ISO 21527-2:2008 PDF

Overview

ISO 21527-2:2008 - Microbiology of food and animal feeding stuffs - Horizontal method for the enumeration of yeasts and moulds - Part 2 - specifies a colony count technique for viable osmophilic yeasts and xerophilic moulds in products with water activity (aw) ≤ 0.95. It is intended for routine microbiological testing of low-moisture foods (dry fruits, jams, cakes, dried meat, salted fish, grains, cereals, flours, nuts, spices, condiments, etc.) using surface-inoculated plates and incubation at 25 ± 1 °C. The standard is a horizontal method (i.e., broadly applicable) but excludes dehydrated products with aw ≤ 0.60, enumeration of mould spores, identification of fungal species, and mycotoxin testing.

Key Topics and Requirements

• Scope and exclusions: Applies to products with aw ≤ 0.95; does not apply to aw ≤ 0.60 products or to halophilic xerophilic fungi (e.g., those in some dried fish).
• Sampling & sample handling: Sample must be representative, not frozen or damaged during transport; sample prep follows ISO 6887/ISO 7218 and product‑specific standards.
• Diluent recommendations: Use 0.1% peptone water as default; for osmophilic/xerophilic organisms, diluents containing 20–35% glycerol or D‑glucose are recommended to reduce osmotic shock. Surfactants (e.g., Tween 80) may reduce spore clumping.
• Culture medium: Dichloran-glycerol agar (DG18) is specified as the selective medium; preparation, pH control and optional additives (chloramphenicol, chlortetracycline, trace elements) are described to limit bacterial overgrowth and optimise mould morphology. Gentamicin is not recommended.
• Procedure: Surface-inoculate plates (typically 0.1 ml per plate, with options up to 0.3 ml for low counts), incubate aerobically at 25 ± 1 °C for 5–7 days (with 1–2 days diffuse daylight if necessary), then count colonies and calculate CFU/g or CFU/ml. Yeasts and moulds are counted separately; doubtful colonies may be examined microscopically.
• Safety: Enumeration of moulds requires care to protect operators and prevent atmospheric contamination with spores.

Applications and Users

ISO 21527-2:2008 is used by:

• Food and feed microbiology laboratories for routine quality control and specification compliance.
• Manufacturers of low‑moisture foods (nuts, dried fruit, cereals, spices, jams) for shelf‑life and safety monitoring.
• Regulatory and third‑party testing labs and HACCP/food safety teams verifying fungal loads.
• Research labs comparing fungal counts across product formulations and storage conditions.

Practical benefits include harmonized enumeration methods, reproducible colony counts on DG18, and guidance to minimize osmotic shock and bacterial interference.

Related Standards

• ISO 21527-1: Colony count technique for products with aw > 0.95
• ISO 6887: Preparation of test samples, initial suspension and dilutions
• ISO 7218: General requirements for microbiological examinations
• ISO 8261: Guidance for milk/milk products sample prep
• ISO/TS 11133: Guidelines on preparation and production of culture media

Keywords: ISO 21527-2:2008, enumeration of yeasts and moulds, DG18, water activity, osmophilic yeast, xerophilic moulds, colony count technique, microbiology of food.