Induction time of crystallization in vegetable oils, comparative measurements by differential scanning calorimetry and diffusive light scattering
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In this work we compared the induction time of crystallization (τi measured by DSC (τiDSC) and scanning diffusive light-scattering (SDLS, τiSDLS) in a vegetable oil blend. Several crystallization temperatures and cooling rates (1, 10, and 30°C/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%27 (TAGS) nucleation than DSC. Furthermore, τiSDLS was more consistent (that is, lower standard deviation) than τiDSC, particularly at high crystallization temperatures and cooling rates. The rheograms showed that τiDSC involves a measurement of crystal growth, while τiSDLS 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 (ΔGc), τiSDLS provided a better estimate of AGe than that obtained by τiDSC.
In this work we compared the induction time of crystallization (τi measured by DSC (τiDSC) and scanning diffusive light-scattering (SDLS, τiSDLS) in a vegetable oil blend. Several crystallization temperatures and cooling rates (1, 10, and 30°C/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, τiSDLS was more consistent (that is, lower standard deviation) than τiDSC, particularly at high crystallization temperatures and cooling rates. The rheograms showed that τiDSC involves a measurement of crystal growth, while τiSDLS 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 (ΔGc), τiSDLS provided a better estimate of AGe than that obtained by τiDSC.
