Studies on the Post-mortem Changes in Genetically Improved Farmed Tilapia (Oreochromis niloticus) During Ice Storage

Studies were conducted on the post-mortem changes in genetically improved farmed tilapia (Oreochromis niloticus) during ice storage. Fish sample kept at room temperature, rigor started 1 hr. after spiking, reached full rigor (100%) within 3 hr which continued for 3 hr. . In ice stored fish, rigor started within one hour and attained full rigor (100%) within 2 hr that continued for 16 hrs. The pH of the muscle was about 7 immediately after catch and started to decrease gradually with the lapse of storage period. But the decrement of pH in samples stored at room temperature was much rapid than those stored in ice. Organoleptically the fish were in acceptable conditions for 16 days. The initial TVB-N and peroxide values were 5.3 mg/100g of fish and 5 meq/kg of fish respectively. These values gradually increased with the lapse of storage time but remained within the recommended limit up to 16 days. Ca2+ ATPase activities in presence of 0.1M KCl and 0.5 M KCl were 0.349 and 0.139 ?mol.pi/min. mg, respectively, and decreased gradually with storage period. Mg2+ ATPase activities in presence and absence of Ca2+ were 0.418 and 0.183 ?mol.pi/min. mg respectively. The myofibrillar solubility decreased gradually from around 85.33% to 38.6% at the end of the 16 days of ice storage. The bacterial loads in muscle of ice stored GIFT varied from 7.6 x 103 to 7.1 x 103 cfu/g at 2nd day of storage and then gradually increased with storage period. At the end of the 16 days of ice storage, bacterial load increased to 4.6 x 106 cfu/g and at this stage the fish were organoleptically in acceptable condition. After 18 days of storage the bacterial load was 3.8 x 108 cfu/g that exceeded the acceptable recommended limit