Amorphous Food and Pharmaceutical Systems, Edited by Harry Levine, The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB4 0WF, UK. ISBN 0-85404-866-9, 7 Oct 02, pp. xliv +346. Price: £99.50.
This is a collection of papers pertaining to the issue of the amorphous state of materials with emphasis on food-related and pharmaceutical concerns and applications. The papers are presented as the outcome of a conference in May 2001 on “The Amorphous State—A Critical Review” held at Churchill College, Cambridge, supported by the BioUpdate Foundation and the Biotechnology Group of the RSC.
The preface of the proceedings is written by Felix Franks who takes the opportunity to relate his own reflections on the early events in the development of understanding the amorphous aqueous phase. It was the recognition by him, the team of Harry Levine and Louise Slade, and others of the interrelationship between molecular mobility and the diffusion-limited properties of foods and pharmaceuticals containing amorphous regions. The conference was the follow-up of an earlier meeting (1995) between prominent scientists and industrialists, and an extensive report of significant aspects of the discussions held in that meeting is included in the book. This is helpful, since it lays the foundations of the quest for further understanding of the fundamental and applied aspects of amorphous materials. Critical questions raised in the book include the effect of molecular structure and network morphology on vitrification phenomena, the choice of the most appropriate experimental techniques for their identification, the rates of enzymatic and chemical reactivity below the glass transition temperature (T g ) and the functionality of carbohydrates as stabilisers of labile biological materials.
Answers to the above questions and other important topics were attempted in the eight conference sessions/themes of the book:
| 1. | Structure and its significance in the application technology of amorphous materials. | ||||
| 2. | Glassy state dynamics and its significance for stabilization of labile bioproducts. | ||||
| 3. | Theories of unstable aqueous systems: how can they help the technologists? | ||||
| 4. | Progress in food processing and storage. | ||||
| 5. | Rational pharmaceutical formulations of amorphous products. | ||||
| 6. | Chemistry in solid amorphous matrices. | ||||
| 7. | Residual water, its measurement and its effects on product stability. | ||||
| 8. | Novel experimental approaches to studies of amorphous aqueous systems. | ||||
The above composition and order is good, however, within individual contributions the flow of the material seems a little disjointed. For example, the invited lecture of the opening theme covers competently the molecular mobility, physicochemical stability and the implications of material polyamorphism or heterogeneity on drug manufacture, a subject which is dealt primarily later in the book (session v). There is an extensive coverage of empirical and theoretical approaches routinely used by material scientists to estimate T g values in single systems and composites using the standard techniques of differential scanning calorimetry (DSC), nuclear magnetic and electron spin resonance spectroscopies, and dynamic mechanical thermal analysis (DMTA). This is not new material, but the strength of this book is that it brings together papers so diverse in their approach and interests (foods and pharmaceuticals) under the unifying umbrella of the glass phenomenon. As far as mechanical measurements go, the myths of T g pinpointed at the maximum of the loss modulus trace, of the equivalence between the DSC T g and the DMTA T g obtained at 0.001 Hz and of the universal WLF constants are hard to beat.
The book goes on to discuss some interesting examples of food processing and storage including the relevance of sucrose state diagrams to ice cream technology, the effect of molecular structure on color and foam stability of soy proteins, and the association between molecular mobility and textural properties during aging of starchy formulations. Other materials outline the difficulty of modeling the distribution of relaxation processes in phase separated/complex mixtures of drug matrices and introduce the concept of mobility transition temperatures of residual water below T g . They also acknowledge the importance of glass density and the specific interactions between reactant and glassy solid in the stability of preparations.
The terminology, theoretical concepts and analytical modeling make this book not an easy read for many food scientists/technologists! However, for those involved in the field and research into the specific areas highlighted above it would be useful both to develop a solid understanding of the properties of amorphous materials and to measure their own work against recent progress in the field.
Stefan Kasapis
Sultan Qaboos University
Muscat, Sultanate of Oman