What exactly does orange juice from concentrate mean? This means that once all the orange juice was squeezed, all the “water” was removed, usually then shipped to another facility or location, and then the “water” was added back in. Basically, the orange was dried and then rehydrated. Oranges are juicy enough when eating them straight off the peel; therefore, you can imagine how much of the nutrients and taste you lose when you unnaturally dehydrate the oranges. Therefore, what manufacturers usually do is add the various flavors and compounds back in after they have processed the juice. However, manufacturers can avoid declaring any of this on the labels because they artificially process the additives from the orange peels and other components that may already be found in oranges and therefore, there is technically nothing to declare.
http://illuminatedhealth.com/concentrated-juices-nutrition/