The field of food colloids is concerned with the physical chemistry of food systems viewed as assemblies of particles and macromolecules in various stages of supramolecular and microscopic organization. Butter, cheese, ice cream, margarine mayonnaise and yogurt are all examples of food colloids. This book describes experimental and theoretical developments in the field over the past 10-15 years. The authors have tried to strike a reasonable balance between theory and experiment, between principles and applications, and between molecular and physical approaches to the subject.

Proceedings of the NATO Advanced Research Workshop, Bergen, Norway, June 24-25, 1991

Until now colloid science books have either been theoretical, or focused on specific types of dispersion, or on specific applications. This then is the first book to provide an integrated introduction to the nature, formation and occurrence, stability, propagation, and uses of the most common types of colloidal dispersion in the process-related industries. The primary focus is on the applications of the principles, paying attention to practical processes and problems. This is done both as part of the treatment of the fundamentals, where appropriate, and also in the separate sections devoted to specific kinds of industries. Throughout, the treatment is integrated, with the principles of colloid and interface science common to each dispersion type presented for each major physical property class, followed by separate treatments of features unique to emulsions, foams, or suspensions. The first half of the book introduces the fundamental principles, introducing readers to suspension formation and stability, characterization, and flow properties, emphasizing practical aspects throughout. The following chapters discuss a wide range of industrial applications and examples, serving to emphasize the different methodologies that have been successfully applied. Overall, the book shows how to approach making emulsions, foams, and suspensions with different useful properties, how to propagate them, and how to prevent their formation or destabilize them if necessary. The author assumes no prior knowledge of colloid chemistry and, with its glossary of key terms, complete cross-referencing and indexing, this is a must-have for graduate and professional scientists and engineers who may encounter or use emulsions, foams, or suspensions, or combinations thereof, whether in process design, industrial production, or in related R&D fields.

Food emulsions have existed since long before people began to process foods for distribution and consumption. Milk, for example, is a natural emulsion/colloid in which a nutritional fat is stabilized by a milk-fat-globule membrane. Early processed foods were developed when people began to explore the art of cuisine. Butter and gravies were early foods used to enhance flavors and aid in cooking. By contrast, food emulsifiers have only recently been recognized for their abil ity to stabilize foods during processing and distribution. As economies of scale emerged, pressures for higher quality and extension of shelf life prodded the de velopment of food emulsifiers and their adjunct technologies. Natural emulsifiers, such as egg and milk proteins and phospholipids, were the first to be generally utilized. Development of technologies for processing oils, such as refining, bleaching, and hydrogenation, led to the design of synthetic food emulsifiers. Formulation of food emulsions has, until recently, been practiced more as an art than a science. The complexity offood systems has been the barrier to funda mental understanding. Scientists have long studied emulsions using pure water, hydrocarbon, and surfactant, but food systems, by contrast, are typically a com plex mixture of carbohydrate, lipid, protein, salts, and acid. Other surface-active ingredients, such as proteins and phospholipids, can demonstrate either syner- XV xvi Preface gistic or deleterious functionality during processing or in the finished food.

The book is devoted to expanding current views on the phenomena of protein functionality in food systems. Protein functionalities in foods have been the object ofextensive research over the last thirty to forty years and significant progress has been made in understanding the mechanism and factors influencing the functionality of proteins. The functionality of proteins is one of the fastest developing fields in the studies of protein utilization in foods. Currently, a broad spectrum of data related to protein functionality in food systems has been collected, however, much more needs to be known. In this volume, the most important functional properties offood proteins are presented: Protein solubility, water holding capacity and fat binding, emulsifying, foaming, and gelling properties as affected by protein source, environmental factors (pH, temperature, ionic strength) and protein concentration; Relationships between protein conformation, physicochemical properties, and functional properties; Protein functional properties as influenced by various food processing conditions, particularly heat treatment, dehydration, freezing and storage when frozen, extraction and other processes; Effects ofprotein modification on the enhancementofprotein functionality; Utilization ofvarious proteins in improving functional properties in food systems. Those aspects of protein functionality are presented which the author believes to be interesting and most important for protein utilization in food systems. The book is recommended to students and food scientists engaged in food protein research and food industry research, and development scientists. Table ofContents Introduction 1 References 5 Chapter 1 Solubility ofProteins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1. 1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1. 1. 1 Factors Affecting Solubility ofProteins. . . . . . . . . . . . . . . . . . . . . . . .

Emulsifiers, also known as surfactants, are often added to processed foods to improve stability, texture, or shelf life. These additives are regulated by national agencies, such as the FDA, or multi-national authorities, such as the EEC or WHO. The amphiphilic molecules function by assisting the dispersion of mutually insoluble phases and stabilizing the resulting colloids, emulsions, and foams. Emulsifiers can interact with other food components such as carbohydrates, proteins, water, and ions to produce complexes and mesophases. These interactions may enhance or disrupt structures and affect functional properties of finished foods. In dairy processing, small molecule emulsifiers may displace dairy proteins from oil/water and air/water interfaces, which affects stability and properties of the foams and emulsions. In baked products, emulsifiers contribute to secondary functionalities, such as dough strengthening and anti-staling. Synthetic food emulsifiers suffer from the stigma of chemical names on a product’s ingredient statement. Modern consumers are seeking products that are “all natural.” Fortunately, there are a number of natural ingredients that are surface-active, such as lecithin, milk proteins, and some protein-containing hydrocolloids. Mayonnaise, for example, is stabilized by egg yolk. This book can serve as both a guide for professionals in the food industry to provide an understanding of emulsifier functionality, and a stimulus for further innovation. Students of food science will find this to be a valuable resource.