BIOCHEMICAL AND MORPHOLOGICAL CHANGES IN GRASS SHRIMP (PENAEUS MONODON) MUSCLE FOLLOWING FREEZING BY AIR BLAST AND LIQUID NITROGEN METHODS
1993; Wiley; Volume: 17; Issue: 3 Linguagem: Inglês
10.1111/j.1745-4514.1993.tb00464.x
ISSN1745-4514
Autores Tópico(s)Protein Hydrolysis and Bioactive Peptides
ResumoGrass shrimp (Penaeus monodon) at prerigor stage were frozen at rates ranging from 3.41 to 16.1 cm/h by using an air blast freezer at –35C or a liquid nitrogen freezer at – 80, – 100 and – 120C. Immediately after freezing, the spacing between muscle fiber bundles was larger (21.3 ± 5.7 μm) in shrimp frozen at 3.4 cm/h than in shrimp frozen at 8.6 ∼ 16.1 cm/h (6.0 ± 0.6 to 8.8 ± 1.1 μm, respectively). The spacing between fibers increased during frozen storage at – 20C and remained different for slow and fast frozen samples within 4 weeks. The lysosomal fraction from fresh shrimp had more cathepsin D-like activity (187 units/mg protein) than that from shrimp frozen at 10.2 cm/h (179 units/mg protein) and at 3.4 cm/h (86 units/mg protein). During frozen storage at – 20C the cathepsin D-like activity of intact lysosomes decreased and was negligible after 4 weeks. The solubility of muscle protein in 0.6 M KCl was not consistently different in samples frozen by different methods and stored at – 20C for 4 weeks. Liquid nitrogen freezing produced frozen shrimp of higher muscle integrity than air blast. But the differences disappeared after one-month storage at – 20C.
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