The safety of feed-grade amino acids is rarely questioned as it is assumed that commercial application of methionine and lysine over recent decades has been accomplished without undue problems. However, in the current regulatory setting it is important that safety standards are unequivocally established along prescribed protocols. In the EU, amino acids are regulated by Directive 82/471/EEC concerning 'Certain Products in Animal Nutrition' and amendments to this Directive. As the related Directive 83/228/EEC on 'Fixing Guidelines for the Assessment of Certain Products' only covers bioproteins, and not amino acids and analogues, usually Commission Directive 2001/79/EC amending Council Directive 87/153/EEC on 'Fixing Guidelines for the Assessment of Additives in Animal Nutrition' will be applied. Future developments will take this into account and re-arrange feed additive legislation. For registration of an additive, there is a detailed and long listing of tests, that have to be performed, e.g. identity, composition, physico-chemical and technological properties, methods of determination, stability, physiolog-
Table 26.9. Industrial production of amino acids.
Hydroxy analogue of methionine
Propylene, methyl mercaptan, methane, ammonia Acrolein, methyl mercaptan, hydrogen cyanide
Mol 3SS6Sj SUCJclCj starch products and their hydrolysates, N-source
Molasses, sugar, starch products and their hydrolysates, N-source Molasses, sugar, starch products and their hydrolysates, N-source
Chemical synthesis DL-Methionine; DL-methionine, sodium salt
Chemical synthesis DL-2-Hydroxy-4-methyI
mercaptobutyric acid, liquid
L-Lysine monohydrochloride; L-lysine concentrate (liquid); L-lysine monohydrochloride (liquid); L-lysine sulphate L-threonine
L-Tryptophan ical and toxicological studies, safety for target species, workers, users and consumers, residue studies and effect on the environment. In the USA, under Section 201(s) of the Federal Food, Drug, and Cosmetic Act, substances added to food, including substances intended for use in animal food (such as amino acids), are 'food additives' regulated by the Food and Drug Administration (FDA). The general safety provisions of the Act requires the FDA to determine whether each food additive proposed for use in food-producing animals is safe for intended animals and whether the edible products derived from treated animals are safe. The manufacturer is required to furnish to the FDA with the scientific data necessary for demonstrating that the residues of the sponsored compound in the edible products of treated animals are safe. In addition to safety concerns, the FDA may require data on the stability of the additive and the origin of the strain, toxicity and residues, if the additive is derived via fermentation technologies.
Regarding amino acids destined for human use, more stringent protocols and legislative measures are enforced. However, in the case of glutamine, Garlick (2001) reported that only four studies have been conducted to specifically assess its safety for intravenous and enteral administration in humans.
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