Casein (3501) is specifically the phosphoprotein derived from milk. Albumins (3502) include egg albumin, milk albumin, and whey protein concentrates. Peptones and other protein derivatives that do not fit the specific definitions of casein or albumin—including hydrolyzed proteins and protein isolates from non-milk, non-egg sources—fall under 3504. The source material and degree of processing are the primary classification criteria.

Enzymes used as food additives or processing aids are regulated by FDA under the FD&C Act and must have GRAS (Generally Recognized as Safe) status or food additive approval for their intended use. Importers of food-grade enzyme preparations should confirm the regulatory status of each enzyme and ensure accompanying documentation supports the intended application.