Polymorphism of POP and SOS. II. kinetics of melt crystallization

Abstract Melt crystallization of the polymorphs of SOS, α, γ , pseudo‐β′, β 2 and β 1 . and of POP, α, γ , pseudo‐β′ 2 pseudo‐ β 1 , β 2 and β 1 was examined using pure samples (99.9%). Induction time τ for newly occurring crystals in the melt phase was measured with a polarizing microscope equipped with a temperature‐controlled growth cell. Rate of crystallization, 1/τ, was obtained for each polymorph of POP and SOS whose identification was done with X‐ray diffraction and differential scanning calorimetry (DSC). Two modes of crystallization, melt‐cooling and melt‐mediation, yielded approximately the same results for POP and SOS: (a) The rates of crystallization were always higher in less stable than in more stable forms, β 2 only crystallized via a γ‐melt mediation, but β 1 did not occur by the melt crystallization; (b) the rate of meltmediated crystallization was always higher than the simple melt‐cooling as examined at the same crystallization temperature; (c) the occurrence behavior of the polymorphs differed between the simple‐cooling and meltmediation. The results were related to the solidification behavior of the polymorphs of cocoa butter.