Freeze-dried vs dehydrated fruit vs dried fruit: the three processes, side by side

Freeze-dried vs dehydrated fruit comes down to one number: how much water is left when the process stops. Dried fruit stops at 15 to 25 percent. Dehydrated fruit stops at roughly 10 to 20. Freeze-dried fruit stops at 2 to 3. Everything else people notice, the texture, the color, how long it keeps, what happened to the vitamins, follows from that number and from the temperature it took to get there. Here are the three processes, in order of heat, and a freeze-dried vs dehydrated fruit table at the end.

Dried fruit: sun, warm air and days

The oldest method. Grapes become raisins on paper trays between the vineyard rows over two to three weeks in the sun; apricots, figs and dates go the same way, sometimes with a sulphur dioxide treatment to hold the color. Commercial dried fruit uses warm air at 50 to 70 °C (120 to 160 °F) over 12 to 36 hours instead. Either way the fruit cooks slowly as it dries. Sugars caramelize, the color browns, most of the vitamin C goes, and what is left is dense, chewy and sticky at 15 to 25 percent moisture. USDA FoodData Central lists raisins at about 15 percent water and dates closer to 20. Nothing has been added unless the label says so: fresh grapes are about 16 grams of sugar per 100 grams and raisins about 59, and the difference is only the water that left.

Dehydrated fruit: hot air, hours

This is what a home dehydrator or a drying oven does. A fan pushes air at 50 to 70 °C (125 to 160 °F) across thin slices for 6 to 24 hours until moisture is down to roughly 10 to 20 percent. It is shorter and more controlled than sun-drying, but it is the same mechanism, so the same things happen a little less: the slice shrinks to a leathery curl, darkens, loses most of its vitamin C and a share of its B vitamins, and keeps its fiber, minerals and sugar. Apple chips, mango strips and fruit leather live here. In the dehydrated fruit vs freeze-dried fruit question, the thing to hold onto is that dehydrating takes the water out with heat, and heat is what the fragile vitamins cannot survive.

Freeze-dried fruit: frozen, then a vacuum

The fruit is frozen solid, typically to around -40 °C (which is also -40 °F), then placed in a chamber where the air pressure drops low enough that ice cannot melt. It sublimates instead, going straight from solid to vapor, and the trays are warmed gently so the sublimation keeps going; a cycle runs 20 to 40 hours, and the fruit itself stays cold through most of it. Because the water leaves as vapor from a frozen structure, nothing collapses. The piece keeps its shape and nearly its size, the color stays, and the cell walls stay open, which is where the crunch comes from and why it rehydrates in minutes. Moisture at the end is 2 to 3 percent, low enough that nothing can grow in it, which is why freeze-dried food is what NASA packs and what backpackers carry. We freeze-dry gently, in small batches, with our own process, so the sour reaches the middle of the fruit and the crunch stays.

Freeze-dried vs dehydrated vs dried fruit, side by side

What survives each one

Freeze-dried vs dried fruit is mostly a question about vitamins. Fiber, minerals and the fruit's sugar are not affected by any of the three. They are solids, and they stay. The vitamins are the difference. Vitamin C breaks down with heat and time: sun-drying has both in quantity, dehydrating has the heat, freeze-drying has little of either. Published comparisons of freeze-dried against air-dried berries, and the one most often cited is a 2003 study in the Journal of Agricultural and Food Chemistry, find that freeze-dried fruit keeps most of its antioxidant compounds while air-dried fruit loses a large share. Studies on freeze-dried berries commonly report vitamin C retention in the 80 to 95 percent range. For dehydrated fruit the figure is usually under half.

Sugar is the other thing to read on a label, and here the three are the same. Any drying concentrates sugar per gram, because the water that diluted it is gone, so dried, dehydrated and freeze-dried fruit all read higher than fresh even with nothing added. What differs is whether something was added. Many dried fruits are sweetened or oiled to stay soft; dehydrated fruit usually is not; freeze-dried fruit is sold both plain and infused, and the panel says which.

Which one you want depends on what you want it for

The dehydrated fruit vs freeze-dried fruit choice, with dried fruit beside it, goes like this. Dried fruit for baking and for sweetness by the handful. Dehydrated for a chewy strip that survives a backpack. Freeze-dried for the fruit as it was, minus its water: the shape, the color, most of the vitamins, and a crunch that gives way to the fruit a second later. Freeze-dried is also the only one of the three with a structure open enough to take an infusion all the way in rather than just on the surface. Sour freeze-dried mangos are mango pieces that have had the water taken out and the sour put in, all the way through, which a dehydrated mango strip could only ever carry on the outside. The rest of the REFRESH'D Sour Freeze-Dried Fruit lineup is made the same way, and none of it has ever been in a dehydrator.

One last thing the freeze dried vs dried fruit comparison turns up: weight. A strawberry is about 91 percent water, so a pound of freeze-dried strawberries began as roughly ten pounds of fresh ones. That is the figure to keep in mind when a 2 oz bag seems small. It was a lot of fruit before the water left.