Whey Protein Dry Heating Selenium Acidification And Its Features

Selenizated whey protein isolate (Se-WPI) was prepared by dry-heating in the presence of selenite, and their physicochemical properties and functional properties were investigated. In addition, selenizated whey peptide (Se-WP) was prepared through Se-WPI was hydrolysed by alcalase, and its in vitro antioxidative activity was investigated.Firstly, whey protein isolate (WPI) was selenizated by dry-heating in the presence of selenite at relative mild conditions, and studied on the effects of pH, heating temperature and heating time for selenization of WPI. The result shows that selenization of WPI was promoted with a decrease of pH from6.0to2.0, but the lower value of pH will lead to poorly solubility of Se-WPI, therefore optimal pH was3.0; selenization of whey protein isolate increased with the raise of heating temperature from25to80℃, so optimal heating temperature was80℃; solubility of Se-WPI descended obviously when heating time was outstripping one day(1d), thus optimal heating time was1d. In conclusion, the optimal conditions of selenization of WPI were:pH3.0,80℃and1d, the organic selenium content of Se-WPI was3.66%.Secondly, physicochemical properties of Se-WPI were confirmed through77Se-NMR and the stability of selenious group. The result of77Se-NMR demonstrated that there was a clear absorption peak of selenium at1317.5ppm, this indicated the form of selenium of Se-WPI is selenious ester. The stability of selenious group also confirmed that the form of selenium is selenious ester, this result was consistent with77Se-NMR.Thirdly, functional properties of Se-WPI were confirmed. The results demonstrated that compared with natural whey protein isolate(N-WPI) and dry-heating whey protein isolate(DH-WPI), except the calcium phosphate-solubilizing ability of Se-WPI was not obviously change, other of Se-WPI functional properties, including the heat stability, emulsifying property, foaming property, ability of absorb oil, digestibility were improved evidently. Se-WP was prepared through Se-WPI was hydrolysed by alcalase, natural whey peptide(N-WP) and dry-heating whey peptide(DH-WP) werer prepared to adopt the same method, and their in vitro antioxidative activity was investigated. The results showed that the scavenging activity of against2,2-diphenyl-1-picrylhydrazyl (DPPH), the anti-lipid peroxidation ability and the reducing power of Se-WP were higher than N-WP and DH-WP, but the scavenging activity of against hydroxyl of three peptide was the same.In summary, WPI was able to selenizated successfully by dry-heating in the presence of selenite. Functional properties of Se-WPI and in vitro antioxidative activity of Se-WP were improved remarkably. Dry-heating was proved a very effective method for preparing the Se-WPI...