Influence of Heat Treatment of Milk on the Flow Properties of Yoghurt

Milk was processed by vat heating (VAT, 85°C for 10 to 40 min), high temperature-short time heating (HTST, 98°C for 0.5 to 1.87 min) and ultra-high-temperature heating (UHT, 140°C for 2 to 8 sec) and made into yoghurt. Apparent viscosity (shear rate 57.75^5-1) ranged from 550–568 mPa.sec for VAT treatments, 260–462 mPa.sec for HTST treatments and 170–333 mPa.s for UHT treatments. Flow behavior indices for all treatments were between 0.55 to 0.65 while consistency index values ranged from 0.3 to 1. Milk processed by HTST systems appeared to be viable alternatives to vat processing. UHT processed milk, however, yielded yoghurts of low viscosity.