EFFECTS OF SUCROSE ESTER ON THE KINETICS OF POLYMORPHIC TRANSITION INHYDROGENATED SUNFLOWER OIL

The effect of a commercial emulsifier, sucrose ester, on the crystalli zation kinetics of hydrogenated sunflowerseed oil was studied by means of an optical method. Induction times were measured for hydrogenated oil with the addition of 0.01, 0.05, and 0.1 wt% sucrose ester. This e mulsifier delayed nucleation, thus affecting the formation of critical nuclei and prolonging induction times. Kinetics of the beta'-->beta p olymorphic transition was followed by X-ray diffractometry. Addition o f the emulsifier delayed the appearance of the signal at 4.6 Angstrom. Moreover, longer times were needed to complete the transition. The ki netic model chosen to describe the transition process was based on the theory of Avrami. Avrami's exponent n was approximately 1 in all case s. The n value was in agreement with the fact that only one beta' patt ern was found. The beta form could not be obtained directly from the m elt, and it is unlikely that the beta'-->beta transition occurred thro ugh a melt-mediated mechanism. Transition was hindered by the rigidity of the sucrose ester structure.