Submitted to: American Journal of Food Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/11/2008
Publication Date: 3/4/2008
Citation: Xu, J., Mohamed, A., Hojillaevangelist, M.P., Sessa, D.J. 2008. Rheology of defatted ultrafiltration-diafiltration soy proteins. American Journal of Food Technology. 3(5):294-302. Interpretive Summary: Soybean proteins are the most important vegetable proteins and widely used. They can be added to formulated bakery products, dairy products, and meat substitutes. Soybean proteins have been widely used in the food industry not only due to their nutrition properties, but also due to their functional properties. Soybean proteins are being used as functional ingredients in many food products. In addition, soybean proteins also have extensive applications in industry such as in many types of paints and inks, in fire-fighting foams, in paper coatings, etc. Conventional methods of producing soy proteins include treatment of soy flour with acid or alcohol to separate proteins followed by centrifugations and/or filtrations. These methods generally can damage the protein functional properties. Purifying soy proteins with the method of ultrafiltration-diafiltration can preserve the functionality of the proteins. Because of above reasons, soy proteins produced by ultrafiltration-diafiltration have great potential in both food and industrial applications. However, literature reports regarding ultrafiltration-diafiltration soy protein physical properties and processing behaviors are limited. A better understanding of soy proteins and products should enhance wider usage of them. The objective of this work is to characterize the linear and non-linear rheological properties of the defatted ultrafiltered-diafiltered (DUD) soy proteins so that we can have some insight for their properties and function relationships, which can be used to guide more food and non-food applications for DUD soy proteins.
Technical Abstract: The linear and non-linear rheological properties of defatted soy proteins produced by ultrafiltration-diafiltration were investigated at three temperatures. Five concentrations ranging from 10% to 30% of the defatted ultrafiltered-diafiltered (DUD) soy proteins were prepared. The properties of DUD soy proteins depended on concentration and temperature. At 10%, DUD soy proteins exhibited almost viscous fluid behavior. When concentration increased or temperature decreased, the properties of soy proteins shifted into viscoelastic. The higher the concentration or the lower the temperature, the stronger of the viscoelasticity for the soy proteins. The non-linear rheological properties were also concentration-and-temperature dependent. The non-linear steady shear measurements for the DUD soy proteins showed shear-thinning behavior, which can be described by a power law constitutive model. The trend of the power law exponent shift is very consistent with the linear viscoelastic behavior change with soy protein concentration and temperature. The results of this work can be used to direct further food and non-food applications for DUD soy proteins.