Continue to ramp up the intensity of your food distractors in your container searches.  Up the ante bit by bit as tolerated by your dog.  This is definitely something that takes time.  This is also a skill that should be revisited every once in a while.  You can see that the first time she encounters cheese in the hot box, it kinda blows her mind and it is hard for her to concentrate.  However, by the end, she is cool.  Other distractors present are Ritz Crackers, leather dog toy, marker, chips, stale pancake, and rib bones.