Survival of Salmonella on Cooked Pig Ear Pet Treats

Introduction:   Pet treats including pig ears have been implicated as vehicles of human salmonellosis.  Although pig ears are cooked to temperatures that are lethal to Salmonella, there is a possibility of post-cooking recontamination prior to or during packaging.  Therefore, behavior of the pathogen on these very low moisture pet treats is of interest. 

Purpose:   The objective of this study was to measure the survival of two Salmonellaserovars on two pig ear products at refrigeration and room temperature. 

Methods:   Natural (a_w = 0.256) and smoked (a_w = 0.306) pig ears were spot inoculated separately with SalmonellaNewport and Typhimurium dt104 at ca. 6 log CFU/sample, sealed in plastic bags, and stored at 4.4 and 22 °C.  Surviving populations of the inocula were enumerated by rinsing pig ears with 50 ml of peptone-tween-salt diluent and plating on tryptic soy agar overlaid with a thin layer of Hektoen enteric agar.  Average log population declines that occurred between 0 and 14 days of storage were analyzed by two-way, repeated measures ANOVA.

Results:   Storage temperature significantly (P < 0.05) influenced decline of Salmonella, but serovar, type of pig ear, and two-factor interactions did not.  At 22 °C decline in Salmonella Newport and Typhimurium dt104 on natural pig ears was 2.65 and 0.81 log, respectively, while both serovars declined by >1 log on smoked pig ears.  At 4.4 °C decline of the Salmonellaserovars was lower, ranging from 0.27 to 0.90 on the two pig ear types.

Significance:   Viable Salmonella slowly declines on very low a_w refrigerated pet treats and more rapidly declines at room temperature.  This information may be useful for pet treat safety assessments and for determining target inactivation levels for post-lethality treatments.