The Precursors of Chocolate Aroma: A Comparative Study of Fermented and Unfermented Cocoa Beans

Abstract

The precursors of chocolate aroma were concentrated, in a fraction amounting to some 5% of the fermented shell-free cocoa bean, by solvent extraction and dialysis.The concentrate, which was soluble in both methanol and water, comprised sugars, amino acids, and flavonoids, and produced chocolate aroma when heated.Examination of unfermented cocoa bean revealed significant differences in these components prior to fermentation.

Changes in free amino acid, peptide-N, sugar and pyrazine concentration during cocoa fermentation

“…Kirchho † et al (1989) reported that the ratio of hydrophobic/acidic/other free amino acids of several unfermented cocoa samples were around 33% : 30% : 35% and an unfermented Malaysian cocoa beans sample showed 41% : 26% : 33%. This variation of free amino acids concentration in unfermented beans could be due to maturity, harvesting season, transportation time, variety and origin of the beans (Rohan 1964). Of these free amino acids, the unfermented beans contained highly signiÐcant (P \ 0É05) concentrations of leucine, proline and lysine (Table 1).…”

“…It is necessary to induce biochemical changes and development of the type and concentration of Ñavour precursors in the beans. It is a prerequisite to obtaining the characteristic cocoa-speciÐc aroma upon roasting (Rohan 1964), since roasted unfermented cocoa beans do not generate cocoa aroma but produce an excessively bitter and astringent taste instead (Lopez 1986). Free amino acids, peptides and reducing sugars have been shown to be precursors of cocoa Ñavour and * To whom correspondence should be addressed.…”

Precursors of typical and atypical roasted peanut flavor

“…peanuts, it was co.n- NMR spectra of the isolated pigment in D 2 0 (Figure 2) showed that about 8 of the 18 protons exchanged instantly with D 2 0. This fact coupled with the strong absorption between 3500 and 3700 cm-1 in the infrared Elpectrum (Figure 3) was interpreted to mean that these protons were hydroxyl or enolic.…”

“…However Deck (18). the main groups of compounds :in the cocoa flavor precursor fraction were separated into flavonoids, amino acids and carbohydrates by lead acetate precipitation anc;l c1;1tion exchange chromatography (18). Fermented beans contained lower concentrations of carbohydrates and ~igher concentrations of amino acids than unfermented ones.…”

“…Pyrazines were apparently the compounds responsible for the roasted-nutty aroma of peanuts (13). However Deck (18). the main groups of compounds :in the cocoa flavor precursor fraction were separated into flavonoids, amino acids and carbohydrates by lead acetate precipitation anc;l c1;1tion exchange chromatography (18).…”