Showing 4 results for Viscosity
G. R. Mesbahi, J. Jamalian,
Volume 6, Issue 2 (7-2002)
Abstract
Pectin is used in a number of foods as a gelling agent, thickener, texturizer, emulsifier and stabilizer. Sugar-beet pulp, the residue left from sugar extraction, is a rich source of pectin. It was the purpose of this study to develop a procedure for the extraction of pectin from sugar-beet pulp and to improve the functional properties of this pectin for more potential uses. To extract pectin, pressed beet pulp was dried and powdered. Then, it was extracted under various conditions (pH 1 and 1.5, temperatures of 80oC and 90oC and extraction periods of 1, 2, 3 and 4 hr). The highest yield (22.35%) was obtained at 90oC after 4 hr at pH 1. Chemical composition of the extracted pectin and that of commercial citrus pectin were determined and compared. Also, the beet pulp pectin was used in certain foods and its functional properties were compared with those of the commercial citrus pectin. The effects of ammonium persulfate and high pH levels on the above mentioned properties were investigated. Finally, the effects of the beet pulp pectin and the commercial citrus pectin on the flavor of certain foods were evaluated. The results indicate that the extracted beet pulp pectin can be used in certain foods such as ketchup sauce as a thickener or as an agent increasing the viscosity however, it does not have the ability to form firm gels in food.
B. Maherani, M. Barzegar, M. A. Sahari, H. Dehghan,
Volume 8, Issue 4 (1-2005)
Abstract
Aqueous extraction of gum from flaxseed was optimized using Response Surface Methodology (RSM). In this study the effect of temperature (45-100 °C), pH (3-7) and water/seed ratio (4-24), on the dependent variables including: yield, protein and apparent viscosity of extracted gum were investigated. The results showed that temperature and pH are two major effective factors on yield and quality of extracted gum (purity and apparent viscosity), whereas water/seed ratio had minor effects. The optimized conditions of extraction were as follows: temperature 85- 90 oC pH 6.5- 7.0 and water/seed ratio 14. Apparent viscosities of extracted gums were determined and the effect of extraction conditions on rheological properties of flaxseed gum was investigated.
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.
