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ARS Home » Southeast Area » Raleigh, North Carolina » Soybean and Nitrogen Fixation Research » Research » Publications at this Location » Publication #208896

Title: The formation and the functionality of soy protein-dextran and soy protein mannose conjugates.

item Kwanyuen, Prachuab

Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: 4/10/2007
Publication Date: 7/28/2007
Citation: Cramp, G.L., Kwanyuen, P., Daubert, C.R. 2007. The formation and the functionality of soy protein-dextran and soy protein mannose conjugates. Annual Meeting of the Institute of Food Technologists.

Interpretive Summary:

Technical Abstract: A thermally modified, readily reconstituted, soy protein isolate (SPI) demonstrated improved heat stability and cold-set gel functionality when prepared at 8% protein (w/w) for three hours at 95°C compared to the control SPI. When SPI was heated at 3% protein (w/w) equivalently, prior to reconstitution to 8% protein (w/w), the final viscosity was about three orders of magnitude less than the original sample. The viscosity of SPI heated at 3% protein (w/w) was still nearly two orders of magnitude less than the original sample after both samples were reheated at 8% protein. These results suggested that heat denaturation at low protein concentrations limited network formation even after the protein concentration and interaction sites increased, which in turn impacted the viscosity parameters of the system. Also, gelation was entirely prevented upon treatment of SPI with iodoacetamide, which carbaminomethylated the cysteine residues, a finding that established the role of disulfide bonds in network formation. The viscosity of the 8% protein (w/w) dispersion was also reduced by two orders of magnitude when treated with 8M urea, and when combined with 10mM DTT the viscosity of the gel was decreased by another order of magnitude. These results suggested that hydrophobic interactions or entanglements played a primary role in gel strength after intermolecular disulfide bonds form. The need for a higher concentration of protein during the heating step indicated that the critical disulfide bonds are intermolecular. Based on SDS-PAGE banding patterns and the reported cysteine content of 11S subunits, it appeared that sulfhydryl/disulfide interactions could be attributed to the 11S basic subunits, while 7S '', ', and ' participated in hydrophobic interactions or entanglements. Ultimately, the functionality produced by these combined protein-protein interactions produced a powdered soy protein isolate ingredient with consistent cold-set and thermal gelation properties.