Overview
ISO/TS 17758:2014 (IDF/RM 87:2014) defines a laboratory method for measuring the dispersibility and provides a rapid routine method for wettability (wetting time) of instant dried milk (skimmed and whole). The specification applies to powders produced by either the “straight‑through” or “re‑wet” processes and gives a repeatable test procedure to assess how readily instant milk powders disperse in water - a key indicator of “instant” quality.
Key topics and technical requirements
- Scope and principle: Dispersibility is determined by spreading a known test portion on water (25 °C), stirring under controlled timing and motion, sieving the decanted liquid and measuring total solids to calculate the proportion dispersed.
- Sample pretreatment: Laboratory sample held at 20–25 °C for at least 48 h to standardize fat physical state.
- Test portions: Typical mass values specified - (26 ± 0.1) g for instant skimmed milk and (34 ± 0.1) g for instant whole milk; (250 ± 0.1) g water at (25 ± 1) °C is used (note: the standard remarks some labs use 40 °C for whole milk).
- Apparatus: Defined glass beaker (600 ml) and plate, glass tubing, spatula, stopwatch, test sieve (200 mm diameter, 150 µm aperture) and balance to specified tolerances.
- Procedure highlights: Controlled drop of powder onto water after a 1‑minute start, timed stirring sequence (total 20 s of active stirring with specific hand movements and beaker rotation), 30 s settling, decanting to the sieve and determination of total solids of the filtrate.
- Results and reporting: Dispersibility is calculated from test portion mass, moisture content (determined per ISO 5537|IDF 26), and total solids in filtrate (ISO 6731|IDF 21 methods referenced). The document includes repeatability data and guidance for interpreting dispersibility (Annex A) and a rapid wettability test (Annex B).
Applications and users
- Quality control: Routine QC of instant milk powder production to confirm “instant” performance and batch consistency.
- Product development and R&D: Compare processing routes (straight‑through vs re‑wet) and formulation changes affecting instant characteristics.
- Conformity & export testing: Demonstrate product performance to customers or regulators.
- Primary users: Dairy processors, analytical laboratories, R&D teams, standards bodies and suppliers of milk powder manufacturing equipment.
Related standards (normative references)
- ISO 5537 | IDF 26 - Dried milk - Determination of moisture content
- ISO 6731 | IDF 21 - Determination of total solids content
- ISO 707 | IDF 50 - Sampling of milk powders (recommended)
- ISO 565 - Test sieve requirements
Keywords: ISO/TS 17758:2014, IDF/RM 87:2014, instant dried milk, dispersibility, wettability, milk powder quality control, wetting time, instant milk powder testing.