oven-drying fruit

[prasantrin]

I posted this in the eG Preserving Q&A, but thought I'd try here, too. My meat grinder has since arrived and I'm anxious to get started making andiesenji's fruit and nut balls!

I decided to try drying my own fruit using my oven (I don't have the space for a dehydrator, nor the room for it). I thought I'd start with nashi (Asian pears) and apples. But I have a couple of questions...

I'm going to oven dry my fruit--the course says to use a temperature of 60C, but says to go as low as your oven will go. My oven goes down to 35C (or maybe 40C), so I was thinking of trying that.

However, I cannot prop my oven door open as the course says to do. If I try to prop it open, the oven will stop working (it's a gas convection oven, large by Japanese standards but pretty small)

In this situation, is it better to go with a higher temperature? My oven goes from 40C to 45C, then straight to 100C, so it's either a low temperature, or 100C. I'm assuming propping the door open is to help any steam escape (which I read elsewhere), so maybe a higher temperature will help deal with the steam? Or should I just open the door once every 15 or 30 minutes?

Next question--for hard fruits, is 5mm still a good thickness, or would thicker or thinner be better? I'm only going to be grinding them, so I wonder if cutting them into eighths wouldn't be good enough...what do you think?

Final question--it's actually quite humid in my area of Japan right now, so are there any precautions I need to take when drying my fruit? Should I leave it in the oven to cool so the humidity doesn't cause it to soften again? Will it mould more quickly because of the humidity? If so, should I keep it in the fridge? (Yes, I know that was more than one final question, but they're all related so they should count as one!)

Someone please help me! I want fruit and nut balls!

[infernooo]

IMO - do it as low as your oven will go. The best dried fruit is dried, not COOKED, and I feel that 60c is much too high.... think of some of the best dried fruit in the world, from the Middle East, Europe and California - layed out in the sun it would get quite hot, but certainly not 60c hot.

I prop my oven door open with a rolling pin, and if you oven stops when the door is open, perhaps you can wedge something in to make the oven think the door is closed ?

I think if all else fails and you have to leave the door closed, leave it at a low temperature and the evaporated water from the fruit shouldn't be a problem... the circulating air and fans inside the oven should take care of that.

If you are just grinding them, don't bother making it too thick - it will just make them harder to grind. Just be careful not to over dry them.

In regards to the humidity, I don't think it really matters. Unless you are leaving them out for a long time, it should be pretty safe. Once the water has gone, the tendency to go off/rancid/mold is much less likely. Just store them in an airtight container and they will be fine !

[flacoman]

What i've done for fruit leather is to run the oven at 50C or so for about a half-hour and the turn the oven off and leave the light on. This will keep things at about 38- 40 all night. If you have a pizza stone, leave it in to add thermal mass.

HTH

Jorge

[dougal]

I'm always surprised by advice to leave a thermostatically-controlled oven's door open...

What happens is that the oven effectively tries to heat the whole room to the set temperature, making for much more heat in at least some areas of the oven! (I learned this many, many years ago. The image of a melted, rather than dried, pair of ski goggles haunts me still!)

Gas ovens are rather well vented - to let the co2 (and water vapour) from the flames escape.

So don't worry about how the fruit's moisture will get out with the door closed!

Put the fruit on a rack or mesh so the air can flow all round it.

Stuff dries faster the thinner it is cut - but it takes up much more rack space!

I dry mushrooms rather than fruit, btw. I think the water content might be similar though.

If the oven will give you 35/40C, you are very lucky. It should do nicely.

However, I suspect that exposure to very high humidity after drying might be a problem.

Two thoughts that occur to me for countering that humidity are using vacuum (Foodsaver-style) packing, or alternatively storing the dried fruit buried in sugar...

My mushrooms just go into a super clean, totally dry (oven dried!), lidded jamjar.

[andiesenji]

I missed this when it was first posted. I was out of town for a couple of days.

Be sure to put the sliced fruit into acidulated water as you prepare it, then pat dry with paper towels.

For apples, pears and etc., after beginning them in the oven and after they begin to feel leathery, you can actually string them (with a heavy needle and dental floss) hang them where you can direct a fan blowing room temp air onto them. They will finish drying just fine this way, even with the ambient humidity.

I have a friend who lives on her boat in a marina and this is her solution.

The easiest way to "test" the sliced fruit is to bite into it. When it resists and is chewy, it should be done.

You might find the following links helpful:

drying fruit 1

drying fruit 2

Edited September 24, 2008 by andiesenji (log)

[prasantrin]

Thanks, all!

My first batch is in the oven. I've got the oven set to 35C as dougal suggested, and right now I just have nashi in there. They're sliced to maybe 1/8 of an inch (I used a Benriner, so the thickness is pretty consistent). I soaked them for 10 minutes in ascorbic acid and water (suggested by one of the links andiesenji posted),

I have some apples, too, but I sliced them more thinly (maybe 1/16 of an inch?). I'll add them to the oven after my first 90 minute cycle is finished, since they should finish more quickly than the thicker nashi. I sure hope it doesn't take more than 4 or 5 hours for all of them to dry, because my bedtime is then!

But if that happens, I'll do what flacoman does with his fruit leathers, and perhaps turn up the heat for a bit, then turn it off and leave the fruits in the oven with the door closed overnight.

I have a foodsaver and a little Reynold's Handivac thing, so I think I'll be OK regarding keeping the fruits. It's a little less humid today, too, so hopefully humidity won't be too much of a problem.

I may be making fruit and nut balls tomorrow! Is it wrong to be this excited over drying fruit?

[prasantrin]

My apple slices are definitely too thin. Oops. Will make some thicker slices tomorrow.

Edited September 27, 2008 by prasantrin (log)

[andiesenji]

For an added bit of crunch, after putting the fruit and nuts through the grinder, you can knead toasted sesame seeds into the mix - I also use toasted sunflower seeds and/or pepitas or pumpkin seeds.

Needless to say, these will not keep quite as long because the seeds can become rancid if stored at room temp.

However, the things I make never seem to last long enough to suffer this fate.

[prasantrin]

For an added bit of crunch, after putting the fruit and nuts through the grinder, you can knead toasted sesame seeds into the mix - I also use toasted sunflower seeds and/or pepitas or pumpkin seeds. 

Needless to say, these will not keep quite as long because the seeds can become rancid if stored at room temp.

However, the things I make never seem to last long enough to suffer this fate.

←

Will do! Good sesame seeds are easily found in Japan, luckily! I also have some sunflower and pumpkin seeds, but they might be stale. I'll have to check them out.

My fruits were in the oven for 4 hours at 35C, but then I decided I needed to go to bed, so I hiked the temperature up to 45C for another 90 minutes and just left them. This morning they're still not done (not even the very thin apple slices), so I'm at it again! This is going to take forever, and I'm not that patient!

ETA: They're done, but...

My nashi are still pliable, but a bit crispy and golden brown around the edges. Oops.

The apples are a complete disaster--they were way much too thin (which I knew), and they're like parchment paper. They're also sticking to the rack, so it looks like I'll have to soak the rack to get them off.

Must try again while it's still morning. I'll have all day to get it right!

Edited September 27, 2008 by prasantrin (log)

[andiesenji]

If you want to make thin apple chips, try putting them on parchment paper on a sheet pan.

Once dried, roll the parchment up, crimp each end and bang them on a counter to loosen the chips. Same thing works with bananas.

I use an apple corer, slicer and set the slices to about 3/8 inch. This comes out with the apple spiral-sliced but one cut down through the stack of slices will separate them into rings (with one side cut) or into halves, which I usually do as it is easier to use them in fried pies, etc., in this shape. They dry to about 1/16 inch thick when finished.

With apricots and peaches, I just cut them in half.

Unfortunately, I don't have a great deal of experience with drying fruit in the oven, though I have done a little.

I have had my Excalibur dehydrators for more than 25 years and before that I used to use screens and dried them out in the sun. (I used screens on frames, like a box so the fruit was covered top and bottom, to keep insects away.)

This worked great for me because I live in the desert and it is both very hot and very dry here.

When I did use the oven, it was a long time ago and I still had a gas oven that had a standing pilot light which produced enough heat to dry small batches of fruits after the initial heating of the oven to get it started.

Later, I had a small electric convection oven, the first countertop one available to consumers, in the early '80s, made by Farberware. It had a low setting 120 degrees F., which worked great for drying very small batches. As I was harvesting and drying huge batches, I got the large Excaliburs and I could have used bigger ones but until recently, there was nothing available and now I no longer do the huge batches.

When I was a child, growing up in western Kentucky, fruits were dried on the galvanized roofs of two of the farm sheds, then covered with fine nylon netting to protect against birds and insects.

There was always a scramble to get the fruit off the sheds when rain threatened, but the results were wonderful, which is why that I began drying my own many years ago.

Edited September 27, 2008 by andiesenji (log)