Effect of Acetic and Lactic Acids on Survival of Hygiene Indicator Microorganisms and Salmonella Typhimurium in a Beef Cube System

Introduction: Organic acids, such as acetic and lactic acids, represent alternative tools to control the microbiological contamination in animal carcasses during slaughtering. In some countries, such as the United States, the spraying of organic acids in bovine carcasses is allowed to reduce their microbiological contamination. However, European countries and Brazil do not allow the use of organic acids in bovine carcasses with this purpose.

Purpose: This study aims to demonstrate the effects of some organic acids over hygiene indicator microorganisms and Salmonella Typhimurium in a beef cube system.

 Methods: Beef cubes of 2 cm³ were cut in sterile conditions and packed in sterile bags until 100 g units. Each set of three units was inoculated with a Salmonella Typhimurium ATCC 14029 in order to achieve approximate concentrations of 1, 10, and 100 CFU/10 g. As control, a set of three units was inoculated with the same volume of sterile distilled water. Then, one bag of each set was added to 12 ml of distilled sterile water, the second bag with 12 ml of acetic acid at 4%, and the last bag with 12 ml of lactic acid at 4%. All sets were incubated at 7 °C, and after 30 min, 24 h and 48 h, the systems were analyzed for Salmonella (ISO 6579), mesophilic aerobes (Petrifilm™ AC), and coliforms and Escherichia coli (Petrifilm™ EC). The obtained counts (log CFU/g) were compared by ANOVA and Tukey to verify significant differences between treatments and storage periods (P < 0.05).

Results: It was observed in beef cube systems control a significant increase of mesophilic aerobes between 30 min (5.8 log CFU/g) and 24 h (6.8 log CFU/g) (P < 0.05), and non significant after 48 h (6.5 log CFU/g, P > 0.05). In beef cube systems treated with acetic and lactic acids, mesophilic aerobes contamination kept stable after 30 min, 24 h, and 48 h (5.4, 5.4, and 5.5 log CFU/g, respectively, for acetic acid, P > 0.05; and 5.4, 5.3, and 5.4 log CFU/g, respectively, for lactic acid, P > 0.05). Coliforms and E. coli were not detected in all beef cube systems treated with organic acids, even after 30 min of incubation. Salmonella Typhimurium was detected in all beef cube systems in distinct frequencies, even in the ones treated with organic acids.

 

Significance: The present study demonstrated the efficacy of acetic and lactic acid to reduce the contamination by mesophilic aerobes, coliforms and E. coli in beef cube systems, and the necessity of additional studies to determine how these substances can eliminate properly Salmonella Typhimurium.