Substances added during manufacture to make rigid materials flexible and workable, most famously in plastics and in edible films and coatings. In food packaging, plasticizer migration is a genuine safety concern: certain phthalates can leach from packaging into fatty foods, so regulations restrict which plasticizers may be used in food-contact materials and set specific migration limits that laboratories verify. Manufacturers must choose approved plasticizers, control their levels, and test finished packaging under realistic conditions of time, temperature, and food type. The same migration principle applies to plasticized coatings, tubing, and gaskets used in food plants.