Quality of Sandwiches and Rolls - January-March 1998

January-March 1998

OBJECTIVE

  • This survey was designed to determine the microbiological status of sandwiches and rolls available in the ACT.

Background

Sandwiches and rolls are widely available in the ACT and a previous survey conducted on sandwich fillings (1991 1993) highlighted some problems with handling, storage and cross contamination. As the analyses from the previous survey were conducted on sandwich fillings and not whole sandwiches the results were not considered suitable for comparison.

Standards

The Australia New Zealand Food Authority (ANZFA) Food Standards Code has no standards for these products. The West Australia State Health Laboratory Service (WASHL) has the only Australian guidelines available for assessing the Microbiological Quality of Ready to Eat Foods (Table 1). The WASHL guidelines include sandwiches and in addition to the criteria contained in Table 1, state that as a general guide a Standard Plate Count (SPC) of less than 1,000,000 colony forming units (cfu/g) is considered satisfactory.

Table 1: WASHL Guidelines

 

Test Criteria

Satisfactory

Fairly Satisfactory

Unsatisfactory

Unacceptable

 

Unlikely to cause disease.

Unlikely to cause disease, Indicate possible hygiene problems with food handling preparation.

May cause disease in some people. Food not manufactured hygienically.

Likely to cause disease in most people.

 

Action: Nil.

Action: If these results are produced regularly, examine hygiene and handling practices.

Action: Investigate production practices.

Action: Withdraw any food still on sale. Follow up with any known contacts. Investigate production practices.

Coagulase positive Staphylococci

<100/gram

Between 100 and 1000/gram

Between 1,000 and 10,000/gram

>10,000/gram

Clostridium perfringens

<100/gram

Between 100 and 1000/gram

Between 1,000 and 10,000/gram

>10,000/gram

Listeria monocytogenes

Not detected in 25grams

No level given

Between 10 and 100/gram

>100/gram

Escherichia coli

<10/gram

Between 10 and 70/gram

>70

Contains verotoxigenic

E. coli

 

Special Note 5: Microorganisms are not always evenly distributed in food. Therefore, even if the food falls into the Fairly Satisfactory category it may be the source of disease in some people.

Survey

Between January and March 1998, the ACT Government Analytical Laboratory (ACTGAL) collected 62 samples from twenty-nine different establishments. Samples were purchased as consumer items over the counter by ACTGAL staff and analysed by the Microbiology Unit. The samples were collected in such a manner as to cover the range of sandwiches and rolls available from food-halls, petrol stations and fast-food outlets. All of the samples were assessed for overall hygiene quality by the Standard Plate Count (SPC), Escherichia coli (E. coli) and coagulase-positive Staphylococcus (Coag+Staph) analyses. Where the foods contained meat, other food pathogens such as Bacillus cereus (B. cereus), Listeria monocytogenes (L. monocytogenes) and Clostridium perfringens (C. perfringens) were tested for. The survey collected multiple samples from single outlets and outlets were only tested once.

Results

Standard Plate Count

Graph 1

Forty seven (77%) samples had an SPC greater than 1,000,000 cfu/g, of which twenty nine (46.8%) had an SPC greater than 10,000,000 cfu/g and seven samples had an SPC greater than 100,000,000 cfu/g. (One sample could not be counted due to spreading organisms).

Graph 2

Graph 2 compares the SPC levels for sandwiches not containing (24) with those containing salad (37). For sandwiches and rolls containing salad, twenty-eight (75.7%) samples had an SPC greater than 1,000,000 cfu/g, nineteen (51.4%) samples had an SPC greater than 10,000,000 cfu/g and five (13.5%) samples had an SPC greater than 100,000,000 cfu/g. Meanwhile for sandwiches and rolls not containing salad, sixteen (66.7%) samples had an SPC greater than 1,000,000 cfu/g, ten (41.7%) samples had an SPC greater than 10,000,000 cfu/g while one (4.2%) sample had an SPC greater than 100,000,000 cfu/g.

Escherichia coli

E. coli was detected in fifteen (27%) samples with the range and median of positive samples tabulated in Table 2. Table 3 tabulates the results according to the WASHL guideline categories.

Table 2

 

Test Organism

% positive

Range cfu/ g

Median of the positive samples cfu/g

E. coli

27% (15 samples)

3 - >1100

15

 

Table 3: WASHL Guidelines

 

Satisfactory

Fairly Satisfactory

Unsatisfactory

Unacceptable

54 Samples (87.1%)

2 Samples (3.2%)

6 Samples (9.7%)

N/A

 

Coagulase Positive Staphylococcus

Coagulase-positive Staphylococcus was detected in seven (11.7%) samples with the range and median of positive samples tabulated in Table 4. Table 5 tabulates the results according to the WASHL guideline categories.

Table 4

 

Test Organism

% positive

Range cfu/g

Median of the positive samples cfu/g

Coagulase-positive Staphylococcus

11.7% (7 samples)

100 - >6800

300

 

WASHL Guidelines Table 5

 

Satisfactory

Fairly Satisfactory

Unsatisfactory

Unacceptable

54 Samples (87.1%)

5 Samples (8.1%)

2 Samples (3.2%)

Nil

 

Clostridium perfringens

C. perfringens was not isolated from any of the 46 samples tested for this organism.

Listeria monocytogenes

L. monocytogenes was isolated from one (2.3%) of the 44 samples tested for this organism. (The presence or absence of the organism in 25g of sample was the only test performed, cfu/g was not determined).

Discussion

As ACTGAL staff collected the samples, they were not able to collect temperature data to determine if this had an influence on SPC levels. Sandwiches containing salads tended to cover a greater range of SPC counts and exceeded the highest non-salad sandwich SPC level by a magnitude of approximately 100 times. No meaningful statistical analysis was performed on the SPC data. It does however appear that a correlation does exit between SPC counts of greater than 1,000,000cfu/g and the presence of salad. The SPC results and the fact that the PHLS4 in England allow up to 9.99 x 106 in sandwichs containing salad, highlights the need to review the WASHL criterion that a SPC of less than 1,000,000 is satisfactory for foods containing salad. In fact the visual quality of "salad" sandwiches did not appear to be affected by SPCs of up to 6.1 x 109. The organoleptic quality of the sandwiches was not assessed during this survey.

E. coli and Coagulase positive Staphylococcus were isolated from a total of 14 of the 29 (48.3%) premises surveyed. This indicates that hygiene and/or handling and storage conditions are unsatisfactory in 1 out of 2 premises surveyed. This level of non-compliance is of concern

Generally the isolation of E. coli from a ready to eat product is indicative of faecal contamination and/or that poor hygiene/handling procedures have taken place during the preparation of the product. While the WASHL guidelines regard an E. coli level of <10/g as "Satisfactory" our survey, which on most occasions collected multiple samples from each premises, found that sandwiches collected from the same premises at the same time could contain a mixture of Satisfactory, Fairly Satisfactory and Unsatisfactory results. In this situation the results are indicative of poor hygiene/processing (washing of vegetables etc) procedures during preparation.

Coagulase positive Staphylococcus is also regarded as an indicator of poor hygiene/handling procedures. The results indicate that 11.7% of samples fell into the WASHL categories of "Fairly Satisfactory" and "Unsatisfactory" for Coagulase positive Staphylococcus.

While the WASHL guidelines include an enumeration level for L. monocytogenes, the presence of this organism in a chicken/salad sandwich is of concern.

Conclusion

This survey has identified that, in the ACT, a significant hygiene/food-handling problem exists for this type of food product.

Bibliography

Australia New Zealand Food Authority, Food Standards Code, incorporating amendments up to and including amendment 38, June 1998.

Food Act 1992 (ACT), reprint as at 31 January 1996.

Food Watch, Western Australian Food Monitoring Program

Microbiological guidelines for some readyto-eat foods sampled at point of sale. PHLS Microbiology Digest 1996;13:41-43