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The presence of heat-stable conformers of ovalbumin affects properties of thermally formed aggregates

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Author: Groot, J.de · Jongh, H.H.J.de
Type:article
Date:2003
Institution: TNO Voeding
Source:Protein Engineering, 12, 16, 1035-1040
Identifier: 237473
Keywords: Nutrition · Food technology · Aggregation · Ovalbumin · Protein denaturation · Stokes radius · Turbidity · ovalbumin · article · chemical reaction kinetics · heat treatment · pH · priority journal · protein aggregation · protein analysis · protein denaturation · protein stability · thermostability · turbidity · Animals · Calorimetry, Differential Scanning · Chickens · Heat · Kinetics · Ovalbumin · Protein Conformation · Time Factors · Gallus gallus

Abstract

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°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°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°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. Chemicals/CAS: ovalbumin, 77466-29-6; Ovalbumin, 9006-59-1