I confess that I never planned to freeze-dry tomatoes. I lived under the assumption that the result would be similar to cucumbers or asparagus, where removing the water actually leaves almost nothing, maybe the skin. I was only led astray by one of my customers, who recommended sprinkling the freeze-dried tomatoes with salt and eating them instead of potato chips.
Note: This test was performed on an earlier model of the AMARU lyophilizer. We have made several improvements since then and today the capacity would be higher and the process faster.
Preparation
So I bought 5 kg of conventional tomatoes and added 1,5 kg of cherry tomatoes for comparison. I cut the cherry tomatoes into quarters, leaving some in halves. I then sliced the large tomatoes and cut some into slices and some into quarters (eighths).
I didn't arrange the load on the trays too much, and tried to have most of the cherry tomatoes sliced flat side up or completely preferably with one sliced side on the tray and the other side facing the side.
Freezing
From room temperature, the tomatoes were at the required -30°C in about 13 hours, but that was mainly because I had already run the chamber prefreeze on the AMARU during slicing. If you were loading all the produce trays at once into the turned off machine, I would add at least an hour.
Drying
Because tomatoes have quite a lot of water, drying 6.5 kg required a full 51 hours of drying alone.
Result
The longer drying time is definitely worth it. Contrary to my suspicions, the tomatoes retain their original shape and size perfectly and there is none of the unwanted collapse that occurs with some products containing over 90% water. Again, the result is best seen in the video below.
Rehydration
Tomatoes can no longer be returned to their original state, so that it is impossible to tell that they have been dried. They simply no longer retain their texture and the slices do not behave as if they have just been sliced. However, this does not detract from their taste and they can still be used in salads, for example, if they are re-watered.
Uses
Probably the best possible use of freeze-dried tomatoes is really as a substitute for unhealthy potato chips and various sticks in front of the TV. It might be worth trying larger tomatoes with some dip.