The reason some people say that plastic should not be used is that the oil from the dog food leaches out and can gets on the plastic. The oil will go rancid after a period of time, and if the plastic isn't thoroughly cleaned, can cause new food to go bad. Glass and ceramics are just easier to clean.
It's the moisture in air that causes most food to go "stale", and many say using the bag the food came in, and squeezing out the air and clipping it is the best way to store it, I do this and keep a weeks worth of food in a plastic container that goes into the dishwasher. So you are looking at two separate issues, staleness and oil rancidity, |