Overview
EN ISO 29822:2014 (identical to ISO 29822:2009) defines a laboratory method for determining the degree of isomerization of diacylglycerols in vegetable fats and oils. The method quantifies the relative amounts of 1,2-diacylglycerols and 1,3-diacylglycerols - important because 1,2-isomers convert to more stable 1,3-isomers during storage or under acid-catalysed conditions. The mass fraction of 1,2-diacylglycerols is reported as a percentage (one decimal place) and can be used as a quality criterion for oils.
Key topics and technical requirements
- Analytes covered: only C32, C34 and C36 diacylglycerols (specific molecular species are taken into account).
- Principle: miniaturized silica-gel column chromatography isolates diacylglycerols, followed by silylation and analysis by gas chromatography (GC) with flame ionization detection (FID).
- Sample prep: prepare test sample per ISO 661; silica gel (activated, water-conditioned) is used in a pipette-tip column.
- Separation & derivatization:
- Non-polar lipids removed, diacylglycerols eluted with diethyl ether.
- Silylation using N‑methyl‑N-(trimethyl‑silyl)heptafluorobutyramide (MSHFBA) with 1‑methylimidazole catalyst.
- Gas chromatographic conditions (example validated settings):
- Capillary column: 5% diphenyl / 95% dimethylpolysiloxane (e.g., RTX‑5), 0.25 mm i.d., 60 m.
- Split injection (do not use on-column or splitless injectors to avoid isomerization), split ratio ~1:50.
- Hydrogen carrier gas, oven program ~240 °C hold → ramp to 320 °C.
- Calculation: degree of isomerization = (sum peak area of all 1,2-diacylglycerols / sum peak areas of all diacylglycerols measured) × 100.
- Safety: method uses hazardous solvents and reagents; follow applicable handling rules.
Practical applications and users
- Food and oil quality control laboratories assessing freshness and storage-induced changes in vegetable oils.
- Manufacturers of vegetable oils, margarines, infant formula fats and processing plants monitoring acid-catalysed reactions.
- Regulatory authorities and standards laboratories verifying compliance and product labelling.
- Research groups studying lipid isomerization, shelf-life, or refining impacts on diacylglycerol composition.
Related standards
- ISO 661 - Preparation of test sample (fats and oils)
- ISO 5555 - Recommended sampling of fats and oils (sampling is outside the method but important for representativity)
- EN ISO 29822:2014 corresponds to ISO 29822:2009 (adopted by CEN)
Keywords: EN ISO 29822:2014, isomeric diacylglycerols, 1,2-diacylglycerols, 1,3-diacylglycerols, vegetable fats and oils, gas chromatography, silylation, silica gel column chromatography, quality criterion.