Induction time of crystallization in vegetable oils, comparative measurements by differential scanning calorimetry and diffusive light scattering

In this work we compared the induction time of crystallization (tau(i) measured by DSC (tau(IDSC)) and scanning diffusive light-scattering (SDLS, tau(iSDLS)) in a vegetable oil blend. Several crystallization temperatures and cooling rates (1, 10, and 30 degreesC/min) were investigated. Additionally, rheograms obtained during the crystallization of the oil blends were obtained to differentiate the stages of nucleation and crystal growth. The results obtained showed that independent of cooling rate and crystallization temperature, SDLS provided an earlier detection of triacylglycerides' (TAGS) nucleation than DSC. Furthermore, tau(iSDLS) was more consistent (that is, lower standard deviation) than tau(IDSC), particularly at high crystallization temperatures and cooling rates. The rheograms showed that tau(iDSC) involves a measurement of crystal growth, while tau(iSDLS) is associated with the early formation of a solid phase in the oil blend (that is, TAGS nucleation). When the Fisher-Turnbull equation was therefore used to calculate the free energy of nucleation (DeltaG(c)), tau(iSDLS) provided a better estimate of DeltaG(c) than that obtained by tau(iDSC).