Mayonnaise enriched with an omega-3 high fat emulsion stabilized with milk protein and surfactants. Image: Thomas Breitenbach, Aarhus University

Caffeic acid can slow down oxidation of fish oil in foods

Thursday 20 Jun 19


Betül Yesiltas
National Food Institute
+45 93 51 89 40


Charlotte Jacobsen
Professor, Head of Research Group
National Food Institute
+45 23 27 90 75

New knowledge from the National Food Institute, Technical University of Denmark, can make it easier to add fish oil to fatty foods without them quickly going rancid.

In Denmark, only a small percentage of people eat the recommended 350 grams of fish a week even though the dietary recommendation exists to help ensure people have a sufficient intake of fish oils and other nutrients that our bodies need, but which it is difficult to cover by eating other foods.

One way of ensuring that people who do not eat enough fish have a sufficient dietary intake of fish oil is to incorporate fish oil into other foods. However, this can prove to be a challenge as fish oil tends to go rancid when exposed to oxygen in the air, which can give the food an unpleasant, rancid taste.

A PhD study from the National Food Institute has produced important knowledge about the oxidation process, which takes place in omega-3 fatty acids in fish oil, when they are added to foods with a high fat content via so-called delivery emulsions. Betül Yesiltas has also studied ways of further developing different emulsions in order to prevent the fatty acids from going rancid.

Encapsulation of fish oil

The oxidation process starts at the oil-water interface. To slow down this process, researchers from Aarhus University have found a way of adding caffeic acid—which is an antioxidant—to various emulsifiers.

In her research, Betül Yesiltas has shown that by adding caffeic acid to an emulsifier it works in two ways: It forms a physical barrier against the environment while also acting as an antioxidant right where the oxidation processes start.

Betül Yesiltas mixed the modified emulsifier, which gave the best result, into mayonnaise. She then studied the oxidative stability—that is, the speed of the oxidation process—in the mayonnaise and compared the results with the oxidation process that occurred in a mayonnaise containing pure fish oil.

The emulsifier proved to be effective in protecting the fish oil from oxidation, which prolongs the shelf life of the mayonnaise and enhances its taste. Knowledge from the study could be used to incorporate fish oil into other foods with a better taste and shelf life than what is currently possible.

Using new technology gives a deeper understanding

Betül Yesiltas has used advanced neutron and x-ray facilities in Hungary and the UK to study the oil / water interface. This has enhanced the fundamental understanding of the oxidation process in high fat products, and this knowledge could help to understand more complex oxidation processes.

In the next few years, similar but more advanced techniques will be available at MAX IV and ESS in Lund, Sweden, and the knowledge gained in the PhD study may therefore form the basis of further research using the facilities in Lund.

Read more

Betül Yesiltas’ experiments are described in further detail in an article in the scientific journal Food Chemistry: Modified phosphatidylcholine with different alkyl chain length and covalently attached caffeic acid affects the physical and oxidative stability of omega-3 delivery 70% oil-in-water emulsions (pdf).

A copy of Betül Yesiltas’ PhD thesis—in which the article is included—is available from the National Food Institute. The thesis will be uploaded to DTU Orbit, when the other articles contained within the thesis have been published. Send an email to if you want to be notified when the thesis is publically available.

Go to the National Food Institute’s website to learn more about the Research Group for Bioactive Substances - Analysis and Use. The group works e.g. to develop technologies and processes that can help increase the population's intake of healthy foods that are rich in vitamins, healthy fats and proteins/peptides.
17 APRIL 2021