Overview
ISO 7305:2019 specifies a laboratory method for the determination of fat acidity in milled cereal products. Applicable to flours and semolinas from wheat and durum wheat and to pasta, the standard defines a reproducible procedure to quantify non‑esterified (free) fatty acids liberated during storage. Results are reported as milligrams of NaOH per 100 g of dry matter (mg NaOH/100 g dm). The document replaces the 1998 edition and updates the indicator and result expression for improved precision.
Key topics and technical requirements
- Scope: Method targeted at milled cereal products (wheat/durum flours, semolinas, pasta). Extension to maize, rye and oat products is suggested but requires further interlaboratory validation.
- Principle: Extraction of free fatty acids with 95–96% ethanol, centrifugation and titration of the supernatant with standard NaOH (in ethanol) using thymolphthalein as indicator.
- Reagents & solutions: 95–96% ethanol; standard NaOH volumetric solution (c ≈ 0.05 mol/L in ethanol), carbonate‑free; thymolphthalein indicator in ethanol.
- Apparatus: Centrifuge (≈2 000 g), rotary stirrer (30–60 rpm), centrifuge tubes, pipettes (20/30 mL), microburette (0.01 mL divisions), grinder (no appreciable heating), analytical balance (±0.01 g).
- Sample preparation: Particle size requirements defined (passes 500 µm and ≥80% through 160 µm) - grind if needed. Store samples sealed at ~4 °C; equilibrate to lab temperature before analysis.
- Moisture correction: Fat acidity is expressed on a dry‑matter basis; moisture shall be determined per ISO 712 or by validated NIR methods per ISO 12099.
- Procedure & reporting: Two determinations are made; repeat until repeatability limits are met. Mean result expressed to the nearest milligram; conversion to grams of sulphuric acid is possible (divide by 816).
- Precision: Repeatability and reproducibility characteristics are provided (interlaboratory results summarized in Annex A).
Practical applications
- Routine quality control in milling, pasta production and flour manufacturing to monitor rancidity and storage degradation.
- Shelf‑life and storage condition assessment for grains, flours and semolinas.
- Specification verification for commercial flour and pasta consignments.
- Support for product development and shelf‑stability testing.
Who uses this standard
- Food testing laboratories and QC analysts
- Flour mills, semolina producers and pasta manufacturers
- Grain handlers and storage operators
- Regulatory agencies and standards bodies
- R&D teams concerned with lipid stability in cereal matrices
Related standards
- ISO 712 - Moisture content determination for cereals and cereal products
- ISO 12099 - Guidelines for near infrared spectrometry in cereals and milled products
Keywords: ISO 7305:2019, fat acidity determination, milled cereal products, flour quality, semolina, pasta, NaOH titration, ethanol extraction, thymolphthalein, ISO 712, ISO 12099.
