Chemistry of Cocoa Bean Roasting

  • This thesis aims to use mass spectrometric chemical profiling methods to deepen the scientific understanding of roasting of cocoa with an emphasis on its organoleptic properties. A series of cyclic dipeptides (2,5-diketopiperazines or DKPs) responsible for the bitter taste of cocoa was studied. Along already known to the literature, new species were identified, and a kinetic model of their formation was established. Their relative concentrations were correlated with their putative peptide precursors in the raw material. Significant positive correlations indicated that short peptides in unroasted cocoa formed during fermentation are taste precursors for bitter 2,5-diketopiperazines. Additionally, it was shown that most DKPs were generated during the degradation of the single most abundant peptide precursor. Furthermore, an investigation of Maillard reaction during cocoa processing, demonstrated a higher than suspected so far variety of Amadori compounds. These first stable reaction products of simple sugars with amino acids were proven to form from oligopeptides as well. Their generation and degradation trends were shown for the first time on cocoa beans processing series from Ghana. Fermentation, drying, and roasting changes of other components such as oligopeptides, sugars, aroma volatiles were illustrated as well. Finally, an HPLC-MS based design of experiments model of cocoa roasting was established. Standard process parameters, such as time, temperature, the addition of water, acid and base, were investigated to demonstrate their influence over the chemical composition of the resulted product. Relative concentrations of procyanidin monomers, dimers, and trimers, an Amadori compound, and a peptide were considered as markers. For each, high-quality models were accomplished and validated, which displayed sound prediction accuracy. These proof-of-concept results show great promise in the optimization of cocoa roasting.

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Publishing Institution:IRC-Library, Information Resource Center der Jacobs University Bremen
Granting Institution:Jacobs Univ.
Author:Paweł Andruszkiewicz
Referee:Nikolai Kuhnert, Matthias Ullrich, Maria Williams
Advisor:Nikolai Kuhnert
Persistent Identifier (URN):urn:nbn:de:gbv:579-opus-1009292
Document Type:PhD Thesis
Language:English
Date of Successful Oral Defense:2019/11/15
Date of First Publication:2020/09/28
Academic Department:Life Sciences & Chemistry
PhD Degree:Chemistry
Focus Area:Health
Other Countries Involved:Belgium
Call No:2019/31

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