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EngineeringPropertiesof Foods

Third Edition

M. A. Rao

Syed S. H. Rizvi

Ashim K. DattaBoca Raton London New York Singapore A CRC title, part of the Taylor & Francis imprint, a member of the Taylor & Francis Group, the academic division of T&F Informa plc.

Published in 2005 by

CRC Press

Taylor & Francis Group

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10987654321

International Standard Book Number-10: 0-8247-5328-3 (Hardcover) International Standard Book Number-13: 978-0-8247-5328-3 (Hardcover)

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Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Λibrary of Τongress ΤatalogingΩinΩ⬧ublication ≠ata Engineering properties of foods / edited by M.A. Rao, Syed S.H. Rizvi, Ashim K. Datta.--

3rd ed.

p. cm. -- (Food science and technology; 142)

ISBN 0-8247-5328-3 (alk. paper)

1. Food--Analysis. 2. Food industry and trade. I. Rao, M. A., 1937- II. Rizvi, S. S. H.,

1948- III. Datta, Ashim K. IV. Food science and technology (Marcel Dekker, Inc.); 142.

TP372.5.E54 2005

664--dc222004056967

Πisit the 2aylor η Φrancis Web site at http?→→www.taylorandfrancis.com and the Τ?Τ ⬧ress Web site at http?→→www.crcpress.com Taylor & Francis Group is the Academic Division of T&F Informa plc. iii

Preface

We are pleased to present the third edition of

Engineering Properties of Foods.

The third edition is comprehensive, with seven new chapters: MassÐVolumeÐ Area-Related Properties of Foods, Properties Relevant to Infrared Heating of Foods, Electrical Conductivity of Foods, Ultrasound Properties, Kinetic Data for Biochemical and Microbiological Processes during Thermal Processing, Gas Exchange Properties of Fruits and Vegetables, and Surface Properties. Two of the previous chapters, Thermal Properties and Dielectric Properties, have been completely rewritten. Thus, 9 out of 16 chapters are new. We have systemat- ically searched and included physical, chemical, and biological properties that are of practical importance and for which signiÞcant data exist. We have added Professor Ashim Datta as a co-editor to help with this rather large undertaking. In looking for experts on topics, we have also made an effort to expand the international participation of authors. We have added authors/co-authors from four additional countries. We have made a special effort to follow a consistent format for the chapters so that readers can follow it easily. Thus, chapters include an introduction, property deÞnition, measure- ment procedure, modeling, representative data compilation, and applications. We have concentrated on clear physical understanding of the properties and their variations, supplemented by representative and sufÞcient data, staying away from extensive data collection, for which electronic formats are likely to be more suitable. By providing a succinct presentation of each prop- erty in a consistent format, we hope to make it useful to the student as well as the professional. As computer-aided engineering (modeling) is becoming more commonplace, the primary use of food properties data is expected to be in computer modeling of food processes. Data correlations with compositions and temperature are particularly useful in this context since they will allow easy inclusion of variable properties in computer models. We have included such correlations as much as possible. ivRao, Rizvi, and Datta Our sincere thanks to all the authors and reviewers whose participation and comments certainly enhanced the chapters. We thank the editors at Marcel

Dekker for their patience and help.

M.A. Rao, Syed S.H. Rizvi, and Ashim K. Datta

v

The Editors

M.A. Rao

is a professor of food engineering at Cornell University, Ithaca, New York. He focuses his research on the measurement and interpretation of rheological properties of foods. Many original papers, reviews, and book chap- ters were contributed by Rao and co-workers, including the book:

Rheology of

Fluid and Semisolid Foods: Principles and Applications, Aspen Publishers Inc.,

1999 (Kluwer Academic/Plenum Publishers, Inc). Professor Rao serves as the

scientific editor of the food engineering and physical properties sect ion of the

Journal of Food Science.

He was elected a fellow of the Institute of Food Technologists in 1997 and the Association of Food Scientists and Technologists (India) in 2000. He received the Scott Blair Award for Excellence in Rheology from the American Association of Cereal Chemists in 2000 and the Distin- guished Food Engineer award from IAFIS/FPEI-ASAE in 2003.

Syed S.H. Rizvi, Ph.D.,

is professor of food process engineering and inter- national professor of food science at Cornell University, Ithaca, New York. His teaching and research focus on engineering aspects of food processing and manufacturing operations. He has authored or co-authored over 100 research articles, co-edited five books, and holds seven patents. He previously taught at Clemson University and The Ohio State University and worked at Nestle and Glaxo. A fellow of the Institute of Food Technologists, Professor Rizvi has received many awards in recognition of his teaching and research efforts including the Chancellor Medal for Excellence in Teaching, State University of New York; International Dairy Foods Association Research Award in Food Processing; and Marcel Loncin Research Prize, Institute of Food Technologists. He received his B.S. and M.S. degrees from Panjab University, M.Eng. (chem- ical engineering) from the University of Toronto, and Ph.D. from The Ohio

State University.

viRao, Rizvi, and Datta

Ashim K. Datta, Ph.D.,

is a professor of biological engineering at Cornell University, Ithaca, New York. He has a Ph.D. degree (1985) in agricultural engineering from the University of Florida, Gainesville. Dr. Datta has served as a visiting professor at the University of Minnesota and the Katholiek e Universiteit Leuven, Belgium. His research interests are in the fundamental studies of heat and mass transport relevant to food processing. His current research focuses on combined microwave and conventional heating and on modeling of microbiological and chemical safety during food processing. Dr. Datta is a member of the American Society of Agricultural Engineers, American Institute of Chemical Engineers, and Institute of Food Technologists.

He has authored and co-authored two books:

Handbook of Microwave Tech- nology for Food Applications and Biological and Bioenvironmental Heat and

Mass Transfer

, and he serves on the editorial boards of several journals. vii

Contributors

Marialuci Almeida

Cornell University

Ithaca, New York

Ashim K. Datta

Cornell University

Ithaca, New York

F.J. Francis

University of Massachusetts

Amherst, Massachusetts

Marc E. Hendrickx

Katholieke Universiteit Leuven

Leuven, Belgium

Indrawati

Katholieke Universiteit Leuven

Leuven, Belgium

Jeroen Lammertyn

Katholieke Universiteit Leuven

Heverlee, Belgium

Zacharias B. Maroulis

National Technical University of

Athens

Athens, Greece

T. Matsuura

University of Ottawa

Ottawa, Ontario, Canada

Michael J. McCarthy

University of California

Davis, California

Kathryn L. McCarthy

University of California

Davis, California

Joseph McGuire

Oregon State University

Corvallis, Oregon

Paul Nesvadba

Rubislaw Consulting Limited

Aberdeen, U.K.

Bart M. Nicola•

Katholieke Universiteit Leuven

Heverlee, Belgium

Ximena Quintero

Frito-Lay

Plano, Texas

viiiRao, Rizvi, and Datta

G.S.V. Raghavan

McGill University

Ste-Anne de Bellevue, Quebec,

Canada

M. Shafiur Rahman

Sultan Qaboos University

Muscat, Sultanate of Oman

D. Rana

University of Ottawa

Ottawa, Ontario, Canada

M.A. Rao

Cornell University

Geneva, New York

V.N. Mohan Rao

Frito-Lay

Plano, Texas

Syed S.H. Rizvi

Cornell University

Ithaca, New York

George D. Saravacos

National Technical University

Athens, Greece

and

Rutgers University

New Brunswick, New Jersey

Arnab Sarkar

University of California

Davis, California

Sudhir K. Sastry

The Ohio State University

Columbus, Ohio

Wendy Schotsmans

Katholieke Universiteit Leuven

Heverlee, Belgium

R. Paul Singh

University of California

Davis, California

Chantal Smout

Katholieke Universiteit Leuven

Leuven, Belgium

S. Sourirajan

Ottawa, Ontario, Canada

G. Sumnu

Middle East Technical University

Ankara, Turkey

Ann M. Van Loey

Katholieke Universiteit Leuven

Leuven, Belgium

Bert E. Verlinden

Katholieke Universiteit Leuven

Heverlee, Belgium

Lu Wang

University of California

Davis, California

ix

Table of Contents

Chapter 1

Mass-Volume-Area-Related Properties of Foods.......................1

M. Shafiur Rahman

I. Introduction........................................................................ .........................1 II. Fundamental Considerations.....................................................................2 A. Volume........................................................................ ............................2

1. Boundary Volume........................................................................

.....2

2. Pore Volume........................................................................

..............2 B. Density........................................................................ ............................2

1. True Density........................................................................

.............2

2. Material Density........................................................

.......................3

3. Particle Density........................................................................

........3

4. Apparent Density ........................................................................

.....4

5. Bulk Density........................................................................

.............4 C. Porosity........................................................................ ...........................4

1. Open Pore Porosity........................................................................

...4

2. Closed Pore Porosity........................................................................

.4

3. Apparent Porosity........................................................................

.....5

4. Bulk Porosity ........................................................................

............5

5. Bulk-Particle Porosity......................................................................5

6. Total Porosity........................................................................

............5 D. Surface Area........................................................................ ...................5 E. Pore Size Distribution........................................................................ ...6 III. Measurement Techniques........................................................................ ...6 A. Density Measurement ........................................................................ ...6

1. Apparent Density ........................................................................

.....6

2. Material Density........................................................

.....................11

3. Particle Density........................................................................

......14

4. Bulk Density........................................................................

...........14 xRao, Rizvi, and Datta B. Measurement Techniques of Porosity.................................................14

1. Direct Method........................................................................

.........14

2. Optical Microscopic Method ..........................................................14

3. Density Method ........................................................................

......14 C. Surface Area........................................................................ .................15

1. Boundary Surface Area..................................................................15

2. Pore Surface Area........................................................................

...15

3. Cross-Sectional Area......................................................................16

IV. Specific Data........................................................................ ......................16 A. Predictions of Density ........................................................................ .16

1. Gases and Vapors........................................................................

...17

2. Liquid Foods ........................................................................

...........18

3. Density of Solid Foods....................................................................19

B. Predictions of Porosity........................................................................ .22 C. Prediction of Surface Area..................................................................25

1. Euclidian Geometry........................................................................

25

2. Non-Euclidian or Irregular Geometry..........................................26

3. Theoretical Prediction....................................................................26

4. Size Distribution.......................................................

......................30 V. Summary........................................................................ ............................33 Acknowledgments ........................................................................ ......................33 List of Symbols ........................................................................ ..........................33 Greek Symbols........................................................................ ...........................34 Subscripts........................................................................ ...................................34 Superscripts........................................................................ ................................35 References........................................................................ ...................................35

Chapter 2

Rheological Properties of Fluid Foods......................................41

M. A. Rao

I. Introduction........................................................................ .......................41 II. Rheological Classification of Fluid Foods................................................42 A. Rheological Models for Viscous Foods................................................47

1. Models for Time-Independent Behavior .......................................47

2. Rheological Models for Thixotropic Foods....................................51

3. Effect of Temperature on Viscosity...............................................52

4. Combined Effect of Temperature and Shear Rate.......................54

5. Effect of Concentration on Viscosity.............................................54

B. Rheological Models for Viscoelastic Fluid Foods...............................56

1. Normal Stress Data on Fluid Foods.............................................56

2. Creep Compliance Studies on Foods.............................................57

III. Structure of Fluid Foods via Solution Viscosity and Physicochemical Approach........................................................................ 59
A. Solution Viscosity........................................................................ .........60 B. Physicochemical Approach..................................................................61 IV. Measurement of Flow Properties of Fluid Foods....................................61 A. Fundamental Methods ........................................................................ 61

1. Capillary Flow........................................................................

........61

2. Couette Flow Viscometers .............................................................63

3. Plate-and-Cone Viscometers..........................................................65

Table of Contentsxi

4. Parallel Plate Geometry.................................................................66

5. Slit (Channel) Rheometers ............................................................67

6. Extensional Flows ........................................................................

..68 B. Empirical Methods....................................................... ........................71

1. Adams Consistometer ....................................................................71

2. Bostwick Consistometer.................................................................71

3. Efflux Tube Viscometer..................................................................72

C. Imitative Methods....................................................... .........................72

1. Mixers for Determining Flow Properties .....................................73

2. In-Plant Measurement of Rheological Behavior of Fluid Foods......77

V. Flow of Fluid Foods in Tubes...................................................................81 A. Isothermal Flow of Fluids in Tubes...................................................82

1. Velocity Profiles and Volumetric Flow Rate Relationships.........82

2. Friction Losses for Power Law Foods in Pipes............................83

3. Pressure Drop Across Valves and Fittings...................................87

4. Friction Losses for Herschel-Bulkley Fluids...............................87

5. Calculation of Kinetic Energy for Non-Newtonian Fluids..........88

VI. Conclusion........................................................................ ..........................89 List of Symbols ........................................................................ ..........................89 Greek Symbols........................................................................ ...........................90 Subscripts........................................................................ ...................................91 Superscript........................................................................ .................................91 References........................................................................ ...................................91 Chapter 3Rheological Properties of Solid Foods.....................................101

V. N. Mohan Rao and Ximena Quintero

I. Introduction........................................................................ .....................101 II. Quasistatic Tests for Solid Foods...........................................................102 A. Introduction........................................................................ ................102 B. Some Simple Tests........................................................................ .....104 C. Rheological Modeling........................................................................ .108 D. Creep........................................................................ ...........................109 E. Relaxation........................................................................ ...................111 III. Dynamic Testing of Solid Foods.............................................................113 A. Introduction........................................................................ ................113 B. Theoretical Considerations ...............................................................114

1. Resonance ........................................................................

.............114

2. Direct Stress-Strain Tests...........................................................117

C. Application of Resonance ..................................................................120 D. Application of Direct Stress-Strain Tests........................................123 IV. Failure and Glass Transition in Solid Foods ........................................126 A. Failure in Solid Foods.................................................................... ....126 B. Glass Transition of Solid Foods........................................................128

1. Factors that Affect Glass Transition...........................................129

2. Measurement of Glass Transition...............................................129

3. Importance of Glass Transition in Solid Foods..........................131

V. Empirical and Imitative Tests ...............................................................132 A. Introduction........................................................................ ................132 B. Texture Profile Analysis....................................................................133 xiiRao, Rizvi, and Datta C. Texture (Shear) Press........................................................................ 135
D. Warner-Bratzler Shear.....................................................................136 E. FMC Pea Tenderometer ....................................................................136 F. Penetrometer........................................................................ ..............137 G. Other Empirical Methods .................................................................137 VI. Conclusions........................................................................ ......................138 References........................................................................ .................................139 Chapter 4Thermal Properties of Unfrozen Foods ..................................149

Paul Nesvadba

I. Introduction........................................................................ .....................149 A. The Importance of Thermal Properties for the Quality and Safety of Foods ........................................................................ ...149 B. Modeling and Optimization of Processes.........................................150 II. Sources of Data on Thermal Properties................................................151 A. Measurement ........................................................................ .............151 B. Literature........................................................................ ...................151 C. Computerized and On-Line Databases............................................151 D. Software for Predicting Thermal Properties of Foods ....................152 III. Density........................................................................ .............................152 A. Definition of Powder Bulk Density...................................................154 IV. Specific Heat Capacity........................................................................ ....154 A. Latent Heat of Melting .....................................................................156 B. Specific and Latent Heat of Fats......................................................156 V. Thermal Conductivity........................................................................ .....157 A. Predictive Equations ........................................................................ .157 B. Influence of Structure of Food on Thermal Conductivity...............160 VI. Measurement Methods for Thermal Conductivity .................................16 A. The Basis of Operation of the Needle Probe...................................161 B. Reference Materials........................................................................ ...165 VII. Other Properties Relevant to Thermal Processing of Foods................165 A. Compressibility and Thermal Expansion ........................................165 B. Glass Transitions........................................................................ .......166 C. Sorption and Hydration Properties..................................................167 VIII.Conclusions........................................................................ ......................167 Symbols, Names, and Dimensions..................................................................167 References........................................................................ .................................168 Chapter 5Thermal Properties of Frozen Foods......................................175

R. Paul Singh and Arnab Sarkar

I. Introduction........................................................................ .....................175 II. Experimental Approaches to Measuring the Thermal Properties of Frozen Foods ........................................................................ ...............176 A. Initial Freezing Point and Unfrozen Water.....................................176 B. Density........................................................................ ........................177 C. Thermal Conductivity........................................................................ 177
D. Enthalpy........................................................................ .....................177

Table of Contentsxiii

E. Specific Heat ........................................................................ ..............178 F. Thermal Diffusivity ........................................................................ ...178 III. General Observations on the Reliability of Experimental Data.........181 IV. Modeling of the Thermal Properties of Frozen Foods..........................184 A. Prediction of Unfrozen Water During Freezing of Foods ...............184

1. Density........................................................................

..................189

2. Thermal Conductivity..................................................................190

3. Enthalpy........................................................................

................194

4. Apparent Specific Heat................................................................197

B. Limitations of Predictive Models......................................................199 List of Symbols ........................................................................ ........................200 Greek Symbols........................................................................ .........................200 Subscripts........................................................................ .................................201 References........................................................................ .................................201 Chapter 6Properties Relevant to Infrared Heating of Foods................209

Ashim K. Datta and Marialuci Almeida

I. Introduction........................................................................ .....................209 II. Fundamentals of Infrared Interactions with Materials.......................210 A. Electromagnetic Spectrum and Near-, Mid- and Far-Infrared Electromagnetic Waves......................................................................210 B. Interaction between Infrared Radiation and Food Materials........210 C. Sources of Infrared Radiation in Heating Applications....................212 D. Emission and Emissivity...................................................................212 E. Reflection, Absorption, and Transmission........................................214 F. Absorptivity and Emissivity .............................................................218 G. Attenuation or Extinction.................................................................219 III. Use of the Radiative Properties in Modeling of Heat Transfer ..........220 IV. Measurement of Radiative Properties of Foods....................................221 V. Radiative Property Data for Food Systems ..........................................224 A. Radiative Property Data for Water, Ice, and Water Vapor.............224 B. Properties of Other Pure Food Components....................................225 C. Spectral Variation of Radiative Property Data: Potato Tissue as an Example ........................................................................ ...........225 D. Moisture Dependence of Radiative Property Data .........................227 E. Temperature Dependence of Radiative Property Data....................228 F. Dependence of Radiative Property Data on Food Structure..........230 G. How Processing Can Change Food Radiative Properties...............232 H. Summary: Use of Radiative Property Data in Modeling ...............234 Acknowledgments ........................................................................ ....................235 References........................................................................ .................................235 Chapter 7Thermodynamic Properties of Foods in Dehydration ...........239

S. S. H. Rizvi

I. Introduction........................................................................ .....................239 II. Thermodynamics of Food-Water Systems.............................................240 A. Chemical Potential and Phase Equilibria .......................................242 B. Fugacity and Activity........................................................................ 244
xivRao, Rizvi, and Datta C. Water Activity in Foods.....................................................................246 D. Measurement of Water Activity........................................................252

1. Measurements Based on Colligative Properties........................252

2. Measurements Based on Psychrometry .....................................255

3. Measurements Based on Isopiestic Transfer .............................256

4. Measurements Based on Suction (Matric) Potential.................256

E. Adjustment of Water Activity ...........................................................256 F. Moisture Sorption Isotherms............................................................261

1. Theoretical Description of MSIs..................................................261

2. Effect of Temperature ..................................................................268

III. Sorption Energetics........................................................................ .........272 A. Differential Quantities......................................................................273 B. Integral Quantities........................................................................ ....276 D. Hysteresis and Irreversibility...........................................................281 E. Kinetic Aspects........................................................................ ...........287 IV. Dehydration Principles and Processes ..................................................288 A. Drying Behavior........................................................................ .........290 B. Constant-Rate Period ........................................................................ 293
C. Falling-Rate Period........................................................................ ....295 D. Equilibrium Moisture Content .........................................................301 E. Energy Requirements........................................................................ 304
V. Conclusion........................................................................ ........................307 List of Symbols ........................................................................ ........................308 Greek Symbols........................................................................ .........................309 Subscripts........................................................................ .................................310 Superscripts........................................................................ ..............................310 References........................................................................ .................................310 Chapter 8Mass Transfer Properties of Foods.........................................327

George D. Saravacos

I. Introduction........................................................................ .....................327 II. Phase Equilibria........................................................................ ..............329 A. Vapor-Liquid Equilibria....................................................................329 B. Gas-Liquid Equilibria.......................................................................333 C. Liquid-Liquid and Liquid-Solid Equilibria ....................................335 D. Gas-Solid and Vapor-Solid Equilibria.............................................336 Water Activity ........................................................................ ............336 III. Diffusion........................................................................ ...........................338 A. Diffusion in Gases ........................................................................ .....339 B. Diffusion in Liquids........................................................................ ...340 C. Diffusion in Solids ........................................................................ .....341

1. Introduction ........................................................................

..........341

2. Diffusion in Polymers...................................................................343

3. Molecular Simulations.................................................................344

D. Estimation of Diffusivity in Solids...................................................345

1. Sorption Kinetics........................................................................

..345

2. Permeation Measurements..........................................................346

3. Distribution of Penetrant.............................................................347

4. Drying Rate.............................................................

......................349

Table of Contentsxv

IV. Interphase Mass Transfer......................................................................349

A. Mass Transfer Coefficients ................................................................349 B. Penetration Theory........................................................................ ....351 C. Analogies of Heat and Mass Transfer..............................................352 D. Effect of Surfactants........................................................................ ..353 V. Mass Transfer in Foods ........................................................................ ..354 A. Moisture Transport........................................................................ ....354

1. Moisture Diffusion........................................................................

354

2. Diffusion in Porous Foods............................................................356

3. Interphase Moisture Transfer.....................................................360

B. Diffusion of Solutes ........................................................................ ...360 C. Diffusion of Aroma Compounds........................................................362 VI. Other Mass Transfer Processes .............................................................364 A. Extraction........................................................................ ...................364 B. Distillation and Gas Absorption.......................................................366 C. Crystallization........................................................................ ............368 D. Food Packaging ........................................................................ ..........370 Acknowledgments ........................................................................ ....................372 List of Symbols ........................................................................ ........................372 Greek Symbols........................................................................ .........................373 References........................................................................ .................................373 Chapter 9Physicochemical and Engineering Properties of Food in Membrane Separation Processes .......................................381

D. Rana, T. Matsuura, and S. Sourirajan

I. Introduction........................................................................ .....................381 II. Transport Theories........................................................................ ..........382 A. Case 1: Preferential Sorption of Water at the Membrane- Solution Interface ........................................................................ ......382

1. Basic Transport Equations..........................................................382

2. Relationship between (DAM/K
)

NaCl and DAM/K
for Other Solutes........................................................................ ...................384

3. RO Process Design.......................................................................387

B. Case II: Surface Force-Pore Flow Model; Generation of Interfacial Surface Force Parameters and Their Application ........389

1. Analysis Fundamentals ...............................................................389

2. Quantities Ra, Rb, and d

.............................................................390

3. Definitions of Dimensionless Quantities....................................390

4. Basic Transport Equations..........................................................391

5. Liquid Chromatography for the Determination of Interfacial

Interaction Force Parameters......................................................396

6. Data on Interfacial Surface Force Parameters..........................397

7. Data on Pore Size and Pore Size Distribution...........................398

III. Problems in Membrane Separation and Concentration of Liquid Foods ........................................................................ ................................403 A. Application of Water Preferential Sorption Model..........................406

1. Separation of Undissociated Organic Solutes Such as Sugars

Present in High Concentration...................................................413

2. Separations of Undissociated Polar Organic Solutes Present

in Low Concentrations.................................................................413 xviRao, Rizvi, and Datta

3. Separation of Partially Dissociated Organic Solutes Present

in Low Concentration...................................................................416

4. Problem of Separations of Low Concentrations of

Undissociated Organic Solutes in Concentrated

Sugar Solutions ........................................................................ ....418

5. Separation of Solutions of Partially Dissociated Acids

Present in Concentrated Sugar Solutions..................................419 B. Application of Transport Equations to Real Fruit Juice Concentration........................................................................ .............421 C. Application of Transport Equations for the Concentration of Green Tea Juice ........................................................................ .........426 D. Some Illustrative Examples of the Surface Force-Pore Flow Model ........................................................................ ..........................431

1. Parametric Studies on Solute Separation and Product Rate ...431

2. Another Parametric Study on Solute Concentration Profile

and Solution Velocity Profile .......................................................434 E. Some Data on the Ultrafiltration of Proteins .................................437

1. Ultrafiltration of Bovine Serum Albumin (BSA) and

a -Casein ........................................................................ ................437

2. Effects of Fouling on Membrane Performance and Pore Size

and Pore Size Distribution ..........................................................440

3. Fractionation of the Protein-Sugar System and the

Protein-Protein System in the Aqueous Solutions.....................443 F. Application of Pervaporation in the Recovery and Concentration of Food Flavors........................................................................ ...........445 IV. Recent Literature on Membrane Applications......................................447 A. Dairy Product Industry.....................................................................447

1. Reverse Osmosis........................................................................

...447

2. Nanofiltration ........................................................................

.......448

3. Ultrafiltration........................................................................

.......448

4. Microfiltration........................................................................

.......448 B. Beverage Industry ........................................................................ .....449

1. Reverse Osmosis........................................................................

...449

2. Ultrafiltration........................................................................

.......450

3. Microfiltration........................................................................

.......450 C. Edible Oil Industry........................................................................ ....450

1. Reverse Osmosis........................................................................

...451

2. Ultrafiltration........................................................................

.......451

3. Microfiltration........................................................................

.......451 V. Conclusion........................................................................ ........................452 List of Symbols ........................................................................ ........................453 Greek Symbols........................................................................ .........................454 References........................................................................ .................................455 Chapter 10Electrical Conductivity of Foods.............................................461

Sudhir K. Sastry

I. Introduction........................................................................ .....................461 II. Basic Definitions ........................................................................ .............462 III. Liquid Foods ........................................................................ ....................462

Table of Contentsxvii

A. Theory of Electrolytic Conductivity..................................................462

1. Strong Electrolytes.......................................................................464

2. Weak Electrolytes........................................................................

.464 B. Relations between Electrical Conductivity and Other Transport Properties ........................................................................ ...................465 C. Effect of Temperature........................................................................ 466
D. Effect of Electric Field Strength.......................................................467 E. Effect of Ingredients........................................................................ ..468

1. Electrolytic Solutes....................................................

...................468

2. Inert Suspended Solids................................................................468

3. Hydrocolloids ........................................................................

........469

4. Phase Transitions of Suspended Solids......................................471

5. Effect of Nonelectrolytic Solutes.................................................474

IV. Solid Foods........................................................................ .......................474 A. Effect of Microstructure ....................................................................474 B. Effects of Temperature and Electric Field Strength.......................475

1. Gels and Noncellular Solids........................................................475

2. Solids with Undisrupted Cellular Structure..............................476

3. Modeling of Cell Membrane Breakdown....................................479

4. Reversibility and Repair of Pores ...............................................479

5. Extension to Eukaryotic Cells.....................................................480

C. Effect of Frequency........................................................................ ....482

1. Relation to Dielectric Constant...................................................484

D. Ingredient Effects ........................................................................ ......487 V. Solid-Liquid Mixtures ........................................................................ ....488 A. Models for Effective Electrical Conductivity...................................488

1. Maxwell Model...........................................................

...................488

2. Meredith and Tobias (1960) Model .............................................489

3. Series Model ........................................................................

.........489

4. Parallel Model........................................................................

.......489

5. Kopelman Model........................................................................

...489

6. Probability Model........................................................................

.490

7. Comparison of Models..................................................................490

B. Effects of Solids in Tube Flow..........................................................490 VI. Methods of Measurement of Electrical Conductivity...........................492 List of Symbols ........................................................................ ........................496 Greek Letters and Other Symbols .................................................................496 Subscripts/Superscripts Not Explained Elsewhere.......................................497 References........................................................................ .................................497 Chapter 11Dielectric Properties of Foods .................................................501

Ashim K. Datta, G. Sumnu, and G.S.V. Raghavan

I. Introduction........................................................................ .....................501 II. Basic Principles........................................................................ ...............502 A. Radiofrequency vs. Microwave Heating...........................................509 III. Measurement Principles........................................................................ .509 A. Waveguide and Coaxial Transmission Line Methods......................510 B. Short-Circuited Line Technique........................................................510 xviiiRao, Rizvi, and Datta C. Open-Ended Probe Technique...........................................................511 D. Time Domain Reflectometry (TDR) Method....................................512 E. Free-Space Transmission Technique................................................512 F. Microstrip Transmission Line...........................................................513 G. Six-Port Reflectometer Using an Open-Ended Coaxial Probe .......513 H. Colloid Dielectric Probe (Hewlett Packard).....................................514 I. Test Cell with Boonton RX-Meter....................................................514 J. Cavity Perturbation Technique.........................................................514

1. Solid Sample Preparation............................................................517

2. Liquid Sample Preparation .........................................................517

3. Semisolid Samples........................................................................

517
K. Summary of Dielectric Property Measurement Techniques...........517 IV. Frequency and Temperature Dependence.............................................518 A. Frequency Dependence......................................................................518 A. Frequency Dependence in Food Materials.......................................521 B. Temperature Dependence in Water, Salt Solutions, and Foods .....522

1. Dielectric Properties below Freezing and above Boiling

Temperatures........................................................................ ........526

2. Temperature Dependence of Loss Factor and Runaway

Heating........................................................................ ..................530 V. Composition Dependence........................................................................ 531
A. Moisture Dependence........................................................................ 531
B. Dielectric Properties of Carbohydrates............................................533

1. Starch........................................................................

....................534

2. Sugar........................................................................

.....................536

3. Gums ........................................................................

.....................536 C. Dielectric Properties of Proteins.......................................................538 D. Dielectric Properties of Fat...............................................................541 E. Dielectric Properties of Meats ..........................................................542 F. Dielectric Properties of Fish and Seafood .......................................543 G. Dielectric Properties of Fruits and Vegetables................................545 H. Dielectric Properties of Dairy Products...........................................547 VI. Dielectric Properties of Insect Pests......................................................550 VII. Dielectric Properties of Packaging Materials .......................................551 VIII.Effects of Processing and Storage on Dielectric Properties of Foods...551 A. Baking........................................................................ .........................551 B. Drying........................................................................ .........................554 C. Cooking........................................................................ .......................554 D. Mixing........................................................................ .........................554 E. Storage........................................................................ ........................554 IX. Assessment of Food Quality by Using Dielectric Properties...............555 X. Further Sources of Data........................................................................ .557 Acknowledgment........................................................................ ......................557 References........................................................................ .................................557 Chapter 12Ultrasound Properties .............................................................567 Michael J. McCarthy, Lu Wang, and Kathryn L. McCarthy I. Introduction........................................................................ .....................567

II. Fundamentals of Acoustics.....................................................................569

Table of Contentsxix

A. Speed of Sound, Density, and Elastic Moduli..................................569 B. Amplitude and Attenuation..............................................................571

1. Scattering........................................................................

..............572

2. Absorption........................................................................

.............572 C. Impedance, Reflection, and Refraction.............................................573 D. Doppler Shift Frequency and Velocity .............................................574 III. Ultrasonic Measurement Techniques ....................................................575 A. Ultrasonic Methods...................................................... ......................576

1. Pulsed-Echo......................................................................

.............576

2. Pitch-and-Catch........................................................................

....578

3. Interferometry ........................................................................

......578

4. Spectral Analysis........................................................................

..579

5. Ultrasonic Imaging.......................................................................579

B. Transducer Selection........................................................................ .580 C. Interpretation of Ultrasonic Measurements....................................582 IV. Compilation of Acoustic Properties........................................................582 A. Composition........................................................................ ................582

1. Solutions and Beverages..............................................................582

2. Concentrated Solutions................................................................587

3. Oils ........................................................................

........................588

4. Emulsions........................................................................

..............589

5. Muscle Foods........................................................................

.........593 B. Phase Transitions........................................................................ ......594

1. Freezing........................................................................

.................594

2. Crystallization of Fats..................................................................594

3. Gelation........................................................................

.................596 C. Texture........................................................................ ........................597

1. Firmness of Fruits/Vegetables.....................................................597

2. Cheese ........................................................................

...................597

3. Starch Products........................................................................

....598 D. Viscosity........................................................................ ......................599

1. Viscosity and Attenuation............................................................599

2. Viscosity and UDV .......................................................................600

V. Conclusion........................................................................ ........................603 List of Symbols ........................................................................ ........................604 Greek Symbols........................................................................ .........................604 Subscripts........................................................................ .................................605 Superscripts........................................................................ ..............................605 References........................................................................ .................................605 Chapter 13Kinetic Data for Biochemical and Microbiological Processes during Thermal Processing.....................................................611 Ann M. Van Loey, Chantal Smout, Indrawati, and Marc E. Hendrickx I. Introduction........................................................................ .....................611 II. Fundamental Considerations.................................................................614 A. Primary Kinetic Models ....................................................................615

1. Zero-Order Model ........................................................................

.616

2. First-Order Model ........................................................................

617
xxRao, Rizvi, and Datta

3. Biphasic Model ........................................................................

.....618

4. Fractional Conversion Model..............................................

.........618 B. Secondary Kinetic Models.................................................................619

1. Influence of Temperature on the Reaction Rate Constant .......619

2. Selection of a Temperature Coefficient Model ...........................620

III. Measurement Techniques.......................................................................621

IV. Specific Data on Properties....................................................................623

A. Microbial Inactivation .......................................................................623 B. Enzyme Inactivation........................................................................ ..625 C. Texture Degradation........................................................................ ..626 D. Color Degradation........................................................................ ......627 E. Flavor Degradation........................................................................ ....629 F. Nutrient Degradation........................................................................ 630
References........................................................................ .................................633 Chapter 14Gas Exchange Properties of Fruit and Vegetables................645 Bart M. Nicola•, Jeroen Lammertyn, Wendy Schotsmans, and Bert E. Verlinden I. Introduction........................................................................ .....................645 II. Fundamental Considerations.................................................................646 A. Respiration and Fermentation..........................................................646

1. Respiration Rate........................................................................

...648

2. Respiration and Fermentation Models.......................................649

3. Gas Transport Properties ............................................................653

B. Measurement Techniques..................................................................655

1. Oxygen Consumption and Carbon Dioxide Production Rate....655

2. Measurement of O

2 and CO 2 Concentration..............................656

3. Measurement of Heat of Respiration......................................

....659

4. Skin Resistance and Gas Diffusion Properties..........................660

C. Gas Exchange Data for Selected Fruits and Vegetables................663 III. Applications........................................................................ .....................663 Acknowledgments ........................................................................ ....................671 List of Symbols ........................................................................ ........................671 References........................................................................ .................................672 Chapter 15Surface Properties....................................................................679

Joseph McGuire

I. Introduction........................................................................ .....................679 II. Fundamental Considerations.................................................................680 A. Definitions........................................................................ ..................680 B. The Gibbs Adsorption Equation .......................................................682 C. The Contact Angle........................................................................ .....684

1. Critical Surface Tension...............................................................686

2. Polar and Dispersive Contributions to Surface Energy............686

3. An Equation of State Relationship between Interfacial

Energies ........................................................................ ................690 D. Effects of Adsorbed Layer Composition and Structure on Interfacial Energy........................................................................ ......690

Table of Contentsxxi

III. Measurement Techniques.......................................................................693

A. Evaluation of the Contact Angle ......................................................693 B. Evaluation of Liquid Surface Tension..............................................694

C. Evaluation of 

Ld and  Sd ...................................................................696 IV. Surface Property Data........................................................................ ....697 V. Summary........................................................................ ..........................699 References...........................

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