Comparison of cocoa butter crystallization measurment methods

Crystallization of cocoa butter and cocoa mass - measurement technology in interlaboratory comparison Results of interlaboratry test for crystallization measurement via DSC, NMR and MultiTherm

Cocoa butter crystallization properties are important for manufacturing of high quality chocolate products. Therefore, characteristics for good and poor crystallization have to be found and measurement needs to be standardized. Currently, a lot of different measuring instruments are used and even for established devices such as NMR or DSC, standardized methods are missing. The idea is to compare different instruments and methods and find benchmarks for good and poor crystallization properties. A supplementary target is to facilitate the comparability of quality control at incoming goods department and specifications given by the supplier.

Low resolution or pulsed NMR (nuclear magnetic resonance) is an easy and fast way to determine solid fat content (SFC) of cocoa butter and other fats. It can also be used to observe the crystallization process. However, in literature several ways of sample preparation and handling, especially for crystallization kinetics measurement are reported. These differences in preparation might not be critical when comparing results from one laboratory, but might be crucial when interlaboratory results are compared. The latter one is the case when it comes to quality control of raw materials. In this study a minispec mq 20 TD-NMR spectrometer (Bruker BioSpin GmbH, Rheinstetten, Germany) was used. Different sample preparation and handling methods described in literature were used and their impact on the final results was investigated.

Cocoa butter crystallization properties are important to produce high quality chocolate products. Therefore, characteristics for good and poor crystallization properties have to be found and measurement needs to be standardized. Currently, a lot of different measuring instruments are used and even for often used devices such as NMR or DSC, standardized methods are missing. The idea is to compare different instruments and methods and find benchmarks for good and poor crystallization properties. A supplementary target is to facilitate the comparability of quality control at incoming goods department and specifications given by the supplier. Hence, cocoa butter samples were analyzed using NMR, DSC and MultiTherm™. Different measuring methods were used and the influence of sample preparation and storage was investigated. To minimize expenditure, we focused on sample preparation methods which are inexpensive, easy to implement and feasible during ongoing production. Regarding the measurement instruments, it can be said that on the one hand, a lot of modelling and interpretation can be done to receive physically meaningful values from NMR and DSC results, which are well-established in science. On the other hand, MultiTherm™ is highly reproducible and the output is a benchmark (BCI = Bühler Crystallization Index) for good and poor crystallizing cocoa butter.

Cocoa butter crystallization is the key factor for many cocoa products, such as chocolate or cocoa powder. Therefore a lot of research has been done on cocoa butter, chocolate and cocoa powder crystallization. Crystallization properties are influenced by cocoa processing, which starts with cocoa bean fermentation, followed by drying and cleaning. Afterwards the beans will be grinded and roasted or vice versa and are then called cocoa mass. The cocoa mass is pressed to gain cocoa butter; the residual cocoa press cake is ground to obtain cocoa powder. In addition, most products are alkalized, to achieve specific flavors, colors, higher solubility and to remove free fatty acids. Usually nibs are alkalized, but cocoa mass and press cake alkalization is also possible. These thermal, mechanical and chemical stress leads to changes in triacylglycerol composition and affects the amount of mono- and diacylglycerols, free fatty acids and other minor components. While the influence of fermentation is well-investigated, little is known about the change of cocoa butter crystallization properties during processing from nibs to final products. The crystallization behavior of semi-finished goods might be helpful to identify the critical production stages. In this study we investigated the crystallization behavior of alkalized and non-alkalized cocoa nibs, mass, butter, press cake and powder, via isothermal DSC measurement at 18°, 19° and 20 °C and isothermal pNMR measurements at 19 °C. The results were evaluated using Avrami- and Gompertz-Analysis. We found significant differences in amount of crystallizable fat, crystallization time and crystal growth rate. Non-alkalized samples crystallized faster, than alkalized samples. Cocoa butter had the highest crystal growth rate, while crystallization time was the longest. Similarities of other samples were temperature-dependent.

Cocoa butter crystallization properties are important to produce high quality chocolate products. Therefore, characteristics for good and poor crystallization properties have to be found and measurement needs to be standardized. Currently, a lot of different measuring instruments are used and even for often used devices such as NMR or DSC, standardized methods are missing. The idea is to compare different instruments and methods and find benchmarks for good and poor crystallization properties. A supplementary target is to facilitate the comparability of quality control at incoming goods department and specifications given by the supplier. Hence, cocoa butter samples were analyzed using NMR, DSC and MultiTherm™. Different measuring methods were used and the influence of sample preparation and storage was investigated. In addition, the experiments were performed in different laboratories to evaluate comparability of results. To minimize expenditure, we focused on sample preparation methods which are inexpensive, easy to implement and feasible during ongoing production. We found that repeatability in each laboratory was good while comparison between the laboratories was difficult, but could be improved by strictly adhering to the given sample preparation procedure and measuring method. Regarding the measurement instruments, it can be said that on the one hand, a lot of modelling and interpretation can be done to receive physically meaningful values from NMR and DSC results, which are well-established in science. On the other hand, MultiTherm™ is highly reproducible and the output is a benchmark (BCI=Bühler Crystallization Index) for good and poor crystallizing cocoa butter. Another method to receive a benchmark is Shukoff-measurements, but it is highly depending on the used Shukoff-flask and on the used evaluation method. Vos1 showed, that repeatability of Shukoff measurements is only granted, if the same flask is used in the same laboratory. 1: Vos, H. J. (1965): Bestimmung der Erstarrungskurven von Fetten mit Hilfe des Shukoff-Apparates. In: Fette, Seifen, Anstrichm. 67 (2), S. 69–72. DOI: 10.1002/lipi.19650670203.

Cocoa butter crystallization is the key factor, in terms of stability and product properties for many cocoa products, such as chocolate or cocoa powder. Therefore a lot of research has been done on cocoa butter, chocolate and cocoa powder crystallization. Crystallization properties are influenced by cocoa processing, which starts with cocoa bean fermentation, followed by drying and cleaning. Afterwards the beans will be grinded and roasted or vice versa and are then called cocoa nibs. The cocoa nibs are finely ground to obtain cocoa liquor. For cocoa powder production, the cocoa butter is partly removed by pressing the cocoa liquor. In addition, often cocoa products are alkalized, to achieve specific flavors, colors, higher solubility and to remove free fatty acids. Usually nibs are alkalized, but cocoa liquor and press cake alkalization is also possible. These thermal, mechanical and chemical stresses might lead to changes in triacylglycerol composition and affects the amount of mono- and diacylglycerols, free fatty acids and other minor components. Little is known about the change of cocoa butter crystallization properties during processing from nibs to final products. The crystallization behavior of semi-finished goods might be helpful to identify the critical production stages for final products.