How to Test Food for Protein at Medallion Labs

Be it a food product or a nutritional supplement, the process of accurately testing and reporting protein is necessary to comply with U.S. Food and Drug Administration labeling requirements.

Of all the components included on a nutritional label, protein has emerged as a popular call-out claim on product packaging. The reason? The protein content is a selling point for products targeted to athletes and fitness fans. In fact, the selling power of protein content has resulted in "amino spiking," a low-cost method of misleading consumers about a product’s protein claims.

There is much to understand about protein testing and the implications on package claims and nutritional labeling. Before we delve into the various testing options offered by Medallion Labs, let’s first understand what protein is and how the FDA classifies it.

How the FDA Classifies Protein

Protein is a nutrient. The FDA declares protein on Nutrient Facts and Supplement Facts as either a Class I or II nutrient depending on its occurrence in a product.

Class I nutrients are those added in fortified or fabricated foods. These nutrients are vitamins, minerals, protein, dietary fiber, or potassium. Class I nutrients must be present at 100% or more of the value declared on the label; in other words, the nutrient content identified by the laboratory analysis must be at least equal to the label value.

Class II nutrients are vitamins, minerals, protein, total carbohydrate, dietary fiber, other carbohydrate, polyunsaturated and monounsaturated fat, or potassium that occur naturally in a food product. Class II nutrients must be present at 80% or more of the value declared on the label.

How Medallion Labs Measures Proteins

Medallion Labs offers eight protein tests grouped into five testing categories. Selecting a test to use is up to the client. Each option has various factors that may shift results in one way or another. The Protein Dumas is an FDA recognized protein method and the default method Medallion uses for nutrition facts panels.

The Medallion Labs protein testing options include:

• Testing for “true” protein
  • Amino Acid Profile Test – Acid Hydrolyzed Amino Acids
  • Amino Acid Profile Test – Base Hydrolyzed Amino Acids (Tryptophan)
  •  Amino Acid Profile Test – Performic Acid Oxidation Amino Acids (Cysteine and Methionine)

• Testing for animal-based sample matrices
  •  Amino Acid Profile Test – Hydroxyproline (Collagen)

•  Testing for Amino Acids that are NOT bound in a protein
  • Amino Acid Profile Test – Physiologically Free Amino Acids (with Tryptophan)
  • Amino Acid Profile Test – Physiologically Free Amino Acids (without Tryptophan)

• Testing to measure digestibility and amino acid score
  • PDCAAS – Invitro (Protein Quality) Test

• Testing for labeling
  • Protein (Dumas) Test

Amino Acid Profile Test – Acid Hydrolyzed Amino Acids

With the Amino Acid Profile Test – Acid Hydrolyzed Amino Acids, a sample is run through an acid digestion and then ion-exchange chromatography.

Results will be reported as “Hydrolyzed Amino Acids as Dehydrates” to signify that the reported values for the individual amino acids in this screen do not include the molecular weight of water.

If you require the hydrated amino acid values (individual amino acids that include the molecular weight of one water molecule), please let us know at the time of sample submission. Cystine, Methionine and Tryptophan are not detected by this method.

Amino Acid Profile Test – Base Hydrolyzed Amino Acids (Tryptophan)

With the Amino Acid Profile Test – Base Hydrolyzed Amino Acids (Tryptophan) option, a sample is run through an alkaline digestion and reverse-phase chromatography for Tryptophan determination.

Results will be reported as “Tryptophan as Dehydrate” to signify that the reported value for the individual amino acid does not include the molecular weight of water.

If you require the hydrated tryptophan value (an individual amino acid that includes the molecular weight of one water molecule), please let us know at the time of sample submission.

Amino Acid Profile Test – Performic Acid Oxidation Amino Acids (Cystine and Methionine)

With the Amino Acid Profile Test – Performic Acid Oxidation Amino Acids (Cystine and Methionine) option, a sample is run through a performic oxidation and quantified through ion-exchange chromatography.

Results will be reported as “Performic Amino Acids as Dehydrates” to signify that the reported values for the individual amino acids in this screen do not include the molecular weight of water.

If you require the hydrated amino acid values (individual amino acids that include the molecular weight of one water molecule), please let us know at the time of sample submission.

Amino Acid Profile Test – Hydroxyproline (Collagen)

With the Amino Acid Profile Test – Hydroxyproline (Collagen) options, a sample is run through an acid digestion and ion-exchange chromatography.

Collagen will be reported as a calculated value using the results from Hydroxyproline.

Amino Acid Profile Test – Physiologically Free Amino Acids (with Tryptophan)

Please contact us for details regarding the method used for the Amino Acid Profile Test – Physiologically Free Amino Acids (with Tryptophan) option.

Results will be reported as “Free Amino Acids as Hydrates” to signify that the reported values for the individual amino acids in this screen include the molecular weight of one water molecule.

Amino Acid Profile Test – Physiologically Free Amino Acids (without Tryptophan)

The Amino Acid Profile Test – Physiologically Free Amino Acids (without Tryptophan) does not measure Free Tryptophan. If Free Tryptophan is needed, please see Amino Acid Profile Test – Physiologically Free Amino Acids (with Tryptophan).

This test uses a sample that is measured for the Amino Acid composition. Results will be reported as “Free Amino Acids as Hydrates” to signify that the reported values for the individual amino acids in this screen include the molecular weight of one water molecule.

PDCAAS – Invitro (Protein Quality) Test

The PDCAAS – Invitro (Protein Quality) Test is not FDA approved for claims. It’s ideally used for the following purposes:

• Ingredient comparison
• Estimating final product claims
• Checking formulation
• Indication or processing effects.

With the PDCAAS – Invitro (Protein Quality) Test, a sample is measured for the Amino Acid composition. A human digestion simulation follows, breaking down the proteins into amino acids, which are reacted with Ninhydrin and measured, determining the digestibility. Taking the limiting amino acid value, the digestibility is corrected, resulting in a Protein Digestibility Corrected Amino Acid Score (PDCAAS).

The following values are reported:

• The full amino acid profile
• First limiting amino acid
• Sample moisture
• Total protein (both by AAA and combustion nitrogen)
• Animal safe digestibility
• Amino acid score

Protein (Dumas) Test

With the Protein (Dumas) Test, a sample is completely combusted at high temperatures in the presence of pure O₂ (99.9%). Combustion products are H₂O, CO₂, NOx, and N₂. Water vapor, oxygen, and CO₂ are removed from the resulting gas stream by a series of thermoelectric coolers and chemical sorbents. NOx is reduced to N₂ when passed through a column packed with hot copper. The resulting N₂ is passed to a thermal conductivity detector where it is quantified (helium is the carrier gas). Protein is then calculated from the nitrogen content using a published conversion factor (e.g., 5.70 for wheat).

Available protein factors:

• 6.25 – general-purpose food products/ingredients (default) except as noted below
• 5.70 – wheat, wheat flour, and wheat flour bread
• 6.38 – dairy
• 5.46 – peanuts and brazil nuts
• 5.18 – almonds
• 5.30 – other tree nuts (coconuts, butternuts, cashews, chestnuts, hazelnuts, hickory nuts, pistachios, walnuts, and pecans)

Accurate protein testing for labeling

Medallion Labs offers a variety of protein testing options, all with reliable results. This breadth of offering provides you with the testing method you deem best for your product or nutritional supplement. You pick the method; we deliver results that can be the foundation for label claims or nutrition information labeling requirements. Our breadth of testing options also helps you maximize your testing budget by providing the results you seek in a cost-efficient manner.

Medallion Labs is ready to use our testing options, expertise, and skills for your protein testing. Connect with us or call 1-800-245-5615 to discuss the criteria and testing needs for your food products.