Quantification of Listeria spp. contamination on shell and flesh of cooked black tiger prawns (Penaeus monodon).
OBJECTIVE
To quantify Listeria levels on the shell and flesh of artificially contaminated cooked prawns after peeling, and determine the efficacy of Listeria innocua as a model for L. monocytogenes in this system.


RESULTS
A L. monocytogenes and L. innocua strain were inoculated separately onto cooked black tiger prawns using two protocols (immersion or swabbing with incubation). Prawns were peeled by two methods (gloved hand or scalpel and forceps) and numbers of Listeria on shells, flesh and whole prawn controls were determined. Prawns were exposed to crystal violet dye to assess the penetration of liquids. Regardless of preparation method or bacterial strain there were ca 1log10 CFU more Listeria per shell than per peeled prawn. Dye was able to penetrate to the flesh in all cases.


CONCLUSIONS
Shell-on prawns may be only slightly safer than shell-off prawns. Listeria innocua is an acceptable model for L. monocytogenes in this system.


CONCLUSIONS
Reduced risk from L. monocytogenes on prawns can only be assured by adequate hygiene or heating.
Dykes
G A
GA
Food Science Australia, Tingalpa DC, Queensland, Australia. gary.dykes@foodscience.afisc.csiro.au
Vegar
M
M
Vanderlinde
P B
PB
D015169:Colony Count, Microbial; D005511:Food Handling / Q000379:methods; D005516:Food Microbiology; D006358:Hot Temperature; D008087:Listeria / Q000145:classification / Q000302:isolation & purification*; D008089:Listeria monocytogenes / Q000302:isolation & purification*; D008954:Models, Biological; D033561:Penaeidae / Q000382:microbiology*; D017747:Seafood / Q000382:microbiology*; D012758:Shellfish / Q000382:microbiology*