SOLVENT EFFECTS ON PHASE-TRANSITION BEHAVIOR OF CANOLA OIL SEDIMENT

Differential scanning calorimetry (DSC) was used to study the melting and crystallization behavior of waxy sediment in canola oil acid in mixtures (1:1, w/w) of oil and acetone or hexane under dynamic heating/cooling regimes. In the presence of a solvent, the DSC melting peak of sediment shifted to lower temperatures, suggesting that sediment was more soluble in the solvent/oil systems than in oil alone. This effect was greater with hexane than with acetone. The influence of a solvent on crystallization was more complex. With inclusion of hexane, the crystallization temperature of sediment was always lower than that in oil. With acetone, however, the crystallization temperature of sediment was slightly lower at high sediment content, but higher at low sediment content than in oil alone. The differences in melting and crystallization behavior of sediment in canola oil and the solvent/oil systems were attributed to solubility and viscosity effects. Variation in the crystalline solid structures of sediment was not evident from the melting enthalpies associated with the phase transformation.