Comparison of Kjeldahl and Dumas methods for determining protein contents of soybean products

The Kjeldahl and Dumas methods for quantifying nitrogen content were compared using nine soybean products having protein contents ranging from 0.5 to 90%. In addition to comparing day‐to‐day variability of the Dumas method, differences between and variabilities of two Kjeldahl systems and Kjeldahl o...

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Bibliographic Details
Published in:Journal of the American Oil Chemists' Society 2003-12, Vol.80 (12), p.1169-1173
Main Authors: Jung, S, Rickert, D.A, Deak, N.A, Aldin, E.D, Recknor, J, Johnson, L.A, Murphy, P.A
Format: Article
Language:English
Subjects:
analytical methods
Animal, plant, fungal and microbial proteins, edible seaweeds and food yeasts
Biological and medical sciences
Dumas method
Dumas nitrogen
food analysis
Food industries
Fundamental and applied biological sciences. Psychology
Kjeldahl method
Kjeldahl nitrogen
nitrogen content
protein
protein content
soy protein
soybeans
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Summary:The Kjeldahl and Dumas methods for quantifying nitrogen content were compared using nine soybean products having protein contents ranging from 0.5 to 90%. In addition to comparing day‐to‐day variability of the Dumas method, differences between and variabilities of two Kjeldahl systems and Kjeldahl operators were also evaluated. The Kjeldahl method gave slightly, but significantly, lower values than did the Dumas method. Both the Kjeldahl and Dumas methods had equivalent variabilities (same SD about the means). The ratios between the means for the Kjeldahl and Dumas (K/D) protein values ranged from 0.66 to 1.03. The conversion equation y=−0.00536+0.97188x (R2=0.9997) was developed and validated to convert from Dumas to kjeldahl protein concentrations.
ISSN:0003-021X
1558-9331
DOI:10.1007/s11746-003-0837-3