Green Chemistry Applied to Ground Coffee Volatile Compounds Modification Aiming Coffee Aroma Improvement

Table 2

Mass fraction (% w/w) of the ground coffee volatile compounds.

Compound	Control (untreated)	50 Hz; 15 min	50 Hz; 30 min	500 Hz; 15 min	500 Hz; 30 min	1000 Hz; 15 min	100 Hz; 30 min
2-Methylfuran	^a	^ab	^e	^b	^d	^c	^d
2-Methylbutanal and 3-methylbutanal	^a	^b	^d	^c	^c	^c	^c
2,5-Dimethyl furan	^a	^a	^c	^b	^b	^b	^b
1,5-Hexadien-3-ol	^a	^ab	^ab	^b	^ab	^ab	^b
2-Methyl-1H-pyrrole	^ab	^b	^a	^ab	^a	^a	^ab
Pyridine	^e	^c	^d	^b	^cd	^a	^c
Not identified	^a	^b	^a	^c	^a	^c	^b
Hexanal	^a	^b	^c	^b	^c	^b	^c
5-Hydrazino-1H-1,2,3,4-tetrazole	^a	^ab	^c	^ab	^bc	^bc	^bc
Furfuryl methyl ether	^a	^b	^ab	^b	^ab	^b	^ab
4-Methyl pyrimidine	^d	^bc	^cd	^ab	^cd	^a	^cd
Furfural	^d	^c	^a	^b	^a	^b	^a
2-Furan methanol	^cd	^d	^a	^c	^b	^c	^b
2-Furyl methyl ketone	^c	^c	^a	^bc	^ab	^bc	^ab
2,6-Dimethylpyrazine	^b	^a	^b	^a	^b	^a	^b
2-Ethylpyrazine and 2,3-dimethylpyrazine	^a	^a	^a	3^a	^b	^a	^ab
5-Methyl-2-furaldehyde	^c	^bc	^a	^bc	^ab	^bc	^a
3-Ethyl-2,5-dimethylpyrazine	^a	^b	^b	^b	^b	^b	^b
2-Pentyl furan	^b	^a	^c	^ab	^c	^ab	^c
2-Furan methanol acetate	3^d	^bc	^a	^c	^b	^d	^b
1-Methyl-1H-pyrrole-2-carbaldehyde	^a	^a	^a	^b	^a	^b	^ab
2-Ethyl-3,5-dimethylpyrazine	^a	^a	^a	1^a	^a	^a	^a
2,2-Methylenedi furan	^a	^a	^a	^a	^a	^a	^a
2-Furan methanol propionate	^a	^a	^a	^a	^a	^a	^a
1-(2-Furanylmethyl)-1H-pyrrole	^a	^a	^a	1^a	^a	^a	^a

Letters indicate significant differences among the treatments for each compound.