What question did this study set out to answer?

To compare the accuracy, precision, and bias of the traditional Kjeldahl method and the Dumas combustion method for determining nitrogen and protein content across various dairy products.

May 1, 1998Journal of AOAC International

Routine Analysis of Proteins by Kjeldahl and Dumas Methods: Review and Interlaboratory Study Using Dairy Products

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Authors

PWPeter G. WilesFonterra (New Zealand)IGI. K. GrayFonterra (New Zealand)RKRoger KisslingFonterra (New Zealand)

Discussion

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Implication

Interlaboratory study reveals equivalent nitrogen quantification between Kjeldahl and Dumas methods in dairy products, suggesting combustion is suitable for standard routine testing.

Key Points

To compare the accuracy, precision, and bias of the traditional Kjeldahl method and the Dumas combustion method for determining nitrogen and protein content across various dairy products.
Conducted an interlaboratory trial involving 11 laboratories analyzing liquid milk, milk powders, whey protein concentrate, infant formula, casein, caseinate, and reference compounds (glycine and EDTA) using international standards.
Reviewed data from more than 10 published comparative trials to evaluate systematic error and consensus bias between the two nitrogen determination methods.
Overall mean nitrogen concentrations were 8.818 g N/100 g for the Kjeldahl method and 8.810 g N/100 g for the Dumas method, demonstrating no consistent or commercially concerning bias between methods.
For samples containing > 2 g N/100 g, the Dumas method exhibited superior precision, maintaining relative repeatability and reproducibility standard deviations of roughly 0.35% and 0.75%, whereas Kjeldahl precision values were significantly larger.

Cite This Study

Wiles et al. (1998) studied this question.

synapsesocial.com/papers/6a802d71826e8e37b93d4bc6 https://doi.org/10.1093/jaoac/81.3.620

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Implication

Interlaboratory study reveals equivalent nitrogen quantification between Kjeldahl and Dumas methods in dairy products, suggesting combustion is suitable for standard routine testing.

Routine Analysis of Proteins by Kjeldahl and Dumas Methods: Review and Interlaboratory Study Using Dairy Products

Discussion

Member takes

Implication

Key Points

Cite This Study

Routine Analysis of Proteins by Kjeldahl and Dumas Methods: Review and Interlaboratory Study Using Dairy Products

Discussion

Member takes

Implication

Key Points

Cite This Study

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