Surface pH of fresh beef as a parameter to validate effectiveness of lactic acid treatment against Escherichia O157:H7 and Salmonella

Authors: Kalchayanand, Norasak - Nor; Arthur, Terrance; Bosilevac, Joseph - Mick; Schmidt, John; Shackelford, Steven; BROWN, TED - Cargill, Incorporated; Wheeler, Tommy

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2018
Publication Date: 7/1/2018
Citation: Kalchayanand, N., Arthur, T.M., Bosilevac, J.M., Schmidt, J.W., Shackelford, S.D., Brown, T., Wheeler, T.L. 2018. Surface pH of fresh beef as a parameter to validate effectiveness of lactic acid treatment against Escherichia O157:H7 and Salmonella. Journal of Food Protection. 81(7):1126-1133. https://doi.org/10.4315/0362-028X.JFP-17-469.
DOI: https://doi.org/10.4315/0362-028X.JFP-17-469

Interpretive Summary: The food safety system implemented by beef processors includes a multi-hurdle approach with many interventions to reduce the risk of contaminated meat. One set of interventions includes antimicrobials such as lactic acid sprayed on beef carcasses after hide removal. For each antimicrobial intervention used by the beef processors, they provide documentation to USDA-Food Safety and Inspection Service indicating that the intervention is effective under the actual conditions that apply in its operation. Because antimicrobial intervention sprays can be applied under many different parameters (concentration, spray volume and pressure, etc) this study was conducted to determine whether surface pH of lean and fatty tissues after applying dilute lactic acid solutions could be used to validate lactic acid as an antimicrobial intervention and as an ongoing process control measure indicator for the level of reduction of the pathogenic bacteria. Results indicate that carcass surface pH had a strong linear correlation with the reductions of both E. coli O157:H7 and Salmonella. Therefore, surface pH after spray treatment with lactic acid could be used as a control measure to indicate the reduction of target pathogens on beef.

Technical Abstract: The U.S. beef industry must provide documentation to the U.S. epartment of Agriculture, Food Safety and Inspection Service (USDA-FSIS) that the antimicrobial interventions implemented or any subsequent changes in the process are effective under the actual conditions that apply in its operation. The main objective of this study was to determine whether surface pH after application of diluted lactic acid solution on surfaces of fresh meat can be used as a control measure indicator for the reduction of E. coli O157: 7 and Salmonella. Samples (240 each) of lean and adipose beef tissues were inoculated with cocktail mixtures of Escherichia coli O157:H7 and Salmonella. Application parameters were varied such that lean and adipose tissues were spray treated with either 2 or 4.5% lactic acid solution at either 38 or 60°C for 1 to 10 s. Lean and adipose tissues were collected before and after spray treatments for enumeration of the pathogens. Based on the conditions of this study, there was no difference between spray treatments at 38 or 60°C, but 4.5% lactic acid solution reduced pathogens more effectively (P = 0.05) than did 2% lactic acid solution. Spray treatment with lactic acid solution for 1 to 10 s reduced surface pH values of lean tissues (3 to 3.8) and adipose tissues (2.75 to 3.65). At surface pH values of 3.0 and 2.75, lactic acid reduced E. coli O157:H7 on surfaces of lean and adipose tissues by approximately 1.60 and 1.54 log CFU/cm2, respectively. At surface pH values of 3.8 and 3.65, lactic acid reduced E. coli O157:H7 on lean and adipose tissues by approximately 0.3 and 0.42 log CFU/cm2, respectively. The surface pH values after lactic acid treatment and the reductions of both pathogens showed a strong linear relationship; this indicates that a surface pH of 3.1 would provide at least 1-log reduction of E. coli O157:H7 and Salmonella, regardless of lactic acid application parameters. Therefore, surface pH after spray treatment with lactic acid could be used to validate pathogen reduction.