I use 9 inch plastic plates filled with water with the cat food bowls in
the middle to protect the food. Usually this works but ants can swim -
proven by the two times they still got into the food even with the water
moat. But it only happened two times in four years so it's a pretty good
deterrent. The same can be done with gladware plastic ovenware filled
with water. Place a cheap plastic bowl in it, and place the food on top
of it. I would do this on a table or counter not against the wall and
preferably on legs to help keep ants off the table/counter.

Now if it is other food, sugar or other things. Place it in zip lock
bags, zip lock plastic containers, or other plastic containers with a
snap on lid - ants cannot get into them.

One thing i do that seems to help is, once ayear, I go around the base
of the house with aBIG can of ant poison and sprinkle it around the
foundation. Helps keep them out.