Interpretation of micro testing guide
Chapter 1. Food safety criteria
Food category
Micro-organisms/their toxins, metabolites
Analytical reference method (3)
Stage where the criterion applies
n
c
m
M
1.1.
Ready-to-eat foods intended for infants and ready-to-eat foods for special medical purposes (4)
Listeria monocytogenes
10
0
Absence in 25 g
EN/ISO 11290-1
Products placed on the market during their shelf-life
1.2.
Ready-to-eat foods able to support the growth of L. monocytogenes,other than those intended for infants and for special medical purposes
Listeria monocytogenes
5
0
Products placed on the market during their shelf-life
5
0
EN/ISO 11290-1
Before the food has left the immediate control of the food business operator, who has produced it
1.3.
Ready-to-eat foods unable to support the growth of L. monocytogenes,other than those intended for infants and for special medical purposes (4) (8)
Listeria monocytogenes
5
0
100 cfu/g
Products placed on the market during their shelf-life
n = number of units comprising the sample; c = number of sample units giving values over m or between m and M.
Would this mean that we need 5x25g tests for Listeria, or make a composite of 5 subsamples and test for 25g. My interpretation is the latter? The note below the chart says "number of units comprising the sample".
Thanks!
Hi qfg,
The answer should be somewhere, maybe as a cross-reference, within the referenced iso11290-2 procedure.
In principle, compositing requires additional justification/validation that the detection sensitivity can be maintained.
(BAM-Salmonella Procedure is one well-known example where some (specified) compositng is possible).
Hi qfg,
whether you can pool or have to analyse each sample separately is depend on the expected test result (what c, n, M defines in mor detail)
n is the number of samples to be taken.
n=5 means you have to take 5 separate and independent samples of e.g, 25 g, which has to be representative for the batch to be tested.
a) if you are test for absence of salmonella you can pool the samples to 125 g and analyse only this single samples. The result is + or - .The result is expressed as absent in 25 g.
b) if tyou have to count numbers, you have to test the 5 samples separately -> c, n, M for assessment of the results.
Rgds
moskito
Hi qfg,
whether you can pool or have to analyse each sample separately is depend on the expected test result (what c, n, M defines in mor detail)
n is the number of samples to be taken.
n=5 means you have to take 5 separate and independent samples of e.g, 25 g, which has to be representative for the batch to be tested.
a) if you are test for absence of salmonella you can pool the samples to 125 g and analyse only this single samples. The result is + or - .The result is expressed as absent in 25 g.
b) if tyou have to count numbers, you have to test the 5 samples separately -> c, n, M for assessment of the results.
Rgds
moskito
Hi moskito,
Please note that the OP is referencing a Procedure for L.mono, not Salmonella.
So maybe Yes, maybe No. It depends.
Hi Charles,
thanks for your response. You are right "it denpends".
Salmonella I have taken as example for never "it depends" and where pooling is accepted -> here c is always 0 and n M not given.
With Listeria you have both.
a) absence or
b) max. 100 cfu/g e.g. acc EU law, where the second case has to be applied (no pooling and not "dilution" of samples) -> each single sample has to be max. 100 cfu/g
Rgds
moskito
Have I understood that if we are testing as ND/25g, we can pool samples for listeria and salmonella?
According to EU legislation?
Thanks in advance