Overview
ISO 29822:2009 - "Vegetable fats and oils - Isomeric diacylglycerols - Determination of relative amounts of 1,2- and 1,3-diacylglycerols" specifies a laboratory method to determine the degree of isomerization of diacylglycerols (DAGs) in vegetable fats and oils. The standard quantifies the mass fraction of 1,2-diacylglycerols (reported as a percentage to one decimal place) relative to the sum of 1,2- and 1,3-isomers. Because 1,2-DAGs convert to the more stable 1,3-isomers during storage or under acidic catalysis, this measure serves as a quality criterion for edible oils.
Key topics and technical requirements
- Scope: Focuses on C32, C34 and C36 diacylglycerols only (typical DAG homologues used in the calculation).
- Separation principle: Miniaturized silica gel column chromatography isolates DAGs as the polar fraction from other lipids.
- Derivatization: Diacylglycerols are converted to trimethylsilyl derivatives (silylation) using N‑Methyl‑N‑(trimethyl‑silyl)heptafluorobutyramide (MSHFBA) with 1‑methylimidazole.
- Analysis: Gas chromatography with a fused‑silica capillary column and flame ionization detector (GC‑FID) is used. The method requires a split injector (on‑column or splitless injectors are not permitted to avoid isomerization during injection).
- Standards and references: Uses reference substances (e.g., dipalmitin, distearin, diolein) to identify retention times and assumes equal response factors for DAG isomers.
- Calculation: Percentage mass fraction w1,2 = (sum peak area of all 1,2‑DAGs / sum peak areas of all 1,2‑ and 1,3‑DAGs) × 100.
- Precision: Method precision (repeatability and reproducibility) is documented based on an interlaboratory study (Annex B).
Practical applications
- Quality control and shelf‑life monitoring of edible oils (olive oil, vegetable oils).
- Detection of storage‑ or process‑induced isomerization and acid‑catalysed degradation.
- Product specification and acceptance testing for manufacturers, refiners and packers of vegetable fats and oils.
- Research and method validation in analytical laboratories studying lipid chemistry and DAG composition.
Who should use this standard
- Food testing laboratories and quality assurance teams in the edible oil industry.
- Regulatory and conformity assessment bodies monitoring oil quality.
- R&D groups and academic researchers working on lipid analysis and oil stability.
Related standards
- ISO 661 - Preparation of test sample for fats and oils
- ISO 5555 - Sampling of animal and vegetable fats and oils
- ISO 5725‑1 / ISO 5725‑2 - Accuracy (trueness and precision) of measurement methods
- DGF Standard Method A‑II (interlaboratory test procedures)
Keywords: ISO 29822:2009, diacylglycerols, 1,2‑diacylglycerols, 1,3‑diacylglycerols, vegetable oils analysis, isomerization, gas chromatography, silylation, quality criterion.
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