Based on some experience utilizing RFID tagging in the vegetable and egg packing industries to meet regulatory and supplier freshness requirements: US FDA fina

Based on some experience utilizing RFID tagging in the vegetable and egg packing industries to meet regulatory and supplier freshness requirements: US FDA final egg rule requires the holding and transporting of shell eggs at or below 45F ambient temperature beginning 36 hours after time of lay. At a producer of any volume, eggs are gathered 2x daily, generally by automated machinery; occasionally still gathered by hand. Eggs are gathered as soon as hens lay them because warmer temperatures encourage physical/chemical changes that affect "freshness" adversely. Justification of refrigeration can be found in the response to public comments on FDA final egg rule (where SE = salmonella) [0]: The 36-hour limit for unrefrigerated holding is supported by a model, contained in the 1998 joint SE risk assessment (Ref. 21), which was developed to examine the relationship among holding time, holding temperature, and yolk membrane breakdown as an indicator of SE risk. (The yolk membrane separates the nutrient-rich yolk and any SE bacteria that might be present in the albumen; breakdown or loss of the yolk membrane results in rapid growth of SE present in the albumen.) The model showed that, at 70 to 90 °F (i.e., temperatures that might be observed in unrefrigerated egg holding areas in farms or warehouses or in transport vehicles), there was much less breakdown of yolk membrane in eggs held no longer than 36 hours than in eggs held no longer than 72 hours. According to the model, eggs held at 70°F will experience at least a 16-percent breakdown of yolk membrane after 36 hours and a 25-percent breakdown after 72 hours. Eggs held at 80 °F will suffer at least a 22-percent breakdown after 36 hours and a 39-percent breakdown in the yolk membrane at 72 hours. At 90 °F, there is at least a 33-percent breakdown after 36 hours and at least a 62-percent breakdown of the yolk membrane after 72 hours. [0]: [pdf] http://www.gpo.gov/fdsys/pkg/FR-2009-07-09/pdf/E9-16119.pdf http://www.gpo.gov/fdsys/pkg/FR-2009-07-09/pdf/E9-16119.pdf