Scanning Electron Microscope coupled with Energy Dispersive X-Ray Spectrometer (SEM-EDS) for Fat Bloom Investigation in Chocolates
Monise Helen Masuchi, Élida Castilho Bonomi, Renato Grimaldi, Theo G. Kieckbusch. School of Chemical Engineering, UNICAMP, Campinas, Brazil

Chocolates can be considered as a dispersion of polar (sugar) and non-polar (cocoa butter, cocoa solids and milk fat) constituents, stabilized by emulsifiers. Cocoa butter and other fats present in chocolate formulations are the main responsible for fat bloom formation during transportation and storage under temperature oscillations. Fat bloom is characterized by the presence of whitish spots or a grayish film on the chocolate surface, which can be easily perceived by visual observation and/or by colorimetric measurements. Fat bloom formation can have many causes, but the most accepted one is attributed to mechanisms involving migration of lower molecular weight lipids from the bulk of the chocolates goods to the surface, combined or not with melting and re-crystallization events associated to polymorphic transitions of the cocoa butter crystals from form V to the most stable form VI. In order to contribute to the elucidation of the mechanism of fat bloom formation in chocolate products, milk chocolates were manufactured with a fat content of 30%. The milk chocolates were incubated during approximately 2 months under two different conditions: isothermally at 20°C and under temperature oscillation (20 and 32°C) to accelerate the fat bloom formation. To monitor fat migration, samples were analyzed with a SEM-EDS equipment to quantify the carbon content at three different positions: lower and upper surfaces and at the inner part of the chocolate bars. As fats contain higher percentage of carbon compared to the other chocolate constituents, carbon-atom mapping obtained by SEM-EDS analyses can be a tool for confirming fat distribution displacements throughout the bars.  X-Ray diffraction, visual observations and colorimetric determinations were also performed. Under the conditions investigated, no significantly differences (p < 0.05) in terms of carbon content were detected at each milk chocolate position during the period of observation for fat bloom formation.