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APPLICABILITY of A SHEAR INDUCED RATE CONSTANT MODEL to CONVERSION of CORN MEAL IN A TWIN‐SCREW EXTRUDER
Author(s) -
GOGOI B.K.,
WANG S.S.,
YAM K.L.
Publication year - 1995
Publication title -
journal of food processing and preservation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.511
H-Index - 48
eISSN - 1745-4549
pISSN - 0145-8892
DOI - 10.1111/j.1745-4549.1995.tb00277.x
Subject(s) - extrusion , plastics extrusion , rheology , shear rate , activation energy , materials science , rheometry , arrhenius plot , differential scanning calorimetry , arrhenius equation , shear (geology) , composite material , thermodynamics , chemistry , organic chemistry , physics
Data obtained from extruding corn meal in a corotating twin‐screw extruder was used to test an Arrhenius type shear induced rate constant model, k s = k s,o exp (—E s /), where k s was shear induced rate constant, E s was shear activation energy, was shear stress, and was molar volume. A rheological zone was created by placing a reverse screw 300 mm from the die where the temperature was at 60C, sufficiently low that thermal effect on conversion of the material into gel or melt could be neglected. Throughput was used as an independent variable to generate various levels of shear input, while screw speed and feed moisture content were kept constant. Conversion of the material in the rheological zone was determined using differential scanning calorimetry, and the rate contant k s was calculated assuming zero order kinetics. A plot of k s vs. 1/ followed a straight line, confirming the applicability of the model to twin‐screw extrusion under the experimental conditions. the shear activation energy E s was 40 cal/mole, comparable to the literature values obtained from single screw extrusion and capillary rheometry.