Lethality of Listeria innocua and Listeria welshimeri
Hi Professionals, can anyone help with lethality of Listeria innocua & Listeria welshimeri by thermal process in RTE pork? I have searched numerous of literatures and couldn't find any. Hopefully I can get some help here. Thanks.
Why innocua and welshimeri? This is a non-pathogenic Listeria spp.
There is plenty of literature on L. mono inactivation across many consumer goods.
Why innocua and welshimeri? This is a non-pathogenic Listeria spp.
There is plenty of literature on L. mono inactivation across many consumer goods.
The reason is that the RTE meat product we sent to lab test L.mono, the results came back L.mono is negative, however, L. innocua and welshimeri were detected present in the products, therefore we plan to recook the product to kill all the listeria spp. However, little information I can found.
This question came at the perfect time for me as I am also facing a Listeria issue as well and came to this site to find some answers! We have Listeria grayi and it was detected in the EXACT same way. I sent our RTE extruded snack out for typical analysis (L. mono specifically by customer request) and the results came back the same. I discussed in depth with my lab and they explained that the detection level they have to narrow it down to reports out the specific type when it is "too close to call" with L. mono or as I understood it at least.
In our situation, we are unable to re-process so I assume the fate of our product will be the dumpster... All 160,000 lbs.
My point is just use the L. mono inactivation models.
If your lab can quantify the cfu/gm (20-<100) you may be able to let the product go to market (not sure about your specific product or storage/end use). Most authoritative bodies only have action levels for pathogenic organisms, and as far as I can see there are no known cases of listeriosis associated with l. innocua or l. welshimeri.
I have attached PHLS brochure which may help (table 1)
PHLS Micro Limits.pdf 3.32MB 10 downloads
However, the FDA has set a tolerance limit for action level at "presence of organism"
Attached is the part 123/117 guidance on controlling growth and inactivation of L. Mono
Appendix-4--Bacterial-Pathogen-Growth-and-Inactivation.pdf 2.08MB 14 downloads
Hi maylao,
IIRC Canada has published, lengthy/ detailed tolerances for RTE L.monocytogenes which differ from those in USA.
Offhand I do not recall any interest being expressed in other Listeria, non-human pathogenic, species.
IIRC most commercial test kits for Listeria note that a further confirmation as to the presence of L.monocytogenes may be Regulatory required.
However I speculate that some facilities simply take a worst-case viewpoint for "Listeria-positive" and assume that L.monocytogenes is likely to be present. Dubious logic.
PS - I daresay you can find some published D-values for Listeria species other than L.mono if a detailed search is undertaken. Hopefully they are not greater than L.mono.
My point is just use the L. mono inactivation models.
If your lab can quantify the cfu/gm (20-<100) you may be able to let the product go to market (not sure about your specific product or storage/end use). Most authoritative bodies only have action levels for pathogenic organisms, and as far as I can see there are no known cases of listeriosis associated with l. innocua or l. welshimeri.
I have attached PHLS brochure which may help (table 1)
However, the FDA has set a tolerance limit for action level at "presence of organism"
Attached is the part 123/117 guidance on controlling growth and inactivation of L. Mono
Hi Slab, Thanks for your information. Our end products are frozen, which I believe wont support any Listeria spp growth. Customers will need to cook/reheat the products before they consume. Therefore, the risk is quite low, to be honest.
PS - I daresay you can find some published D-values for Listeria species other than L.mono if a detailed search is undertaken. Hopefully they are not greater than L.mono.
Hi, Charles
The heat tolerance will not change between species, L. innocua is the most common analogue for L. mono trials
Hi maylao,
IIRC Canada has published, lengthy/ detailed tolerances for RTE L.monocytogenes which differ from those in USA.
Offhand I do not recall any interest being expressed in other Listeria, non-human pathogenic, species.
IIRC most commercial test kits for Listeria note that a further confirmation as to the presence of L.monocytogenes may be Regulatory required.
However I speculate that some facilities simply take a worst-case viewpoint for "Listeria-positive" and assume that L.monocytogenes is likely to be present. Dubious logic.
PS - I daresay you can find some published D-values for Listeria species other than L.mono if a detailed search is undertaken. Hopefully they are not greater than L.mono.
Yes, the tolerances for RTE L.monocytogenes in USA is more stringent than Canada.
Our end products are frozen, which I believe wont support any Listeria spp growth. Customers will need to cook/reheat the products before they consume. Any advise??
This question came at the perfect time for me as I am also facing a Listeria issue as well and came to this site to find some answers! We have Listeria grayi and it was detected in the EXACT same way. I sent our RTE extruded snack out for typical analysis (L. mono specifically by customer request) and the results came back the same. I discussed in depth with my lab and they explained that the detection level they have to narrow it down to reports out the specific type when it is "too close to call" with L. mono or as I understood it at least.
In our situation, we are unable to re-process so I assume the fate of our product will be the dumpster... All 160,000 lbs.
Hi clcapanni, I am sorry to hear that but its for the safety. Our products are different, they are frozen and consumers need to cook/reheat before being consumed. Therefore, we have to do risk assessment whether it is worth to recook the products or just sale as it is.
Hi, Charles
The heat tolerance will not change between species, L. innocua is the most common analogue for L. mono trials
Hi Slab,
Sorry but this is incorrect.
Heat resistance even varies between strains of the same species, eg -
heat resistance L.monocytogenes.pdf 308.73KB 10 downloads
PS - above slightly old ref (2000) also comments "Data on Listeria innocua indicate that it is more heat resistant than some strains of L. monocytogenes when the two organisms are tested under identical conditions and may be a suitable model for estimating the thermal tolerance of L. monocytogenes"
Hi clcapanni, I am sorry to hear that but its for the safety. Our products are different, they are frozen and consumers need to cook/reheat before being consumed. Therefore, we have to do risk assessment whether it is worth to recook the products or just sale as it is.
Hi maylao,
Actually yr Post 3 implied (to me) that product was RTE.
For RTC, this discussion is probably immaterial.
Hi maylao,
Actually yr Post 3 implied (to me) that product was RTE.
For RTC, this discussion is probably immaterial.
Hi Charles, sorry for the confusion. The finished products indeed are claimed as RTE which go through a validated heating kill process. However, due to the characteristic of the products we need to store them frozen before being consumed and people usually cook them and hot served. Thanks.
Hi Charles, sorry for the confusion. The finished products indeed are claimed as RTE which go through a validated heating kill process. However, due to the characteristic of the products we need to store them frozen before being consumed and people usually cook them and hot served. Thanks.
Hi maylao,
Ok, thks. I get it now.
I can understand why you are surprised to detect Listeria species in finished product.
May I ask how do you validate yr cooking process with respect to L.monocytogenes ?
Hi Slab,
Sorry but this is incorrect.
Heat resistance even varies between strains of the same species, eg -
heat resistance L.monocytogenes.pdf
PS - above slightly old ref (2000) also comments "Data on Listeria innocua indicate that it is more heat resistant than some strains of L. monocytogenes when the two organisms are tested under identical conditions and may be a suitable model for estimating the thermal tolerance of L. monocytogenes"
Thanks, Charles. Interesting read. The conclusion is that it is a suitable analogue for L. mono however unnamed 13 serotypes, additionally;
"Because not all strains have been tested under comparable conditions, it is not possible to conclude that one particular strain is the most heat resistant"
Seems contradictory
Thanks, Charles. Interesting read. The conclusion is that it is a suitable analogue for L. mono however unnamed 13 serotypes, additionally;
"Because not all strains have been tested under comparable conditions, it is not possible to conclude that one particular strain is the most heat resistant"
Seems contradictory
Hi Slab,
Yes, I was equally surprised. I didn't do a deep search so maybe the uncertainty has (somehow) now been resolved/reduced.
I don't ever recall lethality tables making allusions to "strain" effects although they usually (footnote) the necessity of selecting an average "k" factor for calculative purposes / varying food matrices. Possibly a less argumentative route. :smile: