Enzyme leakage in muscle tissue of rainbow trout (Oncorhynchus mykiss) related to various thawing treatments

Frozen rainbow trout (Oncorhynchus mykiss) was thawed so that different tempering times, followed by different duration times in the temperature intervall called the latent zone (LZ), were obtained. The different thawing treatments resulted in different effects on the muscle membrane system. To estimate the resulting tissue damage, the leakage of the lysosomal enzymesα-glucosidase (E.C. 3.2.1.20) andβ-N-glucosaminidase (E.C. 3.2.1.30) was measured as the relationship between the enzyme activity in centrifuged tissue fluid (CTF) and in total homogenate. The volume and protein content of the CTF were also measured. The tempering rate seemed to influence the enzyme leakage more than different duration times in the LZ. Slow tempering increased the enzyme leakage more than fast tempering. Samples taken 1 h in the LZ showed an increased activity compared with samples taken directly after completed tempering. No significant further increase was found in samples taken after 10 or 24 h in the LZ, either for the rapidly or the slowly tempered group.