Dehydrating fruit does change some aspects of its nutritional value, but this doesn't make it necessarily better or worse than fresh fruit. The process of removing the water in the fruit concentrates both nutrients and calories, meaning that a person would consume more nutrients and calories in a comparable portion of dried fruit as in fresh fruit. This also means that a portion of dehydrated fruit is typically higher in fiber and antioxidants than one of fresh fruit. The processes used to dehydrate fruit have a large impact on the vitamin and mineral content, but fruit that is gently dried without chemicals often retains much of its vitamin and mineral content.
Calories and Sugars
Commercially dried fruit is usually treated with preservatives and sweeteners, which changes the nutrition content. Even fruit that is not treated with sweeteners is going to be sweeter than non-dried fruit, since the removal of the water concentrates the sugar in the fruit. The removal of the water also makes the fruit lighter, meaning that a person eating the same amount in weight of dried fruit as a piece of fresh fruit would be consuming more calories and sugar. This can be good for hikers or athletes who need lots of quick energy from a lightweight, portable food, but it can be problematic for dieters. Generally speaking, one half cup of dried fruit is considered to be equivalent to one cup of fresh fruit.
Fiber and Antioxidants
Dehydrating fruit doesn't change its fiber content, but the change in weight makes a comparable portion of dried fruit has more fiber than a piece of fresh fruit. This makes it very effective for relieving constipation, and it can also be helpful in lowering cholesterol. Dried figs, raisins, apricots, and dates are particularly high in fiber. The drying process also concentrates the antioxidant content of fruit. Cherries, apples, figs, and blueberries are particularly high in antioxidants.
Vitamins and Minerals
The way that fruit is dehydrated greatly effects its vitamin and mineral content. A lot of commercially dehydrated fruit is pre-treated with sulfur dioxide or sodium sulfite to keep it from getting brown during the drying process, which preserves vitamin A and vitamin C in the fruit, but can get rid of thiamine. Heat in the dehydrator as well as exposure to air can lower fruit's vitamin C content. Boiling fruit before dehydrating it can help preserve carotene, which is broken down by the body into vitamin A, but does lower the vitamin C content. Soaking or boiling before dehydrating can also cause some minor loss of minerals, but fruit generally retains its mineral content well during the drying process.
Dried Fruit vs. Juice and Freeze-Dried Fruit
Dehydrated fruit is generally a much better source of nutrition than fruit juice. Though juice does retain many of the vitamins and antioxidants of fresh fruit, dried fruit is much higher in fiber and typically has less sugar than most juices. Freeze dried fruit has much less water than dehydrated fruit, but is similar in terms of nutrients. It is usually more shelf stable though, and lasts longer under proper storage conditions. It also has a different texture, and is lighter than dehydrated fruit.