[elil17]

The same article goes into additional detail:

> Commercial squeezed orange juice is pasteurized and filtered before being evaporated under vacuum and heat. After removal of most of the water, this concentrate, about 65% sugar by weight, is then stored at about 10 °F (−12 °C). Essences, Vitamin C, and oils extracted during the vacuum concentration process may be added back to restore flavor and nutrition.

So essentially there are components that vaporize during processing. The make sure to condense the same components and add them back in so that the orange juice contains all the components of fresh orange juice.