Impurity effects on crystallization rates of n-hexadecance in oil-in-water emulsions

摘要

Crystallization rtes of n-hexadencane dispersed in oil-in-water (O/W) emulsion (oil 20 wt /100 and water 80 wt /100) were studied by an ultrasonic velocity measurement technique. Twin 20 was employed for emulsification to form the O/W emulsion. A highly hydrophobic food emulsifier, a sucrose polyester involving plasmatic acid moiety (P-170), was added to n-hexadecane, as an impurity, in an attempt to modify the rte of the crystallization of n-hexadecane. The rates of crystallization of n-hexadenane were monitored by variations in the ultrasonic velocity values, which increase with increasing amount of crystal fractions in the oil phase of he emulsion. In comparison with the results of the O/W emulsion systems with those of the bulk systems, the following results were obtained; 9a) the addition of P-170 accelerated the nucleation in the emission system, yet no acceleration was revealed in the bulk system, (b) the rates of crystal growth were retarded by the addition of P-170m, (c0 the acceleration of nucleation occurred through two stages iith increasing concentrations of P-170: e.g., a sharp increase occurred in a low concentrates range of P-170 up to 0.3/100 with respect to n-hjejxadecane, then a moderate acceleration occurred at P=-170 concentrations above 0.6/00. These results were discussed in terms of heterogeneous nucleation occurring at interfaces of the O/W emulsion droplets.