Sugar profile and volatile aroma composition in fermented dried beans and roasted nibs from six controlled pollinated Cameroonian fine-flavor cocoa (Theobroma cacao L.) hybrids

Abstract

The quality of chocolate products proven by consumer acceptability mostly depends on cocoa volatile compounds. In fact, aroma profile of cocoa or chocolate is correlated to cocoa genotype, culture conditions, postharvest practices, and chocolate manufacturing. To the best of our knowledge, no study has been published on both sugars and aromas of controlled cocoa hybrids from Cameroon. The present study aimed at analyzing biochemical and volatile composition of six hand-pollinated cocoa hybrids belonging to different traditional groups. Specifically, the sugar profile was obtained by high performance ion chromatography-electrochemical detector (HPIC-ED) and aroma composition was analyzed using headspace solid phase micro-extraction coupled with gas chromatography-mass spectrometry (HS-SPME/GC-MS) on fermented dried beans and roasted nibs. The content of sugars was variable among hybrids and fructose showed the highest concentration in all hybrids in the two matrices. Roasting decreased sugar content. However, the decrease in sugar content seemed genotype dependent. A total of 48 volatile aromas were classified in six groups according to their odor description (fruity, floral, chocolate/nutty, buttery/creamy, undesirable, and unknown). Fruity flavors were not specific to a given chemical group. However, floral volatiles were specific to terpenes, chocolate/nutty to pyrazines, buttery/creamy to lactones and undesirable to phenols and acids. Principal component analysis (PCA) showed specificity of each hybrid and the hierarchical cluster analysis (HCA) Heatmap presented four distinct groups. SCA12 × ICS40 with the highest pyrazine concentration was associated with important content of sugars. Roasting of nibs reduced total volatiles and particularly fruity volatiles whereas other flavor groups moderately increased. In fact, some volatiles such as 2,3-butanediol, 2-nonanol, linalool, β-myrcene, cis/trans-β-ocimene, 2-nonanone, 2-heptanol, methyl acetate, acetophenone could be used as markers in separating traditional cocoa groups in Cameroon.