The concept of protein spiking, or adding non-protein nitrogen-containing substances to a base protein to increase the product’s nitrogen content, is not new to the dietary supplement and food industries. Still fresh in our minds is the melamine fiasco that brought to light the lengths some companies will go to in order to defraud customers for economic benefit. But over the last few years, we have seen a shift in the way this spiking takes place. This change in tactic involves use of compounds that are cheap, not toxic, and extremely easy to mask due to their relatively bland flavor profile. As a laboratory, we constantly get inquiries from existing and potential clients on the topic of protein spiking and ways of detecting these compounds in the protein supply chain.
The best way to combat this problem is to understand the basics of the product in question, most frequently utilized methods for protein content determination and its limitations, and of course, engaging with your in-house or contract laboratory for additional screening options to ensure your protein is not spiked.
A good rule of thumb for protein calculation is stated in the American Herbal Products Association (AHPA) guidance on the Labeling of Protein in Food and Dietary Supplements, which states that a protein should be calculated by only including proteins that are chains of amino acids connected by peptide bonds and excluding any non-protein nitrogen-containing substances.
Currently, most frequently utilized methods in the dietary supplement and food industries for protein analysis are done by either Kjeldahl or Dumas (commonly referred as combustion) methods. These methods are named after the scientists who are credited to be the developers of the methodology and are widely accepted Compendial methods--great for a quick and easy determination of protein content. However, because both of these methods test for total nitrogen content in a given matrix, it is easy to manipulate the final result by spiking the protein material with other compounds that contain enough nitrogen to artificially inflate the final protein results. The companies that spike their protein powders are well aware of this method limitation and play it to their advantage.
The most recent wave of spikes seen in protein raw materials are compounds (such as glycine, taurine, creatine, and arginine) that all are very inexpensive when compared to the protein raw material prices, are easy to purchase, and account for a significant amount of nitrogen during the Kjeldahl or Dumas analysis. Some of these compounds contribute more than the others based on their molecular formula—a detail you can discuss further with your testing services provider.
It is worth noting that there are some methods that were developed for non-protein nitrogen determination in milk. However, before these methods are put to use for testing in other matrices, they need to be validated to ensure specificity, accuracy, and precision for your protein product.