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Water Induced Mobility and Properties of Food Materials

This video presents the keynote lecture of Professor Emeritus Yrjo H. Roos on Water Induced Mobility and Properties of Food Materials at the 6th International Conference on Food Properties (ICFP6). Food materials, particularly sugars, are known to form solid, transparent fluid states in dry conditions. Conversely, water in such structures may induce dramatic changes in physical state and reaction kinetics. Together with these findings effects of water on food properties, as derived from water sorption and water activity, aw, data, and their contribution to understanding water induced mobility, will be presented and described using stability maps. Developments in cryopreservation, freezing and freeze-drying have also required the understanding of water mobility in noncrystalline food solids. These relationships of food solids and water at various temperatures are often described using state diagrams. When combined with water sorption data, state diagrams show molecular mobility, aw, and glass transition, Tg, relationships. Our mobility data have been derived from differential scanning calorimetry, DSC, dynamic mechanical analysis, DMA, and dielectric analysis, DEA, measurements. Interestingly, multicomponent frozen materials may show mobility induced by unfrozen water, but also separate water interactions in protein hydration and vitrification of sugars. In proteins the hydration water shows apparent antiplasticization by the macromolecular components at decreasing hydration whereas devitrification of carbohydrates occurs above initial ice melting conditions. Typically, small variations in temperature or water content in the vicinity of the glass transition result in significant, but material-dependent, differences in mobility. Such phenomena can be described using the strength-parameter which provides an important measure of changes in material stiffness during thermal or water plasticization. The implications of mobility changes as induced by water are important in the control of food processing and reaction kinetics as well as in obtaining desired food textures, nutrients delivery characteristics and product stability during storage. Brief Biography of Professor Emeritus Dr. Yrjö H. Roos Professor Emeritus Dr. Yrjö H. Roos is affiliated with the School of Food and Nutritional Sciences, University College Cork, Ireland. He holds MSc, PhD and DSc awards from the University of Helsinki, Finland. Following an early industrial career in the dairy Industry, he joined the Department of Food Science, Rutgers, the State University of New Jersey, USA, in 1989. In 1991 he returned to University of Helsinki as Professor and Senior Research Fellow of the Academy of Finland. He was appointed as Professor of Food Technology at University College Cork in 1999 where he also served as Head and Dean. His main research interests are in dairy and food processing technologies and food materials science. He is President of the Central Committee of International Symposium of Water in Foods (ISOPOW) and founding member and Chair of the European Academy of Food Engineering (EAFE). He has h-index of 72 for numerous research publications and books with 23000 citations. He is recipient of the International Association of Engineering and Food (IAEF) Lifetime Achievement Award, the Swiss Thermal Analytical Society Award and ASABE International Food Engineering Award. He is Fellow of the IFT and IAoFST. He has served as member of the working group and Panel for Food Enzymes of the European Food Safety Authority (EFSA) since 2021.