Bloom on tempered chocolate due to oil migration often occurs
when chocolate has direct contact with another fat containing component.
Such is the case with filled or enrobed chocolate products, especially
those with nut-based centers. Two-way oil migration will occur
until fat compositional equilibrium is reached. As oil migrates into the
chocolate, higher melting cocoa butter triacylglycerols (TAG) dissolve
in the oil. These TAG eventually recrystallize on the surface of the
chocolate in the βVI form, which can result in bloom. Oil migration is
enhanced with high temperatures, long contact times between the
chocolate and other fat containing component, and high levels of
liquid oil in one or both of the components in the system