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

A series of experiments were conducted to determine the effectiveness of rapid desiccation with dry heat at one or two points in the slaught er process to reduce bacterial contamination on beef carcass surfaces. In the first set of experiments, several combinations of desiccation and water washes were examined. Beef surfaces were inoculated with bov ine feces and water washed (IW; 125 psi, 15 s, 35 degrees C); desiccat ed (400 degrees C, 15 sl before inoculation and subjected to a water w ash (D-15(400 degrees C) IW); inoculated, water washed and desiccated for 30 s (IWD30400 degrees C); Or desiccated, inoculated, water washed , and desiccated for 30 s (D-15(400 degrees C) IW D-30(400 degrees C)) . Samples treated with (D15C)-C-400 degrees IWD30400 degrees C exhibit ed the lowest populations of APC, coliforms, and Escherichia coli. Whe n E. coli O157:H7, Salmonella typhimurium, Listeria innocua and Clostr idium sporogenes were inoculated on to beef surfaces (3.30, 2.61, 3.97 , and 3.63 log(10) CFU/cm(2), respectively) and monitored following tr eatments with D-15(400 degrees C) IWD30400 degrees C none of the organ isms were detected. To minimize surface discoloration, an additional s et of experiments were conducted using less heat (300 degrees C) for s horter times. When desiccation (300 degrees C) was conducted for 10, 1 2, or 15 s prior to fecal contamination and followed by a water wash D -10,12,15(300 degrees C) IW), it was demonstrated that none of the tre atments were significantly different from the others for reducing APC from shortplates; however, the 10 s treatment was preferred for its sh orter time. When desiccation for 10 s was combined with water washing and a second desiccation step (300 degrees C) for 15, 20, or 25 s (D-1 0(300 degrees C) IWD15,20,25300 degrees C), populations of APC, colifo rms, and E. coli were reduced to the greatest extent when the second d esiccation step was applied for 25 s. This study is the first to repor t that water washing in combination with rapid desiccation with dry he at at one or two points in the slaughter process is more effective tha n water washing alone for reducing bacterial contamination on beef sur faces. (C) 1997 Academic Press Limited.