The Functionality of Milk Fat Fractions in Confectionery and Plastic Fats
The physical properties of chocolate are largely determined by the physical properties of the underlying fat phase . In milk chocolate, cocrystallization of cocoa butter triacylglycerols (TAGs) and milk fat TAGs takes place; this cocrystallization is a key factor influencing the appearance and physical properties of milk chocolate . However, the amount of milk fat that can be added to chocolate is limited by the thermodynamic incompatibility between milk fat and cocoa butter TAGs in the solid state. Because of molecular geometric constraints, as well as environmental factors that influence the kinetics of crystal-
lization, milk fat and cocoa butter TAGs do not form mixed crystals-they crystallize as separate milk fat and cocoa butter solids. This thermodynamic incompatibility results in the formation of a eutectic-a decrease in the melting point of the cocoa butter-milk fat mixture below the melting point of either of the two components. The formation of this eutectic, therefore, leads to a decrease in the hardness of the milk chocolate [3-10]. The exact amount of milk fat that can be added to chocolate before the functional properties of the material are significantly and adversely affected will depend on processing conditions, such as tempering times and temperatures. Reddy et al.  reported the successful production of milk chocolates containing 40% (w/w of the total fat) milk fat with good gloss and demolding properties.