Showing 3 results for Rheology
J. Jamalian, A. R. Rahimi,
Volume 7, Issue 1 (4-2003)
Abstract
Whey powder, due to its lactose and protein contents, can be used as an important flour improver to decrease the rate of staling. In the present investigation, whey powder was added at 5 levels (zero to 5%, W/W) to the flour of Sangak bread. Bread was baked according to the formula and procedure used by traditional Sangak bakeries. Bread samples were kept at room temperature or under refrigeration for 36 hours. They were then evaluated for staling by a taste panel. They were also subjected to proximate analysis. The dough was examined for farinographic, amylographic, extensographic and fermentographic properties. The data of staling tests including color, texture, flavor and also proximate analysis data were analyzed by ANOVA. Finally, differences among treatments were examined by Ducan’s multiple range procedure.
The results indicated that the best treatment was the use of 3% whey powder, as far as staling and texture of bread are concerned. However, the best color of bread was achieved with 5% whey powder so was true of the protein, ash and fat contents. Viscosity, as tested by amylography, and also parameters of farinography reached their highest levels in the dough prepared from flour having 5% whey powder in the formula. The best extensibility was observed with the flours containing 4% whey powder and the highest dough energy was associated with the dough prepared from flour having 5% whey powder. As for the loaf volume, best results were obtained with the dough prepared from flour having 3% whey powder.
Overall, it is concluded that the use of 3% whey powder is the best treatment with regard to the delay in the rate of staling, increase in loaf volume, and color appeal of Sangak bread, and rheological properties of the dough.
S. Abassi, S. Foroughinia,
Volume 11, Issue 41 (10-2007)
Abstract
Salab gum is a hydrocolloidal compound which can be extracted from detached roots, tubers as well as rhizomes of Orchidaceae family. Apart from its applications in pharmaceuticals it has many potential usages in foodstuffs particularly ice cream and local soft drinks. However, there is little evidence about its rheological properties in the literature. Therefore, in the present study, the influence of variables such as concentration (2–7 g l-1), temperature (5–55°C), pH (2, 4, 6, 7, 9, and 11) as well as rotational speed (up to 200 rpm) were examined on the apparent viscosity and flow behavior of the gum solution. Regarding the effect of the abovementioned parameters, our findings revealed that increasing rotational speed or shear rate at low concentrations (3 and 4 g l-1) had no effect on the apparent viscosity and those samples behaved like Newtonian fluids whereas, at slightly higher concentrations (5–7 g l-1), with increasing the rotational speed, the apparent viscosity diminished and the solution consequently showed a Pseudoplastic behavior. In all these experiments, the apparent viscosity was enhanced with increasing the concentration and diminished with increasing the temperature. In addition, changing the pH showed no significant effect on the apparent viscosity in the majority of samples. Furthermore, using mathematical equations, experimental findings (namely rotational speed and torque) were converted to their fundamental counterparts (shear rate and shear stress) and discussed.
A Farahnaki, A Dehghn, Gh Mesbahi, M Majzobi,
Volume 13, Issue 48 (7-2009)
Abstract
Salad dressing is a semisolid emulsion and a colloidal system with high consumer demand. Food polysaccharides (e.g starch) are used in the formulation of salad dressing to improve its physical properties and sensory attributes. In this research, 10% mixture of wheat or maize starches were used to produce pregelatinized starches by a double drum drier, followed by milling and sieving. The pregelatinized starches (10%) were applied in the formulation of a salad dressing instead of native starch. Viscosity (at 25 and 35◦C), Hunter color parameters of the samples were evaluated and compared. Pregelatinized starches were more effective in increasing viscosity of the samples compared to corresponding native starches, and the effect of maize starch was greater than wheat starch. Significant differences were recorded in terms of color parameters of the samples. Pregelatinized starch caused higher L values (lighter samples) while the native starch samples were creamy-light yellow. In general, it can be concluded that the pregelatinized starches had better functional properties in salad dressing compared to native starches, and the produced pregelatinized starches can be used instead of native starch in the formulation of salad dressing.
