Case study n°1

Listeria monocytogenes in diced bacon cubes (first de novo case-study)

In France, 50% of the pork belly are transformed to diced bacon cubes (“lardons” in French) (FICT, 2004). This production increases every year (FICT 2006) : in 2003, 2004 and 2005, 15000, 16167 and 17072 tonnes were produced respectively (+ 5,6% between 2004 and 2005).

Between 1999 and 2001, 54% of the pork meat analysed were contaminated by Listeria monocytogenes (CTSCCV, 2001). Since, this prevalence decreases every year and reached 25% in 2004 (ITP, 2004) due to a better application of the good hygienic practices and HACCP principles. This level of prevalence remains however alarming in particular when the pork cuts are used for the manufacture of raw meat products such as diced bacon cubes.

Indeed, during the diced bacon manufacturing there is no physical or chemical treatment sufficiently drastic to eliminate the possibly present population of L. monocytogenes. Moreover, physicochemical properties of the meat modifications and thus the behaviour of L. monocytogenes is also modified. Consequently, the control of the development of L. monocytogenes can be done only by the control of the parameters of the manufacture process.

This is important because a part of the diced bacon cubes are actually consumed raw, and the « Commission Regulation (EC) No 2073/2005 of 15 November 2005 on microbiological criteria for foodstuffs » imposes L. monocytogenes as a food safety criterium for this food product. This text indicates that the limit for L. monocytogenes is 100 cfu/g when the product is placed on the market and during its shelf-life.
It is then important to know the real impact of the manufacturing process on the behaviour of L. monocytogenes. The use of Bayesian modelling will allow taking into account all the parameters of manufacture and their variability.

Targets established by governments in relation to public health goals could be “The maximum frequency and/or concentration of a hazard in a food at the time of consumption” (food safety objective, FSO) or “at a specified step in the food chain before the time of consumption” (performance objective, PO) (Codex Alimentarius Procedural Manual, 15th ed. 2004). FSOs and Pos should be established “to provide or contribute to the appropriate level of protection” (ALOP) to which the regulatory body does refer. Targets might be also expressed so as to account for the distribution of the hazard concentration, as suggested in the report of a meeting of the WHO Collaborating Centre on Risk Assessment at RIVM (Bilthoven, The Netherlands, 2006-12-01).
At the moment there is some reluctance among risk managers to enter into the process of articulating the ALOP. This reluctance extends to the establishment of FSOs. Nevertheless the PO concept seems to gain more recognition. Two other concepts strongly linked to the PO one are widely accepted as they were in fact used for a long time: “process criteria” and “product criteria” describing the effect on microbial concentration achieved respectively by a process or by food composition factors so as to achieve the PO. According to the Codex Alimentarius or to FAO/WHO Consultations, Pos could be established by the competent authority or the operators at the retail step, or by the operators at any earlier step in the process up to the primary production.
Despite the actual risk-based tendency, the link between hazard-based critical limits and risk based objectives does not seem to be established so far.