Rheological properties of ice cream emulsion prepared from lipase-catalyzed transesterified palm kernel olein : anhydrous milk fat mixture

The effect of different fat sources used in the preparation of ice cream em ulsions was investigated. Anhydrous milkfat (AMF), a mixture of unmodified palm kernel olein (PKO) and AMF (70:30, w/w) and enzyme-transesterified PKO :AMF (70:30, w/w) mixture were used in the preparation of the emulsions. Tr ansesterification was catalyzed by mycelium-bound lipase from Rhizomucor mi ehei. Rheological and viscoelastic properties measured were the creep compl iance, controlled-stress steady state flow and frequency sweep profiles. Re sults indicate that emulsion prepared using transesterified PKO:AMF (TE-PKO :AMF) exhibited a different rheological behavior from that of AMF alone, an d the unmodified PKO:AMF (70:30) blend. Frequency sweep profiles showed tha t the G = values of both AMF and TE-PKO:AMF emulsions were higher than thei r G at values, indicating that these emulsions were dominated by the elasti c component over all frequencies measured. On the other hand, the PKO:AMF e mulsion was dominated by viscous components at low frequency. A plot of vis cosity versus log shear rate illustrated that the ice cream emulsion made f rom TE-PKO:AMF was more viscous than those of unmodified PKO:AMF and AMF. T he lower creep compliance showed a stronger emulsion in the TE-PKO:AMF than that of the unmodified PKO:AMF. Since high viscosity and greater strength are some of the desired properties in ice cream emulsion, this suggests tha t transesterification of PKO:AMF (70:30, w/w) can be used to produce a fat that is suitable for use in the preparation of ice cream emulsions.