Perhaps some ascorbic acid or lemon juice added to the paste balls?
http://www.uga.edu/nchfp/how/dry.html
I dehydrate a lot of different veggies especially hot peppers.
My fav tomato for drying similar to fruit leather is Sungold/Sun Gold cherry-type. Cut in half, place cut side up on the dehydrator shelf. My temperature of choice is 125-130°. Sprinkle the tops with a Creole seasoning such as Tony Chachere's. Aprox 3 days. When finished put in glass jar, screw down lid & put upside down in the cupboard for a day or two. Periodically check for moisture forming in the jar. If see any then back into dehydrator for another day & repeat process. If no moisture forms on inside jar I then keep in the fridge for up to a month or in the freezer for longer storage. It doesn't take long for a handful to thaw out enough to much on.
Tomatoes or peppers dried enough to powder are safe to keep unrefrigerated and as long as stored out of the sun and are in airtight containers keep their flavor for years.
jt