Mendel Friedman - Böcker

A variety of processing methods are used to make foods edible; to pennit storage; to alter texture and flavor; to sterilize and pasteurize food; and to destroy microorganisms and other toxins. These methods include baking, broiling, cooking, freezing, frying, and roasting. Many such efforts have both beneficial and harmful effects. It is a paradox of nature that the processing of foods can improve nutrition, quality, safety, and taste, and yet occasionally lead to the formation of anti-nutritional and toxic compounds. These multifaceted consequences of food processing arise from molecular interactions among nutrients with each other and with other food ingredients. Since beneficial and adverse effects of food processing are of increasing importance to food science, nutrition, and human health, and since many of the compounds formed have been shown to be potent carcinogens and growth inhibitors in animals, I organized a symposium broadly concerned with the nutritional and toxicological consequences of food processing. The symposium was sponsored by the American Institute of Nutrition (AIN) -Federation of American Societies for Experimental Biology (FASEB) for its annual meeting in Washington, D.C., April 1-5, 1990. Invited speakers were asked to develop at least one of the following topics: 1. Nutrient-nonnutrient interactions between amino acids, proteins, carbohydrates, lipids, minerals, vitamins, tannins, fiber, natural toxicants, etc. 2. Effects of radiation. 3. Thermally induced formation of dietary mutagens, antimutagens, carcinogens, anticarcinogens, antioxidants, and growth inhibitors. 4. Effects of pH on nutritional value and safety.

Reports that heat processing of foods induces the formation of acrylamide heightened interest in the chemistry, biochemistry, and safety of this compound. Acrylamide-induced neurotoxicity, reproductive toxicity, genotoxicity, and carcinogenicity are potential human health risks based on animal studies. Because exposure of humans to acrylamide can come from both external sources and the diet, there exists a need to develop a better understanding of its formation and distribution in food and its role in human health. To contribute to this effort, experts from eight countries have presented data on the chemistry, analysis, metabolism, pharmacology, and toxicology of acrylamide. Specifically covered are the following aspects: exposure from the environment and the diet; biomarkers of exposure; risk assessment; epidemiology; mechanism of formation in food; biological alkylation of amino acids, peptides, proteins, and DNA by acrylamide and its epoxide metabolite glycidamide; neurotoxicity, reproductive toxicity, and carcinogenicity; protection against adverse effects; and possible approaches to reducing levels in food. Cross-fertilization of ideas among several disciplines in which an interest in acrylamide has developed, including food science, pharmacology, toxicology, and medicine, will provide a better understanding of the chemistry and biology of acrylamide in food, and can lead to the development of food processes to decrease the acrylamide content of the diet.

Containing 45 papers written by outstanding international authors from 14 countries, this three-volume compendium brings together the elements needed to understand the factors which influence the utilization of amino acids. The wide-ranging topics include descriptions of metabolic pathways and mechanisms of the biological utilization of amino acids, as well as factors that influence amino acid bioavailability in enteral and parenteral nutrition. The use of amino acids to improve the quality and safety of the diet is presented. Also discussed are amino acid precursors of biogenic amines and the role of amino acids in atherosclerosis, cancer, and immunity. Scientists from many disciplines will benefit from this broad overview.

Containing 45 papers written by outstanding international authors from 14 countries, this three-volume compendium brings together the elements needed to understand the factors which influence the utilization of amino acids. The wide-ranging topics include descriptions of metabolic pathways and mechanisms of the biological utilization of amino acids, as well as factors that influence amino acid bioavailability in enteral and parenteral nutrition. The use of amino acids to improve the quality and safety of the diet is presented. Also discussed are amino acid precursors of biogenic amines and the role of amino acids in atherosclerosis, cancer, and immunity. Scientists from many disciplines will benefit from this broad overview.

Containing 45 papers written by outstanding international authors from 14 countries, this three-volume compendium brings together the elements needed to understand the factors which influence the utilization of amino acids. The wide-ranging topics include descriptions of metabolic pathways and mechanisms of the biological utilization of amino acids, as well as factors that influence amino acid bioavailability in enteral and parenteral nutrition. The use of amino acids to improve the quality and safety of the diet is presented. Also discussed are amino acid precursors of biogenic amines and the role of amino acids in atherosclerosis, cancer, and immunity. Scientists from many disciplines will benefit from this broad overview.

Reports that heat processing of foods induces the formation of acrylamide heightened interest in the chemistry, biochemistry, and safety of this compound. Acrylamide-induced neurotoxicity, reproductive toxicity, genotoxicity, and carcinogenicity are potential human health risks based on animal studies. Because exposure of humans to acrylamide can come from both external sources and the diet, there exists a need to develop a better understanding of its formation and distribution in food and its role in human health. To contribute to this effort, experts from eight countries have presented data on the chemistry, analysis, metabolism, pharmacology, and toxicology of acrylamide. Specifically covered are the following aspects: exposure from the environment and the diet; biomarkers of exposure; risk assessment; epidemiology; mechanism of formation in food; biological alkylation of amino acids, peptides, proteins, and DNA by acrylamide and its epoxide metabolite glycidamide; neurotoxicity, reproductive toxicity, and carcinogenicity; protection against adverse effects; and possible approaches to reducing levels in food. Cross-fertilization of ideas among several disciplines in which an interest in acrylamide has developed, including food science, pharmacology, toxicology, and medicine, will provide a better understanding of the chemistry and biology of acrylamide in food, and can lead to the development of food processes to decrease the acrylamide content of the diet.

Metal ions and proteins are ubiquitous. Therefore, not surprisingly, new protein-metal interactions continue to be dis­ covered, and their importance is increasingly recognized in both physical and life sciences. Because the subject matter is so broad and affects so many disciplines, in organizing this Symposium, I sought participation of speakers with the broadest possible range of interests. Twenty-two accepted my invitation. To supplement the verbal presentations, the Proceedings include five closely re­ lated invited contributions. The ideas expressed are those of the various authors and are not necessarily approved or rejected by any agency of the United States Government. No official recommendation concerning the sub­ ject matter or products discussed is implied in this book. This book encompasses many aspects of this multifaceted field. Topics covered represent biochemical, immunochemical, bioorganic, biophysical, metabolic, nutritional, medical, physiological, toxi­ cological, environmental, textile, and analytical interests. The discoveries and developments in any of these areas inevitably illumine others. I feel that a main objective of this Symposium, bringing together scientists with widely varied experiences yet with common interests in protein-metal interactions, so that new understanding and new ideas would result has been realized. I hope that the reader enjoys and benefits from reading about the fascinat­ ing interactions of metal ions and proteins as much as I did.

The word crosslinking implies durable combination of (usually large) distinct elements at specific places to create a new entity that has different properties as a result of the union. In the case of proteins, such crosslinking often results in important changes in chemical, functional, nutritional, and biomedical properties, besides physical properties simply related to molecular size and shape. (Nucleic acids, carbohydrates, and other biopolymers are correspondingly affected.) Since proteins are ubiquitous, the consequences of their crosslinking are widespread and often profound. Scientists from many disciplines including organic chemistry, bio­ chemistry, protein chemistry, food science, nutrition, radiation biology, pharmacology, physiology, medicine, and dentistry are, therefore, minutely interested in protein crosslinking reactions and their implications. Because protein crosslinking encompasses so many disciplines, in organizing the Symposium on Nutritional and Biochemical Conse­ quences of Protein Crosslinking sponsored by the Protein Subdivi­ sion of the Division of Agricultural and Food Chemistry of the American Chemical Society, I sought participants with the broadest possible range of interests, yet with a common concern for theore­ tical and practical aspects of protein crosslinking. An important function of a symposium is to catalyze progress by bringing together ideas and experiences needed for interaction among different, yet related disciplines. To my pleasant surprise, nearly everyone invited came to San Francisco to participate.

The nutritional quality of a protein depends on the proportion of its amino acids-especially the essential amino acids-their physio­ logical availability, and the specific requirements of the consumer. Availability varies and depends on protein source, interaction with other dietary components, and the consumer's age and physiological state. In many foods, especially those from plants, low levels of various essential amino acids limits their nutritive value. This is particularly important for cereals (which may be inadequate in the essential amino acids isoleucine, lysine, threonine, and tryto­ phan) and legumes (which are often poor sources of methionine). Moreover, these commodities are principle sources of protein for much of the earth's rapidly growing population. At the current annual growth rate of about 2 percent, the world population of about 4 billion will increase to 6.5 billion by the year 2000 and to 17 billion by the year 2050. Five hundred milliQn people are presently estimated to suffer protein malnutrition, with about fifteen thousand daily deaths. The ratio of malnourished to adequately nourished will almost surely increase. For these reasons, and especially in view of the limited availability of high quality (largely animal) protein to feed present and future populations, improvement of food and feed quality is especially important.

Naturally occurring antinutrients and food toxicants, and those formed during food processing, adversely affect the nutri­ tional quality and safety of foods. Because of the need to improve food quality and safety by plant breeding, fortification with appropriate nutrients, and processing methods, and because of the growing concern about possible direct relationships between diet and diseases, research is needed to: (1) evaluate the nutritive quality and safety of crops and fortified, supplemented, and processed foods; (2) define conditions that favor or minimize the formation of nutritionally antagonistic and toxic compounds in foods; and (3) define the toxicology, metabolism, and mechanisms of the action of food ingredients and their metabolites. As scientists interested in improving the safety of the food supply, we are challenged to respond to the general need for exploring: (1) possible adverse consequences of antinutrients and food toxicants; and (2) factors which contribute to the formation and inactivation of undesirable compounds in foods. Medical research offers an excellent analogy. Studies on causes and mechanisms of disease processes are nearly always accompanied by parallel studies on preventive measures and cures. Such an approach offers the greatest possible benefits to the public.

Soybean protei ns are wi de 1 y used inhuman foods ina vari ety of forms, including baby formulas, flour, soy protein concentrates, soy protein isolates, soy sauces, textured soy fibers, and tofu. The presence of inhibitors of digestive enzymes in soy proteins impairs nutritional quality and possible safety of this impportant legume. Normal processing conditions based on the use of heat do not completely inactivate these inhibitors, so that residual amounts of plant protease inhibitors are consumed by animals and man. Inhibitors of digestive enzymes are present not only in legumes, such as soybeans, lima beans, and kidney beans, but also in nearly all plant foods, including cereals and potatoes, albeit in much smaller amounts. The antinutritional effects of inhibitors of proteolytic enzymes have been widely studied and can be ameliorated by processing and/or sulfur amino acid fortification. A more urgent concern is reports that rats fed diets containing even low levels of soybean-derived inhibitors, which are found in foods such as soy-based baby formulas, may develop over their lifespan pancreatic lesions leading eventually to neoplasia or tumor formation. On the other hand, recent stUdies suggest that certain enzyme inhibitors from plant foods may prevent cancer formation in other tissues. A key question, therefore, is whether inhibitors from plant foods constitute a human health hazard.

The word crosslinking implies durable combination of usually large, distinct elements at specific places to create a new entity that has different properties as a result of the union. In the case of proteins, such crosslinking often results in important changes in chemical, physical, functional, nutritional, and biome­ dical properties, besides physical properties simply related to molecular size and shape. (Nucleic acids, carbohydrates~ glyco­ proteins, and other biopolymers are correspondingly affected.) Since proteins are ubiquitous, the consequences of their crosslin­ king are widespread and often profound. Scientists from many dis­ ciplines including organic chemistry, biochemistry, protein chemis­ try, food science, nutrition, radiation biology, pharmacology, physiology, medicine, and dentistry are, therefore, very much inte­ rested in protein crosslinking reactions and their implications. Because protein crosslinking encompasses so many disciplines, in organizing the Symposium on Nutritional and Biochemical Consequences of Protein Crosslinking sponsored by the Protein Subdivision of the Division of Agricultural and Food Chemistry of the American Chemical Society, I sought participants with the broadest possible range of interests, yet with a common concern for theoretical and practical aspects of protein crosslinking. An important function of a symposium is to catalyze progress by bringing together ideas and experiences needed for interaction among different, yet related disciplines. To my pleasant surprize, nearly everone invited came to San Francisco to participate.