Canola, Antioxidants Inhibit Oxidation of Fish Oil

LYNGBY, Denmark--Combinations of rapeseed oil and antioxidants inhibited oxidation of a fish-oil-enriched milk emulsion, according to a study published in the Journal of Agricultural and Food Chemistry (53, 13:5429-37, 2005).

Scientists replaced natural tocopherols in rapeseed oil with different tocopherol isomers in concentrations similar to those found in natural rapeseed oil. The effects of different mixtures of altered rapeseed oils and antioxidants upon emulsions of fish oil and milk were observed. Antioxidants used in the study included alpha-tocopherol, gamma-tocopherol, ascorbyl palmitate (AP) and ethylenediaminetetraacetic acid (EDTA). Modified rapeseed oils significantly inhibited oxidation of fish oil and milk emulsions. Emulsions of fish oil, alpha-tocopherol and gamma-tocopherol were less stable than antioxidant-free emulsions of milk and fish oil. Gamma-tocopherol appeared to inhibit oxidation of fish oil and milk emulsions more efficiently than alpha-tocopherol. AP was more effective at preventing oxidation in fish-oil-enriched milk emulsions than tocopherols, as determined by methods including assessment of volatile oxidation products, as well as sensory evaluation. AP also prevented the pro-oxidant effect of tocopherols added to fish oil prior to emulsification. No interactions between AP, tocopherols, and the EDTA were noted, and EDTA added alone to fish oil did not have an antioxidant effect in the milk emulsions.

The researchers concluded AP and rapeseed oil formulated with natural tocopherols were equally efficient in inhibiting oxidation in fish-oil-enriched milk emulsions.