Many milk processing protocols include heat treatment of the colostrum, milk or whey. Of the major immunoglobulin classes in bovine milk, IgG is the most thermostable and IgM is the least thermostable [214] . Commercial milk samples that have undergone a typical pasteurization process, including skim milk powder, can retain 25-75% of the IgG concentration compared with raw milk, while milk undergoing ultra-high temperature (UHT) pasteurization contains little detectable IgG [192, 216] . Nevertheless, antigen-specific IgG in milk is relatively stable under typical conditions of pasteurization when compared with that in UHT milk or cow milk-based infant formulas that undergo high-temperature processing [54, 217] .