Relation of fat bloom in chocolate to polymorphic transition of cocoa butter

A special chocolate with spray-dried sugar (50:50 w/w sucrose/20 Dextrose Equivalent corn syrup solids) was made to study the polymorphic changes in cocoa butter crystals using X-ray diffraction. Anhydrous milk fat (AMF) and high-, middle-, and low-melting milk fat fractions were used to replace 2% (w/w) Of cocoa butter. Chocolates were tempered, and the consistency of temper among chocolate samples was verified by a temper meter. Chocolates were cycled between 19 and 29 degrees C at 6-h intervals to induce fat bloom. The special chocolates were analyzed by X-ray spectroscopy and colormeter. X-ray analysis on the special chocolates showed polymorphic transition from the beta V to the beta VI form of cocoa butter. After a lag phase, the percentage: of the beta VI form rapidly increased. However, the sample made with the high-melting milk fat fraction transformed slowly to beta VI. Visual bloom appeared rapidly on the special chocolates made with AMF, middle- and low-melting fractions, whereas visual bloom was very slow to appear on the special chocolates made with high-melting milk fat fraction and on the cocoa butter control. The commercial chocolate responded consistently; the control bloomed rapidly, the AMF exhibited some bloom resistance, and the high-melting fraction inhibited bloom. Despite the beta V to beta VI transition, the control chocolates with amorphous sugar did not bloom. Since the only difference in the chocolates was sugar microstructure, differences in bloom formation were caused by the microstructure, not the polymorphic transition.