RAPID DESICCATION WITH HEAT IN COMBINATION WITH WATER WASHING FOR REDUCING BACTERIA ON BEEF CARCASS SURFACES

Authors: Cutter, Catherine; Dorsa, Warren; Siragusa, Gregory

Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: A series of experiments was conducted to determine if a combination of rapid drying or desiccation with heat at one or two points in the slaughter process and a water wash could be used to reduce bacterial contamination on beef carcass surfaces. Water washing (125 psi, 15 sec, 121 deg F) was performed with a carcass washer especially designed for research purposes. Rapid desiccation with heat was performed with a forced-air, propane heater applied at 778 deg F or 600 deg F for up to 25 s. In the first experiment, several combinations of desiccation (778 deg F) and water washes were examined. Beef surfaces that were desiccated for 15 sec, contaminated with feces containing pathogens, water washed, and desiccated again for 30 sec resulted in undetectable levels of the pathogens, E. coli O157:H7, Salmonella typhimurium, Listeria innocua, or Clostridium sporogenes. Other experiments were conducted with less heat (600 deg F) for shorter times. When desiccation for 10 sec was combined with water washing and a second desiccation step for 25 s, bacteria were reduced to the greatest extent. In all cases, the desiccation step(s) and water wash combinations were more effective than water washing alone for reducing bacterial contamination on beef surfaces.

Technical Abstract: A series of experiments was conducted to determine the effectiveness of rapid desiccation with heat at one or two points in the slaughter process to reduce bacterial contamination on beef carcass surfaces. In Experiment 1, beef surfaces were inoculated with bovine feces and water washed (A; 125 psi, 15 s, 35 deg C); desiccated (400 deg C, 15 s) before inoculation and subjected to a water wash (B); inoculated, water washed and desiccated for 30 s (C); or desiccated, inoculated, water washed, and desiccated for 30 s (D). Remaining bacterial populations of samples treated with D exhibited the fewest populations of APC, coliforms, and Escherichia coli. When E. coli O157:H7, Salmonella typhimurium, Listeria innocua, and Clostridium sporogenes were monitored following treatments with D, none of the organisms was detected. Additional experiments were conducted with less heat (300 deg C) for shorter times to minimize surface discoloration. When desiccation (300 deg C ) was conducted for 10, 12, or 15 s prior to fecal contamination and followed by a water wash, it was demonstrated that none of the treatments was significantly different from the others for reducing APC from shortplates; however, the 10 s treatment was preferred for its shorter time. When desiccation for 10 s was combined with water washing and followed by a second desiccation step (300 deg C) for 15, 20, or 25 s, populations of APC, coliforms, and E. coli were reduced to the greatest extent when the second desiccation step was applied for 25 s. In all cases, the desiccation step(s) and water wash combinations were more effective than water washing alone for reducing bacterial contamination on beef surfaces.