. 2019 Jan 30;272:251–257. doi: 10.1016/j.foodchem.2018.07.226

Table 2.

Average relative abundance of each volatile compound (relative to Arabica) presented in the headspace was calculated in the eight coffee samples (excludes acetic acid).

	aroma compound	Robusta	0%	1%	2%	3%	4%	5%	Arabica
1	2,6-diethylpyrazine	498 ± 7.9^e	338 ± 35^d	278 ± 24^cd	246 ± 23^bcd	235 ± 20^bc	174 ± 35^ab	208 ± 22^bc	100 ± 17^a
2	3-ethyl-2,5-dimethylpyrazine	435 ± 39^d	340 ± 49^cd	266 ± 22^bc	256 ± 20^bc	221 ± 8.6^b	176 ± 19^ab	226 ± 18^b	100 ± 18^a
3	2-ethyl-6-methylpyrazine	327 ± 21^d	276 ± 27^cd	233 ± 14^bc	210 ± 18^bc	197 ± 16^bc	148 ± 25^ab	183 ± 38^ab	100 ± 26^a
4	trimethylpyrazine	314 ± 27^d	244 ± 23^cd	193 ± 26^bc	176 ± 17^abc	160 ± 19^ab	123 ± 12^ab	150 ± 29^ab	100 ± 14^a
5	2-ethyl-5-methylpyrazine	302 ± 22^d	265 ± 17^cd	228 ± 24^bcd	207 ± 22^bc	197 ± 17^bc	153 ± 21^ab	187 ± 36^abc	100 ± 20^a
6	ethylpyrazine	230 ± 21^c	185 ± 16^bc	172 ± 34^abc	150 ± 26^ab	144 ± 19^ab	118 ± 19^ab	141 ± 27^ab	100 ± 16^a
7	2,5-dimethylpyrazine	223 ± 13^b	165 ± 5.8^b	149 ± 23^ab	123 ± 16^a	122 ± 12^a	86 ± 11^a	104 ± 12^a	100 ± 13^a
8	2,6-dimethylpyrazine	204 ± 21^c	181 ± 17^bc	154 ± 27^abc	134 ± 26^ab	130 ± 25^ab	98 ± 23^a	112 ± 18^ab	100 ± 11^a
9	methylpyrazine	169 ± 16^b	128 ± 15^ab	111 ± 4.6^a	91 ± 5.9^a	90 ± 9.8^a	76 ± 17^a	79 ± 10^a	100 ± 14^a
10	2,3-dimethylpyrazine	178 ± 23^c	137 ± 12^bc	113 ± 6.2^ab	104 ± 9.2^ab	93 ± 6.5^ab	77 ± 8.3^a	92 ± 8.6^ab	100 ± 8.2^ab
11	pyrazine	124 ± 3.1^d	102 ± 5.1^c	76 ± 2.6^b	68 ± 9.0^ab	62 ± 8.6^ab	60 ± 8.3^ab	54 ± 6.8^a	100 ± 3.4^c
12	furfural	94 ± 8.2^a	108 ± 4.2^ab	149 ± 20^abc	152 ± 23^abc	201 ± 22^c	154 ± 19^abc	174 ± 12^bc	100 ± 4.1^a
13	2-furanmethanol	34 ± 12^ab	29 ± 3.9^a	39 ± 6.9^ab	48 ± 7.1^ab	55 ± 6.9^ab	58 ± 6.3^ab	65 ± 12^b	100 ± 5.6^c
14	4-methylthiazole	192 ± 2.3^c	133 ± 17^b	89 ± 2.2^a	77 ± 11^a	68 ± 15^a	63 ± 16^a	64 ± 12^a	100 ± 3.3^ab
15	trimethylthiazole	107 ± 5.1^c	88 ± 6.2^ab	84 ± 1.9^ab	82 ± 9.3^ab	77 ± 2.0^a	73 ± 2.1^a	73 ± 3.5^a	100 ± 2.3^bc
16	3-methylthiophene	96 ± 11^bc	82 ± 17^abc	78 ± 4.1^ab	71 ± 1.2^a	64 ± 3.1^a	73 ± 2.1^a	62 ± 2.3^a	100 ± 3.1^c
17	propanoic acid	37 ± 6.2^a	45 ± 8.1^ab	59 ± 2.3^bc	66 ± 5.3^c	69 ± 4.7^c	66 ± 5.1^c	68 ± 1.1^c	100 ± 5.9^d
18	hydroxyacetone	107 ± 5.9^ab	132 ± 14^b	103 ± 6.1^ab	97 ± 5.2^ab	108 ± 12^ab	89 ± 2.4^a	84 ± 5.1^a	100 ± 8.7^ab
19	hexanal	710 ± 23^c	667 ± 36^bc	876 ± 20^d	475 ± 52^b	607 ± 47^bc	494 ± 5.2^b	520 ± 55^bc	100 ± 15^a
20	1-methyl-2-formylpyrrole	264 ± 6.9^b	131 ± 17^a	128 ± 5.0^a	99 ± 2.8^a	102 ± 1.7^a	93 ± 8.1^a	80 ± 12^a	100 ± 14^a
21	pyrrole	247 ± 15^e	160 ± 7.2^d	106 ± 3.5^c	96 ± 10^abc	84 ± 5.2^ab	81 ± 7.9^ab	78 ± 3.2^a	100 ± 4.2^bc
22	1-methylpyrrole	100 ± 1.6^c	55 ± 2.2^b	46 ± 5.6^ab	35 ± 7.0^ab	34 ± 1.1^a	33 ± 7.5^a	29 ± 2.6^a	100 ± 2.4^c
23	1-ethylpyrrole	94 ± 5.9^b	52 ± 7.9^a	55 ± 8.7^a	44 ± 3.3^a	45 ± 4.2^a	42 ± 3.5^a	39 ± 9.1^a	100 ± 3.2^b

^abcdeSamples with the same letter code in any row are not significantly different (p < 0.05).

Mean ± standard deviation.