Premium
CHANGES IN RHEOLOGICAL PROPERTIES OF RICE FLOUR DURING EXTRUSION COOKING
Author(s) -
GUHA MANISHA,
ALI S. ZAKIUDDIN
Publication year - 2011
Publication title -
journal of texture studies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.593
H-Index - 54
eISSN - 1745-4603
pISSN - 0022-4901
DOI - 10.1111/j.1745-4603.2011.00306.x
Subject(s) - amylose , rheology , die swell , extrusion , plastics extrusion , materials science , starch , food science , shear rate , rice flour , viscosity , chemistry , composite material , raw material , organic chemistry
Flour from two rice cultivars, one (IR‐64) with a high (28.6%) and the other (Agonibora) with a low (5.0%) amylose content, having 20% moisture, was extruded at different barrel temperatures (80–120C), through a twin‐screw extruder at a constant feed rate (15 kg/h) and screw speed (400 rpm). The effect of barrel temperature and amylose content of rice extrudates on pasting and rheological properties were examined using rapid visco‐analyzer and a coaxial cylinder system, respectively. Extrudates from low‐amylose rice exhibited lower paste viscosity than from high‐amylose rice. Different rheological models (Power law, Herschel–Bulkley, Bingham and Casson) were examined for the best description of the shear rate/shear stress data. The Herschel–Bulkley model fitted best ( r ≥ 0.948–0.989, P ≤ 0.01) for the high‐amylose rice, whereas the Power law model showed best fit ( r ≥ 0.998–0.999, P ≤ 0.01) for the low‐amylose rice extrudate. PRACTICAL APPLICATIONS The end use of pregelatinized rice flour prepared by extrusion cooking depends on the pasting and flow behavior characteristics of its starch that are largely controlled by the amylose content of rice cultivar. The present work offers a general approach for characterization of pasting profile and rheological behavior of pregelatinized extruded rice flour. The extruded flour from low‐amylose rice exhibited lower pasting and apparent viscosity than from the high‐amylose one. The low‐amylose rice extrudates render itself more suitable as a base material in food formulations where a high solid density per unit volume is required. The extrudate from high‐amylose rice, on the other hand, could be used as a thickener in convenience foods such as soup mixes. The results obtained may be useful to food industries for development of newer food formulations based on extruded rice flour.