Protein nitrogen content

In vitro assays themselves take a few hours to complete. The protein nitrogen content of a sample must be known. Sample hydration can take one to several hours. Preparation of enzyme solutions takes vivo digestibility assays involve a feeding study, and the investigator faces similar issues as described for PER. 

Fig. 1. Comparison of the protein nitrogen content of chick embryos incubated in ovo under air and cultured in vitro on whole egg homogenate and chemically defined media under 75% air + 25% O, for 0-24 hours and 95% Oz -t- 5% COa for 24-48 and 48-72 hours. Zero time was 40 hours of preincubation in ovo. From Klein et al. (1964).

Protein Nitrogen Content op Embryos and Extraembryonic Mp.mbranes of Chick Embryos Cultured on Various Amounts of Ovalbumin and Conalbumin for 48 Hours ... 

Reductions in dietary protein level may decrease milk yield and, almost invariably, non-protein nitrogen content. Milk protein is httle affected until intake of protein falls below 60 per cent of requirement. This is probably due to an insufficiency of essential amino acids, primarily methionine, followed by threonine and tryptophan. When duodenal amino acid supply has been measured and deficient amino acids infused directly into the bloodstream, there have been large increases (approximately 5-8 g/kg) in milk protein content. The prediction of the amino acid profile at the small intestine in dairy cows is fraught with difficulties, and feeding studies that have attempted to rectify amino acid imbalances through supplementation have produced variable results. 

Table 6. Crude protein and non-protein nitrogen content of flaxseed meal extracted with different solvent systems ...

A further approach to the diagnosis of sulphur deficient plants is the use of amide nitrogen content as an indicator of sulphur deficiency, based on the fact that insufficient sulphur for protein synthesis increased the non-protein nitrogen content of the plant. The method... 

Crude protein = %nitrogen X 6.25. Does not accurately reflect true protein content. Algal cells may contain nonprotein nitrogen substances, eg, 4—6% nucleic acids, dry wt basis. 

Standard method of estimating percent protein from nitrogen content (% N). 

The constraint of extruding whey protein above the useful texturization range is keeping the temperature below the point where pyrolysis will occur as evidenced by relatively constant nitrogen content. However, texturized whey products are sometimes extruded at 150 °C to form... 

Smithies, Gibbons, and Bayley reported a relatively high nitrogen content in the walls of several halophilic bacteria which indicated that the cell material was predominantly protein. They contained only small amounts of lipides. The cell walls were lipoprotein. 

It should be noticed that the formulas shown in Table 3.3 give different compositions of the organic fractions. As an example, the nitrogen content of protein according to the formulas proposed by Henze et al. (1995b) and Kalyuzhnyi et al. (2000) is 8.8% and 16.7%, respectively. 

PER) was modified in several respects. The diets were calculated on a 10 percent protein level rather than on an isonitrogenous basis. This was done because the nitrogen factors of the various blend components varied appreciably from the 6.25 nitrogen factor assumed in the AOAC procedure. A composite nitrogen factor for each blend was calculated from analytical results by dividing the total amino acid content by the nitrogen content. In this manner,... 

The diet must provide those amino acids which the body cannot synthesize (essential amino acids, EAA) and nitrogen in the form of nonessential amino acids (NEA). Both EAA and NEA are required for biosynthesis of proteins and other nitrogen-containing compounds necessary for homeostasis or growth. Thus, the total nitrogen content of a specific food must be considered to be nutritionally significant. 

The Kjeldahl method measures the nitrogen content of a compound and may be used to determine the protein content of a sample provided that the proportion of nitrogen in the protein is known. Protein determinations are complicated by the presence of nitrogen from non-protein sources. The simplest way of eliminating this source of error is to precipitate the proteins using a suitable method and to determine the nitrogen content of the precipitate. 

The nitrogen content of proteins is usually accepted as 16% of the total weight but this may not always be correct as values for individual proteins do differ. This is particularly true if the protein has either a high proportion of basic amino acids (additional nitrogen atoms) or is a conjugated protein with an appreciable non-protein component (Table 11.1). 

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