On-line measurement of rheological properties of wheat flour extrudates with added oxido-reductants, acid, and alkali Original Research Article

The measurements from a slit die rheometer for wheat flour extrudates were compared with the data obtained from a capillary rheometer. The regression of data showed that both rheometers were complementary to extend the range of shear rate from 10 to 500 s−1. The apparent viscosity of extrudates fitted the power law. The flow behaviour index, n, decreased from 0.501 to 0.384 and the consistency, k, increased from 3.1 kPa s0.5 to 9.7 kPa s0.38 when the temperature was raised from 50 to 80 °C. The addition of oxido-reductants, kansui, and lactic acid resulted in the variations of the contents of sulfhydryl group (SH) and disulfide bonds (SS). The protein extractability was reduced by oxidants, KIO3 and L-AA, and kansui due to the increase in SS. Increasing the ratio of SH to SS resulted in decrease in both apparent viscosity and specific mechanical energy.