Where does the sugar go when you dry tomatoes?

Hi all--new member with a dried tomato question. We've been drying LOTS of tomatoes this year, at 150 degrees with air blowing. When they are mostly dry, like a raisin, they are as sweet as raisins--just amazing. If they don't get pulled from the dehydrator at that point and dry to the point of being all crunchy, there is no sweetness at all. This gives me a sad.

Anybody know why that is?

I had to pull out a jar of ours to be sure...but they are still very sweet at as close to crispy as I get them. I use a dehydrator with air blowing also but I start with the temperature at 135 and after an hour or two lower to 115. I have always read that above 115 destroys nutrients...so I compromise between that and what the book with the dehydrator says. I do try to get them close to crispy though so they store well. Sounds like you've had a good garden this year.

Though this is not tomatoes, it is probably a similar process:

When corn is picked, the sugars begin to convert to starch. The longer you store it the more starch it has.
The next time you have sweet corn ready, try this:
Put a pot of water on to boil, then go pick a couple ears, shucking them as you walk back to the house.
Put them in the pot and cook. Much sweeter than any that have been in the 'fridge a few days.

The classic Italian way of drying tomatoes is "sun dried". At 150° you are probably 'cooking' the sugar into starch.
Even solar driers can get too warm for good tomatoes if it is hot weather.

Julia,I too,would think it was the high temperature except that you said that just before crispy they are still sweet. Have you tried to rehydrate any ?
John, I would love to sun dry tomatoes and my shiitakes but our humidity is too iffy around harvest. They would start to dry then reabsord moisture over night attract fruit flies...etc. so an electric dehydrator has become more reliable for us most of the time.

Thanks for the input, everyone! I did rehydrate a bunch of the crispy dried tomatoes last night for a pasta dish. (Home made red pepper sausage on whole wheat gobbetti with creamy pesto sauce--yum!) I poured boiling water over maybe a cup and let them sit, then used kitchen scissors to cut them into smaller bits. They had a lovely tomato taste, but the "sweet" didn't come back.

I also dug around in the fridge to find a container of really squooshy semi-dried tomatoes, and one or two had visible yeast growing on them. I'm working a crazy schedule this week (I leave at 6:30am and get back after 6pm) and things have gotten very disorganized, so I can't say for sure how long those were in the fridge, but it couldn't have been more than several days.

I guess it's o.k. that so many have been dried to a crisp--none of those have developed any growth. It's just that the raisin like half tomatoes (most of these are Juliets, which are either big grape tomatoes or small roma tomatoes, depending on how you see things and how much pruning you do) are SO very delicious. They are literally like candy. My first batch (watched carefully and pulled when a few were only slightly wrinkled--I ate those as I pulled them off the tray) was set out on the kitchen counter and disappeared in one afternoon--all eaten up by my husband and my 6 and 9 yr old daughters. Literally hundreds of little tomatoes--nom, nom, nom, gone.

I suppose I'll have to try freezing the squooshy ones. . . I will also try running at a lower temperature. I think we ended up with the high temperature after having tomatoes get moldy during the dehydrating process, but that was with a smaller tabletop dehydrator.

I thought of a couple other things...I used to peel my romas to dry and then decided to stop...unpeeled and split they take twenty four hours and sometimes a few would have pockets of undried tomato... I would jar the crispey ones and pour olive oil over the lesser dried ones and refrigerate. I don't keep the dry ones in the refrigerator just in the dark pantry.

I was taught to put the dried product straight from the dryer trays...still warm...into the jar and to open the jar after a day to check for moisture under the lid. If there was any dampness they needed more time in the dryer.

The worst thing I lost to inadequate drying was jars of morels....really dissappointing about midwinter when they were supposed to be a treat.

One thing I know about sugar is that the longer you caramelize it the less sweet it is. 150%f doesn't seem hot enough to do that, but it certainly sounds like that's what is happening.