Overview
ISO 22662:2024 (IDF 198:2024) is the reference method for the determination of lactose content in a range of milk and milk products using high-performance liquid chromatography (HPLC). The scope covers raw milk, heat‑treated milks, dried milk, dairy permeate and permeate powder, and raw and pasteurized cream. The method is not applicable to fermented milks, milks with added oligosaccharides, or low‑lactose / lactose‑free products.
Key topics and technical requirements
- Analytical principle: Addition of an internal standard (d(+)-melezitose) to sample and standards, protein/fat precipitation with Biggs‑Szijarto reagent, double filtration (paper then 0.45 µm nylon), separation on a lead‑form cation exchange column and detection by differential refractometer or other suitable detector. Mobile phase: degassed HPLC‑grade water.
- Reagents: degassed HPLC water (ISO 3696 grade 1), d(+)-melezitose hydrate (≈50 mg/ml solution), α‑lactose monohydrate (dried at 70 °C for 4 h), and Biggs‑Szijarto solution (zinc acetate + phosphotungstic acid + acetic acid).
- Apparatus: HPLC ion‑exchange column (300 mm × 7.8 mm, lead form), guard column and micro‑guard holder, column heater maintained at 85 °C ± 1 °C, HPLC pump/autosampler, differential refractometer detector, 0.45 µm syringe or in‑line filters, precision balance, water purification and solvent filtration units.
- Procedure highlights: sample warming and homogenization, internal standard addition, precipitation and removal of fats/proteins, preparation of filtrate, HPLC setup and chromatographic conditions, calculation and expression of lactose mass fraction.
- Quality and performance: the document includes precision data (repeatability, reproducibility) from interlaboratory testing and prescribes reporting requirements.
Practical applications
- Regulatory and official control laboratories validating lactose content claims.
- Dairy industry quality control for raw, processed and powdered products.
- Contract testing laboratories and accreditation bodies requiring a standardized reference method.
- Research laboratories conducting comparative studies of carbohydrate composition in milk matrices.
ISO 22662:2024 provides a robust, validated HPLC protocol for accurate quantification of lactose where precise measurement is required for compliance, lab accreditation, nutritional labelling, product development, and quality assurance.
Who should use this standard
- Food and dairy testing laboratories
- National food control authorities
- Dairy manufacturers and quality assurance teams
- Method developers and academic researchers in dairy science
Related standards
- ISO 707 | IDF 50 - recommended sampling of milk and milk products
- ISO 3696 - water for analytical laboratory use
- ISO 648 - laboratory glassware (single‑volume pipettes)
Keywords: ISO 22662:2024, lactose determination, HPLC lactose method, milk and milk products, dairy permeate, reference method, lactose content analysis.
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