Microbial Quality of Smoked Products

October December 1996

Report prepared by Simon Rockliff, Geoff Millard

Samples collected and analysed by the staff at ACTGAL

1. OBJECTIVE

1.1 To determine the bacteriological status of smoked products within the ACT.

1.2 To determine, where appropriate, if the product complies with Australia New Zealand Food Authority (ANZFA) Food Standards Code (FSC).

2. Background

2.1 This product type was last tested by a small survey in July 1994. That survey identified significant problems in Australian smoked trout which along with cases of Listeriosis caused by New Zealand smoked mussels resulted in the ANZFA setting a level for Listeria monocytogenes in smoked fish and mussels. This product is high risk and has the potential to cause foodborne illness. There is currently no ANZFA Listeria monocytogenes level for smoked meats.

3. Survey

3.1 A total of 66 samples of 23 different smoked products were collected from 16 different establishments, between October December 1996. Samples were purchased as consumer items over the counter by the A C T Government Analytical Laboratory (ACTGAL) staff and analysed by the Microbiology Unit. The samples were assessed for indication of overall hygiene quality by the Eschericha coli (E. coli) and coagulase-positive Staphylococcus

  • (Coag+staph ) analyses and for specific food pathogens such as Clostridium perfringens

  • (C. perfringens), Salmonella spp and Listeria monocytogenes (L. monocytogenes). The survey was designed to cover as much of the ACT market as possible therefore, only a single sample of each product was collected, from various outlets, on each occasion, not five as required by ANZFA FSC criteria. The unit also decided to determine the level of

  • L. monocytogenes in all products which meant samples were not strictly tested for

  • L. monocytogenes according to the FSC but any positive samples could still be regarded as not complying with the ANZFA FSC criteria.

3.2 Those products complying with ANZFA are covered by Food Standard Code D1 clause 4(d) which states:

  • "Smoked fish products which may be eaten without further cooking shall be free from Listeria monocytogenes in 25 g of the food when examined by the method prescribed by subclause (11)(c) of this Standard".

and FSC D1 clause 4(e) states:

  • "Marinated smoked mussels, whether cooked or uncooked, shall be free from Listeria monocytogenes in 25 g of the food when examined by the method prescribed by subclause (11)(c) of this Standard".

3.3 Table 1 gives the surveys acceptability criteria.

Table 1

 

Test Organism

Good

Poor

Unacceptable

E. coli

<2#

2–1000

>1000

Coag+Staph

<50#

50–1000

>1000

C. perfringens

<50#

50–1000

>1000

L. monocytogenes

Not detected*

Detected

Salmonella spp

Not detected*

Detected

 

# Units expressed in terms of Colony forming units (cfu) per gram. * Organism not detected in 25 gms.

4. Results

4.1 Table 2 gives the results of the 49 smoked fish and mussel samples for which the ANZFA FSC could have applied. Samples positive for Listeria monocytogenes do not comply with the FSC.

Table 2

 

Test Organism

Range

L. monocytogenes

<3–460#(Isolated from 2 samples)

E. coli

All samples <2#

Salmonella spp

All samples — Not Detected*

Coag+Staph

All samples <50#

C. perfringens

All samples <50#

 

# Units expressed in terms of Colony forming units (cfu) per gram. *Organism not detected in 25 gms.

4.2 From Table 2. L. monocytogenes was detected in two (4.1%) samples, one of smoked cod at a level of 4 cfu per gram and one of kippers at a level of 460 cfu per gram. E. coli, Salmonella spp, C. perfringens and coagulase + staph were not isolated from any of the 49 samples and therefore recorded as being less than the lowest detectable level.

4.3 Table 3 gives the results of the other 17 smoked product samples which were not covered by the ANZFA FSC. They consisted of smoked chicken, sausages, pork and ribs.

Table 3

 

Test Organism

Results all samples

L. monocytogenes

<3#

E. coli

<2#

Salmonella spp

Not Detected*

Coag+Staph

<50#

C. perfringens

<50#

 

# Units expressed in terms of Colony forming units (cfu) per gram * Organism not detected in 25 gms.

4.4 From Table 3 it can be seen that L. monocytogenes, E. coli, Salmonella spp, C. perfringens and coagulase +staph were not isolated from any sample and therefore recorded as being less than the lowest detectable level.

5. Discussion

5.1 The kippers and cod did not comply with the ANZFA Food Standards Code as L. monocytogenes was isolated from 25g of the food. These products were sold in a loose state and purchased on the same day from the same outlet. Therefore, the cod could have been cross contaminated from the kippers. Kippers are usually heated before consumption but not always as different ethnic cultures prepare the product in different ways. The kippers and the cod were resurveyed two weeks later and no L. monocytogenes was detected in either product.

5.2 The final isolation rate ofListeria monocytogenesfrom samples required to comply with the ANZFA FSC could have been higher as the code requires the absence of this pathogen in 25g of sample which is a more sensitive detection method when compared with the Most Probable Method used by the unit to determine a detection level of <3 cfu/g. Any sample with a L.monocytogenes level of <3 cfu/g is unlikely to be a public health problem.

6. Conclusion

6.1 In general smoked products sold in the ACT are free of potential pathogens. This product is high risk and will be monitored closely in the future. This survey was only possible with the support of the staff of ACTGAL and the Health Protection Service.