Grinding characteristics and batter quality of rice in different wet grinding systems

Grinding characteristics of raw and parboiled rice were evaluated in various wet grinding systems, namely, mixer grinder, stone grinder and colloid mill. The duration of grinding had inverse effect on the particle size and direct impact on the starch damage as well as energy consumption in batch grinders. Stone grinder was the least energy efficient and specific energy consumption for grinding raw rice (160.6 kJ/kg) was nearly twice as that of mixer grinder (74.9 kJ/kg). Parboiled rice required longer duration of grinding compared to raw rice, consequently specific energy consumption was higher (similar to 220 kJ/kg). All the three classical laws of grinding (Kick's, Rittinger's and Bond's) seemed to be applicable while Rittinger's law showed better suitability than the other two followed by Bond's law. Predominant compressive forces involved in stone grinder reflected in higher starch damage in batter which was also evident in the micrographs. Parboiled rice slurry exhibited much greater viscosity than raw rice but both displayed non-Newtonian pseudoplastic behaviour. (c) 2008 Elsevier Ltd. All rights reserved.