Effect of a flax seed (Linum usitatissimum) soaking treatment on the frozen storage stability of mackerel (Scomber scombrus) fillets

The effect of a flax seed (Linum usitatissimum) soaking on the development of rancidity in frozen mackerel (Scomber scombrus) was studied. Fresh mackerel fillets were soaked in an aqueous flax seed extract for 20 min and then kept frozen (-20 degrees C) for up to 7 months. A parallel experiment with non-soaked fillets was carried out under the same conditions. The development of rancidity was measured by biochemical (free fatty acids, peroxides, conjugated dienes and trienes, secondary oxidation products, fluorescent and browning compounds and lipoxygenase activity) and sensory (general aspect, odour and colour) analyses. An inhibitory effect of the soaking treatment on rancidity development was observed according to the peroxide content and the formation of fluorescence and browning. A lower lipoxygenase activity was detected at I month in the soaked fillets; after this, no differences were obtained between either type of sample, whose activities at month 7 were negligible. According to the sensory analyses, non-soaked fillets had fair quality at I month and were rejectable at 3 months, while the soaked ones were still of good quality at I month and rejectable at 5 months. According to the present results, soaking in an aqueous flax seed extract could be useful for inhibiting the development of rancidity in fatty fish fillets. (c) 2006 Society of Chemical Industry.