AS 5013.4:2021 pdf free download – Food microbiology Method 4: Microbiology of food and animal feeding stuffs —Horizontalmethod for the enumeration of coliforms —Colony-count technique (Iso4832:2006, MOD)

AS 5013.4:2021 pdf free download – Food microbiology Method 4: Microbiology of food and animal feeding stuffs —Horizontalmethod for the enumeration of coliforms —Colony-count technique (Iso4832:2006, MOD).
— products intended for human consumption and for the feeding of animals. and
— environmental samples in the area of food production and food handling.
by means of the technique of counting colonies after incubation on a solid medium at 30 °C or at 37 C.
NOTE The temperature is subject to agreement between the parties concerned. In the case of milk and milk products, the temperature of incubation is 30 C.
This technique is recommended when the number of colonies sought is expected to be more than 100 per millilitre or per gram of the test sample.
2 Normative references
The rollowing reterenced documents are indispensable for the application 01 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 food and animal feeding stuffs — Preparation of test samples, initial suspension and decimal dilutions for microbiological examination
ISO 7218:_I). Microbiology of food and animal feeding stuffs — General requirements and .quidance for microbiological examinations
ISO 8261, Milk and milk products — General guidance for the preparation oftest samples, initial suspensions and decimal dilutions for microbiological examination
ISO/IS 11133.1, M,crobiolop,yoffood and onimaifeeding stuffs — Guidelines on preparation and production of culture media — Part 1: General guidelines on quality assurance for the preparation of culture media in the laboratory
ISO/IS 11133-2:2003. Microbiology of food and animal feeding stuffs — Guidelines on preparation and production of culture media — Part 2: Practical guidelines on perjàrmance testing of culture media
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
coliforms
bacteria which, at the specified temperature (i.e. 30 C or 37 °C, as agreed) form characteristic colonies in crystal violet neutral red bile lactose agar, and which in the conhirmation test cause fermentation oh lactose with the production olgas under the test conditions specified In this International Standard
Also count and confirm atypical colonies (e.g. of smaller size), and all colonies derived from milk products that contain sugars other than lactose, immediately after the incubation period according to 9.4. ConversIon of sugars other than lactose may result In colonies with an appearance that looks similar to the typical colilorms.
N0Th The appearance of a reddish zone of precipitated bile around the colonies depends on the type olcoliform and the quality of the medium.
9.4 ConfirmatIon
Inoculate five colonies of each atypical type. If available, Into tubes of brilliant green lactose bile broth (5.4). incubate the tubes in the incubator (6.2) set at 30 °C or 37 ec (as agreed) for 24 h ± 2 Ii. Consider as colifornis colonies that show gas formation in the Durham tube. Take the results into account in the calculation (Clause 10).
10 Expression of results
See ISO 7218.
11 Precision
Given a Poisson distribution of microorganisms in the substrate, the confidence limits of this method vary according to the count of colonies examined from ± 16% to ± 52% (see Reference (31). In practice, even greater variation may he found. In various collaborative studies, the standard deviation of the repeatability (5,.) appeared to be 0,20 log units, the standard deviation of the reproducibility (sg) appeared to be 0.35 log units (see References 141 and [5]).
More information about the confidence limits is given in ISO 7218.
12 Test report
The test report shall specify:
— all information necessary for the complete identification of the sample;
— the sampling method used, if known;
— the test method used, with reference to this International Standard;
— all operating details not specified in this International Standard, or regarded as optional, together with details of any incident which may have influenced the result(s);
— the test result(s) obtained:
— if the repeatability has been checked, the final quoted results obtained.