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Title:Rheological Properties of Soybean and Soybean-Solute Systems
Author(s):Urbanski, Gregory Eugene
Department / Program:Food Science
Discipline:Food Science
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Polymer
Abstract:In developing countries, the high cost of cows milk protein and lack of refrigeration are two problems which contribute to protein deficiencies among the young. Concentrated intermediate moisture soybean beverages, if successfully developed, would represent a partial solution to both the above problems.
However, there have been numerous obstacles in this development. Concentration of soybean beverages above 15% solids is prevented by a viscosity barrier. Secondly, sucrose which is commonly used to preserve intermediate moisture foods, has been shown by some researchers to increase viscosity and by others to decrease viscosity of soybean beverages.
Therefore, the objectives of this study were to identify the soybean components and mechanisms involved in the high viscosity of soybean beverages and to define the effects of solutes, such as sucrose, on soy beverage viscosity.
Soybean cotyledons were separated into full fat flour, defatted flour, desludged full fat flour, protein, cell wall material and soluble carbohydrate. The rheological properties of these materials in suspension with water were determined and correlated with suspension parameters such as water imbibing and water binding. Imbibed water is held within the structure of the material so that it will not flow. Bound water is the equilibrium moisture content of the material at a specified relative humidity.
It was found that the flow properties of the soybean materials in suspension were described adequately by the power law equation. Soybean soluble carbohydrate was Newtonian regardless of concentration and the least viscous soybean material. All other soybean materials showed pseudoplastic flow. The soybean cell wall material and protein were the most viscous materials.
Water imbibing ability was well related to high viscosity and pseudoplastic flow. It was concluded that high viscosity and pseudoplastic flow of soybean materials in suspension are due to an absence of unimbibed water in the suspension. When unimbibed water exists, internal friction in the suspension between the swollen particles is greatly reduced and viscosity is lowered.
Adding sucrose, glucose or sodium chloride to viscous soybean suspensions lowered viscosity and increased Newtonian flow behavior. A ratio of polymer bound water to solute bound water in the suspension was linearly related to viscosity and Newtonian flow. It was concluded that when most of the water is bound to the solute, the suspension exhibits flow similar to those of solute solutions, i.e., low viscosity and near-Newtonian flow. When most of the water is bound to polymers, the suspension shows high viscosity and pseudoplasticity.
Pseudoplastic flow was explained as a migration of water from the polymer to the solute upon high shear. Since the association of water with polymers causes high viscosity, loss of water from the polymer decreases viscosity.
A method for producing an intermediate moisture soybean beverage was proposed. The method called for homogenization of a milled slurry containing blanched cotyledons and sucrose. Sucrose addition prior to milling served to lower water activity, decrease viscosity and increase milling efficiency. Concentration of the beverage does not call for evaporation. Instead concentration is accomplished by formulating with lower amounts of water.
Issue Date:1981
Description:200 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1981.
Other Identifier(s):(UMI)AAI8127722
Date Available in IDEALS:2014-12-13
Date Deposited:1981

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