For instance, vitamin B1 is called thiamine and is added as thiamine hydrochloride, a white powder. In fact I have several bottles of it here in my lab.
Vitamins are simply organic molecules like sugar, and like sugar can be added to foods.
Minerals are added in inorganic forms, or salts. Iron is added as ferrous sulfate although it can be found in a form bound to an organic molecule in which it is more easily absorbed from the stomach. We add copper, iron, zinc, cobalt, selenium, silicon and molybdenum as inorganic salts to one celled algae cultures and they absorb the metals from solution just as we absorb the metals from our stomachs. Argonne National Laboratory, Division of Educational Programs, Harold Myron, Ph.D., Division Director.