Iceberg LineThis is a brief introduction to the key points to be taken into account when developing and producing a chilled food product

Details of hygienic standards and practices, processing parameters etc. are given in the CFA Guidelines

Product safety requires the application of HACCP principles to the design of plant, product and process, the management of hygiene procedures and the control of the process. HACCP is an ongoing system – it must be reviewed when any change is made to plant, raw material specifications, process or packaging.

Product safety must be determined by the proper consideration of the following:-

  1. Ingredient hygienic quality
  2. Product formulation/characteristics
  3. Processing parameters
  4. Intended use of product
  5. Storage and distribution conditions
  6. Manufacturing hygiene
  7. Shelf life

1. Ingredient Hygienic Quality

Points to consider are:-

  • Which pathogen(s) and level of contamination might be expected?
  • Is there a possibility of preformed toxins?
  • What are reasonable specification levels to apply to minimise risk?
  • What further processing is to be applied?

2. Product Formulation/Characteristics

The growth of pathogenic microorganisms can be controlled by product formulation/characteristics.

This might include:-

  • adjustment of pH
  • adjustment of aW (water activity)
  • addition of preservative

An individual factor, such as pH, may be used to reduce microbiological growth. Introducing an another factor, such as water activity (aw), may produce a synergistic effect, i.e. the combination of the two factors as hurdles reduces microbiological growth to a greater than expected or calculated extent. Relatively small changes to both hurdles together (e.g. pH + aW) may be as effective as large changes to either hurdle in isolation.

This phenomenon is generally termed the hurdle effect. It is important that the effectiveness of hurdle preservation is assessed in each case, with reference to specialist advice as appropriate, and possible challenge testing. For more details see Appendix C of the CFA Guidelines.

3. Processing Parameters

This should be considered under the following subdivisions and outcomes:-

  • Heat Treatments
    Tables of lethal rates are given in the CFA Guidelines. None or less than 70ºC for 2 minutes – possibility that all pathogens present will survive. Heated to 70ºC for 2 minutes (or equivalent) – all vegetative pathogens present will be reduced to an acceptable level (6 log reduction), e.g. Listeria monocytogenes, Staphylococcus aureus, salmonellae, verocytotoxigenic E. coli. However, spores and pre-formed toxins may persist. Heated to 90ºC for 10 minutes (or equivalent) – in addition to vegetative pathogens, spores of psychrotrophic (cold growing) Clostridium botulinum
  • Cooling
    Heated product should be cooled as quickly as possible through the temperature range 63ºC to 5ºC or less to minimise risk of spore germination and outgrowth. The time taken for cooling will vary from product to product, but as a guideline, should be no more than 4 hours.
  • Packaging
    This should be considered under the following subdivisions and outcomes:-
  • Product Cooked In-pack
    Pathogens will be eliminated to the extent indicated under Heat Treatments (see above) AND THERE WILL BE NO OPPORTUNITY FOR RECONTAMINATION THAT MAY PRESENT A FOOD SAFETY HAZARD (assuming complete integrity of the pack/seal).
  • Product Cooked, Cooled and Assembled
    Pathogens will be eliminated to the extent indicated under Heat Treatments (see above) BUT THERE IS RISK OF RECONTAMINATION DURING ASSEMBLY THAT MAY PRESENT A FOOD SAFETY HAZARD.

MAP or vacuum packaging may be used to reduce microbiological growth but will not necessarily inhibit the growth of pathogens. There may be particular concerns with respect to Clostridium botulinum. It is important that the effectiveness of MAP or vacuum packaging is assessed in each case, with reference to specialist advice.

4. Intended Use of Product

The key points to consider are:-

  • Is the product to be eaten without further heating (i.e. ready to eat)?
  • Is the product to be eaten following domestic reheating (i.e. requires reheating only prior to consumption)?
  • Is the product to be eaten following domestic cooking (i.e. requires a heat process equivalent to at least 70C for 2 mins prior to consumption)?

5. Storage and Distribution Conditions

TEMPERATURE IS THE PRINCIPAL CONTROLLING FACTOR FOR THE SAFETY OF CHILLED FOODS.

TEMPERATURE IS PARTICULARLY IMPORTANT TO SLOW OR INHIBIT THE GROWTH OF PATHOGENIC BACTERIA.

See Appendix D of CFA Guidelines

Chilled foods, for reasons of safety or quality, are designed to be stored at refrigeration temperatures (at or below 8ºC, targeting 5ºC) throughout their entire life. The performance of the proposed distribution chain should be validated and monitored by the responsible party and taken into account when specifying shelf life.

See also temperature

6. Manufacturing hygiene standards and practices in the various classes of hygiene areas are stipulated in the CFA Guidelines.

The purpose of establishing specified standards of hygiene is to control the hazard of microbiological contamination and recontamination. The level of hygiene required will depend on the risk of recontamination and/or the consequences of recontamination.

Chilled foods are manufactured using a wide variety of raw materials, processes and packaging systems and therefore must be expected to have both differing microbiological profiles after manufacture or storage and differing shelf lives, but must be microbiologically safe at the point of consumption.

Thus products made entirely from ingredients that are heated in a container or are assembled from heated ingredient(s) under the special hygiene conditions defined as High Risk are designed to be free from vegetative pathogens, but not all spore formers. Those containing raw ingredients will from time to time contain vegetative pathogens such as Listeria as well as spore formers. This difference must be taken into account when specifying shelf life in terms of time and temperature and consumer instructions.

7. Shelf Life

Shelf life depends on the control of all the preceding factors, but must be validated by challenge testing and/or modeling for each product and process for defined chill storage conditions. It must be recognised that the integrity of the whole of the chill chain is vital to ensure the safety and quality of chilled foods.

By choice of a combination of factors such as raw material quality, hygienic processing, temperature, water activity, acidity, modified atmosphere, etc., microbiological growth can be controlled and thus spoilage and/or foodborne diseases prevented. The choice and combination of “hurdles” will determine the shelf life and the conditions of use of the products.

Consult CCFRA (Campden) Guideline No. 46 “Evaluation of product shelf life for chilled foods” (2004)

July 2018, guidance from a consortium of UK food industry (CFA and BRC) and UK and Australian research organisations (Leatherhead Food Research, Meat & Livestock Australia and Quadram Institute Bioscience) was issued (Guidelines for Setting Shelf Life of Chilled Foods in Relation to Non-proteolytic Clostridium botulinum). The guidelines are designed to ensure that sufficient information is provided by FBOs and laboratories to arrive at valid decisions regarding the shelf life of chilled foods in relation to non-proteolytic Clostridium botulinum. The Guidelines are intended to also support FBOs when challenged by Competent Authorities.

Download PDF: Non-proteolytic Clostridium botulinum shelf life guidance – 1st Ed 9/7/18