Effects of fat crystallization on the behavior of proteins and lipids at oil droplet surfaces

The effects of fat crystallization induced by thermal treatment on the rheological properties of creams and physical phenomena at the oil droplet surfaces were investigated. Creams A or B were prepared from commercial proprietary fats A or B (vegetable oils with different triaclyglycerol composition) and aqueous solution containing proteins. Thermal treatment of the creams at the “critical temperatures” (temperatures inducing a small percentage of solid fats in the oil droplets) caused a rapid increase of solid fat contents in the following cooling process. The thermal treatment of cream B at the “critical temperature” caused an increase of viscosity of the cream and an increase of protein surface coverage during the subsequent cooling process. These results suggest that the oil droplet aggregation induced by the thermal treatment at the “critical temperature” and the subsequent cooling occurred via further adsorption of proteins. Electron spin resonance measurement demonstrated the dramatic reduction of fluidity of triacylglycerol molecules at the oil droplet surface in cream B during the cooling process after thermal treatment at temperatures below “critical”. Based on these results, we speculated on the mechanism for the destabilization of thermally treated creams during the cooling process.