Complex sentence: They also claim raw milk contains enzymes and other substances which cannot survive the heat process and which may be destroyed during pasteurization, specifically immunoglobulins and the enzymes lipase and phosphatase, which are inactivated by heat.
Split into simpler sentences: They also claim raw milk contains enzymes and other substances which cannot survive the heat process and which may be destroyed during pasteurization. Proponents say that beneficial components of milk are destroyed by pasteurization, specifically immunoglobulins and the enzymes lipase and phosphatase, which are inactivated by heat.