The effect of composition on the rheological behavior of commercial chocolates

Abstract A detailed rheological study was performed on four commercial chocolate samples containing similar solids particle sizes. Two dark chocolates with different cocoa content, a sugar free chocolate and a milk chocolate were studied. Samples were characterized by proximal composition, Differential Scanning Calorimetry, Scanning Electron Microscopy, continuous and oscillatory shear rheometry at different temperatures. The complex shear thinning behavior displayed by the samples was described by several rheological models. The Carreau model provided the best fits in the widest shear rate range. The cocoa content and total fat were the most important parameters of the sample formulation, since the degree of chocolate structuring is a function of the solids content and most rheological properties significantly depended on them. Milk chocolate samples showed a very small frequency dependency resembling the behavior of a strong gel. This type of strong gel character has not been previously reported for milk chocolate. We believe that milk proteins can act as surfactants and stabilizers, that are able to induce the formation of spherical micellar aggregates within the chocolate structure (as evidenced by SEM). At low frequencies, they play an important role in chocolate solid particle packing, helping the suspension structure to become more stable under oscillatory deformation.