Traceability is recognized as an important issue in all aspects of production, marketing and international trade in products derived from intensive animal production systems.

Public health episodes including Bovine Spongiform Encephalopathy (BSE) in cattle, PCB, and dioxin contamination of ingredients, E. coli 0157: H7 infection associated with processed ground beef and the most recent incident involving melamine contamination of pet food, have all contributed to intensive concern over traceability.

The European Union (EU) has been especially active in formulating regulations to protect consumers. Recognition of the high incidence rate of SE among member countries of the EU has resulted in a series of directives regarding traceability from farm of origin to point of sale.

Directive 2002/4/EC mandates compulsory identification on each shell egg effective Jan. 1, 2004. With variations in member nations, eggs are imprinted with a unique code which specifies farming method (organic, free-range, non-confined or caged), country of origin, farm ID, and a "use before" date. In addition, producer associations or individual plants apply logos for promotional purposes.

Trace-Back Program Critical

Apart from legislated identification, a number of food marketing companies in various countries require imprinting, including ECO and other major food chains in Japan. It is evident that identification as a component of a trace-back program is critical to rapidly identifying the source of infection in epidemiological investigations of food borne disease outbreaks.

A further component more recent and specific to the United States involves agro-bioterrorism. One U.S. producer has made claims relating to superior safety associated with eggs individually etched with a code.

In assessing risks associated with deliberate adulteration or tampering of the food supply, eggs can be regarded as fairly insignificant since tampering of packed shell product would be time consuming and limited in impact. Liquid bulk product such as milk, ice cream, juices or pasteurized egg liquid are more likely targets for deliberate adulteration than whole shell eggs.

Components of Traceability Systems

The primary requirement for a trace-back system involves a coded sequence of numbers or digits on each pack or alternatively on individual eggs. The method of application is determined by available technology, cost considerations, durability, susceptibility to fraudulent change, legibility, and compatibility with the shell.

A database is the second component of a traceability system. Consumers and investigators should be able to access records to track product through the various stages of production extending from the farm through processing, including imprinting, storage, transport, distribution, and ultimately to display at point of sale. Traceability involves both trace-back to origin and trace-forward investigation associated with product recall.

Education of Stakeholders

Any system requires education of the various stakeholders involved in production, distribution and marketing through to the consumer. Systems which are mandated by law and are uniform in their presentation are generally accepted by consumers. Introduction of innovative systems requires promotion and education at both point of sale and in the media and may not be perceived as an advantage or a benefit, especially in nations with a low prevalence of SE.

Generally, in the United States, consumers place considerable importance on the USDA seal. Although this designation relates to grade and quality, there is a general misconception that eggs derived from a plant under USDA inspection are wholesome and free of contaminants or pathogens.

Shell eggs may be imprinted with logos to identify branded product with specific attributes. This is not strictly traceability but rather product differentiation. Consumers are provided with an assurance that marked eggs conform to brand specifications, which may include superior nutritional content or indicate that the eggs have been subjected to a process such as in-shell pasteurization.

Marking technologies available today vary in their levels of sophistication, capabilities and costs (see sidebar).

The Bottom Line

The industry should guard against introduction of non-beneficial innovations or mandated adoption of sophisticated technology. New systems will require capital expenditure and purchase of consumables to achieve real or perceived advantages, which may not be commensurate with cost. In the event of an egg borne disease outbreak, current imprinting can identify the plant of origin and open dating allows consumers to recognize expiration dates.

It is important for every plant to maintain internal records for feed mill operation, flocks, and processing that can be applied in the event of a trace-back for a pathogen or contaminant. Incremental advances in technology are necessary in printing on cartons and possibly eggs to ensure legibility.

Both HACCP and SSOPs should incorporate protocols for trace-back and recall. Given the current situation in the U.S. industry, an SE outbreak that is diagnosed and confirmed through the FoodNet will initiate an investigation by the FDA. More complicated or extensive episodes such as contamination of a feed ingredient common to a region will involve more extensive trace-back, which occurred in the recent incident involving melamine contamination of mislabeled imported ground wheat incorporated into pet food.

Available Imprinting Technology

Rubber Stamping


Eggs can be imprinted with an ink impression using a rubber stamp. This simple technology applies a logo identifying a brand or the "U.S." for export, on each egg after cartoning and before closure of the lid. There is no capability to apply unique serial numbers.

In U.S. plants subject to USDA inspection for interstate shipment, cartons are stamped with the packing date, the plant number assigned by USDA, and the "use by" date. To promote internal plant quality control, some processors may apply a packer number.

In the event of a food borne infection, the carton, which may or may not be available at the time of investigation, will provide the most elementary data used to initiate a trace-back investigation. In most well-managed plants with HACCP and trace-back systems in place and that pack off-line product, a paper trail will identify the most probable flock of origin. With in-line units, it is invariably impossible to identify individual flocks responsible for an incident but investigations to determine the possible presence of SE infection by screening individual units can be initiated on the basis of carton information.

A problem relating to rubber stamp imprinting of cartons relates to the readability of the three items of information. Defective stampers, improperly adjusted packers, incompatibility of ink with the surface texture of packaging material (fiber, foam, or plastic) may affect legibility.

Ink Jet Printing

Commercial jet printers can apply the three required items in addition to time of packing to cartons. This additional feature allows more precise identification of source flocks if plant records correlate time of packing with the origin of eggs.

Records are required to relate operation of in-line conveyors transferring eggs from specific flocks to the plant or identifying individual consignments of eggs when packed off-line. Hitachi supplies the KX series of printers operating with continuous ink jet technology.

An advantage of the system is the capability of printing clearly on uneven surfaces and the accommodation of cartons with rounded ends. Although not in commercial use, continuous ink jet printers have the ability to apply a barcodes to cartons. Generally, bar codes are applied to labels then attached to boxes primarily for inventory control rather than product traceability. The Hitachi KX printers offer flexibility in print characters in either 2- or 4-line configurations using a 65 micron nozzle. Currently, cost is a significant constraint to general adoption since each unit, including controller and print head, costs approximately $12,000, compared to the $50,000 total cost of a modern packer equipped with a rubber stamper.

Ink jet printing can also apply logos to individual eggs. Domino of the United Kingdom supplies the A-Series egg coder for Moba, Staalkat, and Diamond graders together with compatible software. Models are approved for use in USDA-inspected plants and ink conforming to FDA specifications is available. The most recent Domino A-300 series is encapsulated in a stainless steel enclosure and these models have a molded keyboard which is used to select logos, farm and plant codes, and dates.A number of supermarket chains in the United States require imprinting of individual eggs both for traceability and as an assurance of brand identity in addition to product differentiation.

Due to the position of the print head in relation to the baskets in the transfer conveyor of the packer, ink jet printing can only be applied to the side of the eggs. The logos and imprinting are not completely visible to consumers when eggs are placed in cells. Rubber stamping, in contrast, places the logo on the large end of the egg that is uppermost when the lid of the carton is opened.

Both rubber stamping and ink jet printing require a dry shell which is a function of appropriate selection of the temperature of wash and rinse water, surfactant additive in the sanitizer, installation of an OEM high efficiency drier, and possibly accessory drying fans. Diligent management of stamping exceeds the requirements for unstamped and generic eggs when graders with up to 10 packers are operated at a throttle setting of 350 to 400 cph.

The EggsacTrac system marketed by Verified Eggs, Canada, has been developed based on ink jet printing of shells. The system is appropriate to the Canadian industry, which has over 1,000 producers with 19 million hens in small flocks (from 10,000 to 20,000 birds) supplying packing plants which operate off-line. Consumers can access data on their purchased eggs using a database operated by the developers of the system.

Laser Etching

Based on initial trials in 1998, EggFusion Inc., in Deerfield, Ill., was established in 2002 to market a system to etch product identity and traceability data on eggs using laser technology. The laser etches the palisade layer to a depth of 50 to 90 nanometers, approximately 5 percent of the thickness of the shell.

Each unit is comprised of a laser generator and an etching head installed on a grader. Three U.S. producers, two in Pennsylvania and one in South Carolina, have installed laser etching systems to service specific supermarkets in the Northeast and a club store.

Etching for the club store requires an "F & T" code which includes a four-digit designation of the plant including the initials of the retailer and the expiration date. It is understood that the client pays a royalty of 2 cents per dozen for the service and EggFusion supplies the installation and an operator. Basically, the imprinting of plant number (incidentally, not the official USDA designation) and expiration date is regarded by the client as desirable but the process offers little advantage in traceability over conventional carton stamping.

Since etched eggs are generics there is little justification for the additional 2 cent per dozen cost. When the etching process was first introduced, it was promoted as a safety feature enabling a consumer to access a computer database to determine the origin of the egg, the date of packing, and the expiration date, however this information is clearly visible on cartons bearing the USDA seal. Subsequently, etched eggs have appeared in the marketplace without the unique numeric code so it is assumed that this feature was found to be impractical or have insignificant commercial application.

Subsequent to the launch of the EggFusion process as a traceability and safety feature, the promoters of the system revealed a business plan which involved sale of advertising and corporate logos on eggs. In September 2006 the CBS network arranged for 35 million eggs to be imprinted to promote their fall program line-up. This experimental use of eggs as "oval billboards" was apparently ineffective since there has been no further adoption of the technology for promotional purposes.

Radio Frequency Identification (RFID)

RFID is a method of electronically imprinting and retrieving data from tags attached to products or cartons. The tags are comprised of a small integrated circuit that stores data and modulates a radio frequency signal. They can be read remotely providing inventory control and security information. The second component of the system is an antenna that communicates with a reader.

Although traceability can be achieved using bar code imprinting, when developed more fully, RFID is expected to offer advantages although at an additional cost. Wal-Mart has been the most progressive developer of RFID application, requiring suppliers of 100 products to apply tags.

Problems associated with this technology include variation in standards (VHF vs. UHF), possible constraints to applications associated with privacy issues, complexity and cost. It is possible that with future development, RFID could be used at the carton level to provide positive identification of product as to source, date of packing, and other details. Although data would be available to both producers and distributors, consumers would be unable to verify product identity unless readers became a conventional kitchen gadget.