Foreword

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This document was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 11, Animal and vegetable fats and oils.

This second edition cancels and replaces the first edition (ISO 21846:2018), of which it constitutes a minor revision.

The changes are as follows:

entry errors have been corrected in Tables B.1, B.2, B.3, B.4 and B.5.

Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.

1 Scope

This document specifies the determination of composition of triacylglycerols and the determination of the composition and content of diacylglycerols by capillary gas chromatography in vegetable oils with a lauric acid content below 1 %.

Applying certain technological processing 1,2-diacylglycerols (1,2-DAGs) are transformed to the more stable isomeric 1,3-diacylglycerols (1,3-DAGs) due to acidic catalysed reaction. During storage, the speed and amount of this rearrangement depends on the acidity of the oil. The transformation normally reaches an equilibrium between the two isomeric forms. The relative amount of 1,2-DAGs is related to oil freshness or to a possible technological treatment. Therefore, it is possible to use the ratio of 1,2-DAGs to 1,3-DAGs as a quality criterion for vegetable fats and oils.

The triacylglycerols profile is of potential interest for the fingerprint of each vegetable oil and may help the detection of certain types of adulteration, such as the addition of high oleic sunflower oil or palm olein in olive oil.

NOTE This document is based on Reference [3].

2 Normative references

3 Terms and definitions

4 Principle

5 Apparatus

5.1

5.2

5.3

5.4

5.5

5.6

5.7

5.8

5.9

5.10

6 Reagents

6.1

6.2

6.3

6.4

6.5

6.6

6.7

7 Procedure

7.1 Gas chromatographic apparatus and capillary column condition

7.2 Choice of operating conditions

7.3 Performance of the analysis

7.4 Peak identification

7.5 Determination of percentage content of each triacylglycerol class

7.6 Determination of percentage content of each 1,2 diacylglycerol

7.7 Determination of weight percentage total content of diacylglycerols

8 Expression of results

8.1

8.2

8.3

9 Precision of the method

9.1 Repeatability, r

9.2 Reproducibility, R

10 Test report

Bibliography