It is processed and hermetically packed beef that has been irradiated. Typically boxed beef will be loaded onto carts hanging from a rail that snakes its way through a concrete maze. In the middle of the maze will be a deep pool of water containing the source. When the carts are all loaded for a production run the source will rise up from the water and the carts will slowly pass by, thereby exposing each box to a predetermined dose of irradiation. The gamma rays will kill any microorganisms in or on the beef. This will allow the beef to remain unspoiled for a much longer period of time, without refrigeration. Irradiation is an expensive process and is more commonly used to sterilize medical products. It's also frequently used to kill all the bugs (visible and microscopic) found in bulk spices prior to processing and packaging.