Crystallisation of 1,3-dipalmitoyl-2-oleoylglycerol and tripalmitoylglycerol and their mixtures from acetone

Smith K.W., Cain F.W., Talbot G., Crystallisation of 1,3-dipalmitoyl-2-oleoylglycerol and tripalmitoylglycerol and their mixtures from acetone, European Journal of Lipid Science and Technology, 2005, 107(9), 583-593

Crystallisation from acetone of 1,3-dipalmitoyl-2-oleoylglycerol (POP), tripalmitoylglycerol (PPP) and their mixtures has been studied at a range of cooling rates, determining the metastable zone width using turbidimetry. A log-log plot of the cooling rate against the maximum undercooling for POP indicated a relative insensitivity of the metastable zone width to the cooling rate. The PPP metastable zone width demonstrated a slight dependence on concentration. POP crystals were spherulitic, having a more open structure at slower cooling rates. PPP crystals were more plate-like, producing powdery, more amorphous crystals at high cooling rates. In pure POP systems, onset of crystallisation was quickly followed by rapid crystal growth. The presence of PPP markedly increased the temperature of the onset of crystallisation (by 17.7°C at 8% PPP), but the temperature at which crystal growth occurred, although raised, did not increase to the same extent. The clear point of the pure systems was independent of the previous cooling rate, but this was not true in the mixed system, where it decreased with increasing cooling rate. This suggests that a greater proportion of the PPP-rich phase separates during slower cooling. The morphology of the crystals from the mixed system differed from that in the pure POP system, with just 2% PPP being sufficient to shift the structure to a more lamellar appearance.