This.
Maybe we're just lucky -- my office is also small (20 people) and pretty close-knit, and I'm 100% confident that no one is ever using old or expired food in anything for the office. I know that I (or the wife) will go out of our way to make sure that we are making something really good -- because that's what everyone does (well, except for the one young single dude who does our video editing and usually brings a store-bought dessert -- but a good one from a good local bakery).
We also do an optional "breakfast club" thing every Friday where we rotate and bring in breakfast for the office -- 90% good home made stuff (last week was some damn good sausage gravy in a crock pot with home-made biscuits) for this also. I'm up in two weeks for this one and going to bring my wife's blueberry / cream cheese coffee cake.
The owners also bring in catered lunches from time to time for us (for anniversaries, new hires, or people leaving usually) -- but the potlucks destroy the catering every time...