ISO 21871:2006 PDF

Overview

ISO 21871:2006 defines a horizontal microbiological method for detection and enumeration of low numbers of presumptive Bacillus cereus in foods, animal feeding stuffs and related environmental samples. The standard uses the Most Probable Number (MPN) technique for enumeration and a complementary enrichment/detection procedure for presence/absence results. It is intended for routine food safety testing, quality control and environmental monitoring in food production and handling.

Key topics and technical requirements

• Scope: Detection or enumeration of low numbers of viable presumptive Bacillus cereus in products for human consumption, animal feed and environmental samples in food production/handling areas.
• Primary techniques:
  • Enumeration (MPN): Inoculation of double‑strength and single‑strength liquid selective enrichment (Tryptone Soya Polymyxin Broth - TSPB) followed by plating and calculation of most probable number per gram or millilitre.
  • Detection (presence/absence): Single enrichment in TSPB, plating on selective agar and confirmation of suspected colonies.
• Selective media referenced:
  • Liquid: Tryptone Soya Polymyxin Broth (TSPB) - polymyxin B added to improve selectivity.
  • Solid: PEMBA (Polymyxin Pyruvate Egg Yolk Mannitol Bromothymol Blue agar) and MYP (Mannitol Egg Yolk Polymyxin agar) for isolation and colony characteristics.
• Incubation parameters (as given): Enrichment tubes typically incubated 48 h at 30 °C; solid media incubated 18–48 h (PEMBA often at 37 °C, MYP at 30 °C).
• Confirmation: Suspected colonies are confirmed by haemolysis or microscopic examination. Results are reported as MPN/g or MPN/mL for enumeration, or “presence/absence” for detection.
• Important limitation: The method identifies presumptive B. cereus; closely related Bacillus species can produce similar results and may not be fully distinguishable by the confirmatory tests in this standard.

Practical applications and users

• Who uses it: Food microbiology and quality control laboratories, food manufacturers, feed producers, public health laboratories and auditors performing routine testing, batch release or environmental monitoring.
• Use cases: Testing low-level contamination in prepared foods, dairy, cereals, spices, animal feed and swabs from food-processing environments; verifying process hygiene and compliance with safety specifications.
• Value: Provides a harmonized, validated approach for low‑level Bacillus cereus detection and quantification using the MPN technique and commonly accepted selective media.

Related standards

• ISO 6887 (sample preparation and dilutions)
• ISO 7218 (general rules for microbiological examinations)
• ISO 8261 (milk and milk products - sampling guidance)
• ISO/TS 11133‑1 and 11133‑2 (culture media production and performance testing)

Keywords: ISO 21871:2006, Bacillus cereus, most probable number, MPN, food microbiology, TSPB, PEMBA, MYP, detection method, enumeration, food safety.