ABSTRACT
CONTENTS Introduction ..................................................................................... 424 Physical Properties of Fat Ingredients .......................................... 427
Crystallization and Melting .................................................. 428 Polymorphism ........................................................................ 430
Tempering and Fat Bloom in Chocolate ......................... 432 Phase Behavior ....................................................................... 433
Interaction between Milk Fat Fractions and Cocoa Butter ........................................................................... 434
Hardness of Chocolate ..................................................... 437 Fat Crystal Network and Microstructure ............................ 439
The Fractal Nature of Fat Crystal Networks ................. 440 Fractal Dimension of Fat Crystal Networks ................... 440
Mechanical Properties of Fat Crystal Networks............................ 445 Rheology ................................................................................. 446 Crystallization Kinetics ......................................................... 446 Melting and Solution Behaviors ........................................... 447 Microstructure ........................................................................ 450
Mass Spatial Distribution ..................................................... 452 Relation between the Fractal Dimension by Image
Analysis and Rheology .................................................... 454 Effect of Processing Conditions on the Texture of Chocolate ..... 457
Effect of Crystallization Temperature and Time on Microstructure .................................................................. 459 Cocoa Butter ..................................................................... 459 Milk Fat ............................................................................. 462 Mass Spatial Distribution ................................................ 465
Cooling Rates ......................................................................... 467 Shear ....................................................................................... 468
Shear-Induced Orientation .............................................. 469 Concluding Remarks........................................................................ 471 References ........................................................................................ 471
Chocolate is a dispersion of cocoa powder, sugar, additives, and milk solids in a continuous phase of fat (1). Fat is the most expensive component in chocolate. A variety of fats can be used in the manufacture of chocolate, including cocoa butter (CB), milk fat, palm oil, and other CB replacers (2). Snap, gloss, mouth-feel, flavor release, shelf life, and stability during storage are the main characteristics that determine the quality of chocolate confections. All of these attributes are highly dependent on the chemical composition as well as the physical properties of the fat ingredients, including crystallization and melting behaviors, polymorphism, degree of compatibility (phase behavior) between fat triacylglycerols, and the final fat crystal network structure. The fat ingredients in chocolate, however, exhibit complicated solidification and polymorphic behaviors due to the interaction between their triacylglycerol (TAG) components. Understanding of the physical properties of these fats and the interactions between their TAG molecules is, thus, necessary for controlling the functional properties of chocolate.
