ISO 17646:2025

Overview

ISO 17646:2025 - Rapid detection of moisture content in fresh meat - Low-field nuclear magnetic resonance (LF‑NMR) method defines a rapid, LF‑NMR‑based procedure for determining moisture in fresh meat. The standard specifies sample preparation, instrument settings, calibration and data-processing steps to obtain quantitative moisture estimates and to resolve water fractions by transverse relaxation time (T2). It was prepared by ISO/TC 34/SC 6 (Meat, poultry, fish, eggs and their products).

Key topics and technical requirements

• Scope: Rapid determination of moisture in fresh meat (fresh meat defined per ISO 23722).
• Principle: LF‑NMR measures 1H NMR signals from water; signal amplitude is used to estimate moisture mass. T2 relaxation is used to distinguish water states.
• Sample preparation:
  • Remove skin, connective tissue and fat.
  • Cut along muscle fiber into 1 cm thick slices, then into 1 × 1 × 2 cm cuboids; at least three cuboids per sample.
  • Sample temperature: 22 °C ± 2 °C.
• Instrument and environment:
  • LF‑NMR analyser (universal), field strength ≈ 0.5–1.0 T, spectrometer frequency ≈ 20–23 MHz.
  • Instrument chamber ambient: 32–35 °C.
• Measurement sequences: Use FID for calibration and CPMG for determination to obtain relaxation attenuation curves and inversion spectra.
• Key parameter ranges (examples from the standard):
  • Sampling bandwidth (SW): ≈100–200 kHz
  • Regulate first data (RFD): ≈0.002–0.5 ms (recommended 0.08 ms at SW = 100 kHz)
  • Time wait (TW): calibration ≈1 000–4 000 ms, determination ≈4 000–8 000 ms
  • Echo time (TE): pork ≈ 0.3 ms, beef ≈ 0.5 ms, chicken ≈ 0.2–0.3 ms
  • Echo number (NECH): ≈2 000–5 000
• Standard curve procedure: Use freeze‑dried meat, add water increments (1%, 5%, 10%, 30%, 50%, 70%) with ≥5 repeats per group to build calibration curves (Annex A).
• Data processing: Convert CPMG decay to T2 inversion spectra (SIRT method), extract peak areas A(T2b), A(T21), A(T22) corresponding to bound, immobilized and free water (T2 ranges given in the standard).

Practical applications and users

Who uses ISO 17646:2025:

• Food testing laboratories performing routine moisture analysis of fresh meat
• Meat processors and quality assurance teams for production control
• Instrument manufacturers and service providers for LF‑NMR systems
• Research labs studying water distribution in muscle tissues
• Regulatory or inspection bodies needing standardized rapid moisture tests

Practical applications:

• Rapid moisture quantification in production and QC workflows
• Generating reproducible standard curves for LF‑NMR moisture calibration
• Differentiating bound, immobilized and free water fractions for product characterization

Related standards

• ISO 23722 (definition of fresh meat) - cited in ISO 17646:2025
• Prepared by ISO/TC 34/SC 6 (Meat, poultry, fish, eggs and their products) - consult national bodies for implementation guidance

Keywords: ISO 17646:2025, LF‑NMR, low‑field nuclear magnetic resonance, rapid detection, moisture content, fresh meat, T2 relaxation, CPMG, FID, standard curve, food testing.