Water is recognized as being a critically important determinant of the properties of many foods. It is therefore appropriate to devote a meeting to the topic. The first such meeting was organized by the late Ron Duckworth, and held in 1974 at the University of Strathclyde in Scotland. As a result of this first meeting, the organization known as International Symposium on the Properties of Water (ISOPOW) was born, and since that first ISOPOW meeting there have been five international meetings. At each meeting, participants from academia and from industry have shared state of the science information pertinent to the role of water in foods. Each meeting has served as a review of the current state of knowledge. ISOPOW 6 is the first of these meetings where Ron Duckworth's presence has not been felt, though he clearly attended the meeting in spirit. A lively group of academics and industrial scientists assembled in Santa Rosa, California, to discuss the current state of the science. As meeting chairperson, I must acknowledge the tremendous contributions made by the organizing committee, by the session chairpersons and by the central committee. Without all their help, nothing could have been achieved. Most important to the success of the meeting, however, was the very active participation of all attendees. In all seven sessions, the papers were excellent and their discussion was very spirited.
Auflage
Sprache
Verlagsort
Zielgruppe
Für höhere Schule und Studium
Für Beruf und Forschung
Editions-Typ
Illustrationen
76 s/w Abbildungen
76 Illustrations, black and white; XXI, 512 p. 76 illus.
Maße
Gewicht
ISBN-13
978-0-7514-0382-4 (9780751403824)
DOI
10.1007/978-1-4613-0311-4
Schweitzer Klassifikation
1 High Moisture Systems.- 1 Supramolecular structures of biopolymer gels.- 1.1 Introduction.- 1.2 Complexity of polysaccharide gels.- 1.2.1 Cationic effects.- 1.2.2 Effects of a second polysaccharide.- 1.2.3 Effects of added proteins.- 1.3 Process manipulation.- 1.3.1 Heat versus high pressure treatments of mixed protein gels.- 1.3.2 Kinetics of heating.- 1.4 Structure engineering.- 1.4.1 Image analysis of structure parameters.- 1.4.2 Correlations with perceived texture.- Acknowledgements.- References.- 2 Water in tissue structures by NMR and MRI.- 2.1 Introduction.- 2.1.1 MRI principles.- 2.1.2 NMR image generation.- 2.1.3 Contrast in NMR images.- 2.2 Application examples.- 2.2.1 Measurement of quality.- 2.2.2 Determination of sample structure.- 2.2.3 Single cell imaging.- References.- 2 Intermediate Moisture Systems.- 3 Physical chemical parameters inhibiting the growth of microorganisms.- Abstract.- 3.1 Introduction.- 3.2 Food mixtures (composite foods) and the equilibration of water activity between layers of different composition.- 3.2.1 Pasteurized filled pasta.- 3.2.2 Shelf-stable soft sponge bars.- 3.3 Comparison of literature values of minimal aw for growth with observed behavior (growth/inhibition) in actual foods.- 3.4 Role of the glassy state in microbial growth inhibition.- 3.5 pH of reduced-moisture foods.- Acknowledgements.- References.- 4 Protein hydration and glass transitions.- 4.1 Introduction.- 4.2 Protein dynamics - a comparison with glass-forming systems.- 4.2.1 Strong and fragile liquids.- 4.2.2 The 200 K transition in hydrated proteins.- 4.2.3 Water as plasticizer - the hydration dependence of Tg.- 4.3 Hydrogen exchange evidence for dynamically distinct protein substructures.- 4.3.1 Properties of the slow exchange core (knots).- 4.3.2 Enthalpy-entropy compensation behavior.- 4.3.3 The basis of knot formation - the cooperative contraction process.- 4.4 Relationship between hydrogen exchange and glass transition behavior.- 4.5 Kinetic and thermodynamic stability of proteins.- 4.5.1 Effect of hydration on protein stability.- 4.6 Protein folding.- 4.7 Concluding remarks.- Acknowledgements.- References.- 3 Low Moisture Systems.- 5 Thermodynamic and kinetic features of vitrification and phase transformations of proteins and other constituents of dry and hydrated soybean, a high protein cereal.- Abstract.- 5.1 Introduction.- 5.2 Experimental methods.- 5.3 Results.- 5.4 Discussion.- 5.4.1 Superposition of endothermic and exothermic features and the resulting artefact.- 5.4.2 Vitreous character of the cooled state.- 5.4.3 Melting of the crystallized constituents and ice.- 5.4.4 Coexistence of ice, protein and the liquid phase.- 5.4.5 Crystallization kinetics of ice from the liquid phase.- Acknowledgements.- References.- 6 NMR dynamics properties of water in relation to thermal characteristics in bread.- Abstract.- 6.1 Introduction.- 6.2 Characterization of transitions from tan ? curves.- 6.3 Molecular investigation by solid state 1H and 2H NMR.- 6.4 Solid and liquid fraction of starch by cross relaxation.- 6.5 Rates of events.- 6.6 Changes in water mobility during bread staling.- 6.7 Conclusions.- Acknowledgements.- References.- 7 Phase and polymorphic transitions of starches at low and intermediate water contents.- Abstract.- 7.1 Introduction.- 7.2 Materials and methods.- 7.2.1 Materials.- 7.2.2 Methods.- 7.3 Results and discussion.- 7.3.1 Structuring role of water.- 7.3.2 Water may induce some polymorphic transitions.- 7.3.3 Heating at low and intermediate moisture contents.- 7.3.4 Melting at low and intermediate moisture contents.- 7.4 Conclusions (overview).- Acknowledgements.- References.- 8 Thermal properties of polysaccharides at low moisture: Part 3 - Comparative behaviour of guar gum and dextran.- 8.1 Introduction.- 8.2 Materials and methods.- 8.3 Results.- 8.4 Discussion.- References.- 4 Drying.- 9 Spray drying of high fat foods.- Abstract.- 9.1 Introduction.- 9.2 Equipment and materials.- 9.3 Properties of spray dried product.- 9.3.1 Morphology and particle size.- 9.3.2 Composition.- 9.3.3 Stickiness.- 9.4 Drying model.- 9.4.1 Sorption isotherm.- 9.4.2 Diffusion coefficient.- 9.4.3 Simulations.- 9.5 Simple heuristic free fat model.- 9.6 Conclusions.- 9.7 Symbols.- Acknowledgements.- References.- 10 Spray drying and quality changes.- Abstract.- 10.1 Introduction.- 10.2 The process.- 10.3 Elaboration of the physical structure of powder during spray drying.- 10.3.1 Atomization.- 10.3.2 Control of moisture content.- 10.3.3 Physical properties of particles.- 10.3.4 Bulk properties.- 10.4 Composition changes during spray drying.- 10.4.1 Thermal history of product during spray drying.- 10.4.2 Sugar-containing powders.- 10.4.3 Retention of volatiles.- 10.4.4 Encapsulation of lipids.- 10.4.5 Spray dried fats.- 10.5 Conclusions.- References.- 11 Mechanical properties of dry brittle cereal products.- 11.1 Introduction.- 11.2 Mechanical terminology.- 11.3 Characterization of irregular and irreproducible force-deformation relationships.- 11.3.1 Stiffness assessment.- 11.3.2 Jaggedness assessment.- 11.4 Jaggedness measures.- 11.4.1 Standard deviation.- 11.4.2 Apparent fractal dimension.- 11.5 Fourier transform.- 11.6 Other mechanical measures.- 11.7 Effects of moisture.- 11.8 Effects of temperature.- 11.9 Effects of plasticizers/antiplasticizers.- 11.10 Conclusions.- Acknowledgements.- References.- 12 Stress development in shrinking slabs during drying.- Abstract.- 12.1 Introduction and literature review.- 12.2 Model development.- 12.2.1 Mechanistic description off biopolymer drying.- 12.2.2 Mathematical development.- 12.3 Results and discussion.- 12.4 Conclusions.- References.- 5 Freezing.- 13 Freezing - nucleation in foods and antifreeze actions.- 13.1 Introduction.- 13.2 Nucleation.- 13.3 Growth.- 13.4 Recrystallization.- 13.5 Antifreeze polymers.- 13.6 Mobility temperature.- 13.7 Summary.- References.- 14 Mechanisms and kinetics of recrystallization in ice cream.- Abstract.- 14.1 Introduction.- 14.2 Mechanisms of recrystallization.- 14.2.1 Migratory recrystallization.- 14.2.2 Isomass recrystallization.- 14.2.3 Accretion.- 14.2.4 Melt-refreeze recrystallization.- 14.2.5 Irruptive recrystallization.- 14.3 Factors affecting recrystallization.- 14.3.1 Initial freezing process.- 14.3.2 Hardening rate.- 14.3.3 Storage temperature and temperature fluctuations.- 14.3.4 Composition of ice cream.- 14.4 Summary.- Acknowledgements.- References.- 15 Biological ice nucleation.- 15.1 Identity and features of ice-nucleating microorganisms.- 15.2 Genetic and biochemical determinants of bacterial ice nucleation.- 15.3 Environmental effects on ice nucleation.- 15.4 Aggregation model of ice nucleation.- 15.5 Structural models of Ice proteins.- 15.6 Summary.- References.- 16 Formation of ice in frozen foods and its control by physical stimuli.- 16.1 Introduction.- 16.2 Nucleation of ice crystals.- 16.2.1 Phase diagram.- 16.2.2 Homogeneous nucleation.- 16.3 Experimental induction of ice nucleation by physical methods.- 16.3.1 Early experiments.- 16.3.2 Promotion of nucleation by friction.- 16.3.3 Onset of freezing following the passage of a shock wave.- 16.3.4 Nucleation by vibration and tearing.- 16.3.5 Nucleation by growth or collapse of cavities.- 16.3.6 Nucleation following electrostatic disruption of water droplets.- 16.3.7 Conclusions drawn from experimental demonstrations.- 16.4 Theoretical discussion of nucleation of ice crystals by physical means.- 16.4.1 Nucleation through increase in local acoustic pressure.- 16.4.2 Cavitation.- 16.4.3 Cavitation threshold in water.- 16.4.4 Dynamics of a cavity in water.- 16.4.5 Vapour filled cavities.- 16.4.6 Transient cavitation.- 16.4.7 Cavitation prediction graphs.- 16.4.8 Generation of high pressures by transient bubble collapse.- 16.4.9 Hickling's theory of nucleation of ice in supercooled water by collapsing cavities.- 16.5 Conclusions.- References.- 6 Water at High Pressures.- 17 Effects of high pressure on food biopolymers with special reference to ?-lactoglobulin.- Abstract.- 17.1 Basic principles underlying the effects of high pressure on macromolecules.- 17.1.1 General aspects.- 17.1.2 Water-mediated effects of high pressure on protein interactions.- 17.1.3 Pressure-induced unfolding of proteins.- 17.2 Pressure-induced aggregation of ?-lactoglobulin and the role of SH/S-S interchange reaction.- 17.2.1 Influence of type of buffer (pH 7) and of pressure level.- 17.2.2 Influence of pressurization time.- 17.2.3 Determination of SH groups.- 17.2.4 Influence of gas atmosphere.- 17.2.5 Influence of N-ethylmaleimide and of reducing agents.- 17.3 Pressure-induced gelation of ?-lactoglobulin.- 17.3.1 Microstructure: effects of protein or sucrose concentration.- 17.3.2 Mechanical and biochemical characteristics: effects of polyols, calcium ions and time after pressure release.- 17.3.3 Effects of pressurization time.- 17.3.4 Effects of pH and type of buffer.- 17.4 Influence of pressure on the formation of pectin gels.- 17.5 Effects of high pressure on starch granules.- Acknowledgements.- References.- 18 Inactivation of microorganisms by high pressure.- Abstract.- 18.1 Introduction.- 18.2 Materials and methods.- 18.2.1 Organisms.- 18.2.2 Media and culture conditions.- 18.2.3 Carbohydrates.- 18.2.4 Heat treatment.- 18.2.5 Pressure treatment.- 18.2.6 Measurement of internal pH.- 18.2.7 Preparation of membrane vesicles and measurement of ATPase activity.- 18.2.8 Lag time determinations.- 18.3 Mathematical analysis of inactivation data.- 18.3.1 Log-logistic analysis.- 18.4 Results and discussion.- 18.4.1 Inactivation by heat and by pressure.- 18.4.2 Lag times.- 18.4.3 Effect of environmental conditions on inactivation by pressure and heat.- 18.4.4 Mechanistic aspects: effect of culture conditions on pressure resistance.- 18.5 Conclusions.- References.- 19 Advantages, possibilities and challenges of high pressure applications in food processing.- 19.1 Introduction.- 19.2 Advantages of high pressure treatment of foods.- 19.3 Opportunities for high pressure processing of foods.- 19.3.1 High pressure blanching.- 19.3.2 Pressure-assisted dehydration/rehydration processes.- 19.3.3 Pressure-assisted frying processes.- 19.3.4 Pressure-assisted extraction processes.- 19.3.5 Pressure-assisted bioconversion processes.- 19.3.6 Pressure-assisted preservation processes.- 19.3.7 Pressure-assisted gelling of protein and polysaccharides.- 19.3.8 Pressure-assisted reduction/removal of antinutritional factors.- 19.3.9 Pressure-assisted plant tissue texture retention/enhancement.- 19.3.10 Pressure shift freezing.- 19.3.11 Pressure thawing.- 19.4 Challenges of high pressure processing of foods.- 19.4.1 Inactivation kinetics of spore-forming bacteria.- 19.4.2 Mechanisms of high pressure effects on biological systems (microbial morphology).- 19.4.3 Mechanisms of high pressure effects on biological systems (plant cell culture model systems).- 19.4.4 Interactions between food components and high pressure.- 19.5 Conclusions.- Acknowledgements.- References.- 7 Biological Systems' Response to Water Stress.- 20 Anhydrobiosis: the water replacement hypothesis.- 20.1 Introduction.- 20.2 Destabilization of membranes during drying.- 20.2.1 Fusion.- 20.2.2 Lipid phase transitions.- 20.3 Mechanism of interaction between sugars and dry phospholipids.- 20.3.1 Vitrification.- 20.3.2 Can vitrification affect Tm in dry phospholipids?.- 20.3.3 Retention of water by dry vesicles.- 20.3.4 Direct interaction.- 20.4 Does trehalose have special properties?.- 20.5 Trehalose as a chemical chaperone.- 20.6 Summary and conclusions.- References.- 21 Bacterial responses to osmotic stress: diverse mechanisms to achieve a common goal.- Abstract.- 21.1 Introduction.- 21.2 Compatible solute accumulation: strategy for ameliorating effects of low water activity.- 21.2.1 Compatible solutes in food.- 21.2.2 Effects of osmotic stress.- 21.2.3 Sensing osmotic stress.- 21.2.4 Water transport in bacterial cells.- 21.2.5 Water flow and turgor regulation.- 21.2.6 Stretch-activated channels.- 21.2.7 Kinetics, stretch-activated channels, elastic modulus of the cell wall and turgor pressure.- 21.2.8 Overview.- 21.3 Safety net: stress survival, stationary phase sigma factor RpoS and osmotic regulation.- 21.3.1 Regulation of RpoS protein accumulation.- 21.3.2 RpoS and osmotic shock.- 21.4 Osmotic regulation of gene expression.- 21.4.1 proU, H-NS and DNA topology.- 21.4.2 Regulatory mechanisms for other osmotically regulated genes.- 21.5 Conclusions.- Acknowledgements.- References.- 22 Bacterial spores - resistance, dormancy and water status.- 22.1 Introduction.- 22.2 Heat resistance.- 22.2.1 Spore characteristics important for acquired heat resistance.- 22.3 Targets for heat damage and radical involvement in spore killing.- 22.3.1 Nature of heat killing.- 22.3.2 Molecular Targets.- 22.4 Future directions.- Acknowledgements.- References.
