Ultrasonic determination of the effect of shear on lipid crystallization

The design and calibration of a novel rheometer incorporating ultrasonic se nsors are described. The instrument is capable of the simultaneous measurem ents of torque, rate of temperature change, and ultrasonic properties of a liquid as a function of time, temperature, and shear rate. The effect of sh ear rate on the crystallization onset temperature of a sample of confection ery coating fat is studied using this device. The instrument detected the p hase transition in the sheared sample as abrupt changes in all of the measu red parameters. The onset temperature increased significantly with shear ra te, implying lipid crystallization can be accelerated by mixing. There were also significant differences between sensing modalities.