The processing of milk to isolate the nutritional compounds that make it such a rich source of protein is a complex undertaking with several steps and multiple methodologies. Of the products these methods may produce, one of the largest categories includes casein products. Since the word casein itself refers to a type of molecule inside milk, there is often confusion concerning how milk proteins, casein, and whey are connected.
What are some of the key things to understand about the different properties and uses for these distinct products created from fresh milk?
Understanding Casein: What is This Milky Molecule?
Casein is a broad, catch-all term for a class of proteins in milk containing all nine essential amino acids. A molecular structure called a micelle holds these casein proteins in suspension within milk. Comprising the vast majority of the protein in cow’s milk, the remaining portion includes the whey proteins. To concentrate the protein in milk to a high enough level to be nutritionally significant, separating the micellular casein and whey protein is a necessary step. How this process occurs determines much about the properties of the resulting product.
To reiterate, casein is a type of protein in milk, whereas milk protein refers to the complete set of proteins in milk including the whey.
Understanding Whey Proteins
Whey Protein Concentrate or Isolate (WPC or WPI) are generally produced from co-products of the cheese making process and contain 100% whey proteins; by definition, there is no casein present in WPC/WPI. MPC and micellar casein form a milky white suspension when dispersed in water and have a bland or creamy flavor. WPC and WPI form somewhat clear, brownish tinted dispersions in water and tend to have a slightly astringent flavor due to the high levels of sodium, potassium, and chlorine. WPC is not very heat tolerant and will denature fairly easily, leading to off-flavors and solubility and dispersion issues. WPC has been around for decades and has become very popular with athletes and bodybuilders. MPCs and micellar casein are starting to attract more attention as people recognize the functional qualities including superior solubility and dispersion and clean, bland flavor profiles that don’t require masking agents.