AS 5013.24.1:2009 pdf free
AS 5013.24.1:2009 pdf free.Food microbiology
This part of ISO 11290 specifies a horizontal method for the detection of Listeria monocytogenes.
Subject to the limitations discussed in the introduction,this part of ISo 11290 is applicabie to products in-tended for hurman consurmption or animai feeding.
The following standards contain provisions which,through reference in this text, constitute provisions of this part of iso 11290. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISo 11290 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Stan-dards.
ISO 6887:1983, Microbiology – General guidance for the preparation of dilutions for microbiological exam-ination.
Within the limits of this part of ISO 11290, the detec-tion of L. monocytogenes necessitates four successive stages (see annex A for a flowchart).
NOTE 1 Listeria spp. may be present in small numbers and are often accompanied by considerabiy iarger numbers of other genera, therefore selective enrichmcnt is nCccs-sary. It is also necessary to detect injured Listeria spp. and the primary selective enrichment medium. with reduced in-hibitor concentration, fuffils at least part of this function.
After incubation for 24h and for an additional 18 h to 24 h (if growth is slight or if no colonies are ob-served atter 24 h of incubation), examine the dishes (9.4.3) for the presence of colonies presumed to be Listeria spp.
Oxford agar; Typical colonies of Listeria spp.grown on Oxford agar for 24 h arc small (1 mm) grcy ish colonies surrounded by black halos. After 48 h colonies become darker, with a possible greenish sheen, and are about 2 mm in diameter, with black haios and sunken centres.
PALCAM agar: For plates incubated micro-aerobically, after incubation expose the PALCAM agar plates to air for 1 h to allow the medium to regain its pink to purple colour. Atter 24 h Listeria spp. grow as smalil or very smali greyish green or olive green colo-nies, 1,5 mm to 2 mm in diameter, sometimes with black centres, but always with black halos. After 48 h Listeria spp. appear in the form of green colonies about 1,5 mm to 2 mm in diameter, with a central de-pression and surrounded by a black halo.AS 5013.24.1 pdf free download.
