what is protein conversion factor

by Avery Heathcote Published 2 years ago Updated 2 years ago

The protein content in a foodstuff is estimated by multiplying the nitrogen content by a nitrogen-to-protein conversion factor, usually set at 6.25. This historical factor (dating back to the 19th century) assumes the nitrogen content of proteins to be 16%.Apr 22, 2019

Is there a difference between protein and nitrogen conversion factors?

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.).

How do you calculate the protein content of food?

Why are conversion factors important in food science?

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).

What is the correct conversion factor for soy protein?

Soy protein has been the subject of considerable debate since publication of the “Jones factors” in 1931, which based the soy conversion factor of 5.71 on the nitrogen content of glycinin. Nonetheless, 6.25 is still used by the soy industry, analytic associations, and government regulatory bodies.

Why is 6.25 the protein factor for most foods?

Historically, 6.25 was applied to all proteins based on two assumptions: (1) all proteins had a nitrogen content of 16% (100/16 = 6.25) and (2) all nitrogen was derived from protein.

Why is the conversion factor from Kjeldahl nitrogen to protein different for various foods?

The conversion from Total Kjeldahl Nitrogen to protein depends on the type of protein present in the sample and what fraction of the protein is composed of nitrogenous amino acids, like arginine and histidine. Different proteins need different correction factors because they have different amino acid sequences.

How do you calculate protein equivalent?

The protein equivalent of nonprotein nitrogen appearance (PNPNA), which, in the individual patient, is equal to PNA minus protein losses, should reflect the net protein intake in the steady state, that is, the total intake of protein by oral and other routes, minus losses of protein in dialysate and urine.

Why is nitrogen in protein?

Nitrogen is one of the main body components, required for protein synthesis and production of several nitrogenous compounds such as hormones, neurotransmitters, and components of antioxidant defense.

What is a factor for converting nitrogen to protein?

N x 6.25On the basis of early determinations, the average nitrogen (N) content of proteins was found to be about 16 percent, which led to use of the calculation N x 6.25 (1/0.16 = 6.25) to convert nitrogen content into protein content. This use of a single factor, 6.25, is confounded by two considerations.

What is the principle of Kjeldahl method?

What is the principle of Kjeldahl method? The Kjeldahl method was developed by a brewer called Johann Kjeldahl in 1883. The protocol is built on the principle that strong acid helps in the digestion of food so that it releases nitrogen which can be determined by a suitable titration technique.

What is protein formula?

Protein invariably have the general formula RCH(NH2)COOH, where C is carbon, H is hydrogen, N is nitrogen, O is oxygen, and R is a group, varying in composition and structure, called a side chain.

How do I measure 30 grams of protein?

A standard 3- to 4-ounce serving (the size of a deck of cards or the palm of your hand) of boneless, skinless chicken breast will give you about 30 grams of protein.

How much protein is too much?

Studies show higher intakes — those more than 40 grams — in one sitting are no more beneficial than the recommended 15–30 grams at one time. Don't waste your money on excessive amounts.

What is the smallest unit of protein?

Proteins are made up of hundreds or thousands of smaller units called amino acids, which are attached to one another in long chains. There are 20 different types of amino acids that can be combined to make a protein.

Which gas is used in protein synthesis?

Nitrogen is the gas which is used in protein systhesis.

Is oxygen present in protein?

Proteins are one of the primary constituents of living matter. They consist of long chains of amino acids, which are bonded together by peptide linkages and thus called polypeptides. There are about 20 amino acids, and the atoms most prevalent in these are carbon, hydrogen, oxygen, nitrogen, and sulfur.

What are the advantages and disadvantages of Kjeldahl method?

The pros of Kjeldahl include a robust technique that has the ability to cope with varying sample matrices, compliance with official methods, a high level of automation, and lower initial costs. The cons include the speed of analysis and use of chemicals for analysis.

Why Kjeldahl method is preferred?

The Kjeldahl method is widely used internationally and is still the standard method for comparison against all other methods. Its universality, high precision and good reproducibility have made it the major method for the estimation of protein in foods.

What factors should one consider when choosing a method for protein determination?

Choosing an appropriate method depends on the properties of proteins present in the samples as well as the characteristics of analytical approaches. The nutritional value of a protein is determined by the amino acid composition and the digestibility of that protein.

What are the different types of protein factors required for protein synthesis?

mRNA, tRNA, and rRNA are the three major types of RNA involved in protein synthesis. The mRNA (or messenger RNA) carries the code for making a protein.

Why does plasma protein change?

Changes in the relative percentage of plasma proteins can be due to a change in the percentage of one plasma protein fraction. Often in such cases the amount of total protein does not change. The A/G - ratio is commonly used as an index of the distribution of albumin and globulin fractions.

Where are plasma proteins synthesized?

Plasma proteins are synthesized predominantly in the liver, plasma cells, lymph nodes, the spleen and in bone marrow. In the course of disease the total protein concentration and also the percentage represented by individual fractions can significantly deviate from normal values. Hypoproteinemia can be caused by diseases ...

What causes hypoproteinemia?

Hypoproteinemia can be caused by diseases and disorders such as loss of blood, sprue, nephrotic syndrome, severe burns, salt retention syndrome and Kwashiorkor (acute protein deficiency). Hyperproteinemia can be observed in cases of severe dehydration and illnesses such as multiple myeloma.

Can you use the conversion factor as a substitute for a doctor's advice?

This site is for information purposes only. You should never use something from the internet as a replacement for your Doctor or Pharmacists' advice. The conversion factors are derived from the current literature and have been applied as published. Therefore we cannot take any responsibility for the validity of the published conversion factors.

What is the difference between a true protein and a crude protein?

1. True protein is a polypeptide (s) of amino acids (essential and nonessential AAs) 2. Crude protein = True protein + NPN. 3. NPN (non protein nitrogen) may be a peptide (s) , amino acid (s), nucleotides etc. Now, as you mentioned that your are going to estimate the pure (!)

Can nitrogen be converted to protein?

A nitrogen content can be converted directly into a protein content if you use the usual conversion factors. In proximate analysis of stock feeds a factor of X 6.25 is used to estimate protein concentration from measured N concentration. I doubt that this approximation applies to pure organics such as amino acids.

Can you make protein with a single amino acid?

Moreover, you cannot make protein with a single amino acid.

How to calculate protein content?

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.

How to determine protein content of milk?

Currently, the reference procedure for determination of the "protein" content of milk is based on measurement of the total nitrogen content of milk by the Kjeldahl method (AOAC method, 920.105). About 6% of the total nitrogen content of milk Is nonprotein nitrogen. Therefore, total nitrogen multiplied by the conversion factor 6.38 overestimates the true protein content of milk on average by about 6%. In the present study, new direct and Indirect methods were developed for measurement of the true protein content of whole milk by Kjeldahl nitrogen determination. Both new methods are sample preparation procedures used to fractionate the nitrogen-containing compounds In milk prior to measurement of the nitrogen content of these fractions by Kjeldahl analysis. The collaborative study consisted of 9 pairs of blind duplicate milk samples that were analyzed for total nitrogen, nonprotein nitrogen, and protein nitrogen by each of 10 laboratories. Both methods for true protein measurement (direct and Indirect) gave acceptable statistical performance characteristics and good agreement between methods. The new direct method requires about half the laboratory analysis work of the indirect method (i.e., total minus nonprotein nitrogen). The methods have been adopted official first action by AOAC as (1) a new method for nonprotein nitrogen determination in milk, (2) a new method (direct) for determination of protein nitrogen content of milk, and {3) an alternative method (indirect) for determination of protein nitrogen content of milk.

What is the nitrogen content of proteins?

century) assumes the nitrogen content of proteins to be 16%.

What is the nitrogen to protein ratio in meat?

18% . Consequently, the nitrogen-to-protein ratio in meat prod-

How do legumes affect Fe and Zn?

The effects of legume protein fractions on Fe and Zn bioaccessibility remain equivocal to date, largely due to the protein's structure and the presence of anti-nutritional compounds. We administered Fe and Zn salts with legume concentrates consisting mainly of albumin or globulin from lupin, pea and faba to in vitro gastrointestinal digestion. Under the fasted intestinal state, faba globulins were found to enhance Fe 2+ and Zn solubility compared to control salts without legume proteins. Meanwhile, other fractions had no effect or significantly lowered Fe and Zn solubility. Under the fed intestinal state, the presence globulins enhanced Fe solubility versus the control, where protein solubilization due to high bile concentration likely played a role in circumventing precipitation. The lupin albumin fraction significantly enhanced Fe 2+ and Zn solubility, whilst other fractions generally reduced Zn solubility under fed state. Our results highlight the complex role of legume proteins towards Fe and Zn solubility.

All Answers (9)

Following the nitrogen determination, crude protein content is calculated using a conversion factor. The original, and still frequently used, conversion factor 6.25 is based on an assumption that the general nitrogen content in food proteins is 16% and that all nitrogen in foods is protein-bound.