Metal and/or glass and/or crocery seem to be about the only sure solution to isolating foodstores from rodents. I have yet to find a plastic that they don't penetrate.

At the remote radio sites I used to frequent, we solved rodent problems in two ways. First, we sealed the building as best we could. We plugged every hole and penetration with steel wool and RTV caulk or duct seal. They can't chew through the steel wool without hurting themselves bad, and the caulk or duct seal held it in place so they couldn't just push/pull it out. We made sure the doors sealed tight enough that anything thicker than a sheet of paper wouldn't pass through. We put double layers of HD metal screen over every vent. Second, we also put down sticky boards with a Frito in the center. Wouldn't you know, despite all those precautions, we would still find dead mice and bugs on the sticky boards later on. Either they snuck in through the open door while we were there or they found another way in somehow.