Seaweed extracts show promise as antioxidant and possible stabilizer for fish oils.

Omega-3 acids reduce symptoms of cardiovascular disease, rheumatoid arthritis and depression. However, fish oil is easily oxidized, and some scientists believe rancid product may be harmful to health. Antioxidants used to date have had variable results, with potentially high levels of oxidized products still being consumed.

Excellent levels of omega-3 fatty acids have been found in the oil of many fish species and they are a focus of New Zealand's Crop & Food Research scientists, who are working to produce more stable and biologically active oils. The researchers have already found natural plant extracts with antioxidant properties in a vegetable oil model system. Now, marine plant researchers have also found several seaweed extracts with antioxidant activity that compare favorably to the commercial antioxidants ascorbic acid and butylated hydroxytoluene (BHT).

The ultimate aim of investigators is to use a completely marine extract in fish oils to deliver a highquality, completely natural oil. They believe that brown seaweeds are, in general, better antioxidants than green or red colored seaweeds. Their research is continuing into the active components found in New Zealand seaweeds and into the differences between species. Much also remains to be discovered on the interactions between different compounds in crude extracts and within complex final products.

In related work, Crop & Food Research scientists suggest that oxidized fish oils are likely to impact on health. Oxidized oil could also account for the variable results of health research trials. Oxidized oils and fats of other types have been shown to increase the risk of atherosclerosis and thrombosis in a small number of human trials. These effects have been seen with relatively low levels of oxidized product, similar to a regular dose of fish oil capsules.

New Zealand scientists are using the by-products from the filleting process, which constitute up to 60% of the fish weight and contain up to 10% oil, to produce a value-added, high-quality nutraceutical oil. As well as looking at ways to improve handling of the raw material after harvest, the researchers are working with industry to modify by-product processing operations, to improve yields and the quality of oil and protein extracts.

Further information. Jenny Smith, Crop & Food Research, Box 5114, Port Nelson, New Zealand; phone: [phone]; fax: [phone]; email: [e-mail].