Water Activity in Foods

Gustavo V. Barbosa-Cánovas, Anthony J. Fontana, Jr., Shelly J. Schmidt, Theodore P. Labuza EDITORS

Fundamentals and Applications

Water Activity in Foods

Fundamentals and Applications

Water Activity in Foods

Gustavo V. Barbosa-Cánovas, Anthony J. Fontana, Jr., Shelly J. Schmidt, Theodore P. Labuza EDITORS

Fundamentals and Applications

The IFT Press series reflects the mission of the Institute of Food Technologists—advancingthe science and technology of food through the exchange of knowledge. Developed inpartnership with Blackwell Publishing, IFT Press books serve as leading edge handbooksfor industrial application and reference and as essential texts for academic programs.Crafted through rigorous peer review and meticulous research, IFT Press publications rep-resent the latest, most significant resources available to food scientists and related agricul-ture professionals worldwide.

IFT Book Communications Committee

Theron W. DownesRuth M. PatrickDennis R. HeldmanJoseph H. HotchkissSteven NagyAlina S. SzczesniakMark BarrettNeil H. Mermelstein

IFT Press Editorial Advisory Board

Malcolm C. BourneFergus M. ClydesdaleDietrich KnorrTheodore P. LabuzaThomas J. MontvilleS. Suzanne NielsenMartin R. OkosMichael W. ParizaBarbara J. PetersenDavid S. ReidSam SaguyHerbert StoneKenneth R. Swartzel

Gustavo V. Barbosa-Cánovas, Professor of Food Engineering, Center for Nonthermal Processing ofFoods, Washington State University.

Anthony J. Fontana, Jr., Senior Research Scientist, Decagon Devices, Inc.

Shelly J. Schmidt, Professor of Food Chemistry, Department of Food Science and Human Nutrition,University of Illinois at Urbana-Champaign.

Theodore P. Labuza, Morse Alumni Distinguished Professor of Food Science and Engineering;Department of Food Science and Nutrition, University of Minnesota.

© 2007 Blackwell Publishing and the Institute of Food TechnologistsAll rights reserved

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First edition, 2007

Library of Congress Cataloging-in-Publication DataWater activity in foods : fundamentals and applications / edited by Gustavo Barbosa-Cánovas ... [et al.].

p. cm. — (IFT Oress series)Includes bibliographical references and index.ISBN-13: 978-0-8138-2408-6 (alk. paper)ISBN-10: 0-8138-2408-7 (alk. paper)1. Food—Water activity. 2. Food—Moisture. I. Barbosa-Cánovas, Gustavo V.

TX553.W3W358 2007664—dc22

2007006958

The last digit is the print number: 9 8 7 6 5 4 3 2 1

Titles in the IFT Press series

• Accelerating New Food Product Design and Development (Jacqueline H.P. Beckley,Elizabeth J. Topp, M. Michele Foley, J.C. Huang and Witoon Prinyawiwatkul)

• Biofilms in the Food Environment (Hans P. Blaschek, Hua Wang, and Meredith E. Agle)• Calorimetry and Food Process Design (Gönül Kaletunç)• Food Ingredients for the Global Market (Yao-Wen Huang and Claire L. Kruger)• Food Irradiation Research and Technology (Christopher H. Sommers and Xuetong Fan)• Food Risk and Crisis Communication (Anthony O. Flood and Christine M. Bruhn)• Foodborne Pathogens in the Food Processing Environment: Sources, Detection and

Control (Sadhana Ravishankar and Vijay K. Juneja)• High Pressure Processing of Foods (Christopher J. Doona, C. Patrick Dunne, and

Florence E. Feeherry)• Hydrocolloids in Food Processing (Thomas R. Laaman)• Microbiology and Technology of Fermented Foods (Robert W. Hutkins)• Multivariate and Probabilistic Analyses of Sensory Science Problems (Jean-Francois

Meullenet, Rui Xiong, and Chris Findlay• Nondestructive Testing of Food Quality (Joseph Irudayaraj and Christoph Reh)• Nonthermal Processing Technologies for Food (Howard Q. Zhang, Gustavo V. Barbosa-

Canovas, V.M. Balasubramaniam, Editors; C. Patrick Dunne, Daniel F. Farkas, JamesT.C. Yuan, Associate Editors)

• Nutraceuticals, Glycemic Health and Diabetes (Vijai K. Pasupuleti and James W.Anderson)

• Packaging for Nonthermal Processing of Food (J. H. Han)• Preharvest and Postharvest Food Safety: Contemporary Issues and Future Directions

(Ross C. Beier, Suresh D. Pillai, and Timothy D. Phillips, Editors; Richard L. Ziprin,Associate Editor)

• Processing and Nutrition of Fats and Oils (Ernesto M. Hernandez, Monjur Hossen, andAfaf Kamal-Eldin)

• Regulation of Functional Foods and Nutraceuticals: A Global Perspective (Clare M.Hasler)

• Sensory and Consumer Research in Food Product Design and Development (HowardR. Moskowitz, Jacqueline H. Beckley, and Anna V.A. Resurreccion)

• Thermal Processing of Foods: Control and Automation (K.P. Sandeep)• Water Activity in Foods: Fundamentals and Applications (Gustavo V. Barbosa-Canovas,

Anthony J. Fontana Jr., Shelly J. Schmidt, and Theodore P. Labuza)• Whey Processing, Functionality and Health Benefits (Charles I. Onwulata and Peter J.

Huth)

Contents

Dedication ix

Preface xiii

Acknowledgments xv

List of Contributors xvii

01. Introduction: Historical Highlights of Water Activity Research 3Jorge Chirife and Anthony J. Fontana, Jr.

02. Water Activity: Fundamentals and Relationships 15David S. Reid

03. Water Activity and Glass Transition 29Yrjö H. Roos

04. Water Mobility in Foods 47Shelly J. Schmidt

05. Water Activity Prediction and Moisture Sorption Isotherms 109Theodore P. Labuza and Bilge Altunakar

06. Measurement of Water Activity, Moisture Sorption Isotherms, and Moisture Content of Foods 155Anthony J. Fontana, Jr.

07. Moisture Effects on Food’s Chemical Stability 173Leonard N. Bell

08. Water Activity and Physical Stability 199Gaëlle Roudaut

09. Diffusion and Sorption Kinetics of Water in Foods 215Theodore P. Labuza and Bilge Altunakar

10. Effects of Water Activity (aw) on Microbial Stability: As a Hurdle in Food Preservation 239María S. Tapia, Stella M. Alzamora, and Jorge Chirife

11. Principles of Intermediate-Moisture Foods and Related Technology 273Petros S. Taoukis and Michelle Richardson

12. Desorption Phenomena in Food Dehydration Processes 313Gustavo V. Barbosa-Cánovas and Pablo Juliano

vii

13. Applications of Water Activity Management in the Food Industry 341Jorge Welti-Chanes, Emmy Pérez, José Angel Guerrero-Beltrán, Stella M. Alzamora, and Fidel Vergara-Balderas

14. Applications of Water Activity in Nonfood Systems 359Anthony J. Fontana, Jr., and Gaylon S. Campbell

15. The Future of Water Activity in Food Processing and Preservation 373Cynthia M. Stewart, Ken A. Buckle, and Martin B. Cole

Appendices

A Water Activity of Saturated Salt Solutions 391Anthony J. Fontana, Jr.

B Water Activity of Unsaturated Salt Solutions at 25°C 395Anthony J. Fontana, Jr.

C Water Activity and Isotherm Equations 399Anthony J. Fontana, Jr.

D Minimum Water Activity Limits for Growth of Microorganisms 405Anthony J. Fontana, Jr.

E Water Activity Values of Select Food Ingredients and Products 407Shelly J. Schmidt and Anthony J. Fontana, Jr.

F Water Activity Values of Select Consumer and Pharmaceutical Products 421Anthony J. Fontana, Jr., and Shelly J. Schmidt

Index 423

viii Contents

Dedication

This book is dedicated to Marcus Karel, EmeritusProfessor of Food and Chemical Engineering (Massa-chusetts Institute of Technology) and Emeritus Stateof New Jersey Professor (Rutgers University).

—Prof. Theodore Labuza (colleague, adopted science son, and confidant)

It was 1962. I had just finished my bachelor’s of science degree at Massachusetts Instituteof Technology, and I had an offer to go to the University of Minnesota to work on a doc-torate in nutrition with Ancel Keyes. He had just received one of the first NationalInstitutes of Health training grants in nutrition and needed a food science student becausethey were working on new military rations.

I had become interested in nutrition, as my undergraduate advisor was Dr. Sandy Miller(later to become the head of Food and Drug Administration’s Bureau of Foods), and I didmy bachelor’s thesis with him. The prior year I took a course taught in part by a recentlyappointed assistant professor, Marcus Karel (Fig. D1). He fascinated me with his under-standing of physical chemistry and kinetics and their applications to food. His work on thestability of military foods and space foods was the “chocolate” to entice me, and I took thebite to work with him, becoming his first doctoral student and getting my degree in 3 years.At the end, though, I had a draft notice in hand to go to Vietnam.

Dr. Karel helped me secure a position as an assistant professor to continue my work onreaction kinetics and stability of space foods. That allowed me to begin to work with the “gi-ants” in the field, as that year I traveled with Marc to Aberdeen, Scotland, for an internationalmeeting on water in foods. There, I met his col-leagues from Europe, including Denise Simatos, LouRockland, John Hawthorne, Ron Duckworth, FelixFranks, and Grahame Gould, and was securely en-thralled in being a part of this group. Several yearslater, in 1974, that group along with others gatheredin Glasgow, Scotland, for the first ISOPOW (Fig.D2) meeting (International Symposium on theProperties of Water), setting the stage for the intro-duction of the concepts of water activity and eventu-ally of glass transition and for the continuation ofmany meetings over the decades. We plan to meet inSeptember 2007 in Thailand for the 10th ISOPOW. Itwas Marc’s foresight to ensure that the meetings in-cluded invitees from other fields so that there would

ix

Figure D2. InternationalSymposium on the Properties ofWater (ISOPOW) logo.

Figure D1. Marcus Karel.

be “cross-fertilization” in both directions, a practice we continue to this day. It was at thesemeetings where many met Marc for the first time and added to his admirers. Unfortunately,he missed the last meeting, where we made a presentation on his impact in food science, butthis book is that substitute. Figure D3 illustrates the attendance to the third ISOPOW meet-ing in 1983 by some of the most influential people working with water activity

Marcus Karel, to whom we dedicate this book, was born in Lwów, Poland, in 1928, be-fore World War II. He worked in the underground in 1945–1946, helping the Jews escapeacross the Iron Curtain. He then studied agriculture at the Munich Technical University.Eventually, he made his way to Boston in 1951 and got a job in 1952 in the food packag-ing lab at the Massachusetts Institute of Technology, working for Bernie Proctor (a formerIFT president) and Sam Goldblith. He certainly must have impressed them with his skills,and while working there, he finished his bachelor’s of science degree at Boston Universityin 1955 and married Cal, his wife for over 50 years. They have four children, two of whomgraduated from the Massachusetts Institute of Technology. Marc did his doctoral studieswith Prof. J. T. R. Nickerson, a food microbiologist, and Marc’s doctoral thesis was the firston the application of kinetics to food reactions as a function of moisture. His minor was inchemical engineering with Alan Michaels. In 1961, my senior year, I entered the picturewhen I took a course he taught, as mentioned earlier. He had an amazing mind, spendingseveral days a week in the library (before the Internet), which gave him a fantastic knowl-edge base. One could see it when he questioned those who gave seminars, starting with apolite compliment followed by, “But let me . . .”, when he would go to the board and showa better answer through a derivation. In 1969, he, Steve Tannenbaum (a fellow Massa-chusetts Institute of Technology faculty member in food science), and I came up with thestability map for reactions as a function of water activity, a map that still is used today (Fig.D4). It was obvious that Marc’s goals included not only research but also the use and dis-semination of that research through the education of students.

A challenge to the concept of water activity began in 1988 with the introduction of theconcept of glass transition by two scientists at General Foods, Louise Slade and HarryLevine. The following six years were the most exciting in this field of water and stability,with much controversy. One of the original ISOPOW people, Felix Franks, wrote an edi-torial in Cryoletters saying that the concept of water activity is now dead. Again, Dr. Karel,

x Dedication

Figure D3. Attendees at the third ISOPOW meeting held in Beaune, France, in 1983.

along with Yrjo Roos, then at the University of Helsinki and a visiting professor at RutgersUniversity, came up with the idea of state diagrams, a way to bring the two concepts to-gether, especially to explain physical states. During that time, my three children presentedposters at the national Institute of Food Technologists (IFT) meeting as prime authorsbased on their grade school science projects (Fig. D5). They knew about Marc from meand were very worried that he would come to the meeting and ask questions. He did askquestions, and he called them his “science grandchildren,” again showing his love for sci-ence and his compassion for instilling education.

My most interesting days with Marc came much later, when he and I became part of atechnical advisory committee to the Pillsbury Company, headed by Dr. James Bhenke, the

Dedication xi

Figure D4. Stability map for reactions as a function of water activity.

Figure D5. Poster presentations at IFT’s 2001 and 2002 meetings.

vice president of research (Fig. D6). Marcus Karel, Owen Fennema, and Daryl Lund col-laborated on one of the best food processing textbooks ever published, Physical Principlesof Food Preservation.

This book was the outcome of an Institute of Food Technologists short course at the2001 annual meeting. The original intent was yet another symposium book, but I suggestedstrongly that it should be designed as a true undergraduate textbook, as there was nothingavailable except books of papers from the ISOPOW meetings and the moisture sorptionisotherm manual I wrote with my former student, Prof. Leonard Bell (professor of foodchemistry at Auburn University and a collaborator in this book). My co-editors, GustavoBarbosa-Cánovas, Shelly Schmidt, and Anthony Fontana, agreed heartily. We were alltaught and influenced by Marcus in many different ways, and this book is dedicated to hisideals of education and the stimulation of new science. We thank you, Marc, for helpingus to advance the field.

xii Dedication

Figure D6. Technical Advisory Committee (TAC) to the Pillsbury Co.

Preface

The coeditors of this book have spent a total of more than 100 years studying and research-ing the properties and stability of foods as related to water, and in particular, as related totwo key property values: water activity (aw) and glass transition temperature. Since 1965,there have been at least 50 symposium books devoted to these properties. One is a work-ing manual on moisture sorption isotherms that one of the coeditors coauthored, and it de-scribes many instruments to measure such properties. Another of the coeditors is a princi-pal in a company that designs, fabricates, and sells many of these instruments, and a thirdcoeditor was involved as editor of one of the many books from the ISOPOW conferences.

All of us have walked among the “giants” in this field and have learned much. We realizedthat many misconceptions existed out there, and this provided a good starting point on the top-ics of aw and glass transition. A well-conceived and -presented short course at the Institute ofFood Technologists Annual Meeting in 2001 (Anaheim, CA) served as the basis for this text-book, as well as the inspiration of Marcus Karel (see Dedication), who truly is a “giant”among the giants in the field. We have gathered the “best of the best” to bring together thephysics and chemistry of water and its interactions in foods. This book complements and goesbeyond the best chapter ever written at a graduate level on the subject of water, that of OwenFennema’s chapter “Water in Food” in the classic textbook Food Chemistry.

Our goal was to introduce basic principles and to teach applications. We have incorpo-rated the “old” ideas on aw from 1965 with the “new” ideas on glass transition introduced20 years ago. This book should serve those in the fields of food science and technology,biotechnology, plant science, meat science, pharmaceuticals, chemical and food engineer-ing, and wood and paper science, as well as assisting in the stability of medical devices. Itis interesting that the foundational principle of aw, while a principle of physical chemistry,took the combined efforts of food scientists and food microbiologists to apply and to cre-ate a new “art and science” related to the understanding of the physical and chemical sta-bility of foods. We congratulate all those who contributed to establishing the foundation ofthe key topics covered in this book, and we hope we have given them due mention in thetext. One cannot teach food science without teaching about aw; the simplicity of treatingaw as a measure of free versus bound water is a misconception, which will be apparent asone learns the true meaning of the activity of water in foods. As coauthors that traveleddown an arduous path, we thank each other for overcoming the hurdles along that path byalways focusing on the outcome. We hope this book will help future students and currentprofessionals understand “a sub w.”

T. P. LabuzaS. J. SchmidtA. J. Fontana Jr.G.V. Barbosa-Cánovas

xiii