Defatted soybean was subjected to isolation procedures as follows: NaOH extraction/acid precipitation (NaOH-IE); water extraction/acid precipitation (H2O-IE); NaOH extraction/cryoprecipitation (NaOH-CP) and citric acid extraction/cryoprecipitation (CA-CP). NaOH-CP and CA-CP each resulted in precipitation of one protein mainly consisting of glycinin and beta-conglycinin, respectively. The proteins were subjected to polyacrylamide gel electrophoresis (PAGE), SDS-PAGE, size exclusion-chromatography (SEC) and differential scanning calorimetry (DSC) for characterization. PAGE, SDS-PAGE, SEC and DSC confirmed the homogeneity of NaOH-CP. The gelation properties and structural characteristics of NaOH-CP were investigated; the minimum protein concentration required for formation of a thermally-induced gel from NaOH-CP was 8%. With cold-set gelation, in the presence of 30 mM CaCl2, the minimum protein concentration required for formation of a self-supporting gel was 4%. At 100 mM CaCl 2, cold-set gelation of 10% protein concentration gave gel of strength 7.4 N compared to the 7.8 N gel strength obtained with thermally-induced gel at 16% protein concentration. The effects of heating on the NaOH-CP structure, in the presence of varying concentrations of NaCl and reducing agents, were examined by Fourier transform infrared (FTIR) spectroscopy and DSC. FTIR spectroscopy revealed that at 25°C the NaOH-CP protein showed four bands at 1633, 1650, 1667, and 1689 cm-1. At 85°C, the temperature associated with gelation, the four bands decreased in intensity with the simultaneous increase in the intensity of a band at 1644 cm-1 as result of the protein unfolding, furthermore two new bands at 1616 and 1685 cm -1 appeared. The latter two bands are attributed to intermolecular mu-sheet formed during gelation. The NaOH-CP did not exhibit any aggregation band between 25--100°C in the presence of NaCl. The DSC studies revealed that the protein denatured at approximately 102°
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.35552 |
| Date | January 2000 |
| Creators | Abdolgader, Ramadan E. |
| Contributors | Alli, Inteaz (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Food Science and Agricultural Chemistry.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001764895, proquestno: NQ64490, Theses scanned by UMI/ProQuest. |
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