To me this sounds like a brillian idea, but only from the first glance. But if I think about it for a moment, more and more questions start to come up.
There are all kinds of regulations in the food industry and just from looking at a person you can not tell if he carries some kind of contagious illness. And in 90 minutes if you want them to provide any result, you don't have time to explain them much about how things run so that leaves them a little time to actually do something. Besides it eats your own time. I am no chef but I wouldn't feel comfortable letting someone from the street to work in my kitchen. Maybe I am just too cautious but I feel that work in food industry should require some basic training.