EFFECT OF MARINADE AND DRYING TEMPERATURE ON INACTIVATION OF ESCHERICHIA COLI O157:H7 ON INOCULATED HOME DRIED BEEF JERKY

Abstract

Beef slices were inoculated (5.7–7.5 log CFU/cm2) with a 4‐strain composite of E. coli O157:H7, stored (4C, 24 h), marinated (4C, 24 h), dried for 10 h at 62.5C or 68.3C, and stored for 90 days at 21C. Unmarinated beef slices dried for 10 h at 62.5C were used to determine the relative contribution of the marinate versus temperature treatment in the 62.5C trials. Samples were analyzed (bacterial enumeration with selective and nonselective agar media, pH, and aw) following inoculation, marinating, at 4, 6, 8 and 10 h of drying, and after 30, 60 and 90 days of storage. Marination resulted in slight changes in bacterial populations (−0.3 to + 0.6 log CFU/cm2), but did not enhance bacterial reduction during drying. For all treatments, most bacterial reductions occurred in the first 4 h of drying, with little reduction thereafter. After 10 h of drying, bacterial reductions were 3.2–3.4 log CFU/cm2 for unmarinated beef slices dried at 62.5C. Reductions of 2.2 and 3.0–4.6 log CFU/cm2 were achieved in marinated jerky slices dried at 62.5C and 68.3C, respectively. No treatment resulted in the recommended 5‐log reduction at the end of 10 h drying. However, bacteria did become undetectable by direct plating (<10 CFU/cm2) following 30 days of storage in all treatments except the unmarinated beef slices plated on tryptic soy agar (TSA). Additional work is needed to develop procedures for adequate destruction of E. coli O157:H7 during drying of beef jerky.

Pretreatment effect on inactivation of Escherichia coli O157:H7 inoculated beef jerky

“…Results of a study in our laboratory (Albright, Kendall, Avens, & Sofos, 2002) indicated that bacterial reductions in marinated whole muscle beef slices dried at 62.5 C and 68.5 C from the unheated state were 2.1-2.3 and 3.5-4.1 log cfu/cm 2 , respectively, after 4 h of drying, but only 2.2 and 3.0-4.6 log cfu/cm 2 , respectively, by the end of 10 h of drying. The authors suggested that casehardening on the surface of the jerky (McWilliams, 1993) might have interfered with further bacterial destruction between 4 and 10 h of drying.…”

Lethality of Home-Style Dehydrator Processes against Escherichia coli O157:H7 and Salmonella Serovars in the Manufacture of Ground-and-Formed Beef Jerky and the Potential for Using a Pathogen Surrogate in Process Validation

“…Faith et al (7) found that the temperature setting on the control dial of a vertical airflow home dehydrator differed by as much as 22uC (39uF) from the air temperature within the dehydrator. Albright et al (1) found that even when a preheated dehydrator, set at 63 to 68uC (145 to 154uF), was used to dry whole-muscle beef jerky, the air temperature of the preheated vertical airflow dehydrator dropped 15 to 21uC (27 to 38uF) after the meat was added, and it took 3 to 4 h for the dehydrator to return to the target temperature. Such lack of temperature control and an inability to maintain temperature can make it difficult to manufacture safe jerky when using home-style dehydrators.…”

Destruction of Escherichia coli O157:H7, Salmonella, Listeria monocytogenes, and Staphylococcus aureus Achieved during Manufacture of Whole-Muscle Beef Jerky in Home-Style Dehydrators

“…Our results clearly show that, over a wide variety of processing conditions, these units fail to achieve adequate pathogen lethality even when used as directed. In addition to this study, other studies have shown that drying jerky at less than 62.8uC (145uF) is not recommended and units operating at 62.8uC, or lower, should not be used (1,9). An added concern would be those consumers who fail to follow written instructions.…”