Overview
ISO/TS 27106:2009 - Cheese - Determination of nisin A content by LC‑MS and LC‑MS‑MS is a joint ISO/IDF Technical Specification that defines a validated laboratory procedure for the quantitative determination of nisin A in cheese. The method is designed for low-level detection with a limit of quantification of 1 mg/kg. It applies specifically to nisin A (not nisin Z) and was prepared by ISO/TC 34 (milk and milk products) in cooperation with the International Dairy Federation (IDF).
Key topics and requirements
- Analytical principle: extraction of grated cheese with dilute formic acid at 80 °C, ultracentrifugation, ultrafiltration (30 kD membrane) and analysis by LC‑MS or LC‑MS‑MS.
- Limit of quantification: 1 mg/kg (results below 1 mg/kg reported as “less than 1 mg/kg”).
- Instrumentation:
- LC‑MS in positive ESI mode (monitor m/z 839.6; alternative charge states noted).
- Optional LC‑MS‑MS using selective transitions (most selective: 672 → 811).
- Preferred reversed‑phase column: PLRP‑S, 300 Å, 3 µm, 150 × 2 mm; controlled column temperatures (LC‑MS ~40 °C, LC‑MS‑MS ~30 °C).
- Centrifuges (≥3 000 g and ultracentrifuge ~20 800 g), ultrafiltration devices, 0.22 µm filters.
- Standards and reagents:
- Nisin A reference (purity > 95%), bovine serum albumin (BSA) buffer, formic acid, acetonitrile, trifluoroacetic acid.
- Standard preparation: stock 100 mg/L and working 300 µg/L - prepared daily.
- Calibration and quantification:
- Single‑point calibration per analysis series; instrument linearity should be checked regularly.
- Result calculation uses the ratio of sample to standard peak area/height and expresses mass fraction as mg/kg (one decimal place).
Applications and users
Who benefits from ISO/TS 27106:
- Dairy quality control and R&D laboratories monitoring preservative residues.
- Contract analytical and food testing laboratories offering LC‑MS services.
- Regulatory and food safety authorities verifying compliance with permitted nisin levels.
- Cheese manufacturers investigating spoilage control (e.g., prevention of late blowing) and shelf‑life studies.
Practical use cases:
- Compliance testing for maximum permitted nisin levels in cheese.
- Verification of nisin dosing in manufacturing and process validation.
- Research on preservative persistence and distribution in cheese matrices.
Related standards
- ISO 707 | IDF 50 (recommended sampling method for milk and milk products) is referenced for sample representativity.
- Document type: ISO/TS (Technical Specification) published jointly as IDF/RM 217:2009.
Keywords: ISO/TS 27106, nisin A, LC‑MS, LC‑MS‑MS, cheese, limit of quantification 1 mg/kg, ultrafiltration, PLRP‑S column, food safety, dairy testing.