Re: what are in vegetable preservatives that make the vegetable last?

This sounds like a very interesting project.

Note that scientists don't say "non-organic" but rather "conventionally grown".

Neither the organic nor the conventional grown tomato should have any preservatives. Organic growers use organically certified pesticides and conventional growers use conventional pesticides.

Some of these pesticides may be fungicides, that is chemicals that stop or slow the growth of molds, (or as scientists call them) fungi.

Wikipedia has a fairly good page on fungicides here: http://en.wikipedia.org/wiki/Fungicides

Happy experimenting!