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

The survival of Salmonella on fresh ginger root (Zingiber officinale) during drying was examined using both a laboratory oven at 51 and 60°C with two different fan settings and a small commercially available food dehydrator. The survival of Salmonella in ground ginger stored at 25 and 37°C at 33% (low) and 97% (high) relative humidity (RH) was also examined. To inoculate ginger, a four-serovar cocktail of Salmonella was collected by harvesting agar lawn cells. For drying experiments, ginger slices (1 ± 0.5 mm thickness) were surface inoculated at a starting level of approximately 9 log CFU/g. Higher temperature (60°C) coupled with a slow fan speed (nonstringent condition) to promote a slower reduction in the water activity (aw) of the ginger resulted in a 3- to 4-log reduction in Salmonella populations in the first 4 to 6 h with an additional 2- to 3-log reduction by 24 h. Higher temperature with a higher fan speed (stringent condition) resulted in significantly less destruction of Salmonella throughout the 24-h period (P < 0.001). Survival appeared related to the rate of reduction in the aw. The aw also influenced Salmonella survival during storage of ground ginger. During storage at 97% RH, the maximum aw values were 0.85 at 25°C and 0.87 at 37°C; Salmonella was no longer detected after 25 and 5 days of storage, respectively, under these conditions. At 33% RH, the aw stabilized to approximately 0.35 at 25°C and 0.31 at 37°C. Salmonella levels remained relatively constant throughout the 365-day and 170-day storage periods for the respective temperatures. These results indicate a relationship between temperature and aw and the survival of Salmonella during both drying and storage of ginger.

Section: Resultssupporting

confidence: 92%

“…The rate of water removal during drying plays a role in the heat resistance of bacteria (18). However, time-temperature combinations used to dry products in home dehydrators or conventional ovens may not be adequate to achieve pathogen lethality (5).…”

mentioning

confidence: 99%

Survival of Salmonella during Drying of Fresh Ginger Root (Zingiber officinale) and Storage of Ground Ginger

Gradl

Sun

Larkin

et al. 2015

“…NRRL B-2354 has been shown to be an acceptable surrogate for the study of thermal inactivation of bacteria in different products (3,15,21). Research has also indicated that this organism is an adequate surrogate for Salmonella for validation of thermal processes in almonds and in beef jerky, which are low-moisture, low water activity products similar to the extruded products described here (1,4,12) According to Fisher and Phillips (7), the temperature resistance of Enterococcus is associated with its membrane structure and has been related to the lipid and fatty acid content. The results from this study corroborate the idea that E. faecium is a good surrogate for thermal inactivation of Salmonella, with this research now expand ing its use for the process of extrusion.…”

Section: Discussionmentioning

confidence: 82%

Use of Enterococcus faecium as a Surrogate for Salmonella enterica during Extrusion of a Balanced Carbohydrate-Protein Meal

Bianchini

Stratton

Weier

et al. 2014

Multiple outbreaks of salmonellosis have been associated with the consumption of low-moisture products, including extruded products. Therefore, there is a need for a nonpathogenic, surrogate microorganism that can be used to validate extrusion processes for Salmonella. The objective of this research was to determine if Enterococcus faecium NRRL B-2354 is an adequate surrogate organism for Salmonella during extrusion. Extrusions at different temperatures were done in material contaminated with both organisms. Results indicated that the minimum temperature needed to achieve a 5-log reduction of E. faecium was 73.7°C. Above 80.3°C, the enumeration of E. faecium showed counts below the detectable levels (<10 CFU g(- 1)). Salmonella was reduced by 5 log at 60.6°C, and above 68.0°C the levels of this organism in the product were below the detection limit of the method. The data show that E. faecium is inactivated at higher temperatures than Salmonella, indicating that its use as a surrogate would provide an appropriate margin of error in extrusion processes designed to eliminate this pathogen. Attempting to minimize risk, the industry could validate different formulations, in combination with thermal treatments, using E. faecium as a safer alternative for those validation studies.

“…The strain of P. acidilactici used in these experiments has been shown to function as an effective pathogen surrogate in the manufacture of whole-muscle and ground-and-formed beef jerky under commercial and homestyle processing conditions (5,6,11,12). For a bacterial strain to function as a pathogen surrogate in a thermal processing operation, the stain should be nonpathogenic and admissible in a processing facility and should have equal or slightly enhanced thermal tolerance compared with the pathogen under identical testing conditions (7).…”

Section: Resultsmentioning

confidence: 99%

“…Cocktail strains of 0157 and non-0157 STEC were chosen based on relative heat tolerance in the single-strain experiments. The Salmonella cocktail was composed of one strain each of Salmonella Enteritidis (chicken ovary isolate, originally acquired from the New York State Department of Health, Albany, NY), Salmonella Typhimurium (a clinical isolate from the Wisconsin Laboratory of Hygiene), and Salmonella Infantis and Salmonella Hadar, the origins of which are unknown, and all of these strains have routinely been used in our laboratory for thermal processing studies (5,6).…”

Section: Methodsmentioning

confidence: 99%

Thermal Tolerance of O157 and non-O157 Shiga Toxigenic Strains of Escherichia coli, Salmonella, and Potential Pathogen Surrogates, in Frankfurter Batter and Ground Beef of Varying Fat Levels

Vasan

Geier

Ingham

et al. 2014

The non-O157 Shiga toxigenic Escherichia coli (STEC) serogroups most commonly associated with illness are O26, O45, O103, O111, O121, and O145. We compared the thermal tolerance (D55°C) of three or more strains of each of these six non-O157 STEC serogroups with five strains of O157:H7 STEC in 7% fat ground beef. D55°C was also determined for at least one heat-tolerant STEC strain per serogroup in 15 and 27% fat ground beef. D55°C of single-pathogen cocktails of O157 and non-O157 STEC, Salmonella, and potential pathogen surrogates, Pediococcus acidilactici and Staphylococcus carnosus, was determined in 7, 15, and 27% fat ground beef and in frankfurter batter. Samples (25 g) were heated for up to 120 min at 55°C, survivors were enumerated, and log CFU per gram was plotted versus time. There were significant differences in D55°C across all STEC strains heated in 7% fat ground beef (P < 0.05), but no non-O157 STEC strain had D55°C greater than the range observed for O157 STEC. D55°C was significantly different for strains within serogroups O45, O145, and O157 (P < 0.05). D55°C for non-O157 STEC strains in 15 and 27% fat ground beef were less than or equal to the range of D55°C for O157. D55°C for pathogen cocktails was not significantly different when measured in 7, 15, and 27% fat ground beef (P ≥ 0.05). D55°C of Salmonella in frankfurter batter was significantly less than for O157 and non-O157 STEC (P < 0.05). Thermal tolerance of pathogen cocktails in ground beef (7, 15, or 27% fat) and frankfurter batter was significantly less than for potential pathogen surrogates (P < 0.05). Results suggest that thermal processes in beef validated against E. coli O157:H7 have adequate lethality against non-O157 STEC, that thermal processes that target Salmonella destruction may not be adequate against STEC in some situations, and that the use of pathogen surrogates P. acidilactici and S. carnosus to validate thermal processing interventions in ground beef and frankfurter batter would be of limited utility to processors.