Influence of oil migration with fats of varying physical properties on chocolate hardness and melting behavior in chocolate-coated products

The objective of this research is to analyze the effect of oil migration on chocolate quality. Three different fats (soybean-based, palm-based, and palm-kernel based) were crystallized under different crystallization conditions to obtain various levels of oil binding capacities. Crystallized fats were mixed with either sugar or peanut flour and covered with a thin layer of tempered chocolate; chocolate without filling was used as a control.  Samples were then placed in an incubator at 22 °C and stored for 24 weeks.  Samples were measured for various physical properties (hardness, melting behavior, and viscoelasticity of the chocolate and the filling along with color of the chocolate) at 48h, 1, 4, 12, and 24 weeks to evaluate if, and to what extent, the migration of oil from the filling affected chocolate quality.

In general, results did not differ significantly between samples stored with sugar and peanut flour. Among the physical properties measured, hardness and melting behavior of the chocolate exhibited the most change.  Results showed the hardness of the chocolate in the control samples did not decrease over time (constant values between 6 and 8 N) while it decreased significantly (p< 0.05) for all samples tested. At 12 weeks, soybean-based samples decreased below 1N while palm and palm-kernel remained between 1 and 3 N.

Melting enthalpy of the control chocolate did not change during storage (60 J/g) but decreased for some of the samples.  The greatest decrease (p< 0.05) was observed for the lowest oil binding capacity soybean-based sample where enthalpy values decreased from 53 J/g at 48h to 35 J/g at 24 weeks. Although less pronounced, the palm-based samples decreased significantly (p< 0.05) from 56 J/g to 49 J/g. No significant differences (p >0.05) were observed in the enthalpy of the chocolate stored with palm kernel-based samples between 48h and 12 weeks.