Skinned, vacuum packed post-rigor gilthead seabream (Sparus aurata) fillets werestored frozen at -22°C for up to 340 days. Sampling was carried out on fresh fillets at days 34, 91, 183, 266 and 340 of frozen storage. Tests related to muscle integrity (activity of α-glucosidase and the protein content of centrifugal tissue fluids), myofibrillar protein denaturation (Ca2+- and Mg2+-ATPase activities in actomyosin extracts) and lipid degradation products (free fatty acids, peroxide values and thiobarbituric reactive substances) showed that storage time affected the integrity of muscles, and caused structural changes to myosin (or ‘actomyosin’) and hydrolysis and oxidation of lipids. A slight decrease in salt soluble proteins was observed after 266 days of frozen storage suggesting that storage time hardly affected the formation of aggregates. The water holding capacity of the stored frozen fillets decreased with storage time and was associated with the damage in muscle structures (protein content in centrifugal tissue fluids), denaturation of myofibrillar proteins and lipid degradation products (free fatty acids and peroxide value). The firmness and toughness of the frozen fillets, as measured by the Warner-Bratzler shear knife, increased slightly with storage time. The changes in toughness were associated with the state of myofibrillar proteins and changes in water holding capacity of the stored frozen fillets.
Key words: Gilthead seabream, fillets, frozen storage, quality.
TBARS, Thiobarbituric acid reactive substances; CTF, centrifugal tissue fluid; AG, α-glucosidase; SH, sulfhydryl groups; EGTA, Ν,Ν,Ν΄,Ν΄ -tetraacetic acid; TCA, trichloroacetic acid.
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