Cocoa rheological properties

Quemada et al. (1985) model (Equation 2.11) was used to analyze data on cocoa dispersions (Fang et al., 1996) and the role of cocoa butter replacers (Fang et al., 1997). Selected values of rheological properties of chocolate are given in Table 5-G. In addition, the data of Fang et al. (1996) (Table 5-H) before and after degasification as a function of temperature are note worthy. 

Many researchers have studied the effect of lipid composition and polymorphism on macroscopic rheological properties but have not sufficiently considered the importance of the microstmcture of the network. Depending on the source and the refining process, the chemical composition of cocoa butter may vary (Dimick, 1999). This has been shown to influence crystallization rates and hardness characteristics. Within the microstmctural level, the polymorphic form of cocoa butter has been shown to affect the shape and size of the crystals (Vaeck, 1960). In terms of final product quality the polymorphic form of the crystals will determine melting characteristics. However, lipid composition and polymorphism alone cannot be used to predict the macroscopic properties of a fat crystal network. 

Sterling, C. and Wuhrmann, J. J. 1960. Rheology of cocoa butter. 1. Effect of contained fat crystals on flow properties. Food Res. 25 460-463. 

The next section, structure-rheology-texture relationships, deals with the quantification and modeling of the structure and the mechanical properties of lipid networks, and then examines cocoa butter and milkfat within this general framework. The chapter on milkfat focuses on the effects of the minor components contained in native milkfat on structure formation and final mechanical properties. This section also contains a chapter on the use of fluorescence depolarization spectroscopy as a tool to determine microviscosity and structural order in lipid systems and an overview of the texture of fat systems. 

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