I found this interesting link for maintaining a wax worm colony (which is pretty different than keeping supers):
http://aqualandpetsplus.com/Live%20Food,%20Wax%20Worms.htm
for keeping supers you can use a medium of rolled oats, wheat bran, chicken mash, corn meal, or "worm chow" (Available thru most bug distributers). Pretty much any grain or cereal can be used as a storage medium/food source (as long as it isn't a "sweetened flavored cereal" natural cereal only like corn flakes, puffed rice, etc.).
Carrots work best for a moisture source for supers, apples tend to put too much humidity into their enclosure so I would only suggest apples with in the 24 hours before you plan on feeding the super so he is properly gut loaded for your herp. Using cornmeal would be more of a storage medium than a gutload food. You should use apples, potato, carrot, and maybe some leafy greens to gutload your feeders. Here is a good article on gutloading:
http://carolinapetsupply.com/gut_loading_insects.html
Here is another helpful link for raising supers:
http://aqualandpetsplus.com/Live%20Food,%20Super%20Worms.htm