Overview
ISO/TS 19046-2:2017 (IDF/RM 233-2:2017) defines a laboratory method for the determination of propionic acid level in cheese using ion exchange chromatography (HPLC). The Technical Specification covers sample preparation, reagent and apparatus requirements, chromatographic conditions, calibration, calculation and reporting of results. It is published jointly by ISO and the International Dairy Federation (IDF).
Key topics and requirements
- Scope and principle: aqueous extraction of propionic acid by dilution in the mobile phase, centrifugation/filtration and quantification by ion exchange chromatography.
- Reagents: propionic acid standard (≥99.5% purity), concentrated sulfuric acid, HPLC-grade water, and a prepared mobile phase (H2SO4 0.02 mol·L−1).
- Sample preparation:
- Grind or grate cheese (remove rind/surface layers if needed).
- Weigh ~5–10 g, add ~35 mL mobile phase, stir 1 hour at 70 °C, cool and dilute to 50 mL.
- Filter (0.2 µm PVDF syringe filter) or centrifuge (~13 000 g) if required.
- HPLC conditions (example parameters given):
- Ion exchange column (e.g., Aminex HPX-87H with Carbo H precolumn) at 50 °C.
- Mobile phase H2SO4 0.02 mol·L−1 (degassed/held under helium), flow 0.6 mL/min.
- Injection volume 10 µL, UV detection at 210 nm.
- Column rinse procedure recommended after each analytical series.
- Calibration and calculation:
- Use a three-point calibration from prepared standard solutions.
- Result calculation: w = (Pe × 50) / m where Pe is propionic acid concentration (g/100 mL) from the integrator; w expressed in mg/100 g (no decimals).
- Precision: Precision data are indicative, derived from an interlaboratory study (ISO 5725 series). A reported indicative repeatability difference is approximately 48 mg propionic acid/100 g cheese.
- Reporting: Test report must identify the sample, sampling method (ISO 707 recommended), method reference, operating details and results.
Applications and users
ISO/TS 19046-2:2017 is targeted at:
- Dairy testing laboratories performing compositional or ingredient analyses.
- Quality control and R&D teams within cheese manufacturing.
- Regulatory and food control authorities requiring standardized analytical methods.
Practical uses include routine measurement of propionic acid levels for product specification, quality monitoring and comparative studies where a harmonized ion-exchange HPLC method is required.
Related standards
- ISO 707 | IDF 50 - recommended sampling of milk and milk products.
- ISO 5725-1 / ISO 5725-2 - interlaboratory precision assessment procedures.
- Other parts of the ISO/TS 19046 | IDF/RM 233 series (see ISO website for the full list).
Keywords: ISO/TS 19046-2:2017, propionic acid in cheese, ion exchange chromatography, HPLC cheese analysis, dairy laboratory method, propionic acid determination.