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Oil penetration into vetkoek analysed at Fluorescence Microscopy
Author: E Els
Published: 25/02/2021

The first study using confocal micrographs on the quantitative analysis of vetkoek or magwinya crumb and crust properties was done by scientists from the University of Venda at the CAF Fluorescence Microscopy facility. The confocal laser scanning microscopy was chosen to visualise the changes in fried foods due to its ability to produce images with clear contrast, differentiating food components (fat, protein or carbohydrates) from each other and from the empty pores. The use of recognizable fluorescent dyes in sample preparation proved adequate for characterisation of oil penetration and structural changes in the samples using an image analysis technique. Important knowledge about the relationship between oil uptake and the microstructure of vetkoek were revealed.

Cross-section micrographs of the fried dough showed notable differences in terms of oil distribution, depth of oil penetration, structure and pore properties of the fried products. This emphasises the impact of ingredient formulation (water and bran variation) on oil penetration. The inclusion of oat and wheat bran in the vetkoek formulation reduced porosity and oil penetration.

The protocol used in this study can be applied to other thick deep-fried foods for qualitative observation and quantitative measurement of a specific physical or chemical property.

Cross-section micrographs of fried dough enriched with oat bran.

  • The article  'Confocal Laser Scanning Microscopy and Image Analysis for Elucidating Crumb and Crust Microstructure of Bran-Enriched South African Fried Dough and Batter ' was published in Foods (2020, 9, 605) and is available online at

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