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In this case you learned:

1. That all food composition data bases contain values on total protein. Most of the time this value is calculated based on total nitrogen. This requires the use of appropriate nitrogen-to-protein conversion factors. Interpreting protein values in food composition databases is only possible if the conversion factor is reported, including information on the source of this conversion factor.

2. Some databases also contain specific amino acid data. Determination of the amino acid profile requires hydrolysis, separation and detection of amino acids. Some amino acids are sensitive to degradation during the hydrolysis step. To interpret amino acid values in food composition databases it is necessary to consult the original source of the data to get information about the hydrolysis and separation methods that were used.

Further readings:

• Greenfield, H. and Southgate D.A.T.(2003). Food composition data, production, management and use. 2nd edition. FAO, pp 101-106.

• Dierckx, S et al (2000). Analysis of proteins, peptides and amino acids in foods (R.A. Meyers. Ed). John Wiley & Sons, Chichester, pp. 4182-4203.

• Van Camp, J and Dierckx, S (2004). Analysis of proteins in foods. In L. Nollet (Ed). Handbook of food analysis. Vol 1.: Physical characterization and nutrients analysis. Marcel Dekker Inc. New York. Chapter 7, pp 167-202.