Microbial Quality of Bain Marie Foods

April June 1997

Report prepared by Simon Rockliff and Geoffrey Millard

Samples collected and analysed by the staff at ACTGAL


1.1 The survey was designed to determine the bacteriological status of Bain marie type foods available from ACT outlets.

2. Background

2.1 Bain maries are heating units designed to keep cooked foods hot for extended periods of time. This product type is high risk as food poisoning events have occurred both in Australia and overseas due to food premises failing to maintain the product/s above 60 degrees Celsius.

3. Survey

3.1 The survey was conducted between April and June 1997 with 65 samples being collected from a total of 18 ACT outlets. Samples were purchased as consumer items over the counter by the ACT Government Analytical Laboratory (ACTGAL) staff and analysed by the Microbiology Unit. The collection of the samples by laboratory staff meant it was impossible to collect data on the temperature of the Bain marie at the time of their collection. The Health Protection Service (HPS) decided to continue the survey even though this significant parameter could not be determined. The samples overall hygiene quality were assessed by the Standard Plate Count (SPC), Escherichia coli (E. coli) and coagulase-positive Staphylococcus (Coag+staph) analyses and for specific food pathogens such as Bacillus cereus (B. cereus), Clostridium perfringens (C. perfringens), thermophilic Campylobacter and Salmonella spp.

3.2 Table 1 gives the surveys acceptability criteria.

Table 1


Test Organism








E. coli












C. perfringens




Campylobacter spp

Not detected*


Salmonella spp

Not detected*



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

4. Results

4.1 Samples collected for analysis included,ten beef, nine lamb, nine pork, seven chicken, ten gravy, three turkey, fifteen kebab, one ham and one meat loaf sample. Kebabs per se are not Baine Marie foods but the cooked meat needs to be maintained above 600C in order to produce a product with a satisfactory level of hygiene quality.

4.2. Results are expressed as colony forming units per gram (cfu/g) of material analysed or as isolated/not isolated in 25 grams of the analysed material in the case of Salmonella and thermophilic Campylobacter spp

4.3 E.coli, coag+staph, C. perfringens, thermophilic Campylobacter and Salmonella spp were not detected in any sample.

4.4 Low numbers of B.cereus were detected in three samples, two at a level of 50 cfu/g and one sample at 100 cfu/g. The acceptable level for B.cereus are counts less than 1000 cfu/g.

4.5 Results for the Standard Plate Count ranged from <50250,000 and are shown in Table 2. From anecdotal evidence, the SPC acceptable level for this product type is counts less than 10,000 cfu/g. Only one sample recorded a count above this level, a roast beef sample with an SPC of 250,000 cfu/g which when repeated the next week was found to be acceptable.

4.6 Table 2. Standard Plate Count Results


Sample Type

SPC range cfu/g
















# The repeat SPC was 7,400 cfu/g.
Ham and meatloaf sample results were 100 and 4,400 cfu/g respectively.

5. Discussion

5.1 Apart from one instance of one sample having an unacceptable SPC level, the samples were found to be acceptable for hygiene indicators and pathogens.

6. Conclusion

6.1 Analysis of the SPC results indicates the samples with SPCs in the higher ranges were associated with particular premises rather than a food type. This trend illustrates the variation in handling/storage practices between food premises. Monitoring of the SPC levels could be a useful tool for detecting possible food handling/storage problems.

6.2 It is pleasing to see most premises are producing and selling an acceptable hygiene quality product free of specific pathogens.