The increasing formulation and fortification of foods with different types of omega-3 polyunsaturated fatty acids (PUFAs) could be further enhanced by better understanding of how to protect them from oxidation, states a new review.
Writing in the journal Trends in Food Science & Technology, researchers from the Technical University of Denmark and the University of Massachusetts stated that, although omega-3-containing food is one of the fastest growing categories in Europe and the US, several challenges and gaps in the knowledge exist.
The key, states lead author Charlotte Jacobsen, is a better understanding of antioxidants and their ability to protect the fatty acids from oxidation.
"The aim is to provide a better base for predicting the protective effects of antioxidants and other antioxidative measures in food emulsions in general and in functional food systems enriched with omega-3 PUFA in particular," wrote Jacobsen.
According to market researcher Packaged Facts omega-3 enriched foods make up the strongest sector of the functional foods market in the US - and there is still room there for significant growth. The market for these goods has grown from approximately $100m to more than $2bn in four years. The firm predicts this category will reach $7bn in sales by 2011.
However, fish oil is notoriously difficult to incorporate into formulations since it is highly susceptible to oxidation. The result is a fishy taste and smell which can be off-putting for consumers.
On the other hand, the nutritional properties of fish oil have been much in the spotlight in recent years, especially omega-3, of which fish is recognized as the best source. In order to help people consume omega-3 in their diet - and especially those who have an aversion to fish - formulators have sought to overcome the stability issues and deliver food products that are untainted by sensory issues.
Jacobsen and co-workers note that the type of food matrix greatly influences the efficacy of select antioxidants to slow or stop oxidation of the fatty acids.
"Until now, selection of the most efficient antioxidants, and determination of other workable principles to retard oxidation in different n-3 PUFA enriched food emulsion systems have been encircled by systematic experimental work," they state.
The principal antioxidants employed to date include EDTA, tocopherols (vitamin E), ascorbic acid (vitamin C), lactoferrin (a milk glycoprotein), gallic acid, and some plant extracts, with the majority used in mayonnaise, salad dressings, and milk products.
However, this trial-and-error approach could be replaced by mathematical and kinetic descriptions, which are currently "clearly lacking".
"Notably, there is a scarcity of knowledge on the movement and redox changes of transition metal ions in heterophasic (many phase) systems such as food emulsions.
"In addition, an estimate of the rates of lipid peroxide diffusion and antioxidant reactivities in different phases of emulsions is missing.
"Provision of a better quantitative understanding of oxidation events and notably of antioxidant reactions in heterophasic food emulsions would allow a much better prediction of effects of antioxidants in foods.
"This knowledge is indispensable for fast, rational design and successful development of functional food products containing non-oxidized n-3 PUFA that are efficiently protected against oxidation," they concluded.
Previously, this website has reported on the potential of a range of antioxidants, predominantly natural, to retard the oxidation of omega-3 fatty acids. These included oregano and rosemary extracts, and chardonnay grape and raspberry extracts.
Source: Trends in Food Science & Technology
February 2008, Volume 19, Issue 2, Pages 76-93
"Antioxidant strategies for preventing oxidative flavour deterioration of foods enriched with n-3 polyunsaturated lipids: a comparative evaluation"
Authors: C. Jacobsen, M.B. Let, N. Skall Nielsen, A.S. Meyer