Qualité du cacao en relation avec quelques génotypes et les stades de fermentation

Abstract

Fermentation is an essential process in flavors precursors development and taste of chocolate which are, on the one hand, amino acids which come from proteins hydrolysis, and on the other hand, reducing sugars which come from sucrose hydrolysis. The effectivity of incubations media and cocoa fermentation and cocoa fermentation arise as effective means to induce biochemical changes of cocoa beans which lead to various stages of cocoa beans such as slaty (not fermented), violets (under fermented) and brown (fully fermented). This heterogeneity of stage in a sample set can influence quality of end products. The present work aims to characterize physico-chemical markers of cocoa beans. To achieve this, quantification and identification of free amino acids were performed by labeling o - phthalaldehyde and detected with a fluorescence spectrophotometer coupled to an RP - HPLC system. Polyphenols were analyzed at 280 nm by HPLC using a photodiode array detector. Physico-chemical parameters of incubated and non-incubated dried beans are evaluated and impact of genetic variability on content of amino acids, polyphenols and reducing sugars of incubated and dried cocoa beans is studied. Amino acid content in violet beans was significantly higher higher (11.165 ± 4281 mg.kg -1 ffdm) that of slaty cocoa beans (4304.5 ± 1927.6 mg.kg -1 ffdm). However, no significant difference between violet and brown cocoa beans was noted. Contents of epicatechin, catechin, cyanidin-3-arabinoside and cyanidin-3- galactoside were significantly low in violet and brown cocoa beans once compared to slaty cocoa beans. Contents of reducing sugars vary according to genotype and pH of treatment. Sucrose and raffinose are present in all non-incubated genotypes at high concentrations. However, galactose and fructose are present in all incubated and non-incubated genotypes, at high concentrations in treatments 1 (acetic acid) and 2 (lactic acid and then acetic acid) but low in non-incubated beans. In addition, glucose is present only in treatments 1 (acetic acid) and 2 (lactic acid and then acetic acid) at high and variable concentrations except in three genotypes. Comparison between treatments applied during incubations revealed that nature of acid influences biochemical markers.