Polyphenols protect flaxseed oil from rancidity

Flaxseed: polyphenols prevent rancidity

Polyphenols, naturally occurring antioxidants, help stabilize Omega 3-richflaxseed oil. Mónica Rubilar and her colleagues at the Universidad de La Frontera in Temuco, Chile, demonstrated this in a study published in the European Journal of Lipid Science and Technology. The discovery could help solve the problem of preserving this oil, allowing different food products to be topped up with Omega-3 without fear of it going rancid and without having to add other antioxidants.

Omega-3 yes, but not oxidized

Flaxseed oil is one of the main plant sources of Omega-3 fatty acids. In fact, it contains abundant amounts of alpha-linolenic acid, a molecule that is converted by the human body into the 2 most important Omega-3s:

• EPA (eicosapentaenoic acid)
• DHA (docosahexaenoic acid)

Like all sources of unsaturated fatty acids, flaxseed oil tends to go rancid.Oxidation of the fats themselves is at the root of this process, and it compromises both the quality of the oil and that of the food products to which it should be added. In practical terms, this all results in a deterioration of:

• flavor
• color
• consistency
• nutritional value of food

Microencapsulation of oil is one of the possible solutions to delay rancidity as much as possible. The procedure hinders theoxidation of unsaturatedfatty acids by placing the oil inside a kind of shell that protects it from external agents. Rubilar and colleagues sought to further delay rancidity by adding to the oil a plant extract rich in polyphenols, natural molecules known for their antioxidant power.Ugni molinae, a small myrtle plant that grows wild on the coasts and preandine mountains of southern Chile, was chosen as a source of polyphenols. The researchers added it to samples of already microencapsulated linseed oil after carefully selecting the most polyphenol-rich myrtle leaf extract. The oxidation status of the unsaturated fatty acids , as well as other lipids in the oil to which the extract was added, was then compared with that of the oil simply microencapsulated or to which commercial antioxidants were added.

Polyphenols also protect other fats

Analysis of the samples showed that microencapsulation succeeds in inhibiting or at least delaying the oxidation of unsaturated fatty acids. However, the addition of the natural polyphenols has an effect similar to that of synthetic antioxidants, and prevents the other fats in the oil from deteriorating as well. According to the researchers, this dual effect should increase the stability of flaxseed oil, making it possible to add it even to freeze-dried foods, such as instant preparations.

An alternative source of Omega-3

The discovery opens a new avenue for the use of flaxseed oil as an alternative to fish oil, a source of Omega-3 already used in the food industry. Its use could be of particular interest to those who, being strictly vegetarian or vegan, do not consume animal products.  

Source 

1. Rubilar M, Morales E, Sáez R, Acevedo F, Palma B, Villarroel M, Shene C, " Polyphenolic fractions improve the oxidative stability of microencapsulated linseed oil," Eur J Lipid Sci Technol, Article first published online: 12 MAR 2012, doi: 10.1002/ejlt.201100230