Impact of mechanical shear on the survival of Listeria monocytogenes on surfaces.
The impact of mechanical surface shear on microbial viability is rarely a subject for exploration in food processing. The objective of this research was to investigate the impact of mechanical shear on the survival of Listeria monocytogenes on surfaces. Mechanical shear created by slicing a model food was explored to investigate the viability of L. monocytogenes. Cell injury/death was readily demonstrated in fluorescence images by confocal microscopy in which the live and dead cells were fluorescently stained green and red, respectively, with a viability dye kit. Images showed that a large percentage of dead cells appeared after slicing, and they were readily transferred from the slicer blade onto the surfaces of sliced agar, indicating that surface shear may cause the lethal effect on L. monocytogenes. Surface transfer results also showed that viable cell counts on agar slices (in a slicing series) followed a consistently decreasing pattern. The cell counts initially at 5 to 6.5 log CFU/slice (slices 1 to 6), decreased to 3 to 4 log CFU/slice (slices 8 to 30), then to 2 to 3 log CFU/slice (slices 31 to 40), and counts would be expected to further decrease if slicing continued. The overall cell recovery (survival) ratio was about 2% to 3% compared to the initial 8.4 log CFU/blade on a 10 cm(2) edge area. The impact of shear on microbial viability during slicing may contribute 99% of viable cell count reduction. This study provides clear evidence that surface shear can kill foodborne pathogens and reduce cross-contamination. The lethal effects of surface shear may further enhance food safety.
Sheen
Shiowshuh
S
Eastern Regional Research Center, U.S. Dept. of Agriculture, Wyndmoor, PA 19038, USA. shiowshuh.sheen@ars.usda.gov
Costa
Sonya
S
Cooke
Peter
P
D016923:Cell Death; D002470:Cell Survival; D015169:Colony Count, Microbial; D004866:Equipment Contamination; D005511:Food Handling / Q000295:instrumentation / Q000379:methods*; D005516:Food Microbiology; D005517:Foodborne Diseases / Q000517:prevention & control; D008089:Listeria monocytogenes / Q000254:growth & development* / Q000302:isolation & purification / Q000648:ultrastructure; D050296:Microbial Viability; D018613:Microscopy, Confocal; D013499:Surface Properties