EFFECTS OF TWIN SCREW PARAMETERS UPON THE MECHANICAL HARDNESS OF READY-TO-EAT EXTRUDATES ENRICHED WITH DE-OILED RICE BRAN

Abstract

Mechanical properties of ready-to-eat extrudates are perceived by the consumers as quality criteria. Texture quality of any product has a strong influence on the sensory evaluation as well as on the acceptability of the product. The main texture characteristics influencing the product acceptability are  crispness,  elasticity, hardness  and  softness.  In  the  present work,  we  investigate  one  of the  most important   texture  characteristics  of  extrudates   i.e.  hardness.  A  five-level,  four-factor  central composite rotatable design was employed to investigate the effect of temperature, screw speed, feed moisture  content  and  feed  composition  mainly  rice  bran content  and  their  interactions,  on  the mechanical hardness of extrudates. Among these, feed moisture was found to be a prominent factor affecting the product hardness. It was found that with the increase of feed moisture content, the rice bran proportion leads to increase in hardness of extrudates whereas the increase of temperature leads to decrease of hardness of product. A good agreement between the predicted (26.4899 N) and actual value (28.73N) of the response confirms the validation of response surface methodology (RSM)-model.