Research has shown that the incidence of E. coli O157:H7 on surfaces of beef cuts intended for blade or needle tenderization is extremely rare. One study showed a 0.2 percent occurrence of E. coli O157:H7 on 1,014 cuts from six processing facilities throughout the United States. The fact that E. coli O157:H7 rarely occurs on beef primal and subprimal cuts makes the risk of its internalization when blade, needle or moisture enhancement tenderization technologies are used very low. Even though the risks are low, the probability of its occurrence is dramatically increased if improper cleaning and sanitizing of equipment is practiced. Past research has also shown that blade tenderization can transfer from 1 to 7 percent of surface contamination to the interior of the muscle. Needle injection during moisture enhancement can result in a 4 to 8 percent translocation of surface contamination to the center of the cut. While cooking needle tenderized or moisture enhanced product to sufficient internal temperatures (140°F or higher) has been shown to destroy E. coli O157:H7, intervention methods applied prior to tenderization should help prevent the transfer of bacteria to internal surfaces, thus reducing any risks of foodborne pathogens being passed to consumers.
Outside rounds were obtained from a commercial packing company and cut into equal halves. The rounds were inoculated with E. coli O157:H7 and were individually vacuum packaged and stored for 10 to 18 days at 2 to 4°C.
Samples were suspended from a sterilized meat hook and one of five pathogen interventions was applied to each outside round piece:
Study A
Outside round pieces (n = 120) were inoculated with a target of 102 CFU/cm2 of E. coli O157:H7. Following storage, individual round pieces were subjected to one of the five bacterial interventions (n = 24 per intervention) and were subjected to either blade tenderization (n = 60; n= 12 per intervention per process) or needle-injected enhancement (n = 60; n = 12 per intervention per process). Samples were analyzed for E. coli O157:H7 using polymerase chain reaction (PCR).
Study B
Outside round pieces (n = 160) were inoculated and interventions were applied as described above (n = 32 per intervention) and subjected to either blade tenderization (n = 80; n = 16 per intervention per process) or needle enhancement (n = 80; n = 16 per intervention per process).
Following processing, a five centimeter slice was removed from each piece, which was subsequently split into two, 2.5 centimeter thick slices. A surface sponge sample was then collected from a newly exposed internal surface of one slice. Surface samples were analyzed to quantitatively determine the surface populations of E. coli O157:H7 by direct plating and counting morphologically typical colonies. All results were reported in log colony forming units per cm2 (CFU/cm2).
Uninoculated (n = 40) outside round pieces were also subjected to the interventions and processing treatments as previously described, so that there was a total of four samples per intervention and per process.
Study A
The prevalence of E. coli O157:H7 found within outside round pieces was 99.2 percent (119 out of 120 samples). Only one sample, sanitized with hot (82° C) water and needle-injected did not return a positive result. The high rates can be attributed to the fact that the inoculation levels used in this study are far higher than levels of E. coli O157:H7 one would expect to find on uninoculated beef surfaces.
Study B
Product Storage
Outside rounds were vacuum packaged and stored (2°C) for 10 to 18 days after inoculation. At the time of inoculation, the samples had surface levels of E. coli O157:H7 of 2.17 log CFU/cm2. Following vacuum packaging and refrigerated storage, surface samples were collected prior to application of any antimicrobial treatments or further processing. During storage, inoculated populations increased from an average of 2.17 log CFU/cm2 to 3.4 to 3.7 log CFU/cm2. These results indicate that E. coli O157:H7, when present in high levels can survive and grow in vacuum packages at refrigerated temperatures.
Antimicrobial Interventions
Intervention treatments resulted in a 0.9 to 1.1 log CFU/cm2 reduction compared to pre- intervention inoculated inside round surface samples. Survival of E. coli O157:H7 ranged from 12.3 to 17.3 percent of pre-intervention surface levels and all interventions equally reduced the presence of pathogens on the surface level.
Results of this study indicate that even when surface levels of E. coli O157:H7 are several hundred fold higher than those reported in national surveys, application of antimicrobial interventions of surface trimming, hot water (82°C), 5 percent lactic acid (55°C) or activated lactoferrin plus 5 percent lactic acid (55°C), can reduce pathogen loads on the surface of subprimal cuts. For those subprimals subjected to further processing, the interventions can subsequently reduce internalization of surface pathogens. Both blade tenderization and moisture enhancement resulted in pathogen transmission into internal surfaces of inoculated subprimals. Moisture enhancement resulted in the greatest transmission rates compared to blade tenderization. Implementation of a surface intervention to beef subprimals, prior to further processing, would reduce the risk of pathogenic organisms being internalized, as well as reducing the risk of encountering foodborne illness from non-intact, blade tenderized or moisture enhanced beef products.
Table 1. Number of positive samples/number of samples tested (percent positive) for prevalence of E. coli O157:H7, as determined by PCR-BAX, after inoculated outside round pieces were subjected to one of four antimicrobial interventions and were blade-tenderized (BT) or moisture-enhanced (ME). Inoculated, untreated outside-rounds served as positive controls.
|
|
Positive Controla |
Trimmingb |
Hot Water (82°C)c |
Warm 5% Lactic Acid (55°C)d |
Activated Lactoferrin +5% Lactic Acid (55°C)e |
|
BT |
12/12 (100) |
12/12 (100) |
12/12 (100) |
12/12 (100) |
12/12 (100) |
|
ME |
12/12 (100) |
12/12 (100) |
11/12 (91.7) |
12/12 (100) |
12/12 (100) |
Table 2. Least square means ± standard errors for E. coli O157:H7 (log CFU/cm2) recovered from the external surface (minimum detection level = 1.0 CFU/cm2) of inoculated outside round pieces prior to application of an antimicrobial intervention (PRE) and following an antimicrobial intervention (POST), and internal surface levels of E. coli O157:H7 (CFU/cm2) following moisture enhancement (ME). Inoculated, untreated outside- rounds served as positive controls (n = 16 for each intervention treatment).
|
|
Positive Controla |
Trimmingb |
Hot Water (82°C)c |
Warm 5% Lactic Acid (55°C)d |
Activated Lactoferrin +5% Lactic Acid (55°C)e |
|
PRE |
- |
3.7±0.08x |
3.6±0.08x |
3.6±0.08x |
3.6±0.08x |
|
POST |
3.6±0.08x |
2.6±0.08y |
2.5±0.08y |
2.4±0.08y |
2.7±0.08y |
|
ME |
2.1±0.08y |
1.3±0.08z |
1.2±0.08z |
1.2±0.08z |
1.4±0.08z |
Table 3. Table 3. Least square means ± standard errors for E. coli O157:H7 (log CFU/cm2) recovered from the external surface (minimum detection level = 1.0 CFU/cm2) of inoculated outside round pieces prior to application of an antimicrobial intervention (PRE) and following an antimicrobial intervention (POST), and internal surface levels of E. coli O157:H7 (CFU/cm2) following blade tenderization (ME). Inoculated, untreated outside- rounds served as positive controls (n = 16 for each intervention treatment).
|
|
Positive Controla |
Trimmingb |
Hot Water (82°C)c |
Warm 5% Lactic Acid (55°C)d |
Activated Lactoferrin +5% Lactic Acid (55°C)e |
|
PRE |
- |
1.0±0.06 |
0.9±0.06 |
1.0±0.06 |
1.2±0.06 |
|
POST |
0.9±0.06 |
0.9±0.06 |
0.9±0.06 |
0.9±0.06 |
0.9±0.06 |
|
ME |
0.9±0.06 |
0.9±0.06 |
0.9±0.06 |
0.9±0.06 |
0.9±0.06 |