Free polyunsaturated fatty acids cause taste deterioration of salmon during frozen storage

Increased intensity of train oil taste, bitterness, and metal taste are the most pronounced sensory changes during frozen storage of salmon (Refsgaard , H. H. F.; Brockhoff, P. B.; Jensen, B. Sensory and Chemical Changes in Fa rmed Atlantic Salmon (Salmo salar) during Frozen Storage. J. Agric. Food Ch em. 1998a, 46, 3473-3479). Addition of each of the unsaturated fatty acids: palmitoleic acid (16:1, n - 7), linoleic acid (C18:2, it - 6), eicosapenta enoic acid (EPA; C20:5, it - 3) and docosahexaenoic acid (DHA; C22:6, n. - 3) to fresh minced salmon changed the sensory perception and increased the intensity of train oil taste, bitterness, and metal taste. The added level of each fatty acid (similar to 1 mg/g salmon meat) was equivalent to the co ncentration of the fatty acids determined in salmon stored as fillet at -10 degrees C for 6 months. The effect of addition of the fatty acids on the i ntensity of train oil taste, bitterness and metal taste was in the order: D HA > palmitoleic acid > linoleic acid > EPA. Formation of free fatty acids was inhibited by cooking the salmon meat before storage. Furthermore, no ch anges in phospholipid level were observed during frozen storage. The result s suggest that enzymatic hydrolysis of neutral lipids plays a major role in the sensory deterioration of salmon during frozen storage.