This paper examines the effect of shear on the crystallization of cocoa butter using a combination of three different experimental techniques and a single crystallization temperature of 20°C. Rheological measurements were carried out to study the effect of a shear step on the crystallization kinetics of the fat. Without a shear step, little rheological change was observed at 20°C; however, with the application of a shear step the onset of significant rheological change occurred and was strongly influenced by the magnitude of the shear step. Detailed crystallographic measurements could be made with in situ X-ray experiments during flow-induced crystallization. The imposition of continuous shear changed both crystal polymorphic structure and crystallization kinetics in a systematic way. Finally, optical measurements were used to follow changes in crystal morphology as a consequence of continuous shear. These results revealed the form and kinetics of crystal growth. In general the results complemented each other, and an overall picture of the way shear influenced cocoa butter growth could be formed. The observations could be the basis for a future mathematical model of growth kinetics and provide insight into the way shear influences crystallization kinetics, morphology, and polymorphic structure.Cocoa butter (CB) is a semisolid fat that exhibits brittleness below 20°C, begins to soften in the region of 28-32°C, and melts completely below body temperature (1). CB is predominantly composed of three monounsaturated TAG-POP, POS and SOS (where P = palmitate, O = oleate, and S = stearate)-which make up approximately 82% of its components (2). It also contains minor concentrations of MAG, DAG, phospholipids, glycolypids, sterols, FFA, and fat-soluble vitamins. The TAG composition of CB from cocoa beans grown in different areas varies slightly according to differences in genetics, climate (temperature, rainfall, and sunlight), and agricultural practices.CB, which itself is tasteless (1), is a key ingredient in chocolate. It typically corresponds to approximately one-third of the chocolate composition. Because of this, the crystallization of CB plays an essential role in controlling the physical and thermal properties of chocolate products. The crystallization behavior of CB is, however, very complex owing to polymorphism, i.e., the ability of the fat to exist in different crystalline forms with different types of crystal packing and thermodynamic stabilities (3). It is now generally accepted that CB can exist in six polymorphs, which in order of increasing thermodynamic stability are termed Form I-Form VI (4). Only Form V is used by the confectionery industry as the optimal polymorph for CB in chocolate (5). This is because Form V is a stable polymorph with a melting range that is high enough to allow chocolate to be stored at room temperature, and low enough that chocolate becomes a smooth liquid when it is heated in the mouth. Form V provides chocolate products with snap (ability to break apart easily), good demolding p...

Cocoa butter equivalent (CBE) was produced from a blend of mango kernel fat (MKF) and palm oil mid-fraction (PMF). Five fat blends with different ratios of MKF/PMF (90/10, 80/20, 70/30, 60/40 and 50/50 (%wt)) and pure MKF, PMF and cocoa butter (CB) were characterized. Similar to CB, all fat blends contained palmitic (P), stearic (S) and oleic (O) acids as the main fatty acid components. The triglyceride compositions of all blends were significantly different from CB. However, blend 80/20, which contained higher content of SOS, similar content of POP and lower content of POS compared to CB, exhibited a slip melting point, crystallization and melting behavior most similar to CB and hence it was recommended as CBE. The chosen CBE was then mixed with CB in a ratio of 1:5.64 (wt), mimicking that of typical dark chocolate where 5 % of CBE is added to the finished product. The crystallization behavior, the crystal morphology and bloom behavior of the mixture was investigated and was found to be not significantly different from CB.

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Structure evolution and bloom formation in tempered cocoa butter during long-term storageStructural evolution in tempered cocoa butter (CB) and CB mixed with a cocoa butter equivalent (CBE) was examined during 26 wk of storage (at 25 7C) using atomic force microscopy, X-ray powder diffraction, colorimetry and pulsed nuclear magnetic resonance. The form V-to-VI polymorphic transition in CB started after 1 week of storage. However, fat bloom was not detected until week 3 when large crystals started to appear on the CB surface. Changes in surface topography coincided with an increase in the surface whiteness index. Addition of CBE delayed bloom development by 1-2 wk. The solid fat content (SFC) of both CB and CB 1 CBE increased gradually during the early wk of storage before reaching a summit and then decreasing slowly with time (at 25 7C). Concurrently, the surface roughened and the whiteness index increased for both CB and CB 1 CBE. We postulate that, upon bloom formation, parallel phenomena took place: (i) There was exclusion of triglyceride molecules from the CB and CB 1 CBE fat crystal networks due to continued contraction, and (ii) less stable crystals melted due to the heat release from the (re)crystallization of liquid fat onto existing surface crystals and from the ongoing form V ? VI polymorphic transition. These events resulted in the gradual decrease in SFC seen at longer storage times. In conclusion, this study demonstrated that kinetic and thermodynamic phenomena take place in CB long after it has been tempered.