The presence of heat-stable conformers of ovalbumin affects properties of thermally formed aggregates.
The aim of this work was to study the effect of the formation of more heat-stable conformers of chicken egg ovalbumin during incubation at basic pH (9.9) and elevated temperature (55 degrees C) on the protein aggregation properties at neutral pH. Native ovalbumin (N-OVA) is converted on the hours time-scale into more heat-stable forms denoted I- (intermediate) and S-OVA, that have denaturation temperatures 4.8 and 8.4 degrees C, respectively, higher than that of N-OVA. The conversions most likely proceed via I-OVA, but direct conversion of N-OVA into S-OVA with slower kinetics can not be excluded. It is demonstrated that both I- and S-OVA have similar denaturation characteristics to N-OVA, except that higher temperatures are required for denaturation. The presence of even small contributions of I-OVA does, however, reduce the Stokes radius of the aggregates formed upon heat treatment of the material at 90 degrees C about 2-fold. This affects the gel network formation considerably. Since many (commercial) preparations of ovalbumin contain varying contributions of the more heat-stable forms mentioned, proper characterization or standardization of the isolation procedure of the material is essential to control or predict the industrial application of this protein.
Wageningen Centre for Food Sciences, Diedenweg 20, 6700 AN Wageningen, The Netherland.
Jolan
J
de Groot
Harmen H J
HH
de Jongh
D000818:Animals; D002152:Calorimetry, Differential Scanning; D002645:Chickens; D006358:Hot Temperature; D007700:Kinetics; D010047:Ovalbumin / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D013997:Time Factors
D010047:Ovalbumin