ISO 9231-2008 PDF

Full title and description

ISO 9231:2008 (also published as IDF 139:2008) — "Milk and milk products — Determination of the benzoic and sorbic acid contents". This International Standard specifies a laboratory method for the quantitative determination of benzoic acid and sorbic acid (and their salts) in milk and milk products for regulatory, quality‑control and laboratory use.

Abstract

ISO 9231|IDF 139:2008 defines a procedure applicable to milk, dried milk, yogurt and other fermented milks, cheese and processed cheese, suitable for measuring the contents of benzoic and sorbic acids at levels above about 5 mg/kg. The standard provides sample preparation, chromatographic determination and reporting recommendations for reliable measurement of these preservatives.

General information

• Status: Published (International Standard; confirmed at review).
• Publication date: 10 July 2008 (Edition 1, 2008).
• Publisher: International Organization for Standardization (ISO), published jointly as ISO/IDF 139:2008.
• ICS / categories: 67.100.01 — Milk and milk products in general.
• Edition / version: Edition 1 (2008).
• Number of pages: 9 (official ISO publication count).

These bibliographic and lifecycle details are given in the official ISO catalogue entry for ISO 9231:2008 (ISO/IDF 139:2008).

Scope

ISO 9231:2008 applies to the determination of benzoic acid and sorbic acid contents in a range of milk and milk products (fresh and dried milks, yogurts and other fermented milks, cheeses and processed cheeses). The method is intended for levels of both compounds typically above about 5 mg/kg and supports conformance testing, routine quality control and laboratory verification. The standard sets out the intended sample types, method principle and limits of applicability.

Key topics and requirements

• Analytes: benzoic acid and sorbic acid (and their commonly used salts).
• Applicable matrices: raw milk, reconstituted dried milk, yogurt and fermented milks, cheese and processed cheese.
• Analytical principle: chromatographic separation with high‑performance liquid chromatography (HPLC) and UV detection (wavelengths commonly used in method: ~227 nm and ~250 nm), with specified injection and mobile‑phase guidance.
• Performance / reporting: validated calibration (linear response), options for single‑point calibration if linearity confirmed, reporting of results in mg/kg and attention to recovery and specificity.
• Limit of practical application: method suited to measure concentrations above about 5 mg/kg (method detection/quantification considerations and LOQ depend on lab validation and instrumentation used).
• Sample preparation: clarification/extraction steps required to remove fats and particulates prior to chromatographic analysis (as specified by the method).

Typical use and users

Primary users are accredited food‑testing and dairy laboratories, national food safety and regulatory agencies, dairy‑sector quality control teams and research laboratories performing residue and preservative monitoring in dairy products. The method is used for routine monitoring, compliance testing, method validation and investigations into preservative use or contamination.

Related standards

Standards commonly used alongside ISO 9231:2008 include ISO 707:2008 (Guidance on sampling of milk and milk products) for correct sampling procedures, and other ISO/IDF analytical and microbiological standards relevant to dairy testing. Food safety management standards (e.g., ISO 22000 series) and national regulatory methods for preservatives may also be referenced in practice.

Keywords

benzoic acid; sorbic acid; sorbate; benzoate; preservatives; milk; dairy products; HPLC; chromatographic method; ISO/IDF 139; dairy laboratory; food analysis.

FAQ

Q: What is this standard?

A: ISO 9231:2008 (IDF 139:2008) is an ISO/IDF international standard that specifies a laboratory method for determining benzoic and sorbic acid contents in milk and milk products.

Q: What does it cover?

A: It covers the scope of sample types (milk, dried milk, yogurts, fermented milks, cheese and processed cheese), sample preparation, chromatographic determination (HPLC with UV detection) and reporting conventions for the two preservative acids at levels above about 5 mg/kg.

Q: Who typically uses it?

A: Accredited food and dairy testing laboratories, regulatory authorities, dairy industry QC teams and researchers monitoring preservative levels in dairy products.

Q: Is it current or superseded?

A: ISO 9231:2008 remains a published International Standard. The ISO catalogue shows the publication as Edition 1 (2008) and that the standard was last reviewed and confirmed in 2024, so the 2008 version is current (not withdrawn) at the time of review.

Q: Is it part of a series?

A: It is part of ISO/TC 34/SC 5 work on milk and milk products and is published jointly with the International Dairy Federation as IDF 139:2008. Laboratories commonly use it together with other ISO/IDF dairy standards (for sampling, microbiological testing and other chemical analyses).

Q: What are the key keywords?

A: Benzoic acid; sorbic acid; preservatives; milk; dairy products; HPLC; ISO/IDF 139; analytical method; food testing.