System and method for electronic pasteurization

#This invention relates generally to the field of irradiation systems, and more particularly to a method and system for electronic pasteurization.

#Irradiation involves exposing a target to an ionizing radiation to change the microbiology of the target. Irradiation is an effective method for killing micro organisms and insects in foods, extending the shelf life of various foods, and sterilizing medical products. Irradiation is particularly suited for treating food, such as meat, to kill foodborne pathogens, such as E Coli, Trichinosis, Salmonella, Yersinia, Campylobacter, Shigella, and the like. Two characteristics determine the effectiveness of an irradiation treatment—the dose, which is the total beam energy delivered per mass of food; and the penetration depth, which is the maximum depth into the food to which the dose is delivered. The penetration depth is a property of the ionizing radiation that is used for irradiation. Food irradiation typically requires a dose of about 300,000 rads to achieve a statistical kill of the pathogenic bacteria.

#Conventional irradiation systems utilize one of three methods to produce the ionizing radiation. γ-ray irradiation systems produce γ-rays from radioactive sources, typically Co60. X-ray irradiation systems produce X-rays by targeting an electron beam, on the order of 5 MeV, on a metal target. Conventional electron beam irradiation systems produce a high-energy electron beam, typically on the order of 10 MeV energy, and deliver it directly into the food. The γ-ray irradiation systems and X-ray irradiation systems deliver a deep penetration, on the order of 30 centimeters into food, but require immense shielding assemblies, on the order of 3 meters thick of concrete, for safe operation. Conventional electron beam irradiation systems deliver less penetration, on the order of 7 centimeters in food, but require somewhat less shielding, on the order of 2 meters of concrete.

#For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings, wherein like referenced numerals represent like parts, in which:

#FIG. 1A is a schematic drawing illustrating an electronic pasteurization system in accordance with the present invention;

#FIG. 1B is a schematic drawing illustrating the operation of a modulation control system in accordance with the present invention;

#FIGS. 1A through 7B illustrate various aspects of an electronic pasteurization system. The electronic pasteurization system comprises an improved accelerator, an improved beam transport system, and improved treatment stations for electron beam irradiation of a target. As described in greater detail below, the electronic pasteurization system and each individual component of the electronic pasteurization system include various distinct inventive aspects that are improvements over conventional electron beam irradiation systems. For example, the construction costs associated with the electronic pasteurization system are much less expensive than conventional irradiation systems. In addition, the electronic pasteurization system may employ a modulation control system to modulate the electron beam such that an electron beam is produced only when a target is to be irradiated. The improved accelerator is less expensive than conventional accelerators and operates at greater than 95% efficiency. In addition, the improved accelerator can deliver multiple independent electron beams, which allows multiple treatment stations to be operated from a single accelerator. The improved beam transport system utilizes permanent magnets that do not require an active control system. Specifically, once the beam transport system has been aligned, no additional work or control systems are necessary. In addition, the improved transport system can communicate multiple electron beams from the accelerator to multiple treatment stations which are distributed within a food processing facility. The improved treatment station utilizes a two-layer shielding system that substantially reduces the thickness of the shielding. In particular, the two-layer shielding system can reduce the thickness of the shielding by a factor of approximately 5. The improved treatment station may also utilize various labyrinth systems to contain the radiation. Specifically, treatment stations that effectively irradiate food patties and chubs are disclosed. In addition, an internal probe for irradiating the internal surfaces of a carcass, such as a chicken, is disclosed.

#The various inventive aspects are illustrated in terms of an electronic pasteurization system used for electron beam irradiation of food products. It will be appreciated that the electronic pasteurization system may be otherwise suitably used without departing from the scope of the present invention. For example, the electronic pasteurization system may be used to sterilize medical supplies, as well as to sterilize insects for insect control programs. It will also be appreciated that the individual inventive aspects may be otherwise suitably used without departing from the scope of the present invention. For example, the accelerator includes several inventive aspects that can be beneficially implemented in other accelerators.

#FIG. 1A is a schematic diagram illustrating one embodiment of an electronic pasteurization system 20. In this embodiment, the electronic pasteurization system 20 comprises an accelerator 22, a beam transport system 24, and at least one treatment station 26. The accelerator 22 produces at least one electron beam 28. The electron beam 28 is communicated by the beam transport system 24 to the treatment station 26. A target 30 travels through the treatment station 26 and is irradiated with the electron beam 28.