To validate how packaging and storage reduces Listeria monocytogenes on whole-muscle beef jerky and smoked pork and beef sausage sticks, four packaging systems (heat sealed [HS] without vacuum, heat sealed with oxygen scavenger, nitrogen flushed with oxygen scavenger [NFOS], and vacuum) and four ambient temperature storage times were evaluated. Commercially available whole-muscle beef jerky and smoked pork and beef sausage sticks were inoculated with a five-strain L. monocytogenes cocktail, packaged, and then stored at 25.5°C until enumerated for L. monocytogenes at 0, 24, 48, and 72 h and 30 days after packaging. The interaction of packaging and storage time affected L. monocytogenes reduction on jerky, but not on sausage sticks. A >2-log CFU/cm 2 reduction was achieved on sausage sticks after 24 h of storage, regardless of package type, while jerky had <2-log reductions for all packaging types. At 48 h, log reductions were similar ( P > 0.05) for all types of jerky packaging, ranging from 1.26 to 1.72 log CFU/cm 2 ; however, at 72 h, mean L. monocytogenes reductions were >2 log CFU/cm 2 , except for NFOS (1.22-log CFU/cm 2 reduction). Processors could package beef jerky in HS packages with oxygen scavenger or vacuum in conjunction with a 24-h holding time as an antimicrobial process to ensure a >1-log CFU/cm 2 L. monocytogenes reduction or use a 48-h holding time for HS- or NFOS-packaged beef jerky. A >3-log CFU/cm 2 mean reduction was observed for all beef jerky and sausage stick packaging systems after 30 days of 25.5°C storage.

Foodborne outbreaks have been linked to jerky produced under insufficient thermal processing schedules. Reduction of Escherichia coli O157:H7 and Salmonella serovars during thermal processing of chopped and formed beef jerky was evaluated under two processing schedules representative of those used by large-scale (LS) and small-scale (SS) jerky production facilities. Fresh chopped and formed all-beef jerky batter was inoculated with 5.8 to 7.3 log CFU of E. coli O157:H7 or Salmonella per g, extruded into strips, and thermally processed by LS or SS schedules. A $5.0-log CFU/g reduction of both pathogens occurred with <10% relative humidity and a cumulative process of 44 min at 55.6°C followed by 46 min at 77.8°C into the LS schedule. Additional drying at 77.8°C for 3.5 h was needed to achieve a water activity of 0.67 and a moisture-to-protein ratio (MPR) of 0.77. For the SS process, a $5.0-log CFU/g reduction of both pathogens occurred with 15 to 20% relative humidity and a cumulative process of 45 min at 52°C, 60 min at 57°C, 45 min at 60°C, 45 min at 63°C, 90 min at 68°C, and finishing with 30 min at 77°C. After processing for an additional 90 min at 77°C, water activity was 0.60 while the MPR was 0.82. The LS and SS processes for producing chopped and formed jerky provided $5.0 log lethality to control E. coli O157:H7 and Salmonella . However, both processes would require additional drying to achieve an MPR of 0.75 to be labeled as jerky.

Cooked, chilled beef and cooked, chilled pork were inoculated with three strains of Clostridium perfringens (NCTC 8238 [Hobbs serotype 2], NCTC 8239 [Hobbs serotype 3], and NCTC 10240). Inoculated products were heated to 75°C, held for 10 min in a circulating water bath to heat activate the spores, and then chilled by circulating chilled brine through the water bath. Samples were chilled from 54.4 to 26.6°C in 2 h and from 26.6 to 4.4°C in 5 h. Differences in initial C. perfringens log counts and log counts after chilling were determined and compared with the U.S. Department of Agriculture (USDA) stabilization guidelines requiring that the chilling process allow no more than 1 log total growth of C. perfringens in the finished product. This chilling method resulted in average C. perfringens increases of 0.52 and 0.68 log units in cooked beef and cooked pork, respectively. These log increases were well within the maximum 1-log increase permitted by the USDA, thus meeting the USDA compliance guidelines for the cooling of heat-treated meat and poultry products.

Standardized microbiological sampling and testing procedures were developed that can be used throughout the beef slaughter and processing industry to facilitate the collection and any desired compilation of comparative data. Twenty samples each from carcasses (brisket, flank, and rump areas combined); subprimal cuts (clods); lean trim; and cutting and/or conveyor surfaces were collected in three slaughter and processing operations, with the first operation being a preliminary trial and resulting in no reported data. Microbiological analyses for Clostridium perfringens , Escherichia coli O157:H7, Listeria monocytogenes , Salmonella spp., Staphylococcus aureus , Campylobacter jejuni/coli , total coliforms, E. coli Biotype I, and aerobic mesophilic bacteria (aerobic plate count, APC) were performed on all samples by an outside laboratory. The procedures developed were effective in allowing samples to be collected, shipped, and analyzed in the same manner for all operations. From a logistical standpoint, approximately 20 samples each of carcasses, clods, lean trim, and surfaces could be taken within 4 to 6 h by five people. Forty samples each of carcass, clod, lean trim, and conveyor surfaces from two plants tested negative for E. coli O157:H7, Salmonella spp., and Listeria spp., with the exception of L. monocytogenes being isolated from one carcass and one clod sample. APCs and total coliform counts were between 10 3 to 10 5 and 10 2 to 10 3 CFU/cm 2 or CFU/g, respectively, for the 40 samples each of carcasses, clods, and lean trim. APCs for surface swab counts ranged from ≤ 10 to 10 3 CFU/cm 2 .