Kinetic Analysis of Rapeseed Oil Crystallization during Isothermal Storage

Abstract

Crystallization behavior of rapeseed oil during isothermal storage was investigated by dilatometry, transmitted light intensity measurement, and differential scanning calorimetry. The volume and transmitted light intensity of the oil samples changed significantly after a certain period (induction period) during isothermal storage. In order to explain these changes, a kinetic model for the crystallization of rapeseed oil was proposed by assuming that stable crystals are formed through meltmediated transition and metastable crystals grow via an "autocatalytic" mechanism. The crystallization process of rapeseed oil is well represented by the model, and it reasonably explains the peculiar relationship between the storage temperature and the induction period for crystallization.

Crystallization kinetics of safflower and olive oils during low-temperature storage

“…The dilatometric apparatus employed and the method used to measure the volumetric change in the oil were the same as those used in our previous study (Miyagawa et al, 2018). Briefly, a calibration curve related the storage temperature, q (°C) and the volumetric change of the brine, X brine (mL/g) was prepared from the brine.…”

“…Because it is difficult to find an alternative appropriate filling, the dilatometry technique for measuring the crystallization behavior of oil has also been discontinued. We showed previously that the crystallization behavior of rapeseed oil can be accurately measured by dilatometry when a using 30% (w/w) CaCl 2 solution (brine) as filling liquid (Miyagawa, Yoshida, Nakagawa, Adachi, 2018). The measurement of turbidity or transmitted light intensity is an effective method for observing microscopic changes occurring in the crystallization process (Wright, Narine, Marangoni, 2000) as well as pNMR.…”

“…The measurement of transmitted light intensity is easily conducted and is more sensitive than pNMR spectroscopy (Wright et al, 2000). We previously applied the transmitted light intensity measurement method to monitor the crystallization of rapeseed oil during its isothermal storage (Miyagawa et al, 2018).…”

“…However, these methods cannot be used to sufficiently express or analyze the crystallization process which includes the induction period. In this context, we previously proposed a kinetic model for the crystallization of rapeseed oil during isothermal storage at low temperatures (Miyagawa et al, 2018).…”

Analysis of Nonisothermal Crystallization of Rapeseed Oil by Deconvolution of Differential Scanning Calorimetry Curve

“…the induction period for crystallization, did not decrease monotonously with decreasing storage temperature 13 . This phenomenon is caused by the difference in the crystallization temperature and crystal structure among the TAGs composing the oil 14,15 . The crystallization behavior in the constant temperature-decreasing process was significantly different from that in the isothermal storage process.…”