Overview
ISO 749:1977 specifies a standardized method for determining the total ash content in oilseed residues. This international standard, developed by ISO Technical Committee ISO/TC 34 on Agricultural Food Products, involves incinerating a test portion of the oilseed residue at 550 ± 15 °C in an electrically heated muffle furnace until a constant mass is achieved. The total ash content represents the inorganic mineral residue remaining after combustion, which is an important parameter for quality control and analytical assessment of oilseed by-products. This method applies only to residues obtained by oil extraction through pressure or solvent methods and excludes compounded products.
Key Topics
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Scope and Application
The method is relevant for determining total ash in oilseed residues post oil extraction but is not applicable to compounded products containing mixtures or additives.
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Test Procedure
- Sample preparation involves grinding the oilseed residue to a uniform particle size passing a 1 mm sieve.
- Approximately 5 g of the prepared sample is weighed into a pre-weighed incineration dish.
- The sample is initially carbonized on an electric hot-plate or gas flame, then transferred to a muffle furnace set at 550 ± 15 °C.
- Incineration continues until the mass of the ash residue is constant, typically requiring 2 to 3 hours, and may be extended if necessary by incremental heating.
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Calculation and Expression of Results
The total ash content is calculated as the percentage of the residue mass relative to the original sample mass. If requested, results can also be expressed relative to dry matter by adjusting for moisture content.
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Repeatability and Accuracy
The method requires duplicate determinations on the same sample with a maximum allowable difference of 0.2 g per 100 g sample, ensuring reliability and reproducibility of results.
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Equipment Requirements
- Analytical balance accurate to 0.001 g
- Mechanical mill for grinding
- Sieve with 1 mm aperture
- Flat-bottomed incineration dishes of platinum, platinum-plated gold, silica or porcelain
- Electrically heated muffle furnace with air circulation capable of controlling temperature at 550 ± 15 °C
- Desiccator for cooling samples
Applications
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Agricultural and Food Industry
This standard is vital for quality control laboratories analyzing residuals from oilseed processing. Ash content determination informs the efficiency of oil extraction, assessing mineral content, and identifying possible contamination or adulteration.
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Research and Development
Researchers studying oilseed residues utilize this method to compare different extraction processes or optimize formulations by measuring inorganic content.
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Regulatory Compliance
Compliance with ISO 749 ensures uniformity in ash content testing, facilitating trade and certification of oilseed by-products internationally.
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Feed and Biomass Evaluation
Ash content is a key factor when oilseed residues are used as animal feed or biomass fuel since mineral content impacts nutritional value and combustion properties.
Related Standards
For comprehensive analysis of oilseed residues, the following related ISO standards may be referenced alongside ISO 749:
- ISO 5500 - Oilseed residues – Sampling procedures ensuring representative test samples for analysis.
- ISO 771 - Determination of moisture and volatile matter content in oilseed residues, critical for correcting ash content to dry basis.
- ISO 735 - Determination of ash insoluble in hydrochloric acid, providing additional mineral content detail beyond total ash.
Utilizing these standards supports a holistic approach to the chemical characterization and quality assessment of oilseed residues.
By adhering to ISO 749:1977, laboratories and industries involved in oilseed processing gain an internationally recognized, reproducible, and accurate methodology for determining total ash, ensuring product quality and facilitating global trade and research consistency.
