The survivability, growth and heat susceptibility of E. coli O157:H7 in enhanced beef brine solutions containing potassium lactate and lactic acid producing bacteria

Meat enhancement is used to increase consumer satisfaction through improved palatability and uniformity. Brine solutions that are re-covered or reused during the processing of enhanced meat cuts have a high risk of cross contamination. The objectives of the present study were to determine the effect of potassium lactate and lactic acid bacteria on the survivability and heat susceptibility of E. coli O157:H7 in brine solutions used to enhance beef products and to determine the effect of these interventions on consumer sensory scores and shelf life characteristics. To characterize safety, beef strip loins were enhanced with brine solutions (0.3% sodium chloride and 0.35% phosphate at 10% pump level) inoculated with high or low levels of E. coli O157:H7 and one of the following interventions: 0, 1.5, 2.5% potassium lactate or lactic acid bacteria (LAB 107 CFU/ml). Treated subprimals were fabricated into steaks and randomly allotted to one of the following internal endpoint temperatures: 0 (not cooked), 50, 55, 60, 65, 70 and 75°C. Once endpoint temperature was reached, the interior of each steak was sampled and E. coli O157:H7 was enumerated (high level) or detected (low level). To characterize palatability and shelf life, beef strip loin subprimals were enhanced with brine solutions containing previously mentioned interventions plus a non-enhanced control. Consumer panelists evaluated palatability at 14 d postmortem and lean color on days 1, 3, and 7 of display (after a 14 d postmortem dark storage period). Display steaks were packaged in high-oxygen (80% O2 / 20%CO2) or low-oxygen (0.4%CO/30%CO2/69.6%N2) modified atmosphere packages. Data analysis showed no significant interactions between intervention treatment and steak temperature endpoints, indicating E. coli O157:H7 from treated brine solutions were not more susceptible to heat during cooking. Results also indicate the transference of pathogens into meat products was low for all interventions, regardless of inoculation level. Internal steak temperature (especially 70 and 75 °C) remains the most effective way to reduce pathogen levels in steaks enhanced with inoculated brine solutions. Steaks packaged in high-oxygen MAP and enhanced with a brine solution containing 1.5 or 2.5% potassium lactate maintained more desirable lean color scores throughout display and were more likely to be purchased by consumers than steaks enhanced with other treatments. Finally, the presence of potassium lactate (1.5 and 2.5%) and lactic acid producing bacteria had no detrimental impact on consumer palatability, while enhanced steaks were more desirable than non-enhanced controls.