Do you need a food dehydrator or can you use your oven?

Food dehydrators are purpose-built to dry foods optimally. But buying one means spending money and finding somewhere to store it. I was curious to see whether I could use my oven instead. I compared using my oven and the Sunbeam Food Lab Electronic Dehydrator DT6000 ($239).

The trial

I chose five foods with different textures and moisture contents:

• kiwifruit puree to make fruit leather
• mushroom slices
• kale pieces to make kale chips
• banana slices to make banana chips
• potato mash.

For each test, I split the food in half by weight, so each appliance had the same amount. I checked the food in both appliances after 2 hours, then hourly and more frequently as needed.

To make the comparison fair, I ran the dehydrator and oven side-by-side, so the room temperature and humidity were the same.

Key findings

Yes, you can dehydrate food in an oven. But there are pros and cons when compared to using an electric food dehydrator. Here’s what I found.

• The oven and the food dehydrator both did a good job. For each test, they produced very similar results for texture, colour and taste. The banana chips test was the exception, with the oven overcooking them (see Results). But I’d expect to get a good result with a lower temperature and shorter drying time.

• The dehydrator is easier to control. It lets you set the temperature in precise 5°C increments. But my oven needed some guesswork – it has no temperature markings below 60°C and, above that, only in 20°C increments.

• The oven dries food faster than the dehydrator. The oven was 10% quicker on average (excluding the overdone banana chips test).

• The dehydrator felt safer to use with little supervision compared to the oven. The oven door must be ajar to let moisture escape when dehydrating food, while the dehydrator has a vent on top.

• Using the dehydrator doesn’t occupy the oven. But you can’t use the oven for cooking while it’s dehydrating food.

• The oven doesn’t take up extra space. The dehydrator does. It didn’t fit on my small kitchen bench, so I had to run it on the floor, which was inconvenient. And it’s too big to store in my kitchen cupboards.

• The dehydrator doesn’t blow food around. But my oven’s powerful fan blew the lightweight kale leaves into clumps.

• The dehydrator is quieter to use. The oven was a bit noisy since the door had to be ajar to let moisture escape. But it wasn’t annoying.

• The dehydrator won’t overheat your house. My oven, however, put out a lot of heat running for several hours with the door ajar. That might not be ideal in summer.

Running costs

We measured the food dehydrator’s energy consumption over 1 hour running at 60°C – it consumed 0.434kWh. The current average cost of electricity in New Zealand is 25¢ per kWh. So, the dehydrator costs about 11¢ per hour to run. If you use it for 10 hours a week – which is usually long enough to dry a batch or two of food – it’ll cost about $57 per year:

An oven is likely to cost significantly more to run because it has a far higher power rating. It also has a larger space to heat and has to maintain that heat with its door ajar while it’s dehydrating food.

Results

Kiwifruit leather

The food dehydrator and oven were both set to 70°C.

• The oven dried the kiwifruit 2 hours faster than the food dehydrator: 4.5 hours vs 6.5 hours.
• The fruit leather came out of both appliances in a solid but pliable sheet that was mildly tacky, and 20% of its original weight. It darkened slightly during drying. It tasted of concentrated kiwifruit, sweet and tangy – very nice. There was no difference in texture or taste between the appliances.

Mushroom slices

The food dehydrator and oven were both set to 60°C. Each set of mushrooms was flipped over after 3 hours.

• Both appliances took 12 hours to dehydrate the mushroom slices.
• Both sets of mushroom slices came out cracker dry, at 9% of their original weight, and they’d darkened slightly. There was no difference between appliances.
• Once they’d cooled, I vacuum sealed and stored the slices in the freezer for 2 weeks. To reconstitute, I added them to a vegetable soup that cooked for 30 minutes.
• Reconstituted, both sets had the texture and flavour of regular mushrooms – delicious.

Kale chips

The food dehydrator and oven were both set to 40°C.

• The oven dried the kale 2.5 hours faster than the food dehydrator: 4 hours vs 6.5 hours.
• Both sets of kale chips were 15% of their original weight and very crisp, but the oven set was slightly crispier.
• The oven set became more vivid in colour, while the dehydrator set faded a little.
• Both sets had a savoury kale flavour, but the oven set had better intensity.

Banana chips

The food dehydrator and oven were both set to 60°C. Each set of banana slices was flipped over at 2.5 hours and then 6.5 hours after start. At 2.5 hours, the oven set was stuck to the baking paper, leaving behind a gooey residue when turned over.

• Both appliances ran for 17.5 hours, but the slices didn’t seem to get any drier for the last few hours, so could have been stopped earlier. Both sets were crispy on the edges but remained slightly pliable through the middle. That pliability made it difficult to know when to call “time”. Some foods don’t get cracker dry without extra treatment (such as frying).
• The oven-dried banana chips were 24% of their original weight vs 25% for the dehydrator set.
• The dehydrator-made banana chips had retained their shape and colour. While the oven set had cooked, darkened, and lost some of their size and shape since they’d gotten stuck to the baking paper.
• The dehydrator’s banana chips had a sweet, concentrated banana flavour. They were chewy but easy and pleasant to eat. The oven-made banana chips tasted sweet and of cooked banana. The texture was very chewy and hard to eat – they were overdone.

Potato mash

The food dehydrator and oven were both set to 50°C. After 5 hours, the solid but pliable sheets of mash were flipped over. The oven set was crispier at this point than the dehydrator set. The baking paper and solid food trays were removed to improve airflow for the rest of the drying time.

• The oven dried the mashed potato 3 hours faster than the food dehydrator – 7.5 hours vs 10.5 hours.
• Both sets of dried mashed potato came out in a crisp, solid, wavy sheet with slightly curled edges, and were 15% of their original weight.
• Both sets had darkened slightly during drying – no difference between the two.
• Once cool, I broke each sheet of dried mash into smaller pieces and blitzed them in a blender, creating potato powder. I stored each set in the freezer in a sealed plastic bag for 2 weeks. To reconstitute, I mixed a cup of potato powder with 2 cups of boiling water in a bowl, added a little butter and milk, then fluffed up with a fork.
• Both sets looked and tasted like regular mashed potato. But the texture of both was a bit grainy in the mouth.

Storing dehydrated food safely

It’s difficult for bacteria and mould to grow in dry conditions. That’s why dehydrating food is a good way to preserve it. While dehydrated foods will eventually deteriorate, they generally have a shelf life of several months or years.

Here are some ways to make your dried foods last as long as possible.

Preparation: Clean and dry your hands, equipment, kitchen surfaces and storage containers before handling food, to prevent contamination.

Suitable containers: Choose airtight storage containers made of glass or food-grade plastic – they won’t taint your food. Make sure they’re clean and dry, and check that seals are in good condition to keep moisture and critters out.

Vacuum sealing: Use a vacuum sealer to suck air out of a storage container or bag, and seal it airtight. This minimises oxidation, limiting the growth of harmful bacteria, and the loss of vitamins, flavours and colours. See our vacuum sealer trial.

Dry environment: Just as drying food limits the growth of harmful organisms, storage spaces should also be dry. If you’re keeping your food in a cupboard, avoid areas exposed to cooking steam.

Temperature control: Store food in a cool place. The bacteria that cause food poisoning can grow at 5°C–60°C. While some bacteria can grow in refrigerated foods (below 5°C), they’ll grow slower than at room temperature. And very few food-spoiling nasties can grow in frozen food. Storing food in the fridge or freezer will extend its shelf life.

Darkness: Store food in a dark place in non-transparent containers, as light exposure can cause food to lose nutrients, colours and flavours.

Rotation and labelling: Label your food and add the date you’re storing it. Rotate batches so newer ones are stored at the back of your storage space. When using stored food, choose the oldest batch and check for signs of spoilage (such as mould or a bad smell) before consuming.

NOTE: Not all foods are suitable for dehydration; some require preparation, and some (such as meat and fish) must stay at a minimum temperature during drying to prevent dangerous bacterial growth. Check what’s required before you start.