Quality Changes in Formalin Treated Rohu Fish (Labeo rohita, Hamilton) During Ice Storage Condition

The study was conducted to evaluate the influence of formalin on the quality changes in rohu fish (Labeo rohita, Hamilton) during ice storage condition. There are complaints from the consumers that the fish traders in Bangladesh use formalin in fish imported from neighboring countries to increase the shelf life. On the basis of organoleptic characteristics, the formalin treated fishes were found in acceptable condition for 28 to 32 days in ice as compared to the control fish, which showed shelf life of 20 to 23 days. Bacterial load in formalin treated fish was below detection level even after 16 days of ice storage whereas bacterial load was significantly higher in fresh rohu stored in ice and at the end of 24 days of ice storage. NPN content was increased gradually in fresh rohu with the increased storage period in ice. On the other hand, NPN content of formalin treated rohu decreased gradually during the same period of storage. Protein solubility in formalin treated fish decreased significantly to 25% from initial of 58% during 24 days of ice storage as compared to 40% from initial of 86.70% for control fish during the same ice storage period. Gel forming ability of formalin treated fish was reduced significantly due to denaturation of muscle protein indicating poor eating quality and poor digestibility of fish contaminated with formalin.