Salmonella presence on beef in Mexico as impacted by lactic acid and potassium lactate treatments applied on retail cuts

In Mexico, foodborne illnesses are a notable cause of death in small children. These cases occur due to numerous reasons, such as animal food products that are produced under sanitary conditions. Animal processing facilities in Mexico that sell their products to the public, do not all require the same type of federal inspection as seen in the United States. Recent studies have reported high Salmonella presence in beef products sold at vendors throughout Mexico. The primary objective of this study was to determine the reduction in Salmonella contamination on retail beef cuts purchased from outdoor markets in Mexico using a 5% lactic acid dip. A sub-objective added after the initiation of the study was to determine the reduction in Salmonella contamination on retail beef cuts purchased in Mexico outdoor markets using a 5% potassium lactate dip. The secondary objective was to evaluate color and sensory changes associated with beef steaks dipped in 5% lactic acid and 5% potassium lactate solutions. Samples for the primary and sub objective study were collected between August 2010 and August 2011. Samples, beef whole muscle steaks (approximately 100 grams each), were purchased from outdoor markets, throughout four major cities of Mexico. In the primary experiment, samples were dipped in 5% lactic acid solution and for the subobjective, samples were dipped in a 5% potassium lactate solution. For the secondary study USDA Choice inside round subprimals (IMPS 169) were obtained at 4 d postmortem. The subprimals were sliced into 0.6 cm thick steaks, to simulate the thin beef steaks of Mexico outdoor markets. Each steak was assigned to its designated treatment: control, 5% lactic acid dip, and 5% potassium lactate dip. Visual and instrumental color were evaluate with PVC overwrapped packaging in a retail case and plastic sacks at ambient temperature. Steaks dipped in 5% lactic acid significantly reduced (P < .0001) the proportion of positive Salmonella samples from 40.64% to 27.24% in control (n= 353) and treated samples, respectively. The lactic acid significantly (P<.0001) reduced Salmonella in samples purchased in Cancun, 65.72% versus 29.90% and in Veracruz (P = 0.0024) 26.48% versus 14.54%. The potential growth of Salmonella on beef steaks was significantly reduced in Cancun (P = .0003) and Merida (P < .0001). Cancun control measured 3.38 to 2.08 log10 MPN /50cm2 Salmonella after the dip and Merida control measured 3.46 to 2.67 log10 MPN /50cm2 Salmonella after the dip. The 5% potassium lactate dip had no significant reductions of Salmonella presence in the samples collected from outdoor markets. Control samples had 34.96% Salmonella positive, where potassium lactate had 32.59% Salmonella positives. The growth of Salmonella found in the control (2.48 log10 MPN /50cm2) versus 5% potassium lactate dip (2.17 log10 MPN /50cm2) was significant (P = 0.0479). A possible reduction of Salmonella by 0.3 log10 MPN/ 50cm2. A significant reduction in Salmonella growth was found on beef steaks purchased in Cancun (P = 0.0731) and Merida (P = 0.0305). In Cancun the potassium lactate treatment reduced the growth of Salmonella 3.38 to 2.08 log10 MPN /50cm2 and in Merida, 3.46 to 2.67 log10 MPN /50cm2. Each packaging type, after dipped in 5% lactic acid, had a darker beef color (> 4.92) and was significantly (P < 0.05) higher than both control and 5% potassium lactate dip. At 2 and 4 h there were no differences between steaks in the control group and steaks in the potassium lactate treated group in regard beef color. At 2 and 4 h, lactic acid samples were moderately dark to very dark and were significantly (P < 0.05) darker than control and 5% potassium lactate dip. Control and potassium lactate treated samples were both darker at 4h than at 2h for both packaging types. For both packaging types (PVC overwrap/ plastic bags) there was an interaction (P<0.05) between treatments, hour 0, 2 and 4. L*, a* and b* were all lower for the 5% lactic acid dip (37.57/39.48, 22.47/18.76, 19.74/18.53, respectively). The results indicate that the 5% lactic acid dip resulted in a darker, less red beef product, with more blue hues, versus the control and 5% potassium lactate dip (L* 43.03/44.06, a* 26.86/24.50, b* 22.49/20.58). Sensory results favored steaks with a 5% lactic acid dip the least. The 5% potassium lactate dip resulted in no negative attributes as determined by the sensory panel. The 5% lactic dip had a significantly (P < 0.05) lower beef flavor (2.45), overall mouth feel (3.13) and highest off flavor (3.81) compared to 5% potassium lactate dip and control. In conclusion, the lactic acid dip significantly reduced the presence of Salmonella on beef steaks purchased in the outdoor markets of Mexico, where the 5% potassium lactate treatment did not. Color and sensory evaluation indicated that the steaks treated with the 5% lactic acid dip to be the least preferred by consumers. Further research would be needed for other 5% lactic acid treatment applications and the effectiveness of potassium lactate against Salmonella.