DIN 10198:2010-07

This standard specifies, in addition to DIN EN ISO 7932, a colony counting method for the determination of the number of presumptive Bacillus cereus (B. cereus, for short) at 37 °C using a PEMBA agar as culture medium for isolating. It is applicable for milk, milk products, ice cream and milk-based baby food. By using a MYP agar as culture medium for isolating the provisions given in DIN EN ISO 7932 apply. For the determination of a low number of presumptive B. cereus a most probable number technique (MPN method) with selective enrichment is available in DIN EN ISO 21871. This standard contains additional national specifications which are not covered by the horizontal method for the enumeration of presumptive B. cereus which has been published as a European Standard EN ISO 7932:2004 and which has been implemented into the national body of standards as DIN EN ISO 7932:2005-03, in compliance with the obligation to adopt European Standards. The new edition of DIN EN ISO 7932 necessitated a revision of DIN 10198-1:1999-09. This standard shall apply together with DIN EN ISO 7932:2005-03. Polymyxin-pyruvate-egg yolk-mannitol-bromothymol blue agar (PEMBA) plates are each inoculated with 0,1 ml of the sample, the initial suspension or the further dilution and incubated at 37 °C for 18 hours to 48 hours under aerobic conditions. Presumptive typical B. cereus colonies are counted. If any further examinations seem to be necessary, they shall give positive results under the conditions specified in this standard. Colonies may be confirmed using a microscopy method or hemolysis test. The presumptive B. cereus colony count per gram or per millilitre of sample is calculated from the number of typical or confirmed colonies. With respect to DIN 10198-1:1999-09, a reference is made in Clause 1 to the MPN method in DIN EN ISO 21871 for the determination of a low number of presumptive B. cereus. The clause "Normative references" has been updated and the clauses "Bibliography" and 5.2.2 "Performance test for the purpose of quality assurance of the culture medium" have been added. In clause 9.3 a reference is made to the hemolysis test according to DIN EN ISO 7932. The standard has been technically and editorially revised and supplemented and therewith adapted to the currently valid design rules. The Committee responsible for this standard is NA 057-05-13 AA "Milch und Milchprodukte - Probenahme- und Untersuchungsverfahren" ("Milk and milk products - Methods of sampling and analysis") at DIN.