Fish and marine invertebrates are important sources of nutrients for the world's population, and many species have exceptionally high market value because of their exquisite sensory properties. Both the utilization of the available catch in different forms and the market price are affected by the quality of the fish. Proteins and nonprotein nitroge­ nous compounds playa crucial role in the nutritional value and sensory quality of seafoods as well as in the suitability of different species to various forms of processing, preservation, and use in other branches of the food industry. This role of proteins results from their basic chemical and biochemical properties and functions in different tissues. A presenta­ tion of the actual state of knowledge on seafood nitrogenous compounds in one volume may contribute to a better understanding of the involve­ ment of these components in all stages of handling and processing fish. It has been possible to prepare this text thanks to the cooperative effort of an international group of specialists. The editors of the book are greatly indebted to all colleagues who have willingly contributed to this volume, sharing their knowledge and experience, as well as to all persons who have granted permission to use their previously published materials. viii Preface ix A large part of the book has been prepared during my sabbatical in the Department of Marine Food Science, National Taiwan Ocean University (NTOU) in Keelung, Taiwan.