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Protecting omega 3 fatty acids from oxidation: the key role of emulsifiers

In emulsions, the structure of the oil-water interface is a key factor in facilitating the protection of lipids from oxidation. The more this interface layer is homogeneous, the less the lipids will oxidise. INRA researchers have proposed new ways to control the oxidation of omega-3 fatty acids in foods.

Huile de colza. © MAITRE Christophe
Updated on 02/08/2013
Published on 02/08/2013

Current guidelines recommend a higher intake of omega-3 fatty acids through the diet. One way in which the food industry has responded to this need has consisted in enriching foods with these polyunsaturated fatty acids (PUFA). Particularly sensitive to oxidation, these new formulations represent a real technological challenge for the industry. Alterations to odour and taste, as well as the colour or even texture of products, together with an erosion of nutritional qualities, can result from a poor mastery of oxidation phenomena. Ultimately, the products will be rejected by consumers.

To preserve the nutritional and organoleptic quality of products containing omega-3 they are currently stored in a protective atmosphere and antioxidant agents are added to the formulations. Processing conditions can be also adapted so than contact with oxygen and high temperature are avoided. But these solutions often remain empirical, and are not appropriate to all conditions; for example, with respect to domestic use. Additionally, they take no account of the specificities of oxidation reactions relative to the composition and structure of the foods.

In omega-3 enriched-foods, PUFA are generally present as oil droplets stabilised with protein or non-protein emulsifiers (e.g. surfactants). They form emulsions, in which the interface between the oil and water phases may constitute a protective barrier against oxidation.
The thesis project carried out in the BIA Research Unit has clearly demonstrated a direct relationship between the structure and composition of the interface and oxidation kinetics. The more homogeneous the interface, the better the lipids are protected from oxidation.

For this reason, the use of surfactants to stabilise the interface is more effective in slowing oxidation than using proteins, whose films display greater structural heterogeneity. On the other hand, proteins that are not adsorbed at the interface play a protective role.

It seems that proteins undergo modifications prior to lipid oxidation, those located at the surface of the oil drops being particularly affected.
Formulations more similar to real foods will make it possible to determine how competition between proteins and surfactants can in practice modulate the impact of interface structure. Research is under way to determine if the type of lipids that carry omega-3 fatty acids, and clarify the location of the fatty acids in emulsion droplets which can modify oxidation kinetics and the metabolic effects of omega-3 oxidation products.

Contact(s)
Scientific contact(s):

  • Claude Genot (+33(0)2 40 67 50 76) UR BIA - Biopolymères, Interactions Assemblages
  • Marie-Hélène Ropers (+33(0)2 40 67 51 89) UR BIA - Biopolymères, Interactions Assemblages
  • Claire Berton Department of Food Science, The Pennsylvania State University
Associated Division(s):
Science for Food and Bioproduct Engineering
Associated Centre(s):
Angers-Nantes

About the methodology

Considerable methodological efforts enabled the design of stable model emulsions with the major fraction of emulsifiers (surfactants or proteins) located at the interface. Analytical protocols were also developed to verify the preferential distribution of emulsifiers at the interface.

For further information

  • Quantification of unadsorbed protein and surfactant emulsifiers in oil-in-water emulsions. Berton, C., Genot, C., Ropers, M.H., Journal of colloid and interface science, 2011, 354, (2), 739-748
  • Contribution of the interfacial layer to the protection of emulsified lipids against oxidation. Berton, C, Genot, C., Ropers, M.H., Viau, M. Journal of agricultural and food chemistry, 2011, 59, (9), 5052-5061
  • Oxidative stability of oil-in-water emulsions stabilized with protein or surfactant emulsifiers in various incubation conditions. Berton, C., Ropers, M.H., Bertrand, D., Viau, M., Genot, C.Food chemistry, 2012, 131, 1360-1369
  • Berton C., Ropers M.H.,Guibert, D., Solé, V. and Genot C., 2012. Modifications of interfacial proteins in oil-in-water emulsions prior to and during lipid oxidation. Journal of Agricultural and Food Chemistry, 60, 8659-8671. http://dx.doi.org/10.1021/jf300490w