ARS | Publication request: Inactivation of Listeria innocua on frankfurters by ultraviolet light and flash pasteurization

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 25, 2008
Publication Date: March 1, 2009
Citation: Sommers, C.H., Geveke, D.J., Pulsfus, S., Lemmenes, B. 2009. Inactivation of Listeria innocua on frankfurters by ultraviolet light and flash pasteurization. Journal of Food Science. 74(3):M138-M141.

Interpretive Summary: Listeria monocytogenes, a bacterium involved in foodborne illness, is an occasional contaminant on frankfurters. Flash (Steam) pasteurization (FP), ultraviolet light(UVC-254 nm) and antimicrobial compounds can be used to control the survival and growth of L. monocytogenes or its nonpathogenic surrogate L. innocua on the surface of frankfurters. In a pilot plant scale study the use of FP(121C, 1.5s) or UVC (2 J/cm2) inactivated 99 percent of the L. innocua on frankfurters that contained the commonly used antimicrobials sodium diacetate and potassium lactate. The use of FP and UVC together inactivated greater than 99.9 percent (3 log) of the L. innocua on the frankfurters. Growth of L. innocua that survived the process was inhibited for 6 weeks during refrigerated storage. The treatments had little effect on frankfurter color or texture. Because the numbers of Listeria that contaminate frankfurters are typically very low, frankfurter manufacturers can use FP and UVC in combination with potassium lactate and sodium diacetate to provide safer frankfurters for consumers.

Technical Abstract: Listeria monocytogenes, a psychrotrophic food-borne pathogen, is a recurring post-process contaminant on ready-to-eat meat (RTE) products including frankfurters. Flash (Steam) Pasteurization (FP) and ultraviolet light (254 nm-UVC) has been shown to reduce levels of L. monocytogenes and L. innocua on frankfurters. In this study the use of UVC light followed by FP to inactivate L. innocua, a nonpathogenic surrogate for L. monocytogenes, on frankfurters that contained sodium diacetate and potassium lactate (SDA/PL) in a pilot plant setting was investigated. Application of UVC (1.0 J/cm2), followed by FP (0.75s steam/121C) resulted in inactivation of 3.19 log L. innocua, while application of UVC (4.0 J/cm2), followed by FP (3.0s steam/121C) resulted in inactivation of 3.89 log of L. innocua. A 2 month refrigerated storage (8C) study of frankfurters that contained SDA/PL and that were treated with UVC followed by FP, revealed an additional 2 log inactivation of L. innocua at week 6, however, the survivors had recovered and begun proliferation at week 8, although not beyond the initial inoculation levels of week 0. The use of UVC in combination with FP had little effect on frankfurter color and texture. The combination of UVC, FP, and SDA/PL was found to be an effective hurdle process for decontamination of frankfurter surfaces.