Overview
ISO 14902:2001 specifies a laboratory method for the determination of trypsin inhibitor activity (TIA) in soya products intended as animal feeding stuffs. The method is used to assess the degree of toasting or heat treatment of soya ingredients because TIA is indicative of residual anti-nutritional factors. The procedure is spectrophotometric, uses L‑BAPA as substrate and measures released p‑nitroaniline at 410 nm. The method detection limit is 0.5 mg/g.
Key topics and requirements
- Scope: Determines TIA of soya products for feed quality assessment.
- Principle: Extract inhibitors at pH 9.5, incubate with bovine trypsin and L‑BAPA (benzoyl‑L‑arginine‑p‑nitroanilide), quantify released p‑nitroaniline spectrometrically.
- Reagents & equipment: Tris buffer with CaCl2, DMSO for L‑BAPA, bovine trypsin, calibrated pH meter, 410 nm spectrometer, controlled water bath (37 °C), centrifuge and grinding apparatus.
- Sample prep & extraction: Grind representative sample (minimal heat), extract 1 g in NaOH solution, adjust pH to 9.5, refrigerate 15–24 h, dilute and sediment before analysis.
- Calibration & controls: Include blanks and standards; check trypsin activity for each batch (specified absorbance range).
- Calculations: Compute inhibition percentage from absorbance readings, convert to TIA (mg inhibited trypsin per g sample) using sample mass, trypsin mass and dilution factors; account for trypsin purity.
- Performance / precision: Interlaboratory data provided. Example repeatability (r) and reproducibility (R) for tested matrices:
- Soya 1 (TIA 1.53 mg/g): r = 0.18 mg/g, R = 1.11 mg/g
- Soya 2 (TIA 1.30 mg/g): r = 0.09 mg/g, R = 2.11 mg/g
- Toasted soya beans (TIA 2.08 mg/g): r = 1.03 mg/g, R = 1.88 mg/g
Applications and users
Who uses ISO 14902:2001:
- Feed quality control laboratories verifying soya processing (toasting) efficacy.
- Animal feed manufacturers monitoring anti‑nutritional factors to ensure product safety and nutritional value.
- Soy processors and oilseed mills optimizing heat treatment to reduce trypsin inhibitors.
- Regulatory authorities and testing bodies enforcing feed standards or tolerance limits.
- Research laboratories studying protein antinutrients and processing effects.
Practical benefits: standardized TIA results improve comparability between labs, support process control (toasting), and help prevent reduced protein digestibility in feed.
Related standards
- ISO 3696:1987 - Water for analytical laboratory use (referenced for reagent water quality).
- ISO 6497 - Recommended sampling method for animal feeding stuffs (sampling guidance referenced).
For implementation, laboratories should follow the full ISO 14902:2001 text for detailed procedural steps, reagent preparation, dilution schemes and reporting requirements.