How do you know if collagen was added to a product?

Collagen is a well-known animal protein. You can find it in tendons, skin, cartilage, and, unfortunately, also in some protein powders. Some manufacturers pump up the apparent protein content of their product by adding collagen. As the cheapest form of collagen is remnants from the slaughterhouse, adding them to whey protein powders basically costs nothing. However, collagen is also easily detected, since it betrays itself: it contains two amino acids that can only be found in collagen – hydroxyproline and hydroxylysine. If these two amino acids can be detected in a product, then we can be suspicious of amino spiking. The presence of hydroxyproline can be cheaply and safely detected with simple laboratory tests, which only cost 10-20 euros, but can save you a lot more.