Background
Highly publicized outbreaks of food-borne illness since 1993, primarily caused by bacteria such as E. coli O157:H7, Salmonella spp. and Listeria monocytogenes, elicited intense consumer concern about meat safety. In response, regulatory authorities, researchers and the beef industry initiated efforts to implement food safety management systems that would improve microbiological quality. The USDA Food Safety and Inspection Service (FSIS) began initiating new regulatory requirements during the mid-1990s. Packers were required to knife-trim carcasses to remove all visible contaminants, comply with written sanitation standard operating procedures (SSOP), implement Hazard Analysis Critical Control Point (HACCP) systems, and meet microbiological performance criteria and standards for E. coli and Salmonella as a means to verify HACCP effectiveness and pathogen reduction.
If E. coli 0157:H7 is present in ground beef (and this is a rare occurrence) cooking to an internal temperature of 160°F will render the bacterium harmless. Premature browning of ground beef could lead to inadequate cooking by consumers and allow the survival of E. coli 0157:H7 if it is present. The objectives of this study were to determine the effect that the following factors have on premature browning:
- The effect of freezing time and thawing practices;
- the effect of adding erythorbic acid (an anti-oxidant);
- the effect of freezing in bulk versus in patty form;
- the effect of modified atmosphere packaging; and
- the impact of muscle source.
Methodology
Eight (8) 10-pound (4.5kg) chubs of coarse ground beef were obtained locally. An erythorbic acid solution was added to half of the ground beef from each chub and distilled water was added to the other half as a control group. The ground beef was then more finely ground and either formed into equal-sized patties or bulk packaged. In order to assess the effects of erythorbic acid, storage methods/times and thawing practices, the patties/bulk ground beef was then packaged/stored as follows:
- Patties-overwrapped with PVC film-stored at 4°C for 48 hours-then cooked;
- Patties-overwrapped with PVC film-stored at -18°C for 21 days-then cooked directly from frozen state;
- Patties-overwrapped with PVC film-stored at -18°C for 21 days-thawed at 4°C for 24 hours-then cooked;
- Bulk packaged-stored at -18°C for 21 days-thawed at 4°C for 24 hours-formed into patties-then cooked.
In order to measure the effect of modified atmosphere packaging (MAP) on premature browning, ground beef patties were packaged/stored as follows:
- Patties-overwrapped with PVC film- stored at 4°C for 48 hours-then cooked;
- Patties-packed in MAP- stored at 4°C for 48 hours-then cooked;
- Patties-packed in MAP- stored at -18°C for 21 days-then cooked directly from frozen state.
Each of the groups listed above consisted of 48 patties (24 with erythorbic acid and 24 without). Eight (8) patties from each treatment group were cooked to the following endpoint temperatures: 140°F (rare); 150°F (medium-rare); 160°F (medium); 170°F (well-done). The extent to which each treatment group exhibited red color at each cooking temperature was then measured and compared.
Findings
Overall, the addition of erythorbic acid inhibited premature browning in cooked ground beef. Specifically:
- Erythorbic acid treated patties exhibited more red color than control group patties at endpoint cooked temperatures of 140°F and 150°F for all storage and packaging (i.e. MAP) conditions.
- Erythorbic acid treated patties exhibited more red color than control group patties at endpoint cooked temperatures of 160°F and 170°F for all storage conditions except bulk packaged.
- In bulk stored ground beef, the greater volume and mass of the individual packages might have prevented the erythorbate from exerting the desired effect.
- Regardless of storage temperature the addition of erythorbate was not as effective at higher internal cooked temperatures versus lower internal temperatures.
Implications
The Centers for Disease Control (CDC) estimates that there are 76 million cases of foodborne illness in the United States annually, with 14 million cases attributed to known pathogens. E. coli alone is estimated to account for 76,000 cases of food-borne illness and 76 deaths annually. Multiple intervention strategies to inhibit or eliminate E. coli in the beef production process are extremely important to the industry. Further, safe handling and proper cooking by consumers is the final defense against food-borne illness. The addition of erythorbic acid resulted in patties with more red color, especially at temperatures below the recommended level to achieve pathogenic inactivation (i.e. 160°F). Therefore, the addition of erythorbic acid to ground beef might induce consumers to cook ground beef patties longer resulting in higher levels of food safety.