The DOI matches its Crossref record.
Converting Nitrogen into Protein—Beyond 6.25 and Jones' Factors
Open accessAbstract
The protein content in foodstuffs is estimated by multiplying the determined nitrogen content by a nitrogen-to-protein conversion factor. Jones' factors for a series of foodstuffs, including 6.25 as the standard, default conversion factor, have now been used for 75 years. This review provides a brief history of these factors and their underlying paradigm, with an insight into what is meant by "protein." We also review other compelling data on specific conversion factors which may have been overlooked. On the one hand, when 6.25 is used irrespective of the foodstuff, "protein" is simply nitrogen expressed using a different unit and says little about protein (s.s.). On the other hand, conversion factors specific to foodstuffs, such as those provided by Jones, are scientifically flawed. However, the nitrogen:protein ratio does vary according to the foodstuff considered. Therefore, from a scientific point of view, it would be reasonable not to apply current specific factors any longer, but they have continued to be used because scientists fear opening the Pandora's box. But because conversion factors are critical to enabling the simple conversion of determined nitrogen values into protein values and thus accurately evaluating the quantity and the quality of protein in foodstuffs, we propose a set of specific conversion factors for different foodstuffs, together with a default conversion factor (5.6). This would be far more accurate and scientifically sound, and preferable when specifically expressing nitrogen as protein. These factors are of particular importance when "protein" basically means "amino acids," this being the principal nutritional viewpoint.
Overview
The claims and statistics of this paper haven’t been checked yet.
Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.
Integrity signals
Registry
Cites
Statistics
Verification
Claims the paper makes
The claims and statistics of this paper haven’t been checked yet.
Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.
Self-check
Percentages, sums and reported differences re-computed from the paper’s own numbers.
The self-check needs the paper’s full text.
Citations
Cited by
Protein content and amino acid composition of commercially available plant-based protein isolates
Gorissen, S. H. M., Crombag, J. J. R., Senden, J. M. G., Waterval, W. A. H., Bierau, J., Verdijk, L. B., & van Loon, L. J. C. (2018) · Amino Acids · doi:10.1007/s00726-018-2640-5 · Cited by 1,169
The protein content of seaweeds: a universal nitrogen-to-protein conversion factor of five
Angell, A. R., Mata, L., de Nys, R., & Paul, N. A. (2016) · Journal of Applied Phycology · doi:10.1007/s10811-015-0650-1 · Cited by 442
Microalgae of interest as food source: biochemical composition and digestibility.
Niccolai, A., Chini Zittelli, G., Rodolfi, L., Biondi, N., & Tredici, M. R. (2019) · Algal Research · doi:10.1016/j.algal.2019.101617 · Cited by 403
Mæhre, H. K., Malde, M. K., Eilertsen, K., & Elvevoll, E. O. (2014) · Journal of the Science of Food and Agriculture · doi:10.1002/jsfa.6681 · Cited by 374
Gold, M., Cassar, C. M., Zurbrügg, C., Kreuzer, M., Boulos, S., Diener, S., & Mathys, A. (2020) · Waste Management · doi:10.1016/j.wasman.2019.10.036 · Cited by 320
Tanger, C., Engel, J., & Kulozik, U. (2020) · Food Hydrocolloids · doi:10.1016/j.foodhyd.2020.105949 · Cited by 280
Lucian, M., Volpe, M., Merzari, F., Wüst, D., Kruse, A., Andreottola, G., & Fiori, L. (2020) · Bioresource Technology · doi:10.1016/j.biortech.2020.123734 · Cited by 121
Identification of Bacteria in Two Food Waste Black Soldier Fly Larvae Rearing Residues
Gold, M., von Allmen, F., Zurbrügg, C., Zhang, J., & Mathys, A. (2020) · Frontiers in Microbiology · doi:10.3389/fmicb.2020.582867 · Cited by 109
Quitain, A. T., Kai, T., Sasaki, M., & Goto, M. (2013) · Industrial & Engineering Chemistry Research · doi:10.1021/ie400527b · Cited by 97
Mixing plant-based proteins: Gel properties of hemp, pea, lentil proteins and their binary mixtures
Guidi, S., Formica, F. A., & Denkel, C. (2022) · Food Research International · doi:10.1016/j.foodres.2022.111752 · Cited by 83
Pinckaers, P. J. M., Kouw, I. W. K., Hendriks, F. K., van Kranenburg, J. M. X., de Groot, L. C. P. G. M., Verdijk, L. B., Snijders, T., & van Loon, L. J. C. (2021) · British Journal Of Nutrition · doi:10.1017/s0007114521000635 · Cited by 76
Calorie delivery and clinical outcomes in the critically ill: a systematic review and meta-analysis
Parikh, H. G., Miller, A., Chapman, M., Moran, J. L., & Peake, S. L. (2016) · Critical Care and Resuscitation · doi:10.1016/s1441-2772(23)00927-4 · Cited by 69
Hochstenbach-Waelen, A., Veldhorst, M. A., Nieuwenhuizen, A. G., Westerterp-Plantenga, M. S., & Westerterp, K. R. (2009) · The American Journal of Clinical Nutrition · doi:10.3945/ajcn.2008.26917 · Cited by 68
Pinckaers, P. J., Kouw, I. W., Gorissen, S. H., Houben, L. H., Senden, J. M., Wodzig, W. K., de Groot, L. C., Verdijk, L. B., Snijders, T., & van Loon, L. J. (2022) · The Journal of Nutrition · doi:10.1093/jn/nxac222 · Cited by 70
Lee, Y. E. J., Goh, H. M., & Huang, D. (2025) · Food Hydrocolloids · doi:10.1016/j.foodhyd.2024.110664 · Cited by 32
Verkempinck, S. H. E., Duijsens, D., Mukherjee, A., & Wilde, P. J. (2024) · Food & Function · doi:10.1039/d3fo04225a · Cited by 28
Multi-Step Biomass Fractionation of Grape Seeds from Pomace, a Zero-Waste Approach
Salem, Y., Rajha, H. N., van den Broek, L. A. M., Safi, C., Togtema, A., Manconi, M., Manca, M. L., Debs, E., Hobaika, Z., Maroun, R. G., et al. (2022) · Plants · doi:10.3390/plants11212831 · Cited by 22
Logan, L. A. P., Latty, T., & Roberts, T. H. (2021) · Journal of Applied Entomology · doi:10.1111/jen.12878 · Cited by 19
Gregersen, S., Pertseva, M., Marcatili, P., Holdt, S. L., Jacobsen, C., García-Moreno, P. J., Hansen, E. B., & Overgaard, M. T. (2022) · Algal Research · doi:10.1016/j.algal.2021.102619 · Cited by 15
Farkas, A., Szabó, E., Horváth, A., Jaksics, E., Németh, R., & Tömösközi, S. (2023) · Journal of Cereal Science · doi:10.1016/j.jcs.2023.103761 · Cited by 6
Gregersen Echers, S., Abdul-Khalek, N., Jensen, N. H., Jørgensen, A. K., Mattsson, T., Jørgensen, M. K., Lübeck, P. S., & Lübeck, M. (2026) · Sustainable Food Technology · doi:10.1039/d5fb00771b · Cited by 5
Binkanat, T. B., & Ozkan, A. (2026) · Algal Research · doi:10.1016/j.algal.2025.104489 · Cited by 2
Metadata
- Authors
- Mariotti, F., Tomé, D., & Mirand, P. P.
- Venue
- Critical Reviews in Food Science and Nutrition
- Publisher
- Informa UK Limited
- Published
- 2008-01-31
- Volume
- 48
- Issue
- 2
- Pages
- 177-184
- ISSN
- 1040-8398 (ISSN-L)
- 1549-7852
- OpenAlex
- W2171737233
- Cited by
- 1,400
- References
- 0
- FWCI
- 12.22
- Type
- journal article
- Language
- en
- Open access
- green
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
Are you an author, or do you see a problem with this page? Request a review
Data sources
Bibliographic data: Semantic Scholar, OpenAlex, Crossref.
Contains information from the Semantic Scholar Academic Graph Datasets, made available under the ODC Attribution License (ODC-BY 1.0).
Semantic Scholar’s data is described in: Kinney, R., et al. (2023). The Semantic Scholar Open Data Platform. arXiv:2301.10140.
