Based on your knowledge of proteins in food do you think it is reasonable to use the same conversion factor for all foods?

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When nitrogen values for a food are known, the protein contents is estimated by multiplying the nitrogen contents by a nitrogen-to-protein conversion factor; this factor is often set at 6.25. This factor (dating back to the 19th century) assumes that all organic nitrogen originates from protein and that the nitrogen contents of protein is 16 %. (Note that 100/16 = 6.25). Protein values based on these calculations

(N x 6.25) are called ‘crude’ protein.

Not right. You selected one or more statements that are not right. If you take a look to food composition data you can easily see that foods differ with respect to their protein content and therefore also with respect to nitrogen content.

Not right. You selected one or more statements that are not right. Proteins do differ with respect to their nitrogen content. The nitrogen content of proteins depends on its amino acid composition.

Not right. You selected one or more statements that are not right. Foods contain also (a small) non protein nitrogen (NPN) fraction: substances such as urea, ammonia, nitrates, certain phospholipids etc. also contain nitrogen.

Not right. You selected one or more statements that are not right. Although different foods do contain different amounts of protein and nitrogen, this is not a reason for not using the same protein-to-nitrogen conversion factor for all foods.

Not right. There are more statements that are right. Remember that the nitrogen content of proteins varies, depending on the specific amino acid composition of the protein. Some foods contain mainly proteins that are rich in nitrogen rich amino acids, while other foods contain amino acids that consist of less nitrogen. Therefore it is reasonable to use different conversion factors for different foods.

Not right. There are more statements that are right. Foods also contain non protein nitrogen (NPN). To convert nitrogen values to protein values using a conversion factor, this conversion factor should take this NPN fraction into account. Since the amount of this NPN fraction differs between foods, different conversion factors should be used for different foods.

Right! So it is reasonable to have food specific nitrogen-to-protein conversion factors

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Yes, because all foods contain approximately the same amount of protein.

Yes, because all foods contain approximately the same amount of nitrogen.

Yes, because all proteins contain the same amount of nitrogen.

Yes, because nitrogen in food only comes from proteins.

No, because all foods contain different amounts of protein.

No, because all foods contain different amounts of nitrogen.

No, because the nitrogen content varies between proteins.

No, because nitrogen in foods not only comes from proteins.