Viscosity of Ice Cream Mix at Pasteurization Temperatures

To calculate the holding times of ice cream mixes in the tubes of HTST pasteurizers, accurate viscosity data are needed for the temperatures and the shear rates of interest. Apparent viscosity was determined for ice cream mixes at 8O'C using shear rate sweeps in a Cani-Med rheometer. Mixes varied in fat percentage, milk SNF, sweetener content, type of polysaccharide (guar, locust bean gum, carboxymethyl cellulose, xanthan), polysaccharide concentration, and blended proprietary stabilizer type and concentration. The effect of dissolution time was also studied. Data were fitted to the power law model, and the best estimate of flow behavior index was .7 for all mixes except those with xanthan gum, in which case the estimate was .5. The consistency coefficient is reported for all combinations described and provides useful data for equipment design and regulatory needs. The effect of the consistency coefficient on Reynolds number in holding tubes is also discussed.