Microbiological research

Page content: Freshly squeezed fruit juice survey | Sushi and asian meat temperature control research | Chinese-style roast duck summary | Kebab survey | Microbe growth in custard & cream products | Cleanliness survey of food contact surfaces in the food industry | Effectiveness of hands free vs manual wash hand basins | Assessment of handling of food and money | Home delivery of perishable foods project

Research on food borne illness germs and the ways they can grow or be transmitted, leading to understanding more effective ways to control these germs.

Freshly squeezed fruit juice survey

A statewide microbiological survey has shown that freshly squeezed juices, when prepared and handled properly, are safe for the consumer.

The survey, conducted to improve knowledge and understanding of the microbiological risk of freshly squeezed fruit and vegetable juices, involved the collection of samples by Environmental Health Officers from 20 councils across Victoria. The 291 juice samples collected between March and May 2004 were analysed for Salmonella spp. Escherichia coli, Listeria monocytogenes and coagulase positive staphylococci. Sample pH levels were also determined.

Overall, the microbiological quality of the juice samples submitted was good, with only one sample being assessed as potentially hazardous.

This is very positive news for the growing number of people who consume freshly squeezed juice and for the businesses that are meeting that demand.

While the study results were extremely good, businesses that produce freshly squeezed juices should always adhere to safe food handling and preparation practices, as documented in their Food Safety Program, to prevent any problems.

Freshly squeezed fruit juice survey report, August 2005 (350kb, pdf)

Sushi and asian meat temperature control research

The Food Safety Standards require all potentially hazardous food to be handled and displayed under temperature control - cold foods at 5C or less and hot foods at 60C or greater. The interpretation guidelines to the Standards, however, permit these foods to be out of temperature control for up to 4 hours. Any greater time than this requires scientific validation.

The increased diversity of Victoria’s ethnic population, involved in food retail and service businesses, has resulted in the availability of a wide variety of cuisine. Some of these foods, when prepared traditionally, could have their quality and flavour compromised if they complied with the strict temperature requirements of the Food Safety Standards.

The Food Safety Unit conducted research on several of these foods, being Sushi products - Nigiri pieces and Nori Rolls, and Asian meats – Chinese style Roast Duck (‘Peking Duck’), Chinese Style Chicken and Chinese Style Roast and Barbequed Porks.

Scientific validation was sought on the safety of these products - under alternative temperature control arrangements (within the temperature danger zone of 5C – 60C).

It was found that with a pH of 4.8 or less the Sushi products, Nigiri pieces and Nori Rolls, can be kept at 15C or less for a period of up to, eight or twelve hours, respectively. Research and microbiological testing of the Asian meats found that, if prepared and handled in specific ways, Chinese Style Duck and Chicken can be left on display, at ambient temperatures, for up to twenty-two hours while the Porks can be on display for up to seven hours

Foods kept under alternative temperature control (39kb, pdf)

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Chinese-style roast duck summary

This project set out to monitor the changes in specific bacterial populations during the preparation and processing of Chinese-style roast duck. The results have provided DHS with information for the establishment of critical control points in the process.

Chinese-style roast duck summary (37kb, pdf)

Kebab survey

Kebabs are a traditional Middle Eastern meat dish made by stacking layers of meat such as chicken, beef and lamb, which is seasoned, marinated, and sliced or minced, onto a vertical skewer to form a cone or cylinder shape. The skewer rotates in front of a heat source as the outer layer of meat is cooked, it is carved off in slices. The meat is then served in flat bread together with salads and dips.

The survey was conducted due to a number of cases of illness that had circumstantial links to the consumption of kebabs

In this survey we wished to establish whether or not illnesses can be transmitted through kebabs. From the information obtained, we can then determine if further cooking steps are necessary after meat has been cut off the vertical spit prior serving to the public.

Survey of Kebabs (219kb, pdf)

Microbe growth in custard and cream products

DHS supplied funding to Dunn Son & Stone, Public Analysts, in 2001 to conduct a challenge testing study (where product is infected with specific microbs to observe growth rates) of custard and cream products with Bacillus cereus, Coagulase positive Staphylococci and Escherichia coli at ambient temperatures to test the 2hr/4hr rule introduced by the FSANZ Food Safety Standards (Standard 3.2.2 Food Safety Practices and General Requirements).

Summary of Results
The study found that over a four hour time period 13.0% of samples were found to sustain the growth of either Bacillus cereus, Coagulase positive Staphylococci or Escherichia coli and that over an eight hour time period 34.8% of samples sustained bacterial growth.

The Study concluded that custard and cream based products should be:

• Safe after 2hrs; and
• Discarded after 4hrs (as per the 2/4 hr rule);

And that:

• Extensive verification would be required by proprietors if they want to keep products outside this time frame, as after 8hrs some produ23 December, 2008evels and would be considered unsatisfactory outside of temperature control over this time period; and
• It must be noted that other samples that had a lower pH and water activity were found to be satisfactory over an eight hour time period. It was not possible to determine what products would fall into this category by observation or cooking process used.

The full report of the study is below:

Microbe growth in custard and cream products (592kb, pdf)

Cleanliness survey of food contact surfaces in the food industry - Mildura Rural City Council, Environmental Health Services

The aim of the project was to select a range of different food premises to:

• determine levels of cleanliness of food contact surfaces;
• assess effectiveness of cleaning measures being undertaken;
• assess level of knowledge of staff in relation to cleaning issues;
• identify any problem areas or deficiencies in relation to cleaning of food contact surfaces;
• provide advice on how to rectify identified problem areas;
• conduct follow-up assessment to assess effectiveness of educative processes; and
• contrast cleanliness of food contact surfaces between:
  • large premises (eg multi franchises) V's small food premises (eg corner store);
  • premises with cleaning schedule V's premises without a cleaning schedule; and
  • other areas of interest

The cleanliness of surfaces was assessed using the ATP lightning swabs - ATP- bioluminescence detects food residues by measuring the adenosine triphosphate (ATP). ATP is found in most food residues and all bacteria, yeasts and moulds.

The results from the first round of swabs was that 17.9 % passed, 19.2 % fell into the Caution category, and 62.8 % failed. This indicated that test point food contact surfaces were in most cases not being effectively cleaned to the test standard and that cleaning processes needed to be addressed. Cutting boards and meat slicers consistently performed poorest of the test items.

Follow-up swab results generally showed significant improvement across the board in comparison to Round 1 results. Average Cleanliness ATP swab results for some categories managed to fall within the caution zone. Of 1st round micro swabs which failed, only 33% failed again at their repeat follow-up micro swab.

Small businesses showed the greatest improvement and actually had the best lowest overall average swab result in Round 2. Smaller sized premises were more likely to implement recommended changes than larger sized premises.

Those items where recommended changes were adopted performed noticeably better. Changes implemented varied depending on the individual circumstance but typically included devising a cleaning schedule, replacing item if in poor condition, and modifying cleaning methods etc.

Cleanliness survey of food contact surfaces in the food industry (412kb, pdf)

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Report on the Wash Hand Basin project - City of Yarra & Swinburne Institute of Technology

Hands free wash hand basins were made a mandatory requirement in Victoria under the Health (Eating House and Food premises) Regulations 1984.

In 2001 the Australian and New Zealand Food Standards Code, Food Safety Standard 3.2.3, was adopted in Victoria. This Standard no longer requires the provision of hands free wash hand facilities in food premises.

There is limited information comparing the effectiveness of hands free wash hand facilities in reducing the microbial load on the hands of food handlers compared to manual wash hand basins.

The project was conducted to investigate the hypothesis that there is no difference in the effectiveness of both these types of wash hand basins.

The results of this pilot indicated that there was no difference between the use of either manual or hands free wash hand basins taking into consideration a number of variables for a small group of food retailers in the City of Yarra. Consideration should be given to a range of factors which may have impacted on this study, including frequency of hand washing, types of foods handled, length of mechanical wash and the number of manual wash hand basins available for the study.

Report on the Wash Hand Basin project (454kb, pdf)

The assessment of the public health risk associated with the simultaneous handling of food and money in the food industry - Central Goldfields Shire Council

The project investigated the potential for the transfer of pathogens due to the simultaneous handling of money and food. The project is of particular interest because it is the first to examine the characteristics of the relatively new, Australian "plastic currency".

Money handled by the same person who is also handling the food was analysed for both the presence and levels of three micro-organisms Enterobacteriaceae, E.coli and Coagulase Positive Staphylococci. A corresponding food sample was taken from the same premises to identify any possible cross contamination issues.

The limited study did not prove that there was any bacterial transfer between money and food. However the potential for pathogen transfer does exist due to the presence of Coagulase positive Staphylococci on the money surface.

The study did not suggest any one denomination was able to inhibit or encourage the presence of Coagulase positive Staphylococci, as it was present and absent on both notes and coins.

The conclusion of the study was that all due care should be taken by food handlers prevent the potential of cross contamination between money and food.

The assessment of the public health risk associated with the simultaneous handling of food and money in the food industry (513kb, pdf)

Home delivery of perishable foods project

This study assessed the risks posed by possible temperature abuse during home delivery in order to give health authorities a scientific basis for exercising control over conditions for home delivery commensurate with the food safety risks.

Supermarket home delivery services are mainly used by elderly customers and demand is expected to rise with increasing numbers in the elderly cohort, and a government desire that they remain in the community for as long as practicable. Community lifestyle changes are also relevant.

The main conclusions are :

• The conditions under which foods are normally handled and delivered to homes by the participant stores do not appear to increase the food safety risk for the majority of foods.
• A minor part of the delivery time is spent in the vehicle, and a large proportion of the delivery time is spent in the store, storage and handling is important. Therefore stores should attempt to limit heat gain in the foods, food not refrigerated after check out should be located in the coolest part of the store and stores should aim to limit the time from purchase to delivery to no more than 4 hours.
• Refrigerated vehicles are not necessary if stores ensure food is kept as cold as possible and transport limited to ½ hour.
• Both refrigeration and the use of "Cold Packs" were effective in limiting temperature rises in home deliveries. Using these systems the time from purchase to delivery to the customer can be extended to 24 hours if the temperature does not exceed 10°C.

Home delivery of perishable foods project report (781kb, pdf)

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