The Jones factors do not include the NPN fraction. What is true? For a food with a high NPN fraction, a conversion factor that includes this NPN fraction has to be

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| * Note that the Jones’ factors are based on protein nitrogen only and do not include NPN. However, in food composition databases, the protein contents in a food is based on the total amount of N measured in that food. For research purposes, a few laboratories may correct for the NPN fraction. ** The value of 16gN/100 g protein is only an example. This value differs between food as was explained on the previous page. |

The figure below shows how the Jones factors have been determined.

Not right. The Jones'factor does not include the NPN fraction. If you calculate the protein contents of a food by multiplying the TOTAL nitrogen fraction by a factor, you will overestimate the protein contents, because in theory you should only use the protein- nitrogen fraction for this calculation (i.e. the total nitrogen fraction - NPN fraction). Consequently the conversion factor should be lower to prevent overestimation.

Right.

a
b
c

higher than the Jones factor

lower than the Jones factor

the same as the Jones factor