Research On Ovalbumin Dry Heat Selenium Acidification And Its Properties And Structure

This study reports a new method of the selenization of food proteins. Ovalbumin (OVA) was selenized by dry-heating in the presence of selenite at pH3.0and60℃for1and3days, and the physicochemical and structural properties of selenized OVA (Se-OVA) were investigated.Firstly, the selenium content of Se-OVA by dry-heating for1d was0.67%, Se-OVA for3d was0.88%, and the electrophoretic mobility of Se-OVA was also increased.Second, although the solubility of dry-heated OVA decreased, the decrease was slightly depressed by selenization. The exchange reation between the sulfhydryl and disulfide groups was enhanced and thesurface hydrophobicity of OVA increased by selenization. The heat-induced insolubility and the digestibility of OVA was improved by selenization at pH7.0. The antioxidant activities of OVA, including ABTS+free radical scavenging capacity, reducing power, Fe2+chelating capacity, hydroxyl radical scavenging capacity, and the superoxide radical scavenging capacity, were remarkably enhanced by selenization. The circular dichroism spectra (CD) showed that the change of the secondary structure in the OVA molecule, measured by α-helix content, was mild by selenization, suggesting that the conformational change occurred in the OVA molecule by selenization. Differential scanning calorimetry thermograms (DSC) of OVA indicated a decrease of the denaturation temperature from78.62℃to77.07℃by selenization. However, the stability of OVA against heat-induced insolubility at pH7.0was improved. The tryptophan fluorescence intensity of OVA was reduced by selenization. The results demonstrated molten (partially unfolded) conformations of OVA formed by selenization through dry-heating in the presence of selenite.Third, some selenized tryptic peptides of Se-OVA was detected by MALDI-TOF-MS. Furthermore, the introduced selenium linking in peptides of Se-OVA was identified.In summary, selenium can be successfully conjuagted to the OVA molecule by dry-heating in the presence of selenite. The functional properties and the antioxidant activity of OVA were improved by selenization. In the OVA molecule, the change of the secondary structure was mild, but the tertiary structure was significant. These results suggested that dry-heating selenization was a novel method for improving the functional properties of food protein. This method also provides a new method for preparing organic selenium.