Intervening in the Meat Mixing Process to Prevent Pathogens

More than 20 commercially available GRAS (generally recognized as safe) antimicrobial compounds were bench tested at Air Liquide’s Delaware Research and Technology Center (DRTC) to determine their efficacy on pathogen control. A further challenge test of the top eight performing compounds was conducted at the USDA Agricultural Research Service facility, Wyndmoor, Penn.

At completion of these trials, a preliminary test was conducted at DRTC to determine the carrying and coverage capacity of the CO2 injection system with the metering pump. The expansion of the CO2 allowed complete coverage of the product during the mixing process.

A full-scale field trial was conducted at a poultry processor utilizing seven different antimicrobial compounds. Dosing rates for these compounds were directed by the antimicrobial supplier. The poultry trim product was added to the mixer following aseptic collection of the control samples and dosing time was adjusted in the instrumentation controls after the metering pump was primed with the compound. A six-minute mix time was utilized for each of the 800-pound batches. Upon completion of the mixing, treated samples were collected.

Field Trial Results

All microbial samples were sent to an independent, third-party lab for analysis of aerobic plate count (APC), Enterobactriacea, and Salmonella ssp. Additional samples were collected to study the quality traits, including surface pH, temperature, and color. Due to minimal dosing issues with two of the compounds, these results were unable to be analyzed and ongoing testing is being performed. As seen in Table 1, all treatments showed a reduction in microbiological levels. Up to a 2 log reduction was realized in APC and a 2.3 log reduction was realized in Enterobacteriacea with differing compounds. One factor that impacted this series of tests was that the customer had an extremely low incidence of Salmonella in the natural control samples that were collected. To that extent, Salmonella reduction rates cannot be statistically projected.

Table 2.

Additional control and treated samples were analyzed at the facility’s quality laboratory for temperature, color, and surface pH to correlate any possible relation between surface pH and microbiological results and to determine the effects the treatment had on the overall appearance and customer acceptance of the treated product. Results showed a temperature reduction from an average of 40.50 degrees Fahrenheit for control samples to 30.6 degrees Fahrenheit for treated samples (see Table 2).

All treated sample temperatures were consistent (+/-0.3 degrees Fahrenheit). Surface pH showed a wide range of variability between both control and treated sample averages as well as between compounds used. Acid-based compounds showed the largest reduction in surface pH, with the largest reduction seen from 6.29 in control samples to a 3.97 in the treated sample for one compound. Non-acidic compounds showed as little as a 0.7 drop in surface pH between control and treated samples. Color measurements were taken as a means to determine customer acceptability based on color changes between untreated and treated samples. Acid-based compounds increased the L* intensity (L* is the value for the lightness of a color reading; the darkest dark is L* 0 and the brightest light is a reading of L* 100) and decreased a* values to unacceptable levels (the a* value depicts intensity of the red hues in the object; the higher the value, the darker the red color, and lower values indicate lighter red hues); however, non-acid compounds had a much lower effect on these readings.

Summary

CO2+ can provide an effective method of reducing bacteria—presumably pathogens—in the meat mixing process. The ability to add an antimicrobial agent as an intervention in the mixer can be a final process before the product is distributed from the processor’s facility. Because of its dynamic dispersal capabilities, CO2 serves as an ideal carrying agent for the compound. Air Liquide is conducting ongoing testing with additional antimicrobial compounds and working with manufacturers to identify dosing levels that allow for appropriate log reduction while limiting the impact on quality and organoleptic traits.