Overview
ISO 734:2023 - "Oilseed meals - Determination of oil content - Extraction method with hexane (or light petroleum)" - specifies a reference laboratory method to determine the oil content (hexane- or light‑petroleum‑extractable fraction) of oilseed meals obtained by pressing or solvent extraction. The standard applies to meals (excluding compounded products) and defines the extraction principle, reagents, apparatus, sample preparation, test procedure and requirements for reporting and precision.
Key topics and technical requirements
- Scope and principle: Oil content is measured as the mass fraction extracted by technical hexane (or light petroleum) using a solvent‑extraction apparatus; the solvent is removed and the extract weighed.
- Reagents: Technical hexane or light petroleum with controlled distillation range (majority between 40–60 °C or 50–70 °C), bromine value < 1 and residue on evaporation ≤ 2 mg/100 ml.
- Sample preparation:
- Representative sample prepared per ISO 5502.
- Grind to pass a 1 mm sieve; microgrinding to <160 µm recommended for thorough extraction.
- Use about 10 g test portions (weighed to 0.001 g).
- Pre‑dry if moisture > 10 % (heat ≤ 80 °C) or mix with anhydrous sodium sulfate as described.
- Extraction procedure:
- Use a suitable straight‑through extractor (examples: Butt, Smalley, Twisselmann, Bolton‑Williams) with 200–250 ml flask.
- First extraction 4 h (reflux ~≥3 drops/s), then grind and re‑extract 2 h using same flask.
- Remove solvent (rotary evaporator or distillation), finish drying in oven (103 °C ± 2 °C), cool in desiccator and weigh to 1 mg. Repeat heating until successive weighings differ ≤ 10 mg.
- Apparatus & safety:
- Mechanical grinder/microgrinder, extraction thimble, rotary evaporator, thermostatic oven, desiccator, analytical balance (0.001 g).
- Strong safety warning: perform solvent reflux/boiling in a chemical fume hood and use equipment appropriate for flammable solvents.
- Quality and precision:
- Method includes provisions for number of determinations, repeatability, reproducibility and interlaboratory testing (precision data section).
Applications and users
- Quality control in oilseed processing (seed crushers, oil mills) to monitor residual oil in meals.
- Feed industry and ingredient suppliers validating nutritional composition of meals (e.g., soybean, rapeseed, sunflower).
- Analytical testing laboratories performing official or reference oil determinations.
- Regulatory bodies and research institutions comparing extraction methods or establishing specifications.
Related standards
- ISO 659 - oil content of oilseeds (related extraction method for whole seeds)
- ISO 5502 - preparation of test samples (sample handling)
- ISO 771 - moisture and volatile matter content of oilseed meals
- ISO 5500 - recommended sampling methods
ISO 734:2023 is a practical, reproducible reference method for determining solvent‑extractable oil in oilseed meals, combining detailed sample preparation, defined extraction conditions and clear safety and reporting requirements. Keywords: ISO 734:2023, oilseed meals, oil content, hexane extraction, light petroleum, solvent extraction method, laboratory analysis, feed ingredient testing.
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