ISO 6887-5:2020

Overview

ISO 6887-5:2020 - "Microbiology of the food chain - Preparation of test samples, initial suspension and decimal dilutions for microbiological examination - Part 5" - provides specific rules for preparing milk and milk products for microbiological testing. Intended to be used together with ISO 6887-1, this part addresses cases where dairy samples require different handling than the general methods. It covers liquid milk, dehydrated milk powders, cheese, casein/caseinates, butter, ice-cream, custards, fermented milks (yogurt, sour cream, probiotic products) and dehydrated infant milk foods.

Key topics and technical requirements

• Scope & exclusions: Applies to a broad range of milk products but excludes preparations already specified in other enumeration or detection standards.
• Diluents and reagents: Lists diluents for general and special use and gives preparation, pH adjustment and sterilization guidance. Examples include quarter‑strength Ringer’s, peptone solutions, phosphate buffer and special diluents such as sodium citrate, dipotassium hydrogen phosphate (with/without antifoam), tripolyphosphate and α‑amylase–containing diluents for starch-containing samples.
• Performance testing of diluents: Specifies that diluent performance should be validated per ISO 11133 and laboratory best practice.
• Sample types & handling: Describes procedures for frozen, hard/dry, liquid/non‑viscous, multi‑component, acidic and high‑fat (>20%) milk foods.
• Specific preparation procedures: Dedicated sections for milk/liquid products, dehydrated powders, cheese, caseins, butter, ice‑cream, custards, fermented milks, and infant foods - including primary suspension and further decimal dilutions.
• Cross references & quality: Aligns with ISO 6887-1, ISO 7218 (general microbiology requirements) and other parts of ISO 6887 series for consistent laboratory practice.
• Safety: Warns users to establish appropriate health and safety practices when handling biological samples and hazardous materials.

Practical applications and users

ISO 6887-5:2020 is used by:

• Food microbiologists and quality control laboratories in the dairy industry
• Regulatory and inspection labs performing official microbiological analyses
• Test method developers and accreditation bodies ensuring method consistency
• Contract testing laboratories handling a variety of milk and dairy matrices

Benefits:

• Ensures consistent, validated sample preparation across dairy microbiology testing
• Improves comparability of enumeration and detection results
• Reduces matrix-specific errors (e.g., poor solubility, foaming, enzyme interference)

Related standards

• ISO 6887-1 - General rules for initial suspension and decimal dilutions (use together)
• ISO 7218 - General requirements and guidance for microbiological examinations
• ISO 11133 - Preparation and performance testing of culture media

Keywords: ISO 6887-5:2020, milk microbiology, sample preparation, initial suspension, decimal dilutions, diluents, dairy testing, ISO 6887-1, ISO 7218, ISO 11133.