Investigation of aromatic compounds in roasted cocoa powder

Abstract

Most of the volatile compounds identified are highly significant in determining cocoa powder flavour, and this paper demonstrates that basic sensory perceptions (undesirable, bitter pungent, repulsive, fruity, nutty, floral, vegetal, and sweet chocolate) can be totally explained by aroma compounds with R²-adjusted values of 0.85 and greater. Samples from five geographical origins of cocoa bean were characterized by chemical compounds and sensory attributes. The aroma extracts were obtained by a two-step procedure involving (1) preliminary steam distillation under reduced pressure to evaluate the methylpyrazines generated in roasted cocoa powder by spectrophotometry (flavour index), and (2) Likens-Nickerson’s simultaneous steam distillation and solvent extraction method with added NaCl. The distilled compounds were separated by adsorption chromatography in six fractions depending on the polarity. A combined total of 114 compounds were detected by gas chromatography/mass spectrometry, 110 of which were identified. About 15 components in the mean milligrams per kilogram range (1.09–4.67 mg kg⁻¹) and 95 components in the mean micrograms per kilogram range (12–980 µg kg⁻¹) were quantified. The major components of cocoa aroma were 2,3,5,6-tetramethylpyrazine, benzaldehyde, 2-phenylacetaldehyde, acetophenone, 3-methylbutyric acid, 5-methyl-2-phenyl-2-hexenal, ethyl phenylacetate, and 3-hydroxy-2-methyl-4-pyrone (mean greater than 1.30 mg kg⁻¹).