.45 ± 0.74ab
21	Furfural		71.93 ± 5.36b	tr	37.05 ± 4.32a	tr	34.59 ± 3.27a
22	Linalool oxide	1077	40.26 ± 1.74d	24.43 ± 0.9b	11.43 ± 0.46a	30.28 ± 2.2c	26.00 ± 0.91bc
	Acids
23	Acetic acid	<700	1415.67 ± 20.75d	746.27 ± 9.08c	219.57 ± 13.07a	747.52 ± 4.99c	614.27 ± 12.93b
24	3-Methylbutanoic acid	898	573.78 ± 13.33d	257.53 ± 8.27c	42.64 ± 2.01a	214.4 ± 3.28b	258.67 ± 4.11c
	Sulfur compounds
25	Dimethyl trisulfide	975	25.34 ± 1.11d	12.8 ± 0.50bc	8.85 ± 0.36a	14.26 ± 0.72c	11.43 ± 0.45b

^aNames: compounds were identified in this work.

^bLinear retention index (LRI) for the odors in DB-WAX and DB-5MS columns.

^cResults stated as the mean ± SD (n = 3), results with different letters (a–e) were significantly different on the concentration at p ≤ 0.05 by Turky’s test.

^dtr means trace amount, tr is equal to <0.1 ng/g.

Figure 2. Sensory evaluation of five cocoa liquors (The scores of aroma were 0, 1, 2, 3, 4, and 5, which represent intensities of none, very weak, weak, middle, strong and very strong, respectively).