Total nitrogen vs. amino-acid profile as indicator of protein content of beef
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Date
Authors
Hall, Nicolette Gibson
Schonfeldt, H.C. (Hettie Carina)
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier
Abstract
In most cited food composition studies and tables, the proximate system measures protein as total nitrogen (N) (determined by Kjeldahl or Dumas method) multiplied by a specific factor. A factor of 6.25 is used for determining total protein from total N (Jones, Munsey, & Walker, 1942). Although more expensive, it is considered more accurate to base protein content of foods on amino acid data (Greenfield & Southgate, 2003).
A study on the nutrient composition of beef analysed the full amino-acid profile of fifteen retail cuts from three age groups and six fat codes, as well as determined total nitrogen content to determine proximate protein composition. For all cuts, the correlation coefficient of total amino acids to protein (N × 6.25) was 0.635. This indicates a poor correlation for predicting actual protein content (as determined by total amino acid count), based on the nitrogen factor of 6.25. On average, the sum of amino acids per cut amounted to 91% of total determined protein (N × 6.25) for the same cut.
Description
Keywords
Nitrogen, Amino acid (AA), Protein content, South African beef
Sustainable Development Goals
Citation
Hall, NG & Schönfeldt, HC 2013, 'Total nitrogen vs. amino-acid profile as indicator of protein content of beef', Food Chemistry, vol. 140, no. 3, pp. 608-612.