Emulsions inhibit lipid oxidation in surimi.

Omega 3 fatty acids offer considerable health benefits. Surimi is a highly functional concentrate of the myofibrillar protein of fish muscle that contains very little fat. Adding emulsions containing omega-3 fatty acids to surimi could create a useful functional food if oxidative deterioration of the product can be controlled.

The aim of research at the University of Massachusetts was to understand the factors influencing lipid oxidation in surimi that contains oils high in omega-3 fatty acid. Scientists also examined the effect of cryoprotectants on lipid oxidation in surimi.

An oil-in-water emulsion containing 30% algae oil and 3% whey protein isolate (WPI) was prepared both with and without ethylene diaminetetraacetic acid (EDTA) by homogenization. A 12.8-g emulsion was added to 237.2 g of surimi to provide 500 mg of omega-3 fatty acids per serving of 85 g of surimi.

Bulk oil was added directly to the surimi to see how the product would differ from surimi containing the emulsion. Color measurements were made, and gel-forming ability was assessed using a torsion test. The investigators determined the existence of lipid oxidation products by measuring lipid hydroperoxide and thiobarbiturc acid-reactive substances (TBARS).

Adding the emulsion had no effect on gel strength. But the use of bulk oil decreased gel strength by an average of 31%. All surimi treatments containing algal oil increased in their Hunter a* and b* values due to the presence of carotenoids in the oil. TBARS values were lower in the surimi that contained the bulk oil than in the surimi with emulsified oil.

Adding EDTA and antioxidants--tocopherol isomers at 1000 ppm, ascorbyl palmitate at 500 ppm and rosemary extract at 1000 ppm--to the WPI-stabilized emulsion decreased lipid oxidation in surimi. Sodium tripolyphosphate (STPP) was the major surimi additive responsible for retarding the formation of TBARS. This information can be helpful when preparing shelf-stable surimi that contains nutritionally beneficial omega-3 fatty acids.

Further information. D. Julian McClements, Department of Food Science, University of Massachusetts-Amherst, Chenoweth Laboratory, Box 31410, Amherst, MA 01003; phone: [phone]; email: [e-mail].