Water Activity in Foods

Fundamentals and Applications
Institute of Food Technologists Series (Verlag)
  • 2. Auflage
  • |
  • erschienen am 14. Mai 2020
  • |
  • 640 Seiten
E-Book | ePUB mit Adobe-DRM | Systemvoraussetzungen
978-1-118-82335-4 (ISBN)
This second edition of Water Activity in Foods furnishes those working within food manufacturing, quality control, and safety with a newly revised guide to water activity and its role in the preservation and processing of food items. With clear, instructional prose and illustrations, the book's international team of contributors break down the essential principles of water activity and water-food interactions, delineating water's crucial impact upon attributes such as flavor, appearance, texture, and shelf life.

The updated and expanded second edition continues to offer an authoritative overview of the subject, while also broadening its scope to include six newly written chapters covering the latest developments in water activity research. Exploring topics ranging from deliquescence to crispness, these insightful new inclusions complement existing content that has been refreshed and reconfigured to support the food industry of today.
weitere Ausgaben werden ermittelt
GUSTAVO V. BARBOSA-CÁNOVAS is Professor of Food Engineering and Director of the Center for Nonthermal Processing of Food at Washington State University, Pullman, WA, USA.

ANTHONY J. FONTANA, JR. is Technical Services Manager, ALS Global USA, Corp., Irvine, CA.

SHELLY J. SCHMIDT is Professor of Food Chemistry in the Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL, USA.

THEODORE P. LABUZA is Morse Alumni Distinguished Professor of Food Science and Engineering in the Department of Food Science and Nutrition at the University of Minnesota, Saint Paul, MN, USA.
Dedication v

Preface to the Second Edition ix

Preface to the First Edition xi

List of Contributors xiii

1. Introduction: Historical Highlights of Water Activity Research 1
Jorge Chirife and Anthony J. Fontana, Jr.

2. Water Activity: Fundamentals and Relationships 13
David S. Reid

3. Water Activity and Glass Transition 27
Yrjö H. Roos

4. State and Supplemented Phase Diagrams for the Characterization of Food 45
Yrjö H. Roos

5. Water Mobility in Foods 61
Shelly J. Schmidt

6. Water-Solid Interactions in Food Ingredients and Systems 123
Lisa J. Mauer

7. Water Activity Prediction and Moisture Sorption Isotherms 161
Theodore P. Labuza and Bilge Altunakar

8. Measurement of Water Activity, Moisture Sorption Isotherm, and Moisture Content of Foods 207
Anthony J. Fontana, Jr. and Brady P. Carter

9. Moisture Effects on Food's Chemical Stability 227
Leonard N. Bell

10. Water Activity and Physical Stability 255
Gaëlle Roudaut

11. Enthalpy Relaxation and Food Stability 271
Roopesh M. Syamaladevi, Shelly J. Schmidt, Gustavo V. Barbosa-Cánovas, and Shyam S. Sablani

12. Diffusion and Sorption Kinetics of Water in Foods 287
Theodore P. Labuza and Bilge Altunakar

13. Applications for Dynamic Moisture Sorption Profiles in Foods 311
Brady P. Carter

14. Effects of Water Activity (aw) on Microbial Stability as a Hurdle in Food Preservation 323
María S. Tapia, Stella M. Alzamora, and Jorge Chirife

15. Baroprotective Effect from Reduced aw 357
Avelina Franco-Vega, Fátima Reyes-Jurado, Nelly Ramirez-Corona, Enrique Palou, and Aurelio Lopez-Malo

16. Principles of Intermediate-Moisture Foods and Related Technology 385
Petros S. Taoukis and Michelle Richardson

17. Desorption Phenomena in Food Dehydration Processes 425
Gustavo V. Barbosa-Cánovas and Pablo Juliano

18. Humidity Caking and Its Prevention 453
Micha Peleg

19. Selected Applications of Water Activity Management in the Food Industry 465
Zamantha Escobedo-Avellaneda, Verónica Rodriguez-Martínez, Vinicio Serment-Moreno, Gonzalo Velázquez, Jorge Welti-Chanes, and J. Antonio Torres

20. Water Relations in Confections 483
Jade McGill and Richard W. Hartel

21. Applications of Probabilistic Engineering in Food Moisture Management to Meet Product Quality, Safety, and Shelf-Life Requirements 501
Verónica Rodriguez-Martínez, Gonzalo Velázquez, Jorge Welti-Chanes, and J. Antonio Torres

22. Applications of Water Activity in Nonfood Systems 521
Anthony J. Fontana, Jr. and Gaylon S. Campbell

23. The Future of Water Activity in Food Processing and Preservation 535
Cynthia M. Stewart, Kenneth A. Buckle, and Martin B. Cole


A Water Activity of Saturated Salt Solutions 553
Anthony J. Fontana, Jr.

B Water Activity of Unsaturated Salt Solutions at 25°C 557
Anthony J. Fontana, Jr.

C Water Activity, Isotherm, and Glass Transition Equations 561
Anthony J. Fontana, Jr. and Shafiur Rahman

D Minimum Water Activity Limits for Growth of Microorganisms 571
Anthony J. Fontana, Jr.

E Water Activity Values of Select Food Ingredients and Products 573
Shelly J. Schmidt and Anthony J. Fontana, Jr.

F Water Activity Values of Select Consumer and Pharmaceutical Products 593
Anthony J. Fontana, Jr. and Shelly J. Schmidt

Index 595

Introduction: Historical Highlights of Water Activity Research

Jorge Chirife1and Anthony J. Fontana Jr.2

1Catholic University, Buenos Aires, Argentina

2ALS - Truesdail, Irvine, CA, USA

The concept of water activity (aw) is more than 50?years old. William James Scott showed in 1953 that microorganisms have a limiting aw level for growth. It is now generally accepted that aw is more closely related to the microbial, chemical, and physical properties of foods and other natural products than is total moisture content. Specific changes in color, aroma, flavor, texture, stability, and acceptability of raw and processed food products have been associated with relatively narrow aw ranges (Rockland and Nishi 1980). Next to temperature, aw is considered one of the most important parameters in food preservation and processing (van den Berg 1986). This chapter is not a review of the literature on aw but rather a highlight of some early key aw research as it relates to microbial growth, moisture sorption isotherms, prediction and measurement of aw in foods, and, to a lesser extent, the influence of aw on the physical and chemical stability of foods.

Australian-born microbiologist Scott (1912-1993) received his bachelor's degree from the University of Melbourne (1933) and a doctorate of science degree from the Council for Scientific and Industrial Research (CSIR) Meat Research Laboratory (1933). He then took a position as senior bacteriologist at the CSIR Division of Food Preservation and Transport from 1940 to 1960. In 1960, he moved to the Meat Research Laboratory, where he served as assistant chief of division until 1964 and officer-in-charge until 1972. In 1979, he became a fellow of the Australian Academy of Technological Sciences and Engineering.

Scott's early work was concerned with handling, cooling, and transport conditions that would enable chilled beef to be successfully exported to Britain. During World War II, he was concerned with the microbiology of foods supplied by Australia to the Allied Forces. After the war, he pioneered studies on the water relations of microorganisms. In 1953, Scott related the relative vapor pressure of food to the thermodynamic activity of water, using the definition aw = p/po, where aw is the water activity derived from the laws of equilibrium thermodynamics, p is the vapor pressure of the sample, and po is the vapor pressure of pure water at the same temperature and external pressure. He showed a clear correlation between the aw of the growth medium and the rate of Staphylococcus aureus growth. The summary of his paper stated:

Table 1.1 Papers by Scott and Christian.

Author Year Title of Paper Scott, W.J. 1953 Water relations of Staphylococcus aureus at 30°C Christian, J.H.B. and Scott, WJ. 1953 Water relations of Salmonella at 30°C Christian, J.H.B. 1955a The influence of nutrition on the water relations of Salmonella oranienburg Christian, J.H.B. 1955b The water relations of growth and respiration of Salmonella oranienburg at 30°C Scott, W.J. 1957 Water relations of food spoilage microorganisms

Fourteen food-poisoning strains of Staphylococcus aureus have been grown in various media of known aw at 30°C. Aerobic growth was observed at water activities between 0.999 and 0.86. The rate of growth and the yield of cells were both reduced substantially when the aw was less than 0.94. The lower limits for growth in dried meat, dried milk, and dried soup were similar to those in liquid media. Aerobic growth proceeded at slightly lower water activities than anaerobic growth. All cells were capable of forming colonies on agar media with water activities as low as 0.92. The 14 strains proved to be homogeneous with similar water requirements.

Scott's classic demonstration that it is not the water content but the aw of a food system that governs microbial growth and toxin production was a major contribution to food microbiology. Many scientists, most notably his Australian colleague, J.H.B. Christian, expanded Scott's work. Key papers published in the 1950s by both Scott and Christian are listed in Table 1.1. These papers laid the foundation for future research into the survival and growth of microorganisms in foods at low aw.

In the field of food science, the general acceptance and application of the concept of a minimum aw for microbial growth began with the review by Scott published in 1957, Water Relations of Food Spoilage Microorganisms. Taken from the table of contents in Scott's classic review, the following are some of the aspects discussed:

  1. III. Methods for controlling aw:
    • Equilibration with controlling solutes
    • Determination of the water sorption isotherms
    • Addition of solutes
  2. IV. Water requirements for growth
    • Molds
    • Yeasts
    • Bacteria
    • General relationships
  3. V. Factors affecting water requirements
    • Nutrition, temperature, oxygen, inhibitors, adaptation
  4. VI. Special groups
    • Halophilic bacteria
    • Osmophilic yeasts
    • Xerophilic molds
  5. VII. Some applications in food preservation
    • Fresh foods, dried foods, concentrated foods, frozen foods, canned foods

Table 1.2 Selected early work on the minimal water activity for growth of pathogenic and spoilage microorganisms.

Author Year Title of Paper Baird-Parker, A.C. and Freame, B. 1967 Combined effect of water activity, pH, and temperature on the growth of Clostridium botulinum from spore and vegetative cell inocula Ohye, D.F. and Christian, J.H.B. 1967 Combined effects of temperature, pH, and water activity on growth and toxin production by Clostridium botulinum types A, B, and E Pitt, J.I. and Christian, J.H.B. 1968 Water relations of xerophilic fungi isolated from prunes Anand, J.C. and Brown, A.D. 1968 Growth rate patterns of the so-called osmophilic and non-osmophilic yeasts in solutions of polyethylene glycol Ayerst, G. 1969 The effects of moisture and temperature on growth and spore germination in some fungi Emodi, A.S. and Lechowich, R.V 1969 Low temperature growth of type E Clostridium botulinum spores. II. Effects of solutes and incubation temperature Kang, C.K., Woodburn, M., Pagenkopf, A., and Cheney, R. 1969 Growth, sporulation, and germination of Clostridium perfringens in media of controlled water activity Horner, K.J. and Anagnostopoulos, G.D. 1973 Combined effects of water activity, pH, and temperature on the growth and spoilage potential of fungi Troller, J.A. 1972 Effect of water activity on enterotoxin A production and growth of Staphylococcus aureus Beuchat, L.R. 1974 Combined effects of water activity, solute, and temperature on the growth of Vibrio parahaemolyticus Northolt, M.D., van Egmond, H.P., and Paulsch, W.W. 1977 Effect of water activity and temperature on aflatoxin production by Aspergillus parasiticus Pitt, J.I. and Hocking, A.D. 1977 Influence of solute and hydrogen ion concentration on the water relations of some xerophilic fungi Lotter, L.P. and Leistner, L. 1978 Minimal water activity for enterotoxin A production and growth of Staphylococcus aureus Hocking, A.D. and Pitt, J.I. 1979 Water relations of some Penicillium species at 25°C Briozzo, J., de Lagarde, E.A., Chirife, J., and Parada, J.L. 1986 Effect of water activity and pH on growth and toxin production by Clostridium botulinum type G Tapia de Daza, M.S., Villegas, Y., and Martinez,...

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