The crystal state of chocolate: Using spectroscopy and multivariate data analysis to evaluate the dynamics

Research output: Book/ReportPh.D. thesisResearch

  • Eleni Ioannidi
There is nothing more disappointing than unwrapping a bar of bloomed chocolate. Fat bloom is responsible for a decrease of the sensory appreciation of the chocolate, as it creates a product with grainy texture and unpleasant mouthfeel. Different pathways explain the mechanism of bloom formation, directly related to improper storage or uncontrolled production conditions. The key element for a successful chocolate product is its crystallization to the right polymorph, namely the V form, and the creation of a dense crystal matrix. Tempering is responsible for creating the first nuclei of the V form that will grow into a network during the cooling step. Consequently, the monitoring and control of the tempering process is of utmost importance during the production of chocolate. Nowadays, several analytical tools are utilized to study fat crystallization in cocoa butter and chocolate goods. Some of them are carried out at a lab setup and contribute to the fundamental understanding of the crystallization phenomena and dynamics (i.e., X-ray diffraction, microscopy, Low-Field Nuclear Magnetic Resonance), while others are implemented at the production site and assist operators on the decision-making processes (i.e., Differential Scanning Calorimetry and Temper-meter). A common challenge of all is the low sensitivity when it comes to complex systems like chocolate, or their inability for at-line measurements at an industrial setup. This Ph.D. project explored the use of infrared spectroscopy in studying the crystal state of industrially tempered chocolates. In combination with the chemometric method Multivariate Curve Resolution-Alternating Least Squares, infrared spectroscopy revealed two phases in the chocolate, the disordered and the crystalline, that coexist at different concentrations. Tests were carried out using two different temper machines, the AMC Super Nova (a conventional temperer) and the Stella Nova that uses a new tempering technology. Several operational settings were examined and indicated the presence of different crystallization dynamics during the cooling process, differences that diminished after prolonged storage. This Ph.D. study proved the applicability of the infrared spectroscopy, coupled with chemometrics, for the analysis of the crystal state of chocolate. The method is fast, non- destructive, and easy to perform, thus favoring at-line measurements and easing the monitoring and optimization of tempering processes.
Original languageEnglish
PublisherDepartment of Food Science, Faculty of Science, University of Copenhagen
Number of pages154
Publication statusPublished - 2023

ID: 359246097