Validation of Ground-and-Formed Beef Jerky Processes Using Commercial Lactic Acid Bacteria Starter Cultures as Pathogen Surrogates

Abstract

Beef jerky has been linked to multiple outbreaks of salmonellosis and Escherichia coli O157:H7 infection over the past 40 years. With increasing government scrutiny of jerky-making process lethality, a simple method by which processors can easily validate the lethality of their ground-and-formed beef jerky process against Salmonella' and E. coli O157:H7 is greatly needed. Previous research with whole-muscle beef jerky indicated that commercial lactic acid bacteria (LAB) may be more heat resistant than Salmonella and E. coli O157:H7, suggesting the potential use of LAB as pathogen surrogates. Of six commercial LAB-containing cultures evaluated for heat resistance in ground-and-formed beef jerky, Saga 200 (Pediococcus spp.) and Biosource (Pediococcus acidilactici) were identified as consistently more heat resistant than Salmonella and E. coli O157:H7. Six representative ground-and-formed beef jerky commercial processes, differing widely in lethality, were used to identify an appropriate level of LAB reduction that would consistently indicate a process sufficiently lethal (> or = 5.0-log reduction) for Salmonella and E. coli O157:H7. Both Saga 200 and Biosource consistently predicted adequate process lethality with a criterion of > or = 5.0-1og reduction of LAB. When either LAB decreased by > or = 5.0 log CFU, processes were sufficiently lethal against Salmonella and E. coli O157:H7 in 100% of samples (n=39 and 40, respectively). Use of LAB as pathogen surrogates for ground-and-formed beef jerky process validation was fieldtested by three small meat processors, who found this technique easy to use for process validation.

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

“…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).…”

“…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).…”

“…Appendix A includes validated time and temperature combinations for cooking (41), but there are few options available for establishments not willing or able to use Appendix A. Our laboratory has proposed and validated a method for in-plant validation of jerky processing lethality using a lactic acid bacterium as a pathogen surrogate (6,7,11). The use of a surrogate that mimics pathogen behavior could be useful for in-plant validation of thermal processes for other beef products.…”

Survival of Listeria monocytogenes, and enterotoxin-producing Staphylococcus aureus and Staphylococcus pasteuri, during two types of biltong-manufacturing processes

“…48 h), a single colony of each of the three bacterial isolates (from plates stored at 4°C) were successively streak plated twice onto Tryptone Soy agar (TSA) (BioLab, Midrand South Africa) and incubated at 37°C for 24 h. Isolates were examined for colony morphology and Gram-stained to confirm culture purity (Borowski, Ingham, & Ingham, 2009;Buege, Searls, & Ingham, 2006). A single colony was selected from these plates, inoculated into 50 ml of Tryptone Soy Broth (TSB) (BioLab, Midrand South Africa) and incubated with shaking (120 rpm) for 24 h at 37°C (Burnham et al, 2008;Ingham, Searls, & Buege, 2006a;Porto-Fett et al, 2009).…”

“…The bacterial pellet was washed and re-suspended in 1 ml of sterile saline diluent (0.85% sodium chloride), and diluted in the same diluent to produce a final cell concentration of ca. 7 Log CFU/ml (Borowski et al, 2009;Buege et al, 2006;Burnham et al, 2008;Ingham et al, 2006a;Porto-Fett et al, 2009;Yoon et al, 2005). Cell concentrations were determined by spread plating in duplicate 1 ml of either L. monocytogenes Shia-L1.1 prepared inoculum onto Rapid 'L.…”