Which microbiological limits do I use?

There are four documents as well as specific food product legislation that need to be considered when interpreting microbiological results.

The documents (other than the specific food product legislation) are:

1. Food Standards Australia New Zealand, Standard 1.6.1 – Microbiological Limits for Food with guidelines criteria (FSANZ, 2001) (External website)

2. ’Microbiological Reference Criteria for Food' published by the Ministry of Health, 1995.

3. Food Standards Australian New Zealand ‘Guidelines for the microbiological examination of ready-to-eat foods (FSANZ, 2001) (External website)

Work is under way to consider the possibility of developing one document that contains all microbiological limits. Until this occurs, all four documents and specific food product legislation needs to be considered when interpreting microbiological results.

Food safety can only be assured by the use of risk based programmes based on the principles of HACCP. Reliance on microbiological limits and product testing alone is not sufficient. Microbiological sampling of end products is a means of verifying that the control systems in place are working. There is little point in sampling if the control measures are not in place.

When do I apply each document?

Legislative based documents

The first documents to consider are those that are part of New Zealand food law.

These are:

1. The Food Standards Australian New Zealand Code, Standard 1.6.1 - Microbiological Limits for Food. It is unlawful to exceed the limits defined in this standard.

2. Specific food product legislation that contain microbiological limits - for example; dairy products, animal products. These limits must also be considered when deciding on a sampling plan and interpreting its results.

Dairy

MPI specifies product outcomes for all dairy produce and products. These are outlined in the DPC1: Animal Products (Dairy) Approved Criteria for General Dairy Processing.

Animal Products

The Microbial limits associated with animal products for human consumption are outlined in notices issued under animal product legislation.

The limits identified in legislation take precedence over any other levels outlined in the following guidance documents.

Guidance Documents

These two documents should be used for various foods not covered in standard 1.6.1 or specific food product legislation.

1. The "Microbiological Reference Criteria for Food".

2. "User guide to Standard 1.6.1 - Microbiological Limits for Food with additional guidelines criteria."

When sampling ready-to eat foods then the following two documents also apply:

1. " Guidelines for the microbiological examination of ready-to-eat foods"

2. Chapter four of the "Microbiological Reference Criteria for Food" should be used. This also outlines a summary of actions to be taken by industry when food samples are found to be positive for Listeria monocytogenes.

The documents in this section are not part of legislation. However, when no standard exists in law, food businesses may use these guidance limits to help verify the microbiological safety of a manufacturing process or the safety of the food.

Regulators may also use the limits contained in these documents to interpret the results of microbiological testing and use these results:

to reinforce other observations made on food safety practices and the processing environment, and

to support a conclusion that the food process not meet sound public health practices and that the food is unsound, thereby not meeting the requirements of the Food Act 1981.

"Acceptable" and "Defective" microbiological levels

Within each of these documents, microbiological limits are generally expressed as 2- or 3-class plans with an "m" value below which processing/product is considered ’acceptable', an "M" value above which processing/product is considered ’defective', and between which processing/product is considered ’marginal'.

When undertaking end product testing, it is important that the following issues are considered:

  • Testing alone does not confirm the safety of a food product. It gives an indication that the controls in place in your business are working.
  • Sampling plans should be consistent with ICMSF guidelines. Microbiological testing laboratories will be able to give advice to businesses on how to design appropriate sampling plans.
  • Food businesses should not use the ’defective' limit as an upper limit for process control. Food businesses should identify limits that are achievable for their food process. These would be expected to be lower than the ’defective' limit for businesses operating under a Risk Management Programme (RMP), a Food Safety Programme (FSP), a Product Safety Programme (PSP) or other programmes where good hygienic practices will be standard. These process control limits should be reviewed regularly particularly if processing conditions change in any way, as part of commissioning of new processes and equipment, or during a review of HACCP.
  • The number of samples taken must comply with the requirements of the relevant document (usually a minimum of 5 samples are required, per batch of a particular food product).
  • Ensure that the organisms chosen for testing in a product will provide useful information.
  • Before you sample, determine and document what your actions will be with regards to all possible results.

Please note that microbiological limits for imported foods are not covered in this guidance note. See MPI's Imported Food website for more information.

Reviewing Standard 1.6.1 - Microbiological Limits for Foods

FSANZ has announced that Standard 1.6.1 – Microbiological Limits for Foods will be reviewed. The Standard became part of the Food Standards Code in 2000 and there have been a number of developments both in scientific knowledge and internationally with the use of different risk management tools in a food safety control system. Further information on the review including the scope, principles and guidelines, as well as a background paper is available from the FSANZ website.

Reminder: Food safety can only be assured by the use of risk based programmes based on the principles of HACCP. Reliance on microbiological limits and product testing alone is not sufficient. Microbiological sampling of end products is a means of verifying that the control systems in place are working. There is little point in sampling if the control measures are not in place.