Any cheap way to test whether a given powder has high protein content?

Protein powders are used as dietary supplements. The photo below is for whey protein powder, which usually has about 24 grams of protein per scoop:


[![enter image description here](https://i.stack.imgur.com/FJzFB.jpg)](https://i.stack.imgur.com/FJzFB.jpg)
*Image: © jirkaejc/Getty Images*


Unfortunately, many forged protein powders are circulating in the market, specially as the price of genuine ones is increasing rapidly. This stresses the necessity of testing purchased protein powders to ensure that they have high protein content.


Unfortunately, lab tests are quite expensive. This brings my question:


* Is there any simple test, or heuristic, to verify that a given powder contains high protein content? Ideally, something that can be done at home. I'm also open to more sophisticated tests in case they are the only way.


Note that I do not necessarily want to know the actual amount of proteins in grams. For my purpose, it suffices to get an approximate decision that the amount of protein is generally high enough.




The answer in general will depend on your desired accuracy and the exact information you are looking for. However, in your specific case you would probably be fine using a Biuret test.


The Biuret reagent is cheap, available online, and easy to see; this test uses a complex of copper (II) sulfate with some salts and reacts with **peptide bonds** which link amino acids together. This should apply to whey like any other protein.


If you choose to do this test, **do not consume the protein tested** and **make sure you keep it stored away from food or materials that may be accessed by people who don’t know what it is**. It would also be wise to **read the Safety Data Sheet (SDS) associated with the reagent**. Proper personal protective equipment and general safety tips outlined [here](https://youtu.be/VRWRmIEHr3A) should be followed.


It is best examined with a ultraviolet / visible light spectrophotometer, but you don’t need to go through the trouble if you don’t need to be all that accurate. You can occasionally find these on eBay or Craigslist, but they are probably not worth your time and while they’re cheap as far as instrumentation goes, they usually aren’t worth the price either. The breaking of peptide bonds results in the originally blue liquid to become a purple-ish solution that is visible to the eye (this is called a **colorimetric test**).


If you have a color-perception deficiency like color-blindness, colorimetric tests can be difficult and you may prefer more dramatic color changes. There are reagents that are slightly more standard and easier to tell a change in (like the ninhydrin test) but those can get more expensive and are more applicable to a lab setting.


 4