Is it safe to eat food that has been through a X-ray scanner, for example at airports?
Yes, it is. X-ray scanners used at airports for baggage control operate at very much lower energy and give rise to radiation levels very much lower than radiation sources used in food irradiation facilities. The radiation doses used to process food can be as high as 10,000 gray, whilst X-ray scanners operate at less than 0.5 gray. It is very difficult, if not impossible, to detect changes to food once it has been through an X-ray scanner.
In fact many of these X-ray machines (at airports for example) operate at such a low dose that they don't affect photographic film.