ISO 14461-2-2005 PDF

Full title and description

ISO 14461-2:2005 (IDF 169-2:2005) — Milk and milk products — Quality control in microbiological laboratories — Part 2: Determination of the reliability of colony counts of parallel plates and subsequent dilution steps. Provides a routine laboratory procedure and acceptance criteria for assessing the reliability of plate‑count results obtained using colony‑count methods with 10‑fold dilution series and one or two parallel plates per dilution.

Abstract

This part of ISO 14461/IDF 169 describes a routine evaluation procedure for the enumeration of microorganisms by colony‑count methods using subsequent 10‑fold dilution steps and one or two parallel plates within each dilution step. It supplies tabulated limits and comparison rules to assess acceptability of differences between parallel plates and between consecutive dilution steps. Exceeding the limits points to technical problems (in plating, dilution or counting); frequent exceedance indicates that the test procedure lacks reliability. The procedure is intended for regular application within microbiology laboratories testing milk and milk products.

General information

• Status: Published (International Standard; confirmed).
• Publication date: April 2005 (2005-04).
• Publisher: International Organization for Standardization (ISO) in cooperation with the International Dairy Federation (IDF) — published as ISO 14461-2:2005 / IDF 169-2:2005.
• ICS / categories: 07.100.30 (Food microbiology). (often referenced alongside related ICS such as 67.120.01 in national catalogues)
• Edition / version: Edition 1 (2005).
• Number of pages: 18 pages.

Scope

Applies to microbiological laboratories performing colony‑count enumerations on milk and milk products. Defines a routine QC procedure for evaluating colony counts obtained from parallel plates and from successive 10‑fold dilution steps, gives tabulated acceptability limits and comparison methods, and describes how laboratory personnel should interpret results to detect technical faults in plating, dilution or counting that may compromise analytical reliability.

Key topics and requirements

• Routine evaluation procedure for colony‑count methods using 10‑fold dilutions.
• Comparison of colony counts from parallel plates against tabulated acceptance limits.
• Comparison of sums of colony counts across two consecutive dilution steps with tabulated limits.
• Criteria to identify technical problems in plating, dilution or counting procedures.
• Guidance on when exceedance frequency indicates lack of method reliability.
• Integration into laboratory quality control and Good Laboratory Practice (GLP) routines.
• Use of the procedure for troubleshooting, corrective actions and analyst training.

Typical use and users

Used routinely by microbiology analysts and laboratory supervisors in dairy testing laboratories to monitor and verify the reliability of plate‑count procedures. Also used by quality managers, laboratory auditors and accreditation assessors to demonstrate method control, to investigate sources of variability (sample homogeneity, dilution accuracy, pipetting, plating and counting), and to support corrective actions and staff competency assessment.

Related standards

Commonly used alongside ISO 14461-1:2005 (IDF 169-1:2005) — Analyst performance assessment for colony counts. Often referenced with general and supporting microbiology standards such as ISO 7218 (general requirements and guidance for microbiological examinations), the ISO 6887 series (sample preparation and decimal dilutions), ISO 4833 (enumeration of microorganisms by plate count) and various ISO/IDF methods for specific organisms in milk and dairy products.

Keywords

milk, milk products, colony counts, plate counts, parallel plates, dilution steps, 10‑fold dilutions, quality control, microbiological laboratories, IDF 169-2, analyst performance, GLP, enumeration reliability

FAQ

Q: What is this standard?

A: ISO 14461-2:2005 (IDF 169-2:2005) is an international standard that defines a routine procedure and acceptance criteria for checking the reliability of colony counts obtained by plate‑count methods used on milk and milk products.

Q: What does it cover?

A: It covers the evaluation and interpretation of colony counts from one or two parallel plates per dilution and from successive 10‑fold dilution steps, provides tabulated limits for acceptability, and describes how to recognise technical problems and when repeated exceedance indicates lack of reliability.

Q: Who typically uses it?

A: Microbiology analysts, laboratory supervisors, quality managers, laboratory auditors and accreditation assessors in dairy and food testing laboratories.

Q: Is it current or superseded?

A: The standard was published in April 2005. It has been subject to periodic ISO reviews and was confirmed in 2025 (confirmed stage), so this edition remains current as confirmed by the ISO review process. For the absolute latest status or any subsequent revisions, consult the ISO catalogue or your national standards body.

Q: Is it part of a series?

A: Yes — it is Part 2 of the ISO 14461 / IDF 169 series on quality control in microbiological laboratories for colony counts. Part 1 (ISO 14461-1:2005 / IDF 169-1:2005) addresses analyst performance assessment.

Q: What are the key keywords?

A: milk, milk products, colony‑count, plate counts, parallel plates, dilution steps, 10‑fold dilution, quality control, microbiological laboratories, IDF 169-2.