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Abstract: Rheological properties of the extruded pastes of various extrusion conditions were investigated by dynamic oscillation and creep-recovery tests. Temperature sweep test showed that the starch gelatinization of non-extruded pastes took place at about 67°C and no gelatinization was observed for the extruded sample. Frequency sweep tests could be represented by a Power law model and the samples showed gel-like behavior since storage modulus was much larger than loss modulus. The creep-recovery data were modeled by the Burger’s model. With the addition of flaxseed, the viscoelastic modulii of pastes were increased due to the formation of starch–protein–fat network, however, with further increasing the flaxseed content the viscoelastic modulii of pastes were decreased due to excessive fat which lead to network weakening. The water holding capacity results indicated that the viscoelastic properties of pastes were depended on the swelled starch–protein complex granules and the formation of new cross-links in the network. [Copyright &y& Elsevier]

Abstract: Flaxseed gum solutions were extracted and dried by different methods: ethanol precipitation, freeze drying, 105°C oven drying, 80°C oven drying, spray drying, and vacuum drying. The effects of these drying methods on the rheological properties of flaxseed gum were investigated in present study. Ethanol precipitation increased the apparent viscosity of flaxseed gum solution, while all the other methods decreased the apparent viscosity. Most of the drying methods slightly increased the activation energy, except ethanol precipitation. In frequency sweep test, all the drying methods reduced the G′ and G″ values. In creep–recovery tests, the data were modeled by Berger’s model. The E 2 and η 1 values were reduced by all of the drying methods in this study. Some relationships were found between the parameters in the Power Law model of the frequency sweep test and the parameters in Berger’s model. [Copyright &y& Elsevier]

Abstract: Rheological properties of 5% (w/w) waxy maize starch (WMS)/xanthan gum (XG) mixed pastes (mixing ratios: 10/0, 9.5/0.5, 9/1) in the presence of sucrose (0%, 15%, and 30%) were studied. The 5% WMS paste displayed strong anti-thixotropic behavior based on the heating method adopted (heating in water bath for 40min with mixing at 200rpm). The addition of XG could accelerate the formation of new structure of the WMS/XG mixed pastes under shear conditions, and XG could also decrease the in-shear recoveries of the mixtures. Both the addition of XG and sucrose increased the apparent viscosity (η a) and dynamic moduli (G′ and G″) of the mixed pastes, with XG contributing to the solid-like properties of the mixtures obviously, while sucrose played a contrary role. Thermostable properties of the mixed pastes could be improved distinctly with the addition of XG, whereas sucrose decreased it slightly. [Copyright &y& Elsevier]

Abstract: Influences of alfalfa powder concentration and granularity on the dynamic rheological properties of alfalfa-wheat dough was studied. Frequency sweep tests at 25°C and 80°C and temperature sweep tests from 25°C to 80°C were applied to wheat dough samples. Elastic moduli (G′) and viscous moduli (G″) of the alfalfa-wheat dough at 80°C were higher than those of the alfalfa-wheat dough at 25°C. The viscoelastic moduli (G′ and G″) of the alfalfa-wheat dough at 80°C showed less frequency dependence compared to those of the samples at 25°C. The viscoelastic moduli (G′ and G″) of alfalfa-wheat dough increased with the increasing of alfalfa powder concentration from 0% to 10% and decreased with further increase in alfalfa powder concentration from 10% to 20% at 25°C. All the alfalfa-added samples showed a delay in the dough gelatinization temperature comparing with the control sample. On the other hand, the viscoelastic moduli (G′ and G″) increased with the increase of alfalfa powder granularity distributed from 80–100 to 40–60 mesh. [Copyright &y& Elsevier]

Abstract: The effects of starch concentration on the rheological properties of dilute aqueous solutions of cassava starch were investigated. Cassava starch suspensions at different starch concentrations (0.2, 0.4, 0.6, 0.8, and 1.0 wt. %) were heated at 90°C for 1h and then rapidly cooled to 25°C. The apparent viscosities of starch solutions were measured as a function of starch concentration. The cassava starch solution with a concentration of 0.2% showed Newtonian behavior, and as the concentration was increased beyond 0.4%, the solutions showed shear-thinning behavior. The flow behavior (apparent viscosity against shear rate) of the solutions was well described using a power law model. The consistency indices increased and the flow behavior indices decreased with the increasing of starch concentration. After storing the solutions at 25°C for 24h, precipitation of starch took place instead of gelation. The volume of precipitation bed increased linearly with starch concentration. [Copyright &y& Elsevier]

Abstract: Both small amplitude oscillatory and steady shear measurements were carried out at 25°C, 50°C, and 75°C in order to determine the rheological properties of the mixtures of flaxseed gum (0.1–0.5%) and native maize starch (3%). It was found that the apparent viscosities of the samples increased with the increasing of flaxseed gum concentration. The apparent viscosities of the samples were fitted well to the power law model (the values of R 2 were between 0.954 and 0.999). The consistency index (K) of the gum–starch mixtures increased with the increasing of flaxseed gum concentration. The gum–starch mixtures showed gel-like behavior since the storage modulus (G′) was much larger than the loss modulus (G″) and the frequency dependence of both modulus was not significant. The G′ and G″ of the gum–starch mixtures was increased with the increasing of flaxseed gum concentration. The influence of temperature was more significant for the flaxseed gum–maize starch mixtures compared to maize starch gel. [Copyright &y& Elsevier]