Sensory and Chemically Measured Effects of Different Freeze Treatments on the Quality of Farmed Rainbow Trout

Sensory and biochemical analyses were done on farmed rainbow trout to estimate quality changes caused by four different freeze handling processes. Trout were frozen as a block (I) and individual (II) drawn fish, and as a block (III) and individual (IV) fillets. Refreezing was done, except for group IV, after filleting group I and II and separating group III into individual filets. A 9‐month storage period followed (‐30C). Enzyme activity of α‐glucosidase (AG) and β‐N‐acetylglucosaminidase (NAG) was measured in centrifuged tissue fluid (CTF). A descriptive sensory test was done after the second thawing and a ranking‐order test after frozen storage. Refreezing resulted in significant increases (p < 0.05) of both enzyme activities in all groups. After storage the activity of NAG was significantly higher (p < 0.05) in all groups and a difference (p < 0.05) between group I and II was also seen. In the descriptive sensory evaluation, only two sensory attributes of group IV were differentiated (p < 0.05, p < 0.01) from the other groups. After storage group II was the preferred group (p < 0.05).