Asian Journal of Agricultural Sciences 2(4): 158-163, 2010 ISSN: 2041-3890 © Maxwell Scientific Organization, 2010 Submitted Date: May 31, 2010 Accepted Date: June 26, 2010 Published Date: October 09, 2010 Corresponding Author: M.S. Reza, Department of Fisheries Technology, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh 158 Quality Changes in Formalin Treated Rohu Fish (Labeo rohita, Hamilton) During Ice Storage Condition T. Yeasmin, M.S. Reza, F.H. Shikha, M.N.A. Khan and M. Kamal Department of Fisheries Technology, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh Abstract: 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. Key words: Bacterial load, formalin, gel forming ability, ice storage, Labeo rohita , NPN, protein solubility, shelf life INTRODUCTION Rohu, Labeo rohita (Hamilton) is a member of the family Cyprinidae within the order Cypriniformes. It is native to the river systems of Bangladesh, India, Pakistan, Myanmar (Talwar and Jhingran, 1991). Among the world’s principal aquaculture species, rohu production ranked seventh (754 677 tonnes) in 1998 (FAO, 2000). In Bangladesh, this species is mostly found in the three river systems including Padma-Brahmaputra and Halda. With the expanding aquaculture practice in the country, rohu culture is practiced in semi-intensive and extensive systems in ponds, low-lying areas like haor and baor. The features that have made this species a potential candidate for aquaculture include faster growth rate, higher market price, greater feed utilization and ability to feed in all three columns in a water body (BBS, 2000). Even though the total fish production in Bangladesh has increased significantly over the last few decades (DoF 2009), it is still not sufficient to meet the growing demand of its population. This paves the way of enter imported fishes from neighboring countries into the domestic market (Kibria, 2007). It was reported that more than 80 MT of fish and fishery products enter into Bangladesh every day through the Teknaf border from Myanmar. In our preliminary study on the detection of formalin in fishes available in the domestic market, we found that fish imported from neighboring countries were contaminated with formalin ranging from 0.5-1%. Other investigations conducted by the Fish Inspection and Quality Control (FIQC) office of the Department of Fisheries (DoF) showed that formalin was added in imported fish somewhere in the marketing chain after entering the country. Several test conducted by FIQC showed that after landing in Teknaf port, no formalin was detected in fishes whereas formalin contamination was detected when samples were collected from the marketing channel. It is likely to assume that the fishes are dipped into formalin solution for a while by the some fish traders before transporting to the different retail markets (DoF, 2007). It is well known that formalin is injurious for human health. Formalin is a solution of 37% (w/w) of formaldehyde (H-CHO) in water which is used as a preservative in medical laboratories, as an embalm fluid and as a sterilizer. Formalin is also used in treatment against fish diseases caused by protozoa and fungi. Food and Drug Administration of the United States approved formalin for use in aquaculture as parasiticides and fungicides. It is, however, not approved for usage in