Document Detail

Nitrogen-to-protein conversion factors for some cereal products in Japan.
MedLine Citation:
PMID:  18387100     Owner:  NLM     Status:  MEDLINE    
To evaluate a practical method of determining more accurately conversion factors for calculating the protein contents of foods from the total nitrogen content, 19 cereal products found in Japan were analyzed for total nitrogen, amino acid nitrogen, and amide nitrogen, and then the nitrogen-to-protein conversion factors were calculated. The average conversion factors were 5.75 for rice, 5.81 for wheat, and 5.95 for others. These values, corresponding to the proportion of the amino acid residue to amino acid nitrogen recovered from 20 amino acids, were lower than the currently applied factors to these foods, except for wheat flour and amaranth. The use of this factor for estimating the protein content results in a considerable difference from the estimate based on amino acid residue concentrations, due to the wide variations in amino acid composition and to the presence of a significant level of nonprotein nitrogen. The distribution of the protein nitrogen recovered from the amino acids to total nitrogen averaged 93%. Adjusted conversion factors corresponding to the proportion of the amino acid residue to total nitrogen averaged 5.26 for rice, 5.47 for wheat, and 5.54 for other cereal products. Protein contents estimated using these factors are in good agreement with the contents defined as amino acid residues.
S Fujihara; H Sasaki; Y Aoyagi; T Sugahara
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of food science     Volume:  73     ISSN:  1750-3841     ISO Abbreviation:  J. Food Sci.     Publication Date:  2008 Apr 
Date Detail:
Created Date:  2008-04-04     Completed Date:  2008-05-09     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0014052     Medline TA:  J Food Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  C204-9     Citation Subset:  IM    
Department of Human Nutrition, Seitoku University, 550 Iwase, Matsudo, Chiba 271-8555, Japan.
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MeSH Terms
Amides / analysis
Amino Acids / analysis
Cereals / chemistry*
Nitrogen / analysis*
Oryza sativa / chemistry
Plant Proteins / analysis*
Triticum / chemistry
Reg. No./Substance:
0/Amides; 0/Amino Acids; 0/Plant Proteins; 7727-37-9/Nitrogen

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