Quality of radio frequency pasteurized shell eggs during extended storage under normal and moderate abuse conditions

Authors: YANG, YISHAN - Oak Ridge Institute For Science And Education (ORISE); GEVEKE, DAVID - Retired ARS Employee; Niemira, Brendan

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2020
Publication Date: N/A
Citation: N/A

Interpretive Summary: Shell eggs can be contaminated with Salmonella. Treating the eggs with radio frequency energy combined with hot water (RF/HW) inactivates the Salmonella, but what happens to the treated eggs in storage is not precisely understood. This study treated Salmonella-inoculated eggs with RF/HW, then stored them for 5 weeks of at 7.2C or 10C. The results showed that regardless of storage temperature, shell eggs pasteurized by RF/HW were Salmonella free during 5 weeks of storage if initial counts ~320 Salmonella per ml. However, when the eggs had much higher initial levels of ~3,200,000 Salmonella per ml, ~5 cells survived the RF/HW treatment. This small population remained stable over 5 weeks when eggs were stored at 7.2C, but grew back to ~25,000,000 cells after 4 weeks when stored at 10C. Physical qualities, including weight loss, yolk pH, albumen pH, Haugh unit, yolk index, and albumen turbidity were also assessed during storage. In general, pasteurized shell eggs had similar quality as untreated eggs during storage at 7.2C for 5 weeks. Therefore, this study demonstrated that shell eggs pasteurized by RF/HW process are microbiologically safe and resemble untreated eggs during 5 weeks of storage at 7.2C.

Technical Abstract: This study investigated the microbiological and physical qualities of shell eggs pasteurized with radio frequency combined with hot water (RF/HW) during 5 weeks of storage at 7.2 or 10C. Shell eggs inoculated with low or high levels of Salmonella Typhimurium were subjected to RF/HW pasteurization. The results showed that regardless of storage temperature, shell eggs pasteurized by RF/HW were Salmonella free during 5 weeks of storage if initial counts were 2.5 log CFU/mL. However, when the inoculation level was 6.5 log CFU/mL, 0.7 log CFU/mL of Salmonella survived the pasteurization process. This small population remained stable over 5 weeks when eggs were stored at 7.2 °C, but grew to 7.4 log CFU/mL when stored at 10 °C after 4 weeks. Physical qualities, including weight loss, yolk pH, albumen pH, Haugh unit, yolk index, and albumen turbidity were also assessed during storage. In general, pasteurized shell eggs had similar quality as untreated eggs during storage at 7.2 °C for 5 weeks. Therefore, this study demonstrated that shell eggs pasteurized by RF/HW process are microbiologically safe and resemble untreated eggs during 5 weeks of storage at 7.2 °C.