FROZEN STORAGE AND THAWING METHODS AFFECT BIOCHEMICAL AND SENSORY ATTRIBUTES OF RAINBOW-TROUT

Rainbow trout were subjected to four thawing treatments after being stored at -18 degrees C and -40 degrees C for 0, 3, 7, 13 and 18 mo. Membrane integrity was estimated as the volume of centrifuged tissue fluid (CTF) and by lysosomal beta-N-acetylglucosaminidase (NAG) activity in CTF. Slow thawing, in air at 5 degrees C, resulted in higher NAG activity in CTF and a larger volume of CTF than fast thawing, at 25 degrees C in water, independent of storage time. After 3 or more months storage, a higher NAG activity in CTF and a larger volume of CTF were found in all -18 degrees C stored samples compared to that at -40 degrees C. Sensory evaluation confirmed differences between trout stored at -18 degrees C and at -40 degrees C for 18 mo.