In this work, the generalized now rate functions arising in file Study of flow problems are introduced. The efficient and accurate formulas through the hypergeometrical and incomplete beta functions are established. It is shown that the now rate functions C(m) and D(m,epsilon) describing the effects of processing on shear rate of yoghurt are Special Cases of generalized now rate functions. Comparative numerical examples are presented to demonstrate the efficiency of the proposed approaches. (C) 2008 Elsevier Ltd. All rights reserved.