In all my years of gardening and preserving, this is a new one on me.
I sliced up a variety of tomatoes and loaded them on to my Harvester trays. Set the temps to the ones in the book, followed the directions to the letter, and...
Some of the tomatoes are blackened. Now, I do like Cajun food, but I don't think my tomatoes are supposed to be black out of the dehydrator.
Here's the mystery: It's not all the tomatoes, and it's not all the same variety.
I loaded Roma, Rutgers, and Celebrity. There is no rhyme nor reason as to location of tray, thickness of tomato (some paper-thin slices are fine), nothing I can think of to distinguish why some of them are burnt black - some are only burned on half of the tomato slice, some all the way across.
Does anyone have any idea as to what's happening? Are the tomatoes somehow sweeter and therefore carmelizing? Or do I have a hoo-doo in my dehydrator?
I have never had that happen. I would suspect the fan is blocked in some places, not evenly ciculating. Maybe the temp control is defective and the temp was a lot hotter than you thought.
As I said, I have had never had the temp hot enough to burn even after they became paper dry.
If you have a thermometer, you might try putting it in there. It's definitely overheating and therefore dangerous.
I was going to suggest a fan blockage too....but I see that has already been mentioned.
Now this may sounds like a silly question but have you moved the dehydrator to a different place than where you normally dehydrate? Is it on a towel or on a cookie sheet or other surface like that? If so, it may be the cause of the problem.
One of my Facebook friends did a quick google for me, and here's what he came up with:
had two seconds and did a quick internet search.
"'Tomatoes that turn black have a lower acid content, so when they dry oxidation takes place and they turn darker. the higher acid content varieties stay "redder", I use Roma's or one of the hybrids of Roma's I buy citric acid from the pharmacy and make a solution that I spray on the prepped tomatoes when I dehydrate them, and they don't get as dark
micro organisms don't like low P.H. It acts like a suppresor for bacteria and mold growth.'
A couple other people said the more ripe maters turn black. Others suggested keeping the temp as low as possible."
So there's another mystery solved.
I'm going to see if I have a mister, and I'll put some lemon juice in it and spritz the tomato slices.