Physica A 304 (2002) 253–265 www.elsevier.com/locate/physa Aggregation, gelation and phase separation of heat denatured globular proteins Dominique Durand ∗ , Jean Christophe Gimel, Taco Nicolai Polym eres, Collo des, Interfaces, UMR CNRS, 6120 Universit e du Maine, Avenue Oliveir Messiaen, 72085 Le Mans Cedex 9, France Abstract -lactoglobulin is a globular protein which aggregates after a heat-induced denaturation. It may be considered as a good model system to investigate the processes of aggregation, gelation and phase separation which play a major role in the chemical physics of complex systems. We present here the main results of an extensive study of the denaturation of this protein in vari- ous experimental conditions: pH, ionic strength, concentration, temperature, and presence or not of polyoside. The structure and distribution of -lactoglobulin aggregates were characterized by dynamic and static light scattering, small angle neutron scattering and size exclusion chromatog- raphy. Microscopy was used to study the eect of phase separation on the morphology. The competition between phase separation and aggregation= gelation process is discussed. c  2002 Elsevier Science B.V. All rights reserved. PACS: 61.43.Hv; 64.60.Ak; 64.75.+g; 87.1.Da Keywords: Globular proteins; Aggregates; Gels; Phase separation 1. Introduction Globular proteins denature if heated which generally leads to aggregation and even- tually a gel is formed if the protein concentration is sucient [1]. The aggregation process and the structure of the gels depend on external conditions such as the pH, the ionic strength (I ), the protein concentration (C ) and the temperature (T ). One of the most intensively studied globular proteins is -lactoglobulin (-lg) which is the major component of whey and has molar mass 18600 g= mol and radius 2 nm [2–4]. Apart from being a good model system, -lg is widely used in food industry ∗ Corresponding author. Tel.: +33-2-43-83-33-21; fax: +33-2-43-83-35-58. E-mail address: dominique.durand@univ-lemans.fr (D. Durand). 0378-4371/02/$-see front matter c  2002 Elsevier Science B.V. All rights reserved. PII:S0378-4371(01)00514-3