Food Survey Reports 2000-2001

Microbiological Quality of Quick Cooked Foods

APRIL - JUNE 2001

Report prepared by Geoff Millard and Simon Rockliff

Objective

  • To determine the microbiological status of Quick Cooked Foods sold in the ACT.

Background

Quick Cooked Foods (QCF) i.e. brands such as Instant Pot Noodles and Cup of Noodles are becoming more commonplace on supermarket shelves. QCF should be considered a low risk item due to the dry nature of these products and the bactericidal action of the boiling water used to reconstitute them. Another product that is becoming popular is minimal cooking time pasta typified by several refrigerated Latina products. These product lines have not been previously tested in the ACT. It was considered prudent to perform a short survey on the above products.

Standards

There are no Australia New Zealand Food Authority (ANZFA) Standards directly applicable to these products, but the levels should not exceed the Draft ANZFA Guidelines for Ready-to-eat-foods. See Table 1.

Table 1

Test

Microbiological Quality (colony forming units per gram)

Satisfactory

Marginal

Unsatisfactory

Potentially Hazardous

Indicator

       

Escherichia coli

<3

3-100

³ 100

*

Pathogens

       

Coagulase + ve staphylococci

< 102

102-103

103-104

³104 SET+VE

Bacillus cereus and other pathogenic Bacillus spp

< 102

102-103

103-104

³104

Salmonella spp

Not detected in 25g

   

detected

Listeria monocytogenes

Not detected in 25g

   

³ 102**

*Pathogenic strain of E. coli, such as E. coli O157, should be absent

**the detection of Listeria monocytogenes in ready-to-eat foods prepared specifically for "at risk" population groups eg the elderly, immunocompromised and infants should also be considered as potentially hazardous

SET+VE = Staphylococcus enterotoxin positive

Survey

During the period 04/06/2001 to 13/08/2001, 48 samples of QCF (10 short cooking time samples and 38 QCF) representing 10 different manufactures were collected from three different ACT retail establishments. All of the samples were tested to enumerate the presence of E. coli, coagulase positive Staphylococci, Bacillus cereus and the presence or absence of Salmonella sp with 23 samples tested for the presence or absence Listeria monocytogenes (L. monocytogenes).

Testing for pathogenic strain specific serotypes of E. coli such as E. coli O157:H7 and Staphylococcus enterotoxin were not undertaken due to the cost involved in testing a low number of positive samples.

Results

Overall isolation rates for the 48 samples is given in Table 2.

Table 2

Organism (n = 62)

No. of samples positive (%)

E. coli

0(0.0)

coagulase positive Staphylococci

0(0.0)

B. cereus

0(0.0)

Salmonella sp.

0(0.0)

Listeria monocytogenes

0(0.0)

TOTAL

0(0.0)

n = Number of Samples

None of the organisms tested for were isolated from any of the samples.

Discussion

All of the samples were free of indicator organism and pathogens. The QCF are prepared by adding boiling water to the container. The contents are said to be ready for consumption in a little over three minutes. Testing of the procedure showed that the noodles stayed over 80 C for approximately 5 minutes. A combination of these factors, militates against bacterial survival.

Conclusion

The quality of Quick Cooked Food sold in the ACT is good. This product in its current form, provided the cooking instructions are followed, does not represent a threat to the Canberra community.

Recommendation

That a future survey be conducted to confirm the continued quality of the product.

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Microbiological Quality of Quick Cooked Foods

Microbiological quality of ready-to-eat foods

September 2000 - August 2001

Report prepared by Geoff Millard and Simon Rockliff

Objective

To determine the microbiological quality of Ready-to-Eat (RTE) foods sold in the ACT.

Background

Ready-to-Eat (RTE) food is food that is ordinarily consumed in the same state as that in which it is sold or distributed and does not include nuts in the shell and whole, raw fruits and vegetables that are intended for hulling, peeling or washing by the consumer (1). Due to the diverse nature of these foods and popularity it was considered prudent to perform an ongoing survey on these products in conjunction with the Environmental Health auditing program for establishments that produce these high-risk foods. This is a report on the first years results.

Standards

There are Australia New Zealand Food Authority (ANZFA) Draft Guidelines for Ready-to-Eat Foods. See Table 1.

Table 1

 

Microbiological Quality (colony forming units per gram) table

*Pathogenic strain of E. coli, such as E. coli O157, should be absent
**the detection of Listeria monocytogenes in ready-to-eat foods prepared specifically for “at risk” population groups eg the elderly, pregnant women, immunocompromised people and infants, should also be considered as potentially hazardous
SET+VE = Staphylococcus enterotoxin positive

Standard Plate Count

The standard plate count (SPC), also referred to as the aerobic plate count or the total viable count, is one of the most common tests applied to indicate the microbiological quality of food. The significance of SPCs, however, varies markedly according to the type of food product and the processing it has received. When SPC testing is applied on a regular basis it can be a useful means of observing trends by comparing SPC results over time.

Three levels of SPC are listed in Table I based on food type and the processing/handling the food has undergone.

Level 1 – applies to ready-to-eat foods in which all components of the food have been cooked in the manufacturing process/preparation of the final food product and, as such, microbial counts should be low.

Level 2 – applies to ready-to-eat foods, which contain some components which have been cooked and then further handled (stored, sliced or mixed) prior to preparation of the final food or where no cooking process has been used.

Level 3 – SPCs not applicable. This applies to foods such as fresh fruits and vegetables (including salad vegetables), fermented foods and foods incorporating these (such as sandwiches and filled rolls). It would be expected that these foods would have an inherent high plate count because of the normal microbial flora present.

Note: An examination of the microbiological quality of a food should not be based on SPCs alone. The significance of high (unsatisfactory) SPCs cannot truly be made without identifying the microorganisms that predominate or without other microbiological testing.

Survey

During the period 04/09/2000 to 28/08/2001, 208 samples representing around 130 different RTE foods were purchased from 72 (16%) ACT retail establishments. The foods purchased covered a wide range of the available RTE food types including salads, pies, quiches, sandwiches, meats and desserts. All of the samples were tested to enumerate the Standard Plate Count (SPC), E. coli and Coagulase Positive Staphylococci. From mid October 2000 all samples were also tested for the presence or absence of Salmonella sp and Listeria monocytogenes (L. monocytogenes). Bacillus cereus was only tested for foods containing rice.

Results

Standard Plate Count
A total of 89 samples were assessed as having to comply with the Level 1 criterion, of these 10 (11.2%) gave unsatisfactory results. The results ranged between <50 and 17,000,000 colony forming units per gram (cfu/g).

A total of 45 samples were analysed according to the Level 2 criterion. 6 (13.3%) were found to be unsatisfactory. Results ranged from <50 to 120,000,000.

There are no set limits for Level 3 samples. The results ranged from as low as 200 to as high as 1,200,000,000. No unsatisfactory samples were resampled.

E. coli
208 samples were tested for E. coli. The following table indicates that E. coli was <3 cfu/g in 97% of samples. 3% of samples had E. coli in the marginal category and no E. coli results were unsatisfactory.

 

e coli table


Coagulase positive Staphylococcus
The following table illustrates the number of samples positive for coagulase positive Staphylococcus (3%) and their individual counts. 5 samples were in the marginal category while 2 samples are unsatisfactory. No resamples were taken for the unsatisfactory samples.
 

Coagulase positive Staphylococcus table


B. cereus
A total of 18 samples were tested for B. cereus. Only one sample was positive with a count of 400 cfu/gm. This result fell into the marginal category and no resample was taken.

Salmonella sp.
Only one sample from 192 analysed was positive for Salmonella. This was a chicken kebab, which also contained 9cfu/g of E. coli. No resample was performed.

Listeria monocytogenes
Listeria monocytogenes was isolated from both pizza meat and a beetroot dip. Neither establishment was resampled.

Overall isolation rates for the 208 samples are given in Table 2.

Table 2

 

isolation rates table

NA= Not applicable


 

Table 3 shows the occurrence of unsatisfactory results. On the whole most samples were satisfactory for most organisms.

Table 3

 

occurrence of unsatisfactory results table

NA= Not applicable

Environmental Health Audit Findings
An evaluation of the bacteriological results and the Environmental Health shop audit finding was not possible as the audit records were destroyed when the Health Protection Service building was partially destroyed in the 18 January 2003 bushfires.

Discussion

No resampling of product with unsatisfactory results occurred for this survey. However, procedures have since been changed. For unsatisfactory results, an e-mail is now sent to the Environmental Health Officer responsible for sample collection requesting another sample be obtained.

Wherever possible the authors have attempted to accurately categorise the products into their respective SPC categories. This process has been difficult and the unit intends to closely monitor this test category to gain a better idea about overall handling practises.

Conclusion

In general the microbiological quality of the Ready-to-Eat foods sold in the ACT is generally good, however there appears that some types of food are being handled incorrectly. More education of the staff and management of retail premises within the ACT may be necessary in order to decrease the incidences of elevated levels of bacteria and presence of pathogens in these types of food.

Recommendation

1 - That the Ready-to-eat Survey continue for the future to confirm the continued quality of the product and co-relation to audit findings.

2 - That the HPS Sampling Working Group formulate and implement re-sampling guidelines.

Bibliography

1 - Australia New Zealand Food Authority (ANZFA) Draft Guidelines for Ready-to-Eat Foods.
2 - ANZFA Food Standards Code.

Microbiological quality of smallgoods

July 2001 - October 2001

Report prepared by Michelle Cartwright and Simon Rockliff

Objective

To maintain surveillance of smallgood products in the ACT to ensure their safety and continued compliance to current ANZFA Standards.

Background

The HPS continued its pro-active surveillance of these high risk products. According to the Western Australian Food Monitoring Program August 1999 smallgoods are considered a potentially hazardous product as the product is:

  • normally intended to be eaten as purchased, ie without further processing,
  • often sliced at the place of purchase and often experiences cross contamination during slicing due to lack of sanitation between customers,
  • by its nature prone to low level of Listeria contamination, which can be amplified by cross contamination,
  • prone to poor temperature control.

Salami has caused a number of food poisoning outbreaks. The most serious was an outbreak of food related Haemolytic Uraemic Syndrome (HUS) in South Australia in 1995. Salami contaminated with a virulent strain of E. coli resulted in the hospitalisation of several people and the death of a child. Following on from this food poisoning outbreak, ANZFA introduced specific requirements into the Australia Food Standards Code concerning their manufacture and sale. This included strict controls on manufacturing processes (to minimise possible contamination) and more stringent labelling requirements.

Standards

The Australia New Zealand Food Standards Code includes microbiological standards for packaged cooked cured/salted meat, packaged heat treated meat paste and packaged heat treated pate and uncooked fermented comminuted meats. Those samples that did not fall into these categories were analysed according to the Draft ANZFA Guidelines for Ready-to-eat food. The acceptable levels for each organism and sample category are shown in Table 1.

Table 1

 

Acceptable Microbiological Quality standards table

#This is extra testing performed by ACTGAL, which is not included in ANZ Food Standards Code.
cfu/g = colony forming units per gram of material analysed.

Survey

This survey was conducted between 4 July and 31 October 2001. During this period a total of 79 samples were collected by Environmental Health Officers (EHO) and processed by the Microbiology Unit of ACTGAL. The smallgoods were collected from a range of retail outlets and covered a number of product manufacturers and types available on the ACT market.

Retrospective testing for Staphylococcus enterotoxin was not undertaken due to the cost involved in testing a low number of positive samples.

Results

Only 41 samples were tested for E. coli and 67 for Coagulase positive Staphylococci while the presence or absence of Listeria monocytogenes (L. monocytogenes) was determined for 46 samples and Salmonella for 70 samples. In response to 3 positive Coagulase positive Staphylococci samples, 2 samples were collected for retesting. An additional 4 samples were collected and retested in response to 2 Listeria monocytogenes positive samples. The 6 additional samples are included in both the results and the total number of samples analysed. Overall isolation rate for the 79 samples is given in Table 2.

Table 2

 

Overall isolation rate for the  samples table

One of the six extra samples contained Listeria monocytogenes for a second time.
Two samples positive for Coagulase positive Staphylococcus were not resampled.
NA= Not applicable.
*expressed as colony forming units per gram.

E. coli
E. coli was not isolated from any of the 41 samples tested.

Coagulase Positive Staphylococci
Coagulase Positive Staphylococci was isolated from 3 (4.5%) samples. These samples were homemade cacciatori, mild Italian salami and mild pancetta. See Table 3.

Table 3

 

Coagulase positive Staphylococci table

NA = not applicable. Resampling was not performed on these samples.


Salmonella sp
No Salmonella was isolated from any of the samples in this study.

Listeria monocytogenes
Listeria monocytogenes was isolated from 2 (4.3%) samples. These samples were a bacon loaf and a cheese and cabanossi tray (retested cabanossi only). Three samples of bacon loaf collected and tested, only one re-samples contained Listeria monocytogenes. The resample of cabanossi was negative. These results are summarised in Table 4.

Table 4

 

Listeria monocytogenes table


The results of the re-sampling indicated that the positive L. monocytogenes were resulting from cross contamination of the meat loaf within the premises.

On 7 November 2001 Environmental Health Officers (EHOs) conducted an intensive audit of the premises’ procedures and operations and submitted 5 legal samples of ham for analysis. The bacon loaf was not on sale that day. EHOs also collected and submitted 4 environmental swabs for analysis. Listeria monocytogenes was isolated from 3 of the 5 ham samples.

The isolation of Listeria monocytogenes from the ham samples lead EHOs to once again assess the premises’ operation and procedures on the 14th November. The equivalent of 53 legal samples were submitted for analysis. Samples consisted of both foods and environmental swabs. Listeria monocytogenes was isolated from roast chicken buffet slices and one environmental swab.

Further food samples and environmental swabs were collected on 21st November and analysed for L. monocytogenes. No Listeria monocytogenes was isolated from these samples and the premise was given a clean bill of health and the investigation ceased.

Discussion

Salmonella does not appear to be a significant contaminant of smallgoods since it was not isolated in this survey or the past survey conducted by the ACT Health Protection Service in 1995-1996.

It is pleasing to see that E. coli was not isolated in any samples tested during this survey.

Coagulase positive Staphylococci were isolated from 3 samples and Listeria monocytogenes from 2 samples. The investigation into the L. monocytogenes indicated that the most likely reason for the presence of the organism in the product was poor handling and allowing cross contamination to occur.

Conclusion

The quality of smallgoods sold in the ACT is generally good, however there appears to be a problem with the handling of these products. More education of the staff and management of retail premises within the ACT may be necessary in order to decrease the incidences of cross contamination.

Recommendation

  • That a future survey be conducted to confirm the proper handling of the product is occurring.
  • That retailers are educated in proper cross contamination prevention procedures and handling practises.

Bibliography

1 - Report on Smallgoods Survey July 1995 – June 1996.
2 - ANZFA Draft Ready to Eat Food Guidelines.
3 - ANZFA Food Standards Code.