Overview
ISO 15914-2:2024 specifies an enzymatic method for determining total starch content in animal feeding stuffs containing starchy ingredients (cereals, tubers, beans) and in animal digestive contents. The method combines a potassium hydroxide (KOH) dispersion step to solubilize starch, enzymatic hydrolysis with amyloglucosidase, and final glucose quantification using a hexokinase (HK) system. Results are calculated to give starch as a percentage (product as‑is).
Key topics and technical requirements
- Scope & applicability: Designed for animal feeding stuffs with starchy matrices and digestive content; also applicable to beans. Note: very high‑amylose products (e.g., amylomaize) can give questionable results.
- Sample preparation: Follow ISO 6498 guidelines for laboratory sample prep; optional degreasing for >5% fat. Washing with 40% ethanol removes soluble sugars before hydrolysis (cereals may omit washing after validation).
- Dispersion & hydrolysis: Residue dispersed in water and 1 mol/L KOH, ultrasonic and thermostatic treatment, pH adjusted to ~4.6–4.8, then hydrolysed with amyloglucosidase.
- Glucose determination: Measured by the hexokinase/glucose‑6‑phosphate dehydrogenase (HK/G6P‑DH) system with NADPH produced and read by UV/Vis spectrophotometry (340 nm or 365 nm). Reagent blank correction and dilution factors are used to compute starch content.
- Reagents & equipment: Requires analytical‑grade reagents, thermostatic bath, centrifuge, grinder (≤0.5 mm), pH‑meter, ultrasonic tank, micropipettes and a spectrophotometer.
- Quality control & validation: Annex A details checking amyloglucosidase activity; Annexes B and C summarize interlaboratory precision data and washing tests. Method precision includes defined repeatability and reproducibility performance characteristics.
Practical applications
- Quality control and routine laboratory testing for feed manufacturers, contract testing labs and feed ingredient suppliers.
- Product formulation and batch release to ensure accurate energy/starch specifications in compound feeds.
- Regulatory and compliance testing where standardized starch quantification in feed matrices is required.
- Research in animal nutrition and digestive studies where starch content of feed and digesta is measured.
Who should use this standard
- Feed analytical laboratories and QC departments
- Animal nutritionists and feed formulators
- Regulatory laboratories and certification bodies
- Researchers conducting starch digestibility or feed composition studies
Related standards
- ISO 6498 - Guidelines for sample preparation of animal feeding stuffs (referenced for sample prep).
- ISO 3696 - Water for analytical laboratory use (reagent water quality).
- ISO 15914 series - other parts of the series for alternative starch determination methods and context.
Keywords: ISO 15914-2:2024, total starch, animal feeding stuffs, enzymatic determination, hexokinase system, potassium hydroxide dispersion, amyloglucosidase, feed analysis, starch quantification.
Open preview (PDF)Animal feeding stuffs — Enzymatic determination of total starch content — Part 2: Method by enzymatic determination with a hexokinase system and potassium hydroxide dispersion