Trace Elements in Food
Contents: Preface. 1. Copper. 2. Lead. 3. Zinc. 4. Tin. 5. Arsenic. 6. Antimony. 7. Selenium. 8. Iron. 9. Nickel. 10. Cobalt. 11. Manganese. 12. Iodine. 13. Bromine. 14. Fluorine. 15. Boron. 16. Silicon. 17. Aluminium. 18. Silver. 19. Cadmium. 20. Chromium. 21. Bismuth. 22. Mercury. 23. Molybdenum. 24. Vanadium. 25. Titanium. 26. Indium. 27. Barium Strontium. 28. Lithium and other metals. Index.
"The term \'trace element\' is usually applied in the biological sense to those elements which, in extremely small amounts, play some part in the nutrition of plants or animals. It may equally well be applied to the larger number which have for the food chemist a toxicological rather than nutritional interest, and the presence of which in food must, on public health grounds, be subject to close scrutiny and control.
There is for most trace elements a wide range between those quantities which are by common consent innocuous or even essential to health, and those which show signs of being injurious. To decide on the limits within this range to which foods should conform is not easy, and it is one of the trials of the food chemist that he is so often called upon for an expert opinion in the absence of any pronouncement, statutory or otherwise, by higher authority. He must therefore have as wide a knowledge as possible of all the questions involved; the biochemistry, nutritional significance and toxicology of trace elements; how far their presence in food is due to their being essential or occasional constituents of plants, or to the use of their compounds in agricultural practice; the many ways in which they may gain access to food from manufacturing processes or commercial usage; the bearing of existing Acts and regulations; and finally the determination of trace elements in animal and plant tissues and in foods. An attempt is made to give a comprehensive survey of the whole field.
In this book included among trace elements those which may be present in the human body, and in most foods, in amounts up to 0.005 per cent. This brings in iron, which is not usually regarded as a trace element in the body but is certainly so in food.
Trace elements may be roughly grouped according to whether they are essential or non-essential to life, toxic or non-toxic in moderate excess, universally distributed or of casual occurrence. Of the twenty or so which occur commonly in foods about five or six only are known to be necessary to human or animal life (copper, zinc, iron, manganese, iodine, and to a limited extent cobalt). Three more (Boron, Molybdenum and Silicon) are apparently essential only to plant life. Of the others a few occur spasmodically in plants (e.g. Selenium), while a good many (lead, tin, arsenic, antimony, cadmium, nickel, etc.) gain access to food from industrial processes. Some of them are highly toxic, others are relatively harmless. Elements closely related chemically do not necessarily show any resemblance in their biological behaviour, toxicity or effects on food, and each of them must be considered separately according to its particular characteristics. The arrangement of the elements depends partly upon their relative significance as constituents of food and partly on their chemical relationships.
The analytical sections are in the form of a general outline rather than a detailed laboratory guide; a companion to, and not a substitute for, existing literature on the subject. Discussion is confined for the most part to salient points and principles, and for each elements several alternative methods are reviewed and compared. Emphasis is laid on those suitable for general work rather than on specialized methods used in routine control." (jacket)
