https://profdoc.um.ac.ir/articles/a/1016826.pdf

Steady shear flow behavior of gum extracted from Ocimum basilicum L. seed: effect of concentration and temperature.

The enrichment of gluten-free baked products with dietary fibre seems to be necessary since it has been reported that coeliac patients have generally a low intake of fibre due to their gluten-free diet. In the present study different cereal fibres (wheat, maize, oat and barley) were added at 3, 6 and 9 g/100 g level into a gluten-free bread formulation based on corn starch, rice flour and hydroxypropyl methyl cellulose (HPMC). Doughs were evaluated based on consistency, viscosity and thermal properties. Results showed that maize and oat fibre can be added to gluten-free bread with positive impact on bread nutritional and sensory properties. All breads with 9 g/100 g fibre increased the fibre content of control by 218%, but they were rated lower than those with 3 and 6 g/100 g fibre due to their powdery taste. The formulation containing barley fibre produced loaves that had more intense color and volume comparable to the control. During storage of breads a reduction in crumb moisture content and an increase in firmness were observed. The micrographs of the crumb showed the continuous matrix between starch and maize and/or oat fibre obtaining a more aerated structure.

Effect of dietary fibre enrichment on selected properties of gluten-free bread.

Rheological properties and quality of rice cakes formulated with different gums and an emulsifier blend

The effect of successively replacing (10%, 20%, and 30%) wheat flour with dietary fiber (DF) from wheat, oat, barley, and maize or cereal bran (CB) from wheat, oat, and rice on cake batter, final cake quality parameters, as well as on product shelf-life was studied. Batter viscosity (control, 2.96; wheat fiber 30%, 20.21; rice bran 10%, 0.47 Pa sn), cake-specific volume (control, 2.27; wheat fiber 20%, 2.83; rice bran 30%, 1.94 cm3/g), porosity (control, 0.75; wheat fiber 30%, 0.81; rice bran 30%, 0.69), and crumb moisture content (control, 20.07%,; wheat fiber 30%, 26.45%; oat bran 30%, 13.89%) increased significantly (P < 0.05) with DF addition but decreased with CB addition. Addition of DF resulted in softer crumb texture (Control, 4.20 N; wheat fiber 20%, 3.19 N), while CB addition increased crumb firmness (rice bran 30%, 10.84 N), respectively. Minor differences were observed in the crumb and crust color of the DF cakes with respect to the control. Addition of CB decreased the L values of crumb color significantly and the decrease increased with increased level of CB incorporation. DF addition led to cakes with greater acceptance by panelists than CB addition, similar to the control. DF cakes stored in polyethylene bags at 25 °C and 60% relative humidity for 6 days showed delayed moisture loss and lower firmness compared to CB cakes. The optimal level of incorporation based both on the objective and sensory characteristics results was found 20% for DF and 10% for CB, respectively. Concluding, by incorporating DF or CB properly, cakes with improved nutritional value can be manufactured.

Effect of the Addition of Different Dietary Fiber and Edible Cereal Bran Sources on the Baking and Sensory Characteristics of Cupcakes

Rheology of industrial polysaccharides — Theory and applications

Using a strain-controlled rheometer, the steady shear flow properties of aqueous xanthan gum solutions of different concentrations were measured over a wide range of shear rates. In this article, both the shear rate and concentration dependencies of steady shear flow behavior are reported from the experimentally obtained data. The viscous behavior is quantitatively discussed using a well-known power law type flow equation with a special emphasis on its importance in industrial processing and actual usage. In addition, several inelastic-viscoplastic flow models including a yield stress parameter are employed to make a quantitative evaluation of the steady shear flow behavior, and then the applicability of these models is also examined in detail. Finally, the elastic nature is explained with a brief comment on its practical significance. Main results obtained from this study can be summarized as follows: (1) Concentrated xanthan gum solutions exhibit a finite magnitude of yield stress. This may come from the fact that a large number of hydrogen bonds in the helix structure result in a stable configuration that can show a resistance to flow. (2) Concentrated xanthan gum solutions show a marked non-Newtonian shear-thinning behavior which is well described by a power law flow equation and may be interpreted in terms of the conformational status of the polymer molecules under the influence of shear flow. This rheological feature enhances sensory qualities in food, pharmaceutical, and cosmetic products and guarantees a high degree of mixability, pumpability, and pourability during their processing and/or actual use. (3) The Herschel-Bulkley, Mizrahi-Berk, and Heinz-Casson models are all applicable and have equivalent ability to describe the steady shear flow behavior of concentrated xanthan gum solutions, whereas both the Bingham and Casson models do not give a good applicability. (4) Concentrated xanthan gum solutions exhibit a quite important elastic flow behavior which acts as a significant factor for many industrial applications such as food, pharmaceutical, and cosmetic manufacturing processes.

Rheology of concentrated xanthan gum solutions: Steady shear flow behavior

The objective of the present study is to experimentally investigate the transient rheological behavior of concentrated xanthan gum solutions in start-up shear flow fields. Using a strain-controlled rheometer, a number of constant shear rates were suddenly imposed to aqueous xanthan gum solutions with different concentrations and the resultant shear stress responses were measured with time. The main findings obtained from this study can be summarized as follows: (1) For all shear rates imposed, however low it may be, the shear stress is rapidly increased with time (stress overshoot) upon inception of steady shear flow before passing through the maximum stress value and then gradually decreased with time (stress decay) until reaching a steady state flow. (2) As the imposed shear rate is increased, a more pronounced stress overshoot takes place and the maximum stress value becomes larger, whereas both times at which the maximum stress is observed and needed to reach a steady state flow are shortened. (3) The maximum shear stress is linearly increased with shear rate in a double logarithmic scale and becomes larger with increasing concentration at equal shear rates. In addition, the time at which the maximum stress occurs exhibits a linear relationship with the inverse of shear rate in a double logarithmic scale for all xanthan gum solutions, regardless of their concentrations. (4) The shear stress is sharply increased with an increase in strain until reaching the maximum stress at small range of deformations. The maximum stress is observed at similar strain values, irrespective of the imposed shear rates lower than 10 1/s. (5) The Bird-Leider model can be successfully used with regard to quantitatively predicting the transient behavior of concentrated xanthan gum solutions. However, this model has a fatal weakness in terms of describing a decrease in shear stress (stress decay).

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Transient rheological behavior of natural polysaccharide xanthan gum solutions in start-up shear flow fields: An experimental study using a strain-controlled rheometer

Yong-Seok Kim

Papers

Rheology of concentrated xanthan gum solutions: Steady shear flow behavior

Transient rheological behavior of natural polysaccharide xanthan gum solutions in start-up shear flow fields: An experimental study using a strain-controlled rheometer