1992: The 10 Day Rule is Created
The 10 day rule has been in place since 1992 when the Advisory Committee for the Microbiological Safety of Food published its guidance on the safety of chilled vacuum packaged/modified atmosphere packaged products and other foods with low oxygen characteristics that are stored at 3-8oC. Specifically, the 10-day rule requires controls to be put in place for non-proteolytic Clostridium botulinum if such a food is given a shelf life of more than 10 days.
CFA was successful in re-securing the 10 day rule in 2005, working to change FSA‘s then proposed guidance to restrict the shelf-life of these foods from 10 to 5 days. This would have had a detrimental effect on chilled foods making the production and distribution of many chilled foods impractical. We also argued that the 5 day restriction was unnecessary as current measures (the 10 day rule) are effective in assuring the safety of chilled prepared foods.
We were instrumental in drawing together various industry and research parties, resulting in FSA’s draft guidance being roundly criticised for lacking scientific basis, with the result that ACMSF (Advisory Committee on the Microbiological Safety of Food) put the matter to independent review.
2006: Proposed 5-Day Rule Rejected
This review was carried out in 2006 and the report presented to ACMSF by the Institute of Food Research (IFR) on 8 June 2006 where the ACMSF concurred with its conclusions, rejecting the proposed 5 day limitation. The ACMSF also noted that the 10-day shelf life recommendation for the UK was already quite restrictive and was not applied in many other countries. In particular, they welcomed the epidemiological evidence included in the review which showed that, over the last 20 years, there were no reported cases of botulism linked to properly stored chilled prepared foods. The ACMSF also recommended that the guidance should be brought to the attention of other Member States via the European Commission.
The review concluded that there was no evidence to require moving from the previous ’10-day rule’ and that it should be reflected in the guidance. A small drafting group was set up to redraft the guidance on this basis, and our Director was invited to participate along with representatives of the Chartered Institute of Environmental Health, British Retail Consortium, Campden BRI, the Institute of Food Research, and Cryovac.
10-day Rule Guidance
Redrafted guidance, which was further revised after consultation during the summer of 2007, was supported by ACMSF at its December 2007 meeting, reinstating the ’10-day rule’.
FSA published the ‘Guidance on the Safety and Shelf-life of Vacuum and Modified Atmosphere Packed Chilled Foods with Respect to Non-proteolytic Clostridium botulinum in July 2008, and a revised version in January 2017, which was not subject to expert group review prior to publication.
Key controls from that Guidance are, as in the 1992 original Report:
- storage throughout shelf life at <3.0°C, or
- storage chill temperature (3-8°C) & shelf-life <10 days [10 day rule], or
- storage chill temperature (3-8°C) & 90°C/10 min (or equivalent) [max. shelf-life used by UK industry ~ 42 days], or
- storage chill temperature (3-8°C) & pH <5.0 throughout food, or
- storage chill temperature (3-8°C) & NaCl >3.5% throughout food, or
- storage chill temperature (3-8°C) & Aw <0.97 throughout food, or
- storage chill temperature (3-8°C) & combination of factors which can be shown consistently to prevent growth/toxin formation
CFA’s SUSSLE projects utilise the final option listed above.
The first peer-reviewed paper arising from the SUSSLE projects was published in January 2016: Quantification of non-proteolytic Clostridium botulinum spore loads in food materials, Barker G. C., Malakar P. K., Plowman J., Peck M. W. Applied and Environmental Microbiology doi: 10.1128/AEM.03630-15.6
2016-2017 FSA review of guidance
2018: Industry Shelf Life Guidance
In July 2018, 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) issued Guidelines for Setting Shelf Life of Chilled Foods in Relation to Non-proteolytic Clostridium botulinum, 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
2021-2024: ACMSF Risk Review
ACMSF reviewed the risk basis of FSA’s guidance on the control of non-proteolytic Clostridium botulinum in vacuum-packed and modified atmosphere packed (VP/MAP) chilled foods. In June 2022, CFA Director Karin Goodburn presented evidence to the group (CFA News #58 & #59).
ACMSF in June 2023 published its report on Botulinum Neurotoxin-Producing Clostridia.
The report reviews botulism incidents globally, noting there is no correlation between the major growth in the chilled prepared food market and botulism, and any outbreaks have only occurred in very rare occasions in chilled foods only when not sold or stored chilled. The report also refers to CFA’s SUSSLE projects as a positive example of how collaborative research should tackle major food safety topics.
CFA is pleased to see that the report also includes a number of its recommendations, which are critical to food safety:
• ‘at the first opportunity’ to correct thermal process z values for temperatures below 90°C
• Toxin testing as a minimum requirement in challenge testing
Outstanding issues include:
– current FSA guidance not specifically covering product storage at less than 3°C (although CFA’s SUSSLE work found that such storage time can be added onto the shelf life)
– the unique nature of the ‘10-day rule’, and exclusion of fresh meat considerations from the review.
Notwithstanding these points, CFA supports the ACMSF Report and seeks its rapid implementation through revised guidance to enable FBOs, enforcers and labs to correctly apply requirements. Out of date guidance not reflecting current science is misleading and potentially causes food safety and enforcement issues.
Once comments received have been reviewed by FSA, outcomes of which are still awaited at today’s date (4/7/24), CFA is hoping to be involved in the next phase, which will be drafting revised guidance.
A full list of CFA recommendations included in the report can be found here.
18/6/24