Why do certain foods lose their nutritional value when they change form?

heat, light, and exposure to air destroys vitamin c. and with the passage of time, vitamin c degenerates naturally.

In the case of the raisins, probably oxidation. In the case of popcorn, probably intense heat. In the case of greens, long cooking. Other reasons for other foods.

To change form you’re altering their composition, which in turn has consequences.

I have some dried apricots that say 15% Vitamin A…why is that? wouldn’t the Vitamin A also be destroyed with this?

different vitamins have different vulnerabilites

Vitamins are often added during processing (see otherwise nutritionless cereals, such as Total.)

That’s true, thanks. They should add vitamin c to these foods then :)

http://www.beyondveg.com/tu-j-l/raw-cooked/raw-cooked-2e.shtml
here is a list of vitamins and there susceptibility to environmental influences.

They loose water and are dry…
.Corn contains vitamin C?

Okay thanks, yeah I see what you mean about the vit. c.

yeah it does and potatoes.

@ames83 hmm I didn’t know that…I’ll try to keep that in mind. :)