RHEOLOGY OF STIRRED YOGURTS

Rheological characteristics of 2 commercial brands of stirred yogurt were evaluated using a Haake Rotovisco Model RV 20 with an M-5-Osc measuring head and MV-1 rotor assembly from measured shear stress values under a programmed 3-cycle up- and down-shear rate at 100 s-1/min from 0-500 s-1 (5 min). The upward shear-rate flow behavior of the yogurt samples could be described by a Herschel-Bulkley model while the downward shear-rate curves were essentially linear. Both upward and downward shear rate curves demonstrated progressive structural degradation with repeated shearing. The dependency of rheological parameters on temperature in the range 10-25-degrees-C followed both Arrhenius and Turian models.