Water Activity and Food

Water Activity and Food

1st Edition - May 28, 1978

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  • Author: John Troller
  • eBook ISBN: 9780323159012

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Water Activity and Food explores the role of water activity in the water relations of microorganisms and in food processing, packaging, and storage. It reviews the literature and provides numerous examples demonstrating the use of water activity to predict the reactions of microorganisms or the stability of food components. It also highlights cases where water activity is not a reliable predictor of events and considers some interesting interactions with other environmental parameters. Comprised of 11 chapters, this volume begins with an overview of water in foods and solutions, water activity values for foods, and water relations of enzyme activity. It then discusses lipid oxidation, enzyme reactions and non-enzymatic browning, and several other food-related factors. The reader is also introduced to water relations of microbial growth; the effects of water on microbial survival; the spoilage and preservation of foods at various levels of water activity; the water relations of food-borne pathogens such as Salmonella and toxigenic molds; the importance of water activity in non-microbiological aspects of food processing and storage; and the influence of atmospheric relative humidity on sanitation and the protection of food products. This book is an important source of information for researchers in food microbiology and microbial water relations.

Table of Contents

  • Foreword


    1 Water Activity—Basic Concepts

    Water in Foods

    Properties of Solutions

    Water Binding

    Water Sorption Isotherms

    Temperature Effects


    Frozen Foods

    Nonequilibrium Conditions


    Water Activity Values for Foods


    2 Methods

    Desired Characteristics

    Water Activity Methods

    Relative Humidity Methods

    Total Moisture Methods


    Control of aw


    3 Enzyme Reactions and Nonenzymatic Browning

    Effect of Water Activity on Enzymatic Reactions

    Effect of Water Activity on Nonenzymatic Browning Reactions


    4 Lipid Oxidation, Changes in Texture, Color, and Nutritional Quality

    Effect of aw on Lipid Oxidation

    Effect of aw on Food Texture

    Effect of aw on Food Pigments

    Effect of aw on Nutrients


    5 Microbial Growth



    Interactions with Water Activity

    Sporulation, Germination, and Outgrowth

    Solute Effects

    Hysteresis Effects

    Physiological Basis of Tolerance of Reduced Water Activity


    6 Food Preservation and Spoilage

    Cereals and Legumes



    Milk Products





    7 Microbial Survival

    Survivor Curves

    Survival at Freezing Temperatures

    Survival at Moderate Temperatures

    Survival at Elevated Temperatures

    Sublethal Impairment


    8 Food-Borne Pathogens

    Staphylococcus aureus

    Toxigenic Molds


    Clostridium perfringens

    Clostridium botulinum

    Vibrio parahaemolyticus

    Bacillus cereus



    9 Control of aw and Moisture


    Concentration by Water Removal

    Intermediate Moisture Foods


    10 Packaging, Storage, and Transport

    Bulk Storage of Commodities


    Refrigerated Storage of Bulk Products

    Packaged Foods

    Measurement of Water Vapor Permeability

    Permeability of Packaging Materials

    Unrefrigerated Packaged Foods

    Refrigerated Packaged Foods


    11 Food Plant Sanitation

    Process Equipment Cleaning

    Food Storage Sanitation

    Effect of Relative Humidity on Insects and Insect Control

    Effect of Relative Humidity on Fumigants and Antimicrobial Agents

    Effect of Relative Humidity and aw on Bacterial Survival on Surfaces

    Effect of Relative Humidity on Airborne Microorganisms


    Appendix A

    Appendix B


Product details

  • No. of pages: 252
  • Language: English
  • Copyright: © Academic Press 1978
  • Published: May 28, 1978
  • Imprint: Academic Press
  • eBook ISBN: 9780323159012

About the Author

John Troller

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