Acceleration of crystallisation of palm kernel oil in oil-in-water emulsion by hydrophobic emulsifier additives

Crystallisation and polymorphic behaviour of palm kernel oil (PKO) dispersed in oil-in-water emulsion were observed using the ultrasonic velocity technique, DSC and in situ X-ray diffraction. Three sucrose oligoesters having palmitic acid (P-170), stearic acid (S-170) and lauric acid (L-195) moieties were added to PKO as additives, in an attempt to accelerate the crystallisation of PKO in the O/W emulsions that was suppressed due to dispersion of the oil phase into many droplets. It was found that the S-170 and P-170 additives accelerated the rate and extent of the crystallisation of PKO in the emulsion system. An independent measurement of crystal growth rate showed that the addition of S-170 and P-170 retarded the crystal growth of PKO. In contrast. L-195 did not show any effects of acceleration of crystallisation and retardation of crystal growth of PKO. X-ray diffraction spectra and DSC thermopeaks showed that the emulsion without the additives crystallised in the a polymorph. whereas beta' was crystallised with the addition of S-170. The results are discussed in terms of heterogeneous nucleation occurring at the oil-water interface where the additives may form molecular aggregates that act as a template for nucleation, as previously discussed for n-hexadecane emulsions (Colloids Surf., B 20 (2001) 229). (C) 2002 Elsevier Science B.V. All rights reserved.