In most cases, yes, you can use MPC/MPI to replace casein and/or caseinates in food formulations.
Obviously, since MPC/MPI forms water dispersions that are most similar in appearance to calcium caseinate, one can easily substitute MPC/MPI into any calcium caseinate application. Usually, substituting MPC/MPI for calcium caseinate will result in an improvement in food product quality as MPC/MPI is more water soluble/suspendable than calcium caseinate, imparts a creamier mouth feel, and has a more preferable flavor profile compared to calcium caseinate. Many people use calcium sodium caseinates to gain a better mouth feel and better water solubility (compared to calcium caseinate). MPC/MPI is very comparable to the best calcium sodium caseinates and even many sodium calcium caseinates in solution appearance, suspension stability, mouth feel, and viscosity. MPC/MPI also has a cleaner, blander flavor than calcium sodium caseinate or sodium calcium caseinate. Even though sodium caseinate is the least similar to MPC/MPI, one can still replace sodium caseinate with MPC/MPI in many applications. MPC/MPI has been used to replace or extend sodium caseinate in coffee whiteners, whipped toppings, and cheese analog products.