BS EN ISO 11290-1:2017 pdf free.Microbiology of the food chain – Horizontal method for the detection and enumeration of Listeria monocytogenes and of Listeria spp- Part1:Detection method.
The main changes, listed in the foreword, introduced in this document compared to Iso 11290-1:1996 are considered as major (see ISO 17468). The technical changes were assessed and were considered to have no significant effect on the method performance characteristics or test results.
Because of the large variety of food and feed products, this horizontal method may not be appropriate in every detail for certain products for which it may be necessary to use different or specific methods. Nevertheless, in all cases, this horizontal method is intended to be applied as far as possible and deviations from this only be made for justified technical reasons.
When this document is next reviewed, account will be taken of all information then available regarding the extent to which this horizontal method has been followed and the reasons for deviations from it in the case of particular products.
The harmonization of test methods cannot be immediate, and for certain groups of products International Standards and/or national standards may already exist that do not comply with this horizontal method. It is hoped that when such standards are reviewed, they will be changed to comply with this document so that eventually the only remaining departures from this horizontal method will be those necessary for well-established technical reasons.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
Iso 6887 (all parts), Microbiology of the food chain — Preparation of test samples, initial suspension and decimal dilutions for microbiological examination
Iso 7218, Microbiology of food and animal feeding stuffs — General requirements and guidance for microbiological examinations
Iso 11133, Microbiology of food, animal feed and water — Preparation, production, storage and performance testing of culture media
4 Principle
4.1 General
Listeria spp. may be present in small numbers and are often accompanied by considerably larger numbers of other microorganisms, therefore selective enrichment is necessary. It is also necessary to detect injured and stressed Listeria spp. and the primary selective enrichment medium, with reduced inhibitor concentration, fulfils at least part of this function.
NOTE Presence of L. monocytogenes can be masked by the presence of other Listeria species, in particular L. innocua or L. ivanovil.
Within the limits of this document, the detection of L. monocytogenes and of Listeria spp. necessitates four successive stages, as described in the flowchart in AnnexA.
4.2 Primary enrichment in a selective liquid enrichment medium with reduced concentration of selective agents (half-Fraser broth)
Inoculation of a selective primary enrichment medium containing half the concentrations of acriflavine and nalidixic acid (half-Fraser broth, see Li), which is also used as a dilution fluid for the test portion (91).
Incubation of the initial suspension at 30 °C for 24 h to 26 h.