ISO 21703:2019

Overview

ISO 21703:2019 - "Surface active agents - Microbiology - Microbiological test methods for liquid hand dishwashing" - is an ISO standard (first edition 2019) that defines microbiological test methods for liquid hand dishwashing products. The standard specifies procedures for enumeration and detection of aerobic mesophilic bacteria, and for detection of Escherichia coli and Pseudomonas aeruginosa in liquid hand dishwashing detergents. Key principles include use of non‑selective agar for counts and enrichment culture for presence/absence testing, plus mandatory neutralization of antimicrobial activity in products before analysis.

Key Topics

• Scope & definitions: terms such as sample, initial suspension, dilution and enrichment broth are defined for consistent testing of liquid hand dishwashing products.
• Principle of testing: enumeration on non‑selective media and detection after enrichment (presence/absence) for target organisms.
• Diluents & neutralizers: specification of suitable neutralizing diluents (for example SCDLP 20 broth - Fluid casein digest with soy lecithin and polysorbate 20 - is listed) and other diluents required to neutralize antimicrobial properties prior to analysis.
• Culture media: recommended media include soybean‑casein digest agar (SCDA/TSA) for counts, MacConkey and EMB for Enterobacteriaceae/E. coli, cetrimide and Pseudomonas agar P for P. aeruginosa, plus enrichment broths.
• Enumeration & detection methods: procedures and dilution schemes for plate counts, and presence/absence detection after enrichment.
• Neutralization validation: requirement to demonstrate that neutralizers and dilution methods effectively neutralize product antimicrobial activity; suitability tests for pour‑plate, surface spread and membrane filtration methods are included.
• Identification tests: guidance on basic identification steps (Gram stain, oxidase test, colony characteristics) for E. coli and P. aeruginosa and expression of results.
• Reporting: content requirements for the test report and annexes listing neutralizers and alternative media.

Applications

ISO 21703:2019 is intended for:

• Manufacturers of liquid hand dishwashing detergents for in‑house quality control and formulation microbiological risk assessment.
• Microbiology laboratories performing product testing and validation of neutralizers and methods.
• Regulatory bodies and compliance teams verifying product safety claims and compliance with microbiological requirements.
• R&D groups developing preservative systems or assessing contamination risk in surfactant formulations.

Practical benefits include standardized microbiological assessment, demonstrable neutralization of antimicrobial effects, and clear criteria for detecting key contaminants (E. coli, P. aeruginosa) that affect consumer safety and regulatory compliance.

Related standards

• ISO 21148 - Cosmetics - Microbiology - General instructions for microbiological examination (referenced normative guidance).
• ISO 29621 - Guidance on microbiological risk factors in non‑sterile products (useful for risk assessment and applicability decisions).

Keywords: ISO 21703:2019, liquid hand dishwashing, microbiological test methods, surface active agents, SCDLP 20, aerobic mesophilic bacteria, Escherichia coli, Pseudomonas aeruginosa.