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THE UNIVERSITY ~-ef 

WISCONSIN MADISON 

Critical Limit Summary: Post-Packaging Pasteurization of Beef Snack 

Sticks and Natural Casing Wieners to Control Listeria monocytogenes 

Background: If a processors wishes to employ a post-lethality treatment to operate 

under Alternative 1 or Alternative 2 of the USDA Listeria regulation, that treatment must 

be validated and included in the HACCP plan. This treatment will almost undoubtedly be 

designated as a CCP. 

One potential post-lethality process is post-packaging pasteurization (PPP) of RTE 

products. Pasteurization can be done in hot water or steam. Critical Limits associated 

with such a process would include amount of product in a package and how it is 

packaged, amount and type of heating medium, time of exposure to heating medium. 

In order to be considered effective, a post-lethality treatment must result in a 1-log 

reduction in L. monocytogenes (Lm) numbers. If a reduction of at least 2 logs is 

achieved, USDA testing frequency for treated products will decrease. 

Research Study: We inoculated three brands each of beef snack sticks and natural 

casing wieners with L. monocytogenes and then packaged these products using a 

commercially available plastic packaging film specifically designed for PPP applications. 

Beef sticks were packaged individually or with 4 or 7 sticks per package. Wieners were 

packaged 4 per package. Each individual package was submerged in 0.7 gal (2.8 liters) 

of boiling water in a sauce pan on a hot plate and held for a designated time. After PPP, 

packaged products were cooled in an ice-water slush and then numbers of surviving Lm 

were determined. 

Research Results: An average reduction in Lm numbers of at least 2 logs was obtained 

using heating times of 1.0 minute for individually packaged beef snack sticks and 4.0 

minutes for 4- or 7-per-package beef snack sticks. A treatment of 7.0 minutes for fourper-package natural casing wieners was also judged to be of potential commercial use. 

For all products tested in consumer sensory evaluation panels, the products treated by 

hot-water PPP (with cooked-out fat and moisture removed) were rated equal to or 

significantly better than corresponding untreated products. 

Validated Critical Limits: 

• Single beef sticks packaged in Curwood, Inc. film SPP94 (Material No. CPS302976; 

New London, WI) and heated in boiling water (1 package in 0.7 gal) for 1.0 minute. 

• Four or seven beef sticks packaged in Curwood, Inc. film SPP94 (Material No. 

CPS302976; New London, WI) and heated in boiling water (1 package in 0.7 gal) for 

4.0 minutes. 

• Four natural casing wieners packaged in Curwood, Inc. film SPP94 (Material No. 

CPS302976; New London, WI) and heated in boiling water (1 package in 0.7 gal) for 

7.0 minutes. 

Ingham, S.C., M.D. DeVita, R.K. Wadhera, M.A. Fanslau, and D.R. Buege. 2005. Evaluation of smallscale hot-water post-packaging pasteurization treatments for destruction of Listeria monocytogenes on 

ready-to-eat beef snack sticks and natural-casing wieners. Journal of Food Protection. 68: 2059-2067. 

For more information contact: Steve Ingham, Extension Food Safety Specialist (608) 265-4801, 

scingham@wisc.edu August, 2007