Squinting at her, and then squinting at the food thereafter.

"...Cheese can be left in the sun for up to two hours. It's been forty-five minutes. You have some time before it's been tampered with."

Clearly neither understanding the implication she was making, nor the implication on his own actions. Ironic, for a man who was not above poisoning people, to obviously have very little clue that that was a tactic used by the modern man to re-enact the cave man.