THE X-RAY EMITTER SCANNING HORN IS IDEALLY LOCATED 1 METER FROM THE CENTER OF THE PRODUCT TO BE X-RAY TREATED. THE SYSTEM TO BE USED BY AGSCAN WILL HAVE PALLET LOADS OF COMMODITIES MOVED INTO THE SCANNING POSITION, ALONG THE CONVEYANCE MECHANISM. A STANDARD PALLET MEASURES 40" X 48" AND CAN BE AS HIGH AS 72" (OR MORE FOR SOME PRODUCTS). THIS PALLET "LOAD" AT A DENSITY OF 0.6 GM/CC WILL WEIGH ABOUT 2,900 POUNDS. THE AGSCAN SYSTEM ALWAYS ROTATES THE ENTIRE PALLET TO ACHIEVE THE MOST UNIFORM ABSORBED DOSE OF ENERGY THROUGHOUT THE PRODUCT.

X-RADIATION SCANNING HORN

POINTED VERTICALLY DOWNWARD.

CONVEYOR MOVES PRODUCT UNDER

THE SCANNING HORN.

	The Process
	Receiving Your Shipment. Each incoming shipment is received at the loading dock where it is quickly off-loaded with electric forklifts, and placed into a chiller or freezer section of the facility. Your order is next clearly labeled with bar coded customer name, lot, and type commodity. These labels remain with the order throughout the process. The X-radiation Process. Your order will be placed upon the conveyor system and taken through the x-ray scanner zone where it is exposed to the correct, predetermined dose.. The system is controlled by a computer which sets up the control of all parameters necessary to reach the correct dose. A printout of the dosimeter value is provided and available to the customer. A copy is stored with the company records for this lot. All lot data are digitally archived at AgSCAN. Added Quality Control AgSCAN operates a microbiology laboratory where each commodity from individual customers is tested to determine the bio-burden and other factors related to the commodity. Three sample lots are required from each customer for processing, levels of infestation or pathogens are determined and the correct dose is determined prior to accepting a commercial lot of the commodity. Each customer commodity undergoes these three lot testing to achieve the validation of the x-radiation process to a specific commodity, and to provide data for future setups to run this commodity. Process validation for a specific commodity is an annual requirement at AgSCAN. Packaging Services. AgSCAN works closely with each customer, using its expertise in packaging products for x-ray processing.. The optimized packaging design will reflect require- ments for ease of handling throughout the process, and will be directed to the consumer level whenever appropriate. Storage. Storage of customer product will be on a short term basis only. Storage areas for cooled or frozen foods are provided for longer term storage, and will be utilized per customer requirements with normal fees charged by AgSCAN. Process Certification. Upon completion of the X-radiation process, a Certificate of Absorbed Dose will be provided the customer for each lot processed. A copy of this certificate is retained in the Agscan digital archive. Environmental Requirements. AgSCAN meets environmental requirements. There are no radioactive isotopes on the premises, so there is not a chance that radioactive materials can mingle with the food going through the X-Radiation system. As far as the rest of our operating system, little water is consumed and the only unusual material released to the atmosphere is a small amount of gaseous ozone, and that is maintained within the limits set by EPA. Ozone is not a stable molecule. It easily and quickly returns to stable oxygen, the molecular form of oxygen that we all breathe from the atmosphere. We consume mostly electric energy from commercial utility companies. Some energy is co-generated back to our utility. So, we are good neighbors within the local community, carrying the full responsibility for our portion of the environment. Worker Safety. AgSCAN facilities must conform to OSHA requirements for safety. We go even further than OSHA in assuring worker safety. Equipment, clothing, atmosphere control and material handling are studied and operated with the utmost concern for worker safety. And, we are a clean facility. We maintain proper air filtration as well as refrigeration throughout AgSCAN facilities. You might think you could eat your next meal from our clean floors. AgSCAN considers itself the most advanced facility of the type for X-radiation. And, AgSCAN will continue its program of engineering excellence in the design and development of this socially beneficial service. Consumer Safety. AgSCAN performs X-radiation in compliance with international, federal and state regulations pertaining to this type of process. Also, AgSCAN works closely with its customers to assure that complete understanding and agreement between parties exists prior to processing of any commodities, and that all factors pertaining to consumer safety are clearly followed in both X-Radiation and the packaging of commodities for the safety and benefit of the consumer.

	AgSCAN: 805-684-9374 Fax: 805-566-9739 Email: info@agscan.net
	All material and information copyright AgSCAN 2004

Table 1. Types of radiation that can be used for food and medical products.

Radiation Type	Source	Half-Life	Energy (MeV)
gamma ray	Co-60	5.3 years	1.17, 1.33
gamma ray	Cs-137	30.0 years	0.06
Electron Beam	Generated from electricity	not applicable	10.0
X-ray	Generated from electricity	not applicable	5.0

CHARACTERISTICS OF IRRADIATION TECHNOLOGY

Types of irradiation

1)Radiation is everywhere, whether recognized or not. Radiations are composed of gamma. electrons, and X-ray radiated from the radioisotopes, X-ray generated by mechanical devices, electron beam produced by linear accelerator and neutron from nuclear reactor. X- and gamma-rays have a very short wavelength and they are the type of energy we encounter from the Sun, in small amounts as not to be harmful.

2) When the x-radiation passes through a material it can ionize atoms and molecules to form ions. Radiation with those attributes is called ionizing radiation and gamma, X-ray, electron beam, ultraviolet, and neutron are included in this category. At present the types of radiation that can be safely used for food and medical products approved by FAO/IAEA/WHO and CODEX and national regulatory agencies.

3) Among radiations listed the gamma-ray is used 80% for commercial use and the electron beam is less than 20% for food and medical products. The use of X-rays for practical purposes is still limited, but is considered to be the major technology over the next few years.

4) Because the penetration of electrons is less than that of gamma radiation, the range of the utilization was also limited. However, some applications such as disinfest and surface pasteurization of grains and sterilization of medical products are successfully adapted for commercial purposes. Since the generation of the electron beam can be controlled by power at the source, it has potential advantages in aspects of process control, speed, energy efficiency, and consumer acceptance. Therefore, development of electron beam irradiation has been actively conducted by the advanced countries.

The gamma-ray which is the most frequently used radiation for commercial purposes since it can penetrate materials much deeper than electrons. Therefore, it can be used for completely packaged end products, thus avoiding the possibility of secondary contamination after pasteurization. The use of the gamma-ray also improves efficiency and minimizes the destruction of the composition which often results from temperature increase of the products. When food products having the same specific heat as water are irradiated at 10 kGy, the dose permitted by international organizations and generally recognized as wholesome, the temperature is increased about 2.4 degrees C. Furthermore, there are no residues remaining in the products, unlike those treated by fumigants or chemical preservatives, and the environmental factors do not effect the processing. Irradiation with x-rays is the most efficient form of irradiation, and best lends itself to large throughput food irradiation.

Table 2. Comparison of energy required for various processing methods

PROCESS	ENERGY Consumption (kJ/kg)
Inhibition of germination (0.01 kGy)	12
Defestation (0.25-0.50 kGy)	7
Pasteurization (2.5- 10.0 kGy)	21.0 - 84.0
Sterilization (25.0 - 30.0 kGy)	157
Refrigeration (35 degrees F) 5.5 days	318
Refrigeration (35 degrees F) 10.5 days	396
Heat Sterilization	918
Cooking Process	2,558
Freezing -25 degrees F ( 3.5 weeks)	5,149
Blast Freezing (4.4 F- 25 F)	7,552

* Reference: Brynjoifossn, A, -Food- Energy developing countries-food irradiation IAEA-SM-250/26, 421 (1981).

MORE INFORMATION ON FOOD IRRADIATION

Food irradiation has proven to be a safe and effective process for increasing food safety and extending product shelf life. Nearly 50 countries have approved or allow food irradiation, although the foods and doses differ by country. In the US, all fruit and vegetables, poultry, red meat and spices/seasonings are approved for irradiation at specified maximum dose levels. There are petitions under review by the FDA for irradiation treatment of processed meats (hot dogs and deli meat), processed vegetables, fruit juices, molluscan shellfish and crustaceans.

Irradiation can be accomplished with three available technologies: gamma ray processing, X- rays and high-energy electrons, also known as electron beam or E-beam processing. High-energy electrons, gamma and X-rays can kill or inactivate bacteria, fungi and insects by breaking molecular bonds in the microbial DNA. It has been suggested that there are differences in the effects of these technologies on microbial inactivation due to the differences in free radicals formation, but the comparison is inconclusive because of the different doses applied. Comparison of the radiation technologies, which involves examination of the radiation dose yield, dose rate, related biological effects and post irradiation storage, and radiolytic effects can be helpful for understanding their performance.

Radiation processing speed is determined by the source power, product density and the minimum dose requirement; increase the product density or the dose requirement and the throughput falls. Gamma activity is measured in curies (Ci), i.e. 1 MCi is a moderate size source. E-beam and X-ray activity are measured by beam-power that ranges from 25 to 50 kW in typical food applications.

Penetration Depth. Gamma and X-ray sources emit packets of photons with no mass or electric charge and travel further into the product than E-beam, gradually losing energy. Cobalt photons have monoenergetic spikes at 1.17 MeV. X-rays and E-beams can be generated with almost any energy; 5 and 10 MeV are the respective legal maximal for food irradiation. Since electrons have mass and electric charge, the penetration depth for E-beam is shorter compared to gamma irradiation. For food products with densities similar to water (1g/cm3), the penetration depth is limited to a few centimeters at 10 MeV.

Absorbed dose is the energy absorbed by a unit weight of product, measured in gray (Gy). A few thousand gray is a typical dose for food. The cascade of secondary electrons caused by e-beam produces a high dose near the surface. Gamma and X-rays give a much more homogeneous dose. However, E-beam treatment has a higher dose rate. Dose rate is the energy absorbed per unit weight of product per unit of time. It is proportional to the number of photons or electrons per unit area or radiation flux density or current. A representative dose rate for gamma is measured in terms of kGy per hour compared with kGy per second for E-beam and X-ray. A 15 kW E-beam source can be highly focused into a few square centimeters whereas gamma source radiates in all directions. The techniques of dosimetry are now sufficiently established in food irradiation to provide one of the most reliable means of quality control.

Post irradiation dosimetry is part of a validation process and is necessary in order to find optimal irradiation conditions and to learn about radiolytic effects in foods. Analytical techniques for identification methods for irradiated foods are well developed and based upon irradiation-mediated chemical, physical or biological changes in the foods. Existing methods for identifying irradiated foods are based on measuring changes in composition such as radiolytic products, lipid-derived volatiles, lipid oxidation products, unusual carbohydrates, and vitamins.

The future of food irradiation is filled with promise since it can effectively reduce or eliminate pathogens or spoilage microorganisms while maintaining wholesomeness and sensory quality. Comparison of key processing parameters of irradiation can be helpful in understanding technology performance for specific food application.

Comparison of typical radiation processing parameters

GAMMA RADIATION ELECTRON BEAM

Processing Speed (@ 4kGy, tons/hr)	12	10	10
Source Energy (MeV)	1.33	5	5-10
Penetration Depth (cm)	80-100	80-100	8-10
Dose Homogeneity	high	high	moderate
Dose Rate (kGy/h)	low	high	higher
Best Application	Bulk processing large boxes or palletized product in shipping cartons	Bulk processing large boxes or palletized product in shipping cartons	Sequential processing of primary packaged products in-line

COMPARISON OF POWER RATING

Type of Radiation	GAMMA	X-RAY	ELECTRON BEAM
TYP Power	50 kW (3.5 MCI)	25 kW	150 kW

Some useful rules:

1 MCi " 15 kW of power

1 kWh " 36 000 kGy / kg of product

1 kGy will raise product temperature by approx. 0.24oC

Dr. Tatiana Koutchma's work is concentrated in the field of microwave, UV and electron beam irradiation. She can be reached at (708)563-8178 or by e-mail at koutchma@iit.edu

e-mail info@agscan.net