Vol. 26 No. 5
September-October 2004

Thermodynamics and Non-equilibrium Criteria for Development and Application of Supplemented Phase Diagrams

A supplemented phase diagram includes data describing the influence of temperature and water content on physical and chemical equilibrium phenomena, and on non-equilibrium processes such as glass transition. Practitioners recognize its importance in controlling the storage and processing of food, pharmaceuticals, and biomaterials. Many basic questions are still unresolved, and more precise definitions are needed for a correct interpretation of the phenomena.

A new project supported by the Physical and Biophysical Chemistry Division will help improve the storage and processing of pharmaceuticals and food.

A new project supported by the Physical and Biophysical Chemistry Division aims to establish rational links between thermodynamic aspects of phase diagrams, supplemented by the non-equilibrium curve of the glass transition temperature, for mixtures of water with vitrifying agents used in the cryo- and dehydro-preservation of natural (foods, seeds, etc.) and synthetic products (pharmaceuticals). The project is designed to have a very broad and interdisciplinary scope in order to impact on the many fields related to chemistry and biophysical chemistry.

Practically, the project will provide the information necessary to develop supplemented state diagrams for aqueous glass-formers, which will improve our understanding of the influence of water content, nature of the vitrifying agent, and temperature on the physico-chemical stability of natural and synthetic products. To fulfill this goal, this study proposes to analyze the following:
• areas of food and pharmaceutical processing in which a theoretical basis is needed for a better definition of involved phenomena
• practical/theoretical applicability of equations extensively employed to predict transition temperatures
• best standard procedure for determining the glass transition curve as a function of water content
• differences between methods based on thermodynamics and kinetics for determining phase/state transitions, and how they might be standardized
• effects of water content on the kinetics of phase/state transitions (glass temperature, crystallization temperature) in biomaterials
• ways in which supplemented phase diagrams can be applied to analyze the stability of biomolecules on cooling or under high-pressure conditions

Besides technical reports to be published in Pure and Applied Chemistry and in other food and pharmaceutical research journals, the dissemination plan will also include the design of a Web page and guidelines, in electronic format, for use by practitioners.

This project started in May 2004 and the first draft is expected in December 2004 following the group meeting to be held in September during the 9th International Symposium on the Properties of Water. The project team consists of Harry Levine and Louise Slade (Kraft Foods, USA), David Reid (University of California, Davis, USA), Yrjo Roos (University College, Cork, Ireland, UK), Tony Auffret (Pfizer Central Research, Sandwich, UK), Pilar Buera and Horacio Corti (University of Buenos Aires, Argentina) and Austen Angell (consultant, Arizona State University).

For more information, contact the Task Group Chairman Horacio Corti <[email protected]>.

www.iupac.org/projects/2003/2003-036-2-100.html