In this article:

The surface lipids of the grapes from varieties used for the production of sultanas, raisins and currants were extracted with chloroform.

A further separation of the extracts with light petroleum yielded the insoluble ‘hard wax’ which consists mainly of oleanolic acid, and the soluble ‘soft wax’.

This fraction was separated by chromatography into the hydrocarbon, ‘ester-aldehyde’, alcohol and acid fractions.

The resulting fractions were analysed to determine the detectability of various oils.

It was found the addition of mineral oil can easily be detected and determined by thin-layer chromatography.

If mineral oil is replaced by animal or plant oils, these oils would appear on chromatography on aluminium oxide in the ‘ester-aldehyde fraction’ or on hydrolysis in the saponifiable part.

The Surface Lipids of Fresh and Processed Raisins

1965, Journal of the Science of Food and Agriculture, vol 16, month 11, pages 638 – 643

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