2001 AACC Annual Meeting Charlotte, North Carolina October 14-18, 2001 Charlotte Convention Center

The science of sugar glasses has been studied for over 70 years. In the past two decades, the "food polymer science" (FPS) approach was developed to study glasses and glass transitions, and their effects on processing, product quality and storage stability, in foods. FPS has been fruitfully used to understand structure-function relationships, the effects of plasticization by water on thermal, mechanical, rheological and textural properties, and physical (meta)stability in the non-equilibrium glassy solid state, vs. instability in the rubbery or viscous liquid state. Key concepts of the FPS approach include a practical understanding of the significance of the glass transition temperature, Tg, and its temperature range, how Tg is defined for multi-component, aqueous amorphous blends, and how Tg relates to the relative mobilities of individual components, including water, in such blends. Due to water's well-known plasticizing effect on cereal polymers such as starch and gluten, Tg decreases monotonically with increasing moisture content, but the linear relationship is between Tg and system relative humidity, rather than moisture content. Like the glass transition itself, plasticization is a kinetic process, so the presence of water is not a guarantee that softening or other changes in rheological properties have already occurred. Brief examples of some applications of the FPS approach to studies on cereal polymer processing (e.g. extrusion) and product quality attributes (e.g. textural crispness) will illustrate the significant progress made in recent years, based on amorphous product technology, as applied to the setting of processing conditions and the control of resulting rheological properties.