AS 5013.13:2018 pdf free
AS 5013.13:2018 pdf free.Food microbiology
This document has been validated for test portions of 10 g. A smaller size of the test portion may be used without the need of additional validation/verification providing that the same ratio between pre-enrichment broth and test portion is maintained. A larger test portion than that initially validated may be used, if a validation/ verification study has shown that there are no negative effects on the detection of Cronobacter spp.
NOTE 1 Validation can be conducted in accordance with the appropriate documents of ISO 16140 (all parts).Verification for pooling samples can be conducted in accordance with the protocol described in ISO 6887-1:2017,Annex D (verification protocol for pooling samples for qualitative tests).
NOTE 2 Large sample sizes can compromise the recovery of stressed Cronobacter spp. when interfering microflora are present, such as probiotics.[5],[6]
Using a platinum-iridium or plastic loop (7.3), take a portion of a well-isolated colony from each individual plate (10.5.2) and streak it on to a filter paper moistened with the oxidase reagent (B.5.1); the appearance of a mauve, violet or deep blue colour within 10 s indicates a positive reaction. If a commercially available oxidase test kit is used, follow the manufacturer’s instructions.
Using a loop or wire (7.3), suspend an individual colony grown on the non-selective agar such as TSA (10.5.2) in 2 ml of physiological salt solution, 0,85 % NaCl (B.5.2.4). Add 2 ml of the a-Glucosidase enzymatic assay solution (B.5.2). Incubate in a water bath at 37 °C (7.12) for 4 h and measure the formation of yellow colouration in a spectrophotometer (7.9) at 405 nm. A minimal absorption of 0,3 at 405 nm after 4 h, equivalent to 16 mM PNP, can be considered positive.
Using a loop or wire (7.3), inoculate a tube of MR-VP broth (B.5.6) with each of the selected colonies (10.5.2) just below the surface of the medium. Incubate the tubes at 37 °C (7.2) for 48h±2 h. Add five drops of methyl red solution (B.5.6.2) to each tube. A distinct red colour indicates a positive reaction. A yellow colour indicates a negative reaction.AS 5013.13 pdf free download.
