PARTICLE SIZE CHARACTERISTICS OF GROUND SOY AND RED GRAM

Grinding characteristics of soy and red gram were compared employing single- and two-stage grinding in a mixer grinder. The initial size as well as hardness of soy (216 N) and red gram (220 N) were nearly equal. However, final particle size of red gram (61 m) was much lower than soy (255 m), indicating that red gram was relatively easier to grind. Analysis of microstructure indicated that typical internal structure and intercellular forces could play a significant role in determining the grinding characteristics of individual grains. With the same amount of energy input (200 kJ/kg), size reduction ratio in soy increased from 12 to 16 during two-stage grinding. Energy and particle analyses revealed that a two-stage segregated grinding is suitable for soy while a single-stage grinding is adequate for red gram. Classical dry grinding laws were applicable after initial break up suggesting their suitability for secondary grinding of soy and red gram.