Non-protein nitrogen

Nitrogen soluble in 12% TCA is referred to as non-protein nitrogen (NPN), of which milk contains 250-300mgl i.e. 5-6% of total milk nitrogen. The NPN is a very heterogeneous fraction (Table 4.7). 

The unaccounted N includes some phospholipids, amino sugars, nucleotides, hippuric acid and orotic acid. The a-amino N includes free amino acids and small peptides almost a complete range of amino acids, including ornithine, has been identified in milk, but glutamic acid predominates. 

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Atkinson, S.A. 1985 Characterization of the non-protein nitrogen fraction of human milk methodological considerations. In Jensen, R.G. and Neville, M.C., eds.. Human Lactation. Milk Components and Methodologies. New York, Plenum Press 39-43. 

Fresh and stored yams were examined for protein and selected nitrogen-metabolizing enzymes. Yams stored at room temperature lost weight (water), protein, and non-protein nitrogen. Sprouting depleted all of the protein. The major protein of yams is a 60-70%... 

Synthetic nitrogen or non-protein nitrogen compounds shall not be used. Specific criteria for additives and processing aids state ... 

Research findings reviewed by Ravindran and Blair (1993) suggest that the type of insect preferred by poultry is soft-bodied. Insects are high in CP, with contents ranging from 420 to 760 g/kg (Ravindran and Blair, 1993). Accurate determination of protein levels in insect meals, however, requires correction for the non-protein nitrogen contributed by the chitin. 

Henry RJ. 1964. Non-protein nitrogenous constituents. Clinical chemistry principles and technics. Los Angeles, CA Harper Row, 325-331. 

In Switzerland, 92% of the whey is used for pig feed. Reaction with urea to form lactosyl urea permits greater quantities of non-protein nitrogen to be used in ruminant feeds. 

Synthesis of microbial protein from protein and non-protein nitrogen in the diet. The microbial protein is later digested and the amino acids used by the host. 

Rettgerl Berman and St urges, 1916. Further studies an bacterial nutrition the utilisation of protein and non-protein nitrogen. Journal of Bacteriology, Vd. 1, pp. 15-33. 

Urine is an aqueous solution of inorganic and organic compounds including mineral substances, nitrogen compounds from protein metabolism, as well as of non-protein nitrogen compounds, vitamins, hormones and enzymes. 

In addition to the caseins and whey proteins, milk contains two other groups of proteins or protein-like material, i.e. the proteose-peptone fraction and the non-protein nitrogen (NPN) fraction. These fractions were recognized as early as 1938 by Rowland but until recently very little was... 

Total nitrogen = Kjeldahl I Casein = Kjeldahl I-Kjeldahl n Non-protein nitrogen = Kjeldahl III... 

NCN, Non-casein nitrogen NPN, non-protein nitrogen TN, total nitrogen. 

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