Des hybrides controles de cacao (theobroma cacao l.) du Cameroun et chocolat correspondant

Abstract

Among cocoas which present fine or flavor aroma, Trinitario and mainly Criollo are the needed. Forastero cocoas, in their majority, are classified as bulk cocoa. In Cameroon, there are many clones of Trinitario cocoas whose metabolites and mainly aroma volatile compounds have not been really described. This work aimed to characterize genotypes with Trinitario clones, metabolites which influence cocoa aroma and volatile aroma compounds. hybrid pods were obtained by hand-pollination from available clones numbered. Ten clones were selected according to their susceptibility to Phytophthora megakarya (black pod disease pathogen). Agronomic parameters (number of beans, pod cortex thickness, pod length) and physicochemical (pH, Cut-test, fermentation index) were assessed. Total polyphenol, flavonoids, condensed tannins, antiradical, and antioxidant and polyphenol oxidase activities were determined by spectrophotometry. Free amino acids, monomeric units of bioactive compounds and sugars were determined by RPHPLC-PAD, UPLC-DAD-ESI-MS TOF and HPIC-ED respectively. Sensory profile of dark chocolate bar of each hybrid and volatile aroma compound of fermented/dried and roasted beans and chocolate bars were analyzed and semi-quantified by HS-SPME-GC-MS. The general ability combination between cocoa clones depends on the pollen genetic origin. Results showed that compatibility between Trinitario cocoa is less successful. Meanwhile, crosses between Trinitario and Forastero are to be encouraged. Agronomic parameters of cocoa hybrids are subjected to pollen genetic origin and the pH describes the genetic group of cocoa clones. Physicochemical parameters supply information’s about postharvest practices and thermal conditions of chocolate production. Secondary metabolites (polyphenols and purine alkaloids) are genotype-dependent and are influenced by postharvest practices and thermal processes. Total polyphenol, flavonoid, and condensed tannin contents are positively correlated to antioxidant and antiradical capacities. Inversely, the polyphenol content is negatively correlated to polyphenol oxidase activity. Important variations of monomeric units of polyphenol and purine alkaloids were observed. The general order of compound content was showed as followed: theobromine > (-)-epicatechin > caffeine > ferulic acid > chlorogenic acid > procyanidin C1. The sensory analysis according to the experimented panelists revealed 13 descriptors of aroma among which: fruity, floral, spicy, chocolate. Specific aroma volatile compounds which describe flavour notes of fine cocoa, were determined by HS-SPME-GC-MS. Compounds like linalool (fruity), myrcene (spicy), trans-beta-ocimene (grassy) describe the "floral" note of some hybrids (SCA12×ICS40). Indeed, 3-mehtylbutyl acetate (isoamyl acetate) and 2-hepthanol with the banana and creamy aroma respectively describe "fruity" note of ICS40 and SNK hybrids. 2,3,5,6- tetraméthylpyrazine (chocolate/cocoa), benzaldehyde (almond/cherry) and the 2,3,5- trimethylpyrazine (cocoa/nutty) are main aroma compounds for "chocolate/nutty" note. At the end, 3-hydroxybutan-2-one (milked) and 2,3-butanedione (buttery) describe the "creamy/buttery" note of ICS40 hybrids. These results highlighted that with respect to postharvest treatments, cocoa hybrids used in this study show similarities with fine cocoa and may be popularized to farmers