Listeria Management for Ready-to-eat Meat Products PrimeSafe Technical Guideline

Listeria is a food borne pathogen found frequently in raw foods. It spreads to processed foods through cross contamination, poor hygiene and inadequate processing. The most common foods associated with Listeria include dairy, meat, seafood, fruits and vegetables. Listeria has created significant problems for consumers and the food industry, including serious illnesses, product recalls and short-term plant closures. The growth of Listeria is enhanced in processed “ready to eat” (RTE) products, especially those packed under vacuum or modified atmosphere using nitrogen gas. RTE foods are at risk of being contaminated prior to packaging as they may not always be cooked or reheated prior to consumption.

There are a few different types of Listeria but the most common one associated with food borne illness is Listeria monocytogenes that can cause serious illness or even death in vulnerable people such as the very young, elderly, pregnant or immunocompromised individuals. The related food borne illness “Listeriosis” can display a range of symptoms including fever, chills, convulsions, backache, headache, gastroenteritis, diarrhoea, vomiting and in extreme cases meningitis, septicaemia and spontaneous abortion.

Listeria survival and growth

• Can occur at temperatures as low as 1°C and survives the freeze-thaw process.
• Is unlikely to grow below pH 4.6, with ideal growth conditions in the pH range 5.0 – 9.0.
• Continues in dry conditions with low water activity of 0.90 (e.g. dry soil, straw, faeces and hides of animals).
• Can occur in salt solutions of up to 10% (e.g. pre-prepared brine solutions).
• Is possible without oxygen and can be found in vacuum packed and modified atmosphere products.
• Is destroyed by cooking or heating to a core temperature of at least 65°C for ten minutes.

All businesses processing and packaging RTE meat and poultry products must be licensed by PrimeSafe and have a Listeria Management Plan in place as part of the Food Safety Program. The Plan must ensure that raw products are segregated at all times from cooked RTE products. Listeria as a food safety hazard can be managed collectively using two key indicators:

• Environmental Monitoring.
• Product Testing.

The Listeria Management Plan must include the following:

1. Identification of the trained personnel who will be responsible for the Plan (e.g. QA Manager).
2. Schedule and records for training of samplers and key production personnel.
3. A sampling plan showing each area where environmental and product samples are collected (see example below).
4. Procedures for collecting environmental and product samples.
5. Testing arrangements – NATA certified laboratory or in-house testing.
6. Record keeping of all test results.
7. The response taken when Listeria is found.
8. A review of the plan annually as part of internal audits, or when there is a change in manufacturing processes.

Sampling sites across the processing environment must be selected based on a risk assessment. All possible contamination sites should be included and be specific to the processing operations of the business. For areas where RTE products are manufactured, swabbing should be conducted at a minimum of five times a month before and during processing operations. Testing must be done using approved methodology and by NATA registered laboratories. Any in-house testing must be done using methodology approved by independent bodies such as the Association of Official Analytical Chemists (AOAC). If test kits are used, then verification (proficiency testing) must occur annually to validate the kit methodology compared to a laboratory-based methodology. For ease of testing, sampling sites can be divided into two zones.

Swabbing must be done using sterile implements such as cotton buds, sponges or gauzes. Use a dry swab for a moist surface area. Use a swab moistened with sterile peptone water for a dry surface area. The swab must be taken following a zig zag pattern, close together covering at least 50cm² as shown below. If using a cotton bud, it should be rotated to cover the whole swab. Swabs must be hygienically stored at temperatures below 5°C and tested within 24 hours of sampling.

Correct swabbing technique

Incorrect swabbing technique

Given the severe risk of foodborne disease, all businesses that produce or pack RTE meat products either under vacuum or modified atmosphere must test products quarterly to verify the procedures and the hygiene status of the establishment even if production is only for a short period each year. RTE meat products that are cooked after packing (e.g. in-pack pasteurisation at a core temperature of 65°C for 10 minutes) is not required to be tested for Listeria. There may be other testing requirements for other pathogens that will depend on the product type and the cooking technique.

A minimum of five independent samples of each product/process type (whole, portioned or sliced) must be taken from each batch irrespective of species. Samples must be taken as unopened, undamaged packs and as they would be presented for sale. Samples must be kept and transported below 5°C and tested within 48 hours of sampling. The removal of 25g product portions must be done at the laboratory.

Figure 1: Five independent unopened samples to be provided for testing.

Figure 2: Five samples to be provided for testing after slicing, dicing or packaging.

Figure 3: Five samples taken, at least one for each product type samples for (largest cuts sampled with core temperature of 65°C for 10 minutes).

Figure 4: Insufficient number of tests, more samples required.

Approximate Timelines for Listeria Monocytogenes Testing of RTE Meat Products