Publisher: Nofima AS
Number of pages: 21
International Standard Numbers:
Open Access: none
An accelerated storage experiment has been carried out after the addition of two commercial natural antioxidants, rosemary extract and mixed tocopherol, in refined mackerel oil from residual raw material. Two levels of rosemary extract (625 and 1250 ppm) and mixed tocopherol (750 and 1500 ppm) and a mixture of the two antioxidants at two levels were used. The oils have been stored for 4 weeks at 40 ° C and with air access together with refined mackerel oil without added antioxidant. The oils from the storage experiment have been analyzed for peroxide and anisidine value and volatile compounds using HS-GC/MS. After 2 weeks, high levels of rosemary extract have about the same effect as mixed tocopherol. But there was no significant difference between the two levels of mixed tocopherol. After 3 and 4 weeks, mixed tocopherol clearly has the best effect on the stabilization of the mackerel oil. By adding rosemary extract to mixed tocopherol, a small synergistic effect on PV and AV is obtained after 3 and 4 weeks. But the best effect on stabilization has mixed tocopherol. Volatile components were dominated by secondary lipid oxidation products of which 2-ethyl-furan, 1-penten-3-ol and acetic acid accounted for 30-60% of the total volatile components. The secondary lipid oxidation products showed a significant positive correlation with anisidine number (r> 0.9, p <0.0002). An overall assessment of the results indicate that tocopherol added to refined mackerel oil in an amount of 750 ppm gives a good storage stability of the oil with regard to rancidity. Best effect on mackerel oil stabilization was achieved by combining mixed tocopherol and rosemary extract at low (750 ppm) and high (1250 ppm) levels, respectively.