Rothwell GrainEssentials Center

What is Protein Quality?


Katie Harris, Product Development & Nutrition Scientist

It’s undeniable that protein is currently one of the most popular ingredient trends within the food and nutrition industry.  Protein claims are vibrantly visible on product packages ranging from bar applications to bottled water.  Most of us know protein as an essential nutrient that is necessary for the growth and maintenance of our muscles and other organ tissues.  But, what more and more people are starting to learn about is how the protein quality influences the ability of a protein to carry out these necessary growth functions.

Proteins are made up of building blocks called amino acids.  There are 20 amino acids, all with different physical and chemical structures that yield unique functionalities within our body.  There are 11 amino acids that are considered “non-essential.” While these amino acids can be consumed through foods, our body is also sophisticated enough to make them when needed.  The other nine amino acids are considered “essential”, which means the only way our body can obtain them and utilize them is to consume them through foods.  When we look to understand the protein quality of a food or ingredient, the quantity of these nine essential amino acids is only half of the necessary analysis.  We also need to look at the overall digestibility of the protein source.  Animal-based proteins, like whey protein, are highly digestible whereas plant-based proteins are slightly less digestible due to the presence of anti-nutrients and other food components.

The FDA has previously concluded that an individual’s daily value for protein should be 50 grams of high quality protein per day.  To determine whether or not the protein is high quality, the FDA tests the food for the “Protein Digestibility Corrected Amino Acid Score”, or the PDCAAS for short.  The PDCAAS is determined by the following equation:

The fecal digestibility component of the equation can be measured either in vitro or in vivo, and can range from 0% digestible to 100% digestible; the higher the percentage, the better the digestibility.  The product will also be tested for crude protein and amino acid quantity.  When analyzing these results, the amino acid that is present in the lowest amount is called the limiting amino acid.  The quantity of the limiting amino acid in your test product is then compared to the amount of that same amino acid in the FDA pre-defined reference pattern for high quality proteins.  The PDCAAS score ranges from 0-1, with 1 being the highest quality protein possible.  Animal-based proteins are typically higher quality and have a score of ~1, whereas most plant-based proteins are within the 0.5-0.7 range.

The protein content of plant-based proteins varies depending on the source.  There are two different ways you can use this protein content data.  You could use the data to formulate your products to have higher protein values on the label; or you could use it in conjunction with the PDCAAS data and not only increase the protein value on the label, but also make a protein claim on the package.

The PDCAAS data for plant-based proteins can be tricky to come by since historically we’ve always consumed animal-based proteins that have been highly researched.  The R&D team at Bay State Milling has been working on understanding the PDCAAS scores of some of their higher protein plant-based ingredients.  You can see that the majority of the plant-based proteins lie within the 0.55-0.70 range for PDCAAS, but what we’ve also found through our research is that combining two or more different plant based protein sources can increase the protein quality due to the complementary effects.

So What?

If you have the protein content data and you have the PDCAAS data, you can calculate how much of the protein in your product is considered “high quality” by using the equation for the % Daily Value (DV).

% DV = (Grams Protein * PDCAAS Score)/50

If the % DV is greater than or equal to 10%, then you can make a “good source of protein” claim.  If the % DV is greater than or equal to 20%, then you can make an “excellent source of protein” claim.  This is an important distinction because using higher quality proteins means that you can get these nutrient content claims easier than if you were to use the lower quality proteins.  Imagine you had 10 grams of protein in your product and you were using whey protein as the protein source; you’re % DV equation would look something like this: 10* 1 = 10% and thus a “good source of protein”.  But, imagine instead of using whey protein you used quinoa; you’re % DV equation would now look like this: 10* 0.63 = 6.3% which is not enough for a “good source of protein”.  Finding out ways to improve the protein quality of plant-based proteins is so important now that consumers are shifting more towards plant based living.  To learn more about ways you can increase the protein quantity or quality of your products, please contact Bay State Milling for more information.

Note: the suggestions made in this blog do not serve as regulatory advice.  Always consult your internal regulatory experts to make the decisions for your product packaging*

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