In this article:
Berries of Vitis vinifera L. cv Sultanina were partly immersed in commercial oil emulsion before drying in an oven at 40oC.
The treated part dried to a yellow colour without visible surface bloom, while the untreated part dried to a bluish-violet colour with surface bloom characteristic of untreated berriers.
Colour development was prevented in partly treated berries if they were fully immersed in oil emulsion before they lost about 50% of their fresh weight.
The browning reaction was inhibited in isolated grapeskins by sodium diethyldithiocarbamate.
The results support the hypothesis that browning of sultanas during drying under mild conditions is caused by o-diphenol oxidase acting on substrates released from cell compartments.
Uneven colour development in dried sultanas can be prevented be a second spraying with oil emulsion within seven days of the first.
Browning of Sultana Grape Berries During Drying
1971, Journal of the Science of Food and Agriculture, vol 22, issue 5, pages 270 – 272
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