Overview
ISO 2917:1999 - Meat and meat products: Measurement of pH - Reference method specifies a laboratory reference procedure for measuring the pH of all kinds of meat and meat products (including poultry). The method covers both destructive (homogenized samples) and non‑destructive (in‑situ on carcasses, quarters and muscles) measurements and defines reagents, apparatus, sampling/preparement, calibration, measurement technique and reporting requirements.
Keywords: ISO 2917:1999, meat pH measurement, reference method, pH‑meter calibration, meat quality control.
Key topics and technical requirements
- Principle: measurement of potential difference between a glass indicator electrode and a reference electrode immersed in a meat sample or extract.
- Apparatus: pH‑meter with 0.01 pH resolution; combined glass/reference electrode (Ag/AgCl or Hg/HgCl); homogenizer (knife rotor or mincing plate ≤4 mm); disperser‑homogenizer (≈20 000 min‑1); magnetic stirrer.
- Reagents and buffers:
- Use analytical‑grade reagents and laboratory water per ISO 3696.
- Recommended buffer solutions for calibration: pH ≈ 4.00, 6.88 (or 6.85–6.98 depending on temperature), and 5.45 (preparation details given).
- 0.1 mol·L‑1 KCl solution used as extraction medium; where pre‑rigor muscle is measured, add iodoacetic acid and adjust pH to 7.0 as specified.
- Sample preparation:
- Representative sample mass ≥ 200 g.
- Homogenize samples, keeping temperature ≤ 25 °C; analyze within 24 h of homogenization.
- For extracts, mix sample with KCl solution at a ratio of 1:10 (sample:solution) before measurement.
- Calibration & temperature:
- Calibrate with two buffers near the expected pH. If the pH‑meter lacks temperature compensation, perform measurements at (20 ± 2) °C.
- Procedure details:
- Insert electrodes into sample or extract, stir, wait for stable reading; read to 0.01 pH and report results to 0.05 pH.
- Electrode cleaning: wipe with cotton wetted in diethyl ether then ethanol, rinse with water.
- Precision:
- Repeatability: difference between two results in same lab normally ≤ 0.04 pH (95% level); s_r ≈ 0.014 pH.
- Reproducibility between labs: difference normally ≤ 0.12 pH (95% level); s_R ≈ 0.042 pH.
Applications and users
ISO 2917:1999 is used by:
- Meat processors and quality assurance laboratories for product quality control and process monitoring.
- Regulatory and inspection agencies needing standardized pH data.
- Food research labs studying meat physiology, shelf‑life and processing effects.
- Accredited testing laboratories requiring a reference method for interlaboratory comparison.
Practical uses include pH monitoring during processing, verification of product specification, research on meat maturation and forensic/traceability analyses.
Related standards
- ISO 3696 - Laboratory water quality (referenced for analytical water).
- ISO 3100‑1 - Sampling and sample preparation for meat testing.
- ISO 5725 series - Determination of repeatability and reproducibility (method accuracy and interlaboratory trials).
For implementation, laboratories should follow the full ISO 2917:1999 text and complement it with appropriate sampling and quality‑assurance procedures.
