Submitted to: International Journal of Agricultural Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 24, 2008
Publication Date: July 2, 2008
Citation: Xu, J., Mohamed, A., Sessa, D.J. 2008. Rheological properties of lupin protein suspensions. International Journal of Agricultural Research. 3(4):317-324. Interpretive Summary: Lupin is an important legume plant. Since its seeds unique characteristics of containing high concentrations of protein and oil, as well as being easy to grow and harvest; lupin could have more food and non food applications. However, there is very little research done on lupin and its protein and oil, especially their physical properties and structure/function relationships, which restricted the usage of lupin in the United States. This paper investigated and compared thermal and rheological properties for lupin and soy protein. We found that lupin protein had many similarities as soy protein, which could open a potential market for lupin protein usage. This information can be used by other researchers in the lupin field, and for further food and non food application studies of lupin protein.
Technical Abstract: The thermal and rheological properties of non defatted and defatted lupin protein as well as industrial soy protein were investigated by DSC and rheometry. DSC study exhibited that whole (non defatted) and defatted lupin protein as well as soy protein had some similar thermal properties. The glass transition temperatures for these three proteins were very close to each other. The energies of glass transition for these three proteins were only slightly different. By measuring the linear rheological properties of a series of concentrations of whole and defatted lupin protein, as well as soy protein in suspension, we found that all three protein suspensions exhibited similar viscoelastic solid properties. Both storage (G') and loss (G') moduli increased with an increase in concentration. The linear range of the rheological properties of all three protein suspensions was very small. The stress relaxation studies showed that the three protein suspensions relaxed quickly indicating that the molecules of these three kinds of protein have neither cross linking nor strong physical interactions. The non linear rheological properties of the suspensions for whole and defatted lupin protein, as well as soy protein, all displayed similar shear thinning behavior and viscosities.