Rheological Modeling of Corn Starch Doughs At Low to Intermediate Moisture

Abstract

A generalized model for predicting the extrudate viscosity of starch based products at low to intermediate moisture content is presented. It incorporates the effects of shear rate, temperature, moisture content, time-temperature history and strain history. The model was tested using corn starch dough-at various moisture contents. An Instron capillarv rheometer and a Baker Perkins MPF 50 D/25 co-rotatinn twin scre& extruder were used to collect all data. Viscosity was fo;nd to be a function of cook temperature and moisture content but not cook time. Observed versus predicted viscosity gave an R* of 0.975 after accounting for shear rate, temperature, moisture content and timetemperature history in the capillary rheometer. Extrusion tests indicated that correction for strain history was important for highly puffed extrudates.

Physicochemical Changes and Rheological Properties of Starch during Extrusion (A Review)

“…In all these studies, the viscosity of cereal dough was assumed to have a power function dependency on shear rate, an Arrhenius dependency temperature, and an exponential dependency on moisture: q ( i ) = m(;)"-' exp(AH/RT) exp(-k,C) (20) The apparent viscosities of cereal doughs during extrusion were shown to be pseudoplastic with n values from 0.25 to 0.75 in the temperature range between 67 and 158 "C and at moisture contents between 13% and 50%. Mackey and Ofoli (1990), assuming that the increase in viscosity due to the transformation of starch granules was similar to the viscosity increase caused by an increase in the effective polymer molecular weight during a plastic polymerization process, developed a model incorporating the effect of shear rate, temperature, moisture content, time-temperature history, and strain history for starch doughs:…”

“…The dependence of starch viscosity on temperature, moisture content, time-temperature history, and shear rate has been studied by a number of researchers (Harper et al, 1971;Senouci and Smith, 1988a). A few attempts have been made to model gelatinization and fragmentation kinetics during extrusion (Davidson et al, 198413;Diosady et al, 1985;Bhattacharya and Hanna, 198713;Wang et al, 1989) and to model apparent viscosity including reaction kinetics during extrusion (Morgan et al, 1989;Mackey and Ofoli, 1990;Lai and Kokini, 1990). In addition, the elastic properties of cereal dough during extrusion have also been studied (Jasberg et al, 1981;Jao et al, 1978;Senouci and Smith, 198813;Padmanabhan and Bhattacharya, 1989).…”

Ovalbumin thermal Gelation Prediction by Application of Temperature‐Time History

“…Apparent viscosity was assumed to be a relative measure of the consistency or strength of gels formed by heat driven denaturation and subsequent cooling (Hickson et al, 1980). Apparent viscosity (viscosity index) has been reported to successfully evaluate thermal gelation of starch, egg and other protein systems by several investigators (Harper et al, 1978;Morgan, 1979;Hickson et al, 1980;Mackey and Ofoli, 1990). Also, polymer melt rheology was incorporated as a means of approximating viscometric behavior of denatured proteins (Ferry, 1970;Shah and Darby, 1976).…”

Fully Biodegradable Lubricated Thermoplastic Wheat Starch: Mechanical and Rheological Properties of an Injection Grade

“…The rheological behaviour of materials during extrusion has been studied by many authors [10][11][12][13][14][15][16][17][18]. Our interest is focused on the study of rheological behaviour of compounds used in injection moulding to produce a compound which will serve as a reference to future studies.…”