Recent petitions to FDA and USDA have requested the re-evaluation of carbon monoxide gas as an approved packaging component. The Food and Drug Administration (FDA) and USDA FSIS requires that approved processes and/or ingredients do not in any way result in the product becoming adulterated or misbranded, which includes making the meat product look better or of greater value than untreated products and the normal spoilage indicators cannot be masked (FSIS, 2003). Thus, research is needed to provide industry and government officials with scientific data regarding the safety and spoilage characteristics of modified atmosphere packaging systems containing carbon monoxide gas.
Pactiv Corporation received approval by the Food and Drug Administration in 2002 to use carbon monoxide (0.4%) as a component of a gas mixture in a modified atmosphere packaging systems to maintain wholesomeness, provide flexibility in distribution and reduce shrinkage in meat (FDA, 2002). Carbon monoxide use in MAP systems has been shown to reduce aerobic plate counts (Brewer et al., 1994 and Luno et al., 2000), psychrotrophic bacteria counts (Brewer et al., 1994 and Luno et al., 1998), and Brochothrix thermosphacta levels (Luno et al., 2000 and Sorheim et al., 1999) on the surface of beef steaks. Similar reductions in psychrotrophic bacteria counts were also observed in ground beef samples (Luno et al., 1998), while the effect of carbon monoxide gas on lactic acid bacteria counts seems to be dependent on application (Brewer et al., 1994 and Luno et al., 2000). Nissen et al. (2000) reported that packaging atmospheres containing 0.4% carbon monoxide could increase the growth of certain strains of Salmonella at abusive temperatures in ground beef. However, Brashears et al. (2006) recently reported that a MAP environment consisting of 0.4% carbon monoxide/30% carbon dioxide/69.6% nitrogen reduced E. coli O157:H7 and Salmonella spp in ground beef patties stored under simulated retail display by 1 x 102 log cfu/g compared to traditional packages. This research contradicts concerns expressed by several authors (Hintlian and Hotchkiss, 1986; Sivertsvik et al., 2002; Farber, 1991; O’Connor-Reyes and Shaw, 2000) who feared MAP atmospheres may inhibit organisms that are typical indicators of spoilage to consumers while promoting the growth of pathogens. However, most research suggesting a relationship between MAP and pathogen growth/survivability was performed by inoculating samples through a septum placed on the packaging film. Palmore (2005) showed this approach was very difficult to control and resulted in leaks, which caused the package environment to change during the course of the study. Therefore, pre-packaged inoculation studies examining carbon monoxide effects on the survival of E. coli O157:H7 and Salmonella spp on ground beef stored at abusive temperatures are limited.
The stated objectives for this work were to determine the impact of packaging methods and temperature abuse on the pathogen loads in ground beef inoculated with E. coli O157 and Salmonella.
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