This is the obvious followup to my just-prior post.
The answers are:
Yes, you can. All it takes is four or five consecutive good drying days. After four days, most of the batch was dry enough to be put in a jar and put on the shelf. A small — but distinctly different — residual will get a fifth day of drying.
The catch is that it’s rare to get a string of good drying days in a Virginia summer. You ideally need the weather to be consistently sunny, hot (85+ is ideal), breezy, and dry (relative humidity below 60% mid-afternoon). So you can air-dry, if the weather is right, but you can’t count on being able to air dry, the way they can in a Mediterranean climate. You can occasionally air-dry.
Achieving leathery versus crispy with open-air drying? So far, the best I’ve gotten is “leathery”. And I suspect that’s the limit of open-air drying here in USDA Zone 7, Northern Virginia. Whether or not “leathery” is shelf-stable, absent further preservation steps, I’m going to find out. (Near as I can tell, “crispy” keeps for at least a year.)
As a snack, I’ve already gotten the feedback that crispy beats leathery. So for best end-user value, I’m probably going to stick most of these in my electric dehydrator, for a finishing step to get them all the way to crispy.
Does the low temperature of “sun-dried” tomato production result in a product superior to properly electrically dried tomatoes? No. For sure, the sun-drieds are processed at a low temperature. But I think the 135F limit for electrically-dried tomatoes was chosen specifically to avoid degrading the flavor of the finished product. Bottom line, other than the leathery texture, neither my wife nor I could tell sun-dried from heat-dehydrated tomatoes
Leathery versus still too wet: Listen to your inner “ick”. It turned out to be remarkably easy to tell when the tomatoes were dry enough to be called “leathery”. For some, it was obvious because they were still visibly wet. For the rest, pick them up, and if the flesh of the tomato still moves when you rub it, it’s still too wet. I say “ick” because that’s the sensation it gave me. Like a gummy worm, but less firm.
A better rule for cutting tomatoes for drying.
One nice thing about air-drying is that you can cut your tomato slices thicker, and so pack more tomatoes into a given tray area. (You can’t put really thick slices in a Nesco dryer because the space between the tray surfaces is only about a half an inch.) In fact, traditional Italian sun-dried tomatoes are literal tomato halves, and so are quite thick in the middle.
For this batch, I aimed for 1/2″ thick slices, versus the 1/4″ slices typically recommended for use in an electric dehydrator. Some of the slices did not dry fully in four days. But that wasn’t due to their thickness.
All of my tomato slices that failed the “leathery” test had tomato skin on one side. And conversely, all the slices with skin on one side failed the “leathery” test at four days.They were either slices from the end of the tomato, or cherry tomatoes that I had simply cut in half. And I’m pretty sure that makes sense. The skin is going to be nearly impervious to water.
I’m far too lazy to skin the tomatoes before drying, so my new rule is to cut very thin (1/4″) slices off the ends, and thicker (1/2″) slices in the middle. That way, all tomato flesh is at most 1/4″ from a surface through which water may evaporate. I’m still not sure what I’m going to so for cherry tomatoes.
Summary.
Yes, you most certainly can sun-dry tomatoes in a humid climate. I dried most of a batch of tomatoes to a stable, leathery state in four days.
You need to have a string of good drying days. The most common rule is that you need considerable time with air temperatures 85F or higher and relative humidity 60% or lower. Plus sunlight and a breeze. In my case, the past four days have been brutally hot (flirting with 100F), sunny, and reasonably dry.
You can predict afternoon relative humidity based on morning conditions, and the use of an on-line relative humidity calculator. (That’s at the end of the prior post).
In my case, the slices that failed to dry in four days were the same as the slices with tomato skin covering one side. (E.g., from cherry tomatoes, halved). I had no problem drying 1/2″ slices, as long as there was raw tomato on both sides of the slice.
Otherwise, just follow standard guidance. Cut and salt the tomatoes. Put them in the sun, with some sort of netting to keep off bugs. Bring them in at night and flip them. Dry until leathery.
The only thing I can’t seem to achieve is drying tomatoes to the point of crispness. But crisp is preferable for snacking. So I’m going to have to use a bit of electricity to get them to that point.
By far, the hardest point for me was getting over my aversion to having sliced tomatoes sitting around at room temperature. But, as a matter of logic, everybody says this takes about four days. So for most of that time, those tomato slices are going to be quite wet. And that’s normal. Ideally, the high acidity of the tomato (and maybe the salting), plus the sterilizing effects of the UV in sunlight, all combine to keep mold at bay long enough for the tomatoes to dry.
