Overview
ISO 23293:2020 specifies a standardized analytical method for quantifying whey protein content in cow milk‑based infant formula powders using sodium dodecyl sulfate‑capillary gel electrophoresis (SDS‑CGE). The method determines the whey:casein protein ratio in the range 20:80 to 80:20. It is not applicable to formulas containing hydrolysed proteins or proteins from non‑bovine sources (e.g., plant proteins or milk from other mammals). ISO 23293:2020 is published jointly by ISO and IDF and is equivalent to AOAC Official Method AOAC 2016.15.
Key topics and technical requirements
- Analytical principle: Proteins are denatured with SDS and reduced (β‑mercaptoethanol), separated by capillary gel electrophoresis and detected by UV at 220 nm. Whey and casein appear as distinct, non‑overlapping peak groups; quantification uses integrated peak areas.
- Mass‑area correction: A correction factor of 1.4 (whey vs. casein) is applied when converting integrated area to mass.
- Reagents: Typical reagents include Tris, boric acid, SDS, EDTA, glycerol, dextran 2000, β‑mercaptoethanol and internal/size standards (10 kDa internal standard, SDS‑MW size standard 10–225 kDa).
- Apparatus: Capillary electrophoresis instrument with UV detector at 220 nm; recommended capillary: 50 µm ID × 30 cm (effective length 20 cm); instrument and sample tray maintained at 25 °C ± 2 °C.
- Sample prep & run conditions: Example procedure-disperse 500 mg powder in 5 ml water, mix with sample running pre‑solution and internal standard, heat at 95 °C ± 5 °C for 10 min, centrifuge and inject. Capillary preconditioning and run cycle timings are specified (e.g., precondition with basic wash 3 min, acidic wash 1 min, fill with gel buffer 10 min; separation run time 30 min; injection electrokinetic at −5 kV for 20 s).
- Quality & precision: System suitability criteria, electropherogram integration rules, and interlaboratory precision data are provided (see Annexes A and B in the standard for examples and numerical precision results).
Applications and users
- Infant formula manufacturers for formulation verification and quality control.
- Food testing laboratories performing compositional analysis and regulatory testing.
- Regulatory authorities assessing label claims and product compliance.
- R&D teams monitoring protein fractionation during formulation or processing changes.
Practical keywords: ISO 23293:2020, SDS‑CGE, whey protein quantification, whey:casein ratio, milk‑based infant formula testing, capillary gel electrophoresis.
Related information
- Equivalent to AOAC Official Method AOAC 2016.15.
- For full procedural details, precision metrics and annex examples, consult the complete ISO 23293:2020 document available from ISO or your national standards body.
Open preview (PDF)Milk-based infant formula powders — Quantification of whey protein content by sodium dodecyl sulfate-capillary gel electrophoresis (SDS-CGE)
