OXIDATIVE STABILITY OF TRIGLYCERIDES FROM ORBITAL FAT OF TUNA AND SOYBEAN OIL IN AN EMULSION

Triglycerides (TGs) from orbital fat of tuna (tuna-TG) and from soybean oil (soy-TG) were dispersed in a buffer with milk casein and their oxidative stabilities in an emulsion were compared with those in the air. Since the average number of bisallylic positions in tuna-TO molecule was higher than that in soy-TG molecule, tuna-TO was more susceptible to oxidation than soy-TG in the air. However, tuna-TC became oxidatively more stable than soy-TG in an emulsion. PV of soy-TG increased rapidly after 100 h of oxidation in an emulsion, but such an increase was not observe in the oxidation of tuna-TG. Gas chromatographic analysis also showed that 94.0+/-3.8% of polyunsaturated fatty acids (PUFAs) in tuna-TG remained unchanged after 240 h of oxidation in an emulsion, while soy-TG was more rapidly oxidized in an emulsion with loss of 76.2+/-1.1% of PUFAs after 240 h of oxidation. These results show the possibility that fish oils may be protected from their oxidations by emulsification.