Milk chocolate is a suspension of very fine particles (up to 25 µm) of cocoa, milk solids and sugar, coated by a fatty phase composed of cocoa butter and milk fat. Milk fat is a complex lipid system composed of about 400 different fatty acids, forming a wide variety of triacylglycerols that tend to interact with the cocoa butter. The objective of this work was to evaluate and compare the rheological properties, whiteness index and snap of standard milk chocolates (formulated with anhydrous milk fat) and milk chocolate produced with milk fat stearin. Milk fat stearin was obtained by thermal fractionation of anhydrous milk fat at 27ºC, and attained a high proportion of triglycerides with a high melting point. Casson's plastic viscosity and yield stress showed expressive differences between the two types of chocolate. The chocolates produced were stored for 5 months in two BOD incubators, one maintained at a constant temperature (20ºC) and the other subjected to temperature cycling (20ºC-32ºC every 24 hours). The evaluation of the colour of the samples subjected to temperature cycles showed an increase in the whiteness index for both types of chocolate, although with lower intensity for the chocolates produced with stearin, signaling that this formulation is more stable to the formation of fat bloom. The snap of both types of chocolate stored under the two conditions remained similar. Scanning electron microscopy (SEM) images indicated that the fat bloom formed in milk chocolate has a more uniform crystal structure than the microstructure of fat bloom-free chocolates.
Milk chocolate; Anhydrous milk fat; Milk fat stearin; Fat bloom
