Overview
ISO 29981:2024 / IDF 220:2024 specifies a standardized colony‑count technique for the selective enumeration of bifidobacteria in milk products. The method uses incubation at 37 °C under anaerobic conditions and is applicable to fermented (e.g., yoghurts) and non‑fermented milks, milk powders and formulae (including infant and follow‑up formulas), whey protein concentrates, and starter/probiotic cultures where bifidobacteria are present and viable.
The standard targets commonly used species such as B. adolescentis, B. animalis (subsp. animalis and lactis), B. bifidum, B. breve and B. longum (subsp. infantis and longum), and provides a validated, reproducible approach for routine dairy microbiology and probiotic labelling.
Key technical topics and requirements
- Selective culture media: use of TOS‑MUP agar (with mupirocin) and the newly introduced TOS agar for selective growth of bifidobacteria.
- Incubation conditions: incubation at 37 °C in anaerobic conditions to promote bifidobacterial colony formation.
- Sample preparation: procedures for preparation of initial suspension and decimal dilutions, with added guidance for dried milk products (e.g., infant formulae).
- Three‑stage method flow: suspension/dilution → inoculation/incubation → colony counting and confirmation (microscopy and selective tests).
- Counting and expression of results: colony counting, calculation and expression of results in accordance with ISO 7218.
- Validation and performance: method validation in line with ISO 17468, performance characteristics, and interlaboratory study results provided in Annex C.
- Supporting requirements: specifications for culture media and reagents, equipment, sampling, storage of incubated plates, quality assurance and reporting.
Practical applications and users
Who benefits from ISO 29981:2024:
- Dairy industry quality control and microbiology laboratories performing routine bifidobacteria enumeration.
- Manufacturers of probiotic and starter cultures validating product counts for labelling and specification compliance.
- Infant formula and milk powder producers ensuring viable bifidobacterial counts in finished products.
- Regulatory and food safety authorities assessing microbiological quality of dairy products.
- Research labs studying probiotic viability, formulation stability and strain quantification.
Practical uses:
- Verifying probiotic label claims and shelf‑life performance.
- Routine QC testing during production and before release.
- Comparative studies of culture media or strain recovery in dairy matrices.
Related standards
- ISO 6887‑1 and ISO 6887‑5 - sample preparation and dilutions for food and milk products.
- ISO 7218 - general requirements and guidance for microbiological examinations.
- ISO 11133 - production and performance testing of culture media.
- ISO 19036:2019 - estimation of measurement uncertainty for quantitative determinations.
- ISO 17468 - validation framework referenced for major technical changes.
Keywords: ISO 29981:2024, bifidobacteria enumeration, milk products, colony‑count technique, TOS‑MUP agar, anaerobic incubation, dairy microbiology, probiotic enumeration, infant formula testing.
