Abstract
This thesis industrial partner, Valrhona SA, a premium quality chocolate maker, sorts the cocoa bean lotes arriving in its production site into four “sensory groups” representing flavour trends or chocolate sensory characteristics.This thesis objective is to link the polyphenolic composition of cocoa beans and chocolates to the four sensory poles defined by Valrhona. More precisely, it aims at predicting the sensory pole of a given lot from the quantities of some polyphenols markers analysed in cocoa or chocolate after an ultra-high liquid chromatography mass spectrometry analysis (UHPLC-MS).The first step was to determine which polyphenols are involved in the sensory pole discrimination. Therefore, a protocol has been optimized to extract polyphenolic compounds from cocoa beans and chocolates samples. These extracts have been analysed by UHPLC-MS in order to create a polyphenolic fingerprint. Using a chemometrics approach, lists of variables corresponding to cocoa or chocolate markers involved in the sensory poles discrimination have been selected from these mass signal fingerprints. Most of the compounds have been identified as polyphenolic molecules and few were non-phenolic molecules. Among phenolic variables, new compounds, formed by condensation of phenolic compounds with acetaldehyde which is a fermentation metabolite, have been identified.The second step consisted in developing a quantitative method specific to the markers previously highlighted in both cocoa bean and chocolate samples. The analyses have been conducted using UHPLC-MS/MS in Multiple Reaction Monitoring (MRM) mode, and the quantitative methods have been validated.The last step was to study the link between the quantitative data previously generated and the sensory poles, and follow the cocoa bean composition through the chocolate making process using chemometrics analysis. PLS (Partial Least Square) models have been tested as well as a multiblocs analysis called CCSWA (Common Component Specific Weight Analysis). This shed light onthe complex link between the polyphenolic composition of cocoa bean or chocolate samples and the sensory analysis data provided by Valrhona.