关键词: 核磁共振, 弛豫现象, 玻璃态转化, 食品理化特性

Abstract: The sensory quality and shelf stability of food products are closely related to their physiochemical properties. Theglass transition concept borrowed from polymer science has been applied to the study of physiochemical properties of foodmaterials and products. Water is seen as a plasticizer of solids, and therefore plays a key role in the characteristics of foodmaterials. A state diagram based on the glass transition concept usually describes the relationship between water content (orsolid content) and temperature-dependence of physiochemical properties (e.g., phases). State diagrams are useful in character-izing material behavior at various temperatures and water contents.The present paper demonstrates a new concept, called “NMR State Diagram”, which is based on the relationships betweenNMR (nuclear magnetic resonance) relaxation and temperature dependence of physiochemical properties. An NMR statediagram is a curve of NMR relaxation time (usually spin-spin relaxation time or T2) against temperature. Our studies have shownexcellent correlations between curves characteristics and many physiochemical properties. The potential applications of thisNMR State Diagram concept may include: (1) ingredients screening, useful for product formula development, (2) prediction ofphysiochemical changes (texture, viscosity, caking, water and fat migration, etc), chemical degradation of nutrients and microbio-logical activity, which are associated with mobility of water and polymers, (3) Combined with MRI (magnetic resonanceimaging) techniques, the concept would greatly improve our understanding of quality and safety of food products, especiallyintermediate moist foods (IMF). In this conceptual paper, the basic principles of NMR, theoretical aspects of NMR relaxationand its relations to food properties, methodology, and data from real food systems are presented.

Key words: NMR, relaxation, glass transition, physiochemical properties of food