Microbiological Quality of School Canteen Food

October—December 1998

Report prepared by Susan Leonard and Simon Rockliff

Objective

  • To determine the microbial status of school canteen food available in the ACT.

Background

Everyday thousands of Canberra children buy food from their school canteen. It is essential that food sold from school canteens is prepared in a hygienic manner and in all respects is safe to eat.

Food hygiene is just as important in school canteens as it is in restaurants or the home. School canteens are often run by a group of dedicated and hard-working managers and volunteers.

No previous surveys have been done involving the sampling of foods available in school canteens.

Food standards

There are no prescribed standards; however, the Food Act 1992 (2) states in no uncertain terms that food for sale must state correctly what it is, that it shall not cause injury, be unfit for consumption or contaminated.

Survey

The survey was conducted between 12th October and 14th December 1998. A total of 60 samples were collected by Environmental Health Officers (EHOs). The samples were sourced from a large range of ACT school canteens from primary, high schools and colleges. Each Monday for ten weeks during the fourth term of the school calendar, six schools were visited between 10 am and 2 pm. Each school was only visited once. A variety of sandwiches, rolls and burgers were purchased. Some of these were pre-prepared for sale on the day and other purchases were made upon request from the EHO. After purchasing the samples, they were held in an esky with ice and transported to the laboratory for analysis.

The samples were assessed for an indication of overall quality by the Standard Plate Count (SPC). Pathogen testing included the enumeration of E. coli, coagulase-positive Staphylococcus, and Clostridium perfringens, and the detection of Salmonella sp and Listeria monocytogenes.

Table 1 outlines the Health Protection Service (HPS) microbiological acceptability criteria for this type of food. These criteria were devised by the HPS and based on ACT historical food data, WA microbiological guidelines (4) and incorporate the level of concern based upon the food type and preservation procedures. Sandwiches, which include salad, will have a higher SPC as most salad vegetables naturally have elevated levels of bacteria as part of their natural flora. This has resulted in the splitting of the Standard Plate Count (SPC) criteria into sandwiches with and without salad.

 

Table 1

 

Test Organism Good Poor Unsatisfactory
SPC for sandwiches containing salad 105 105-107 >107
SPC for sandwiches not containing salad 103 103-105 >105
Coagulase positive Staphylococcus <50 <50-1000 >1000
E. coli <2# 2 - 100 >100
Salmonella spp Not detected* - Detected*
L. monocytogenes Not detected* - Detected*

# Units expressed in terms of colony forming units (cfu) per gram.

* Organism not detected in 25 gms

Results

The samples collected consisted of 11 Ham & Salad Rolls, 12 Chicken & Salad Rolls, 2 Chicken Patty & Salad Burgers, 26 Ham & Salad Sandwiches, 8 Chicken & Salad Sandwiches and 1 Roast Beef & Salad Roll. Only 6 sandwiches did not include salad.

 

Table 2

 

Overall Quality Results (cfu/g)
Standard Plate Count
Sandwiches with salad
42 Samples
10 samples < 105
36 samples > 105 to ≤ 107
8 samples > 107
Standard Plate Count
Sandwiches without salad
6 samples
3 samples < 105
3 samples > 105

 

Table 3

 

Pathogen tested Results (cfu/g)
E. coli 57 samples < 3
1 sample = 4
1 sample = 9
1 sample >1100
Coagulase positive Staphylococcus 59 samples < 50
1 sample = 400
Cl. perfringens 60 samples all lt; 50

 

Pathogen tested Results Presence/Absence
Salmonella spp 60 samples all NP
L. monocytogenes 58 samples NP
2 samples Present

cfu/g = colony forming unit/gram material analysed.

NP = Not Present

Discussion

Most canteens did not prepare high risk food, except for three premises, where fresh chicken was bought, cooked, prepared and diced to prepare sandwich filling. Most foods were ready to heat or eat and sandwich meats were purchased as either precooked frozen or cooked on the day and sliced for immediate use or freezing. Thawing of these frozen meats was carried out by microwave before placing the product on the sandwich or roll. Only the amount required to fill the days orders was thawed.

The results show a small percentage (1.7%) of the samples contained low levels of the pathogen, coagulase positive Staphylococcus while Listeria monocytogenes was isolated from two samples (3.3%) and Escherichia coli found in three samples (5%). One sample had greater than 1100 cfu/gm E. coli which is indicative of faecal contamination and improper handling/storage practices. Meanwhile another 18.3% of samples tested for SPC had counts which are regarded as unsatisfactory also suggesting improper handling/storage practices.

This survey was used to gain an insight into the microbiological quality of foods produced in ACT school canteens and will provide a useful base line for future surveys.

Conclusion

The unsatisfactory SPC and E. coli results do indicate that problems with lapses in hygiene, cross contamination, poor temperature control or a combination of these factors are occurring in the food handling at school canteens.

The Australian Supermarket Institute conducted a survey which identified lack of hand washing as one of the most likely sources of contamination along with the use of unclean utensils, inadequately disinfected food preparation areas, poor personal hygiene during food preparation (e.g. uncovered cuts on hands), poor temperature control and use of poor quality food. (3)

Recommendations

The following results be relayed to schools/canteens managers by telephone or a food premises audit undertaken.

  • SPC > 106
  • E. coli > 10
  • Coagulase positive Staphylococcus > 400

A copy of this report and education material, "Hygienic Preparation of Sandwich Fillings", sent to all the participating schools.

Follow up

A premises audit was carried out in the canteens that received the above results. During these audits temperatures of refrigerators, freezers, food warmers and hot water were taken. The accessibility to hand wash facilities and the availability of soap and hand towels was noted. Advice was given on the correct way to store and display sandwiches to achieve a quality product.

Bibliography

  • Australia and New Zealand Food Authority, Food Standards Code, incorporating amendments up to and including Amendment 38, April 1998.
  • Food Act 1992 (ACT), reprinted as at 31 January 1996.
  • Foodmonitor, 6th March 1998, Vol.3.
  • Food Watch, Microbiological Guidelines for Ready-to-Eat Foods, , Western Australian Food Monitoring Program April 1999.

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Microbiological Quality of School Canteen Food