A thesis submitted in partial fulfillment for the requirements for the degree Master of Science, School of Environment, Resources, and Development

Thesis (M.Sc.) - Asian Institute of Technology, 1995

The first part of this study was to determine and classify off-flavour of Nile tilapia in various management regimes. Fifty fives fish samples were collected from 8 provinces in Central and Eastern Thailand. Fish were skinned, dressed and bones removed before storage in a freezer. Fillets were portioned into 10 g pieces, wrapped in a aluminum foil and cooked in a pressure cooker. A taste panel evaluated the cooked fish for off-flavour. The taste panel classified and rated fish numerically as excellent (7-10), good (4-6.9) and poor (0-3.9). Off flavours were found in most of the fish samples consisting of a total of 23 flavours. There was no relationship between environment parameters and off-flavour. Live fish, identified by the panel as off-flavoured fish , were transported from the farm and 80 fish were stocked into each circular tank (1.5 m diameter). Static and exchanged of both freshwater and 10 ppt brackish water were used to treat off-flavour. It was found that off-flavour of tilapia sized between 450-600 g could be reduced or eliminated within 3-7 days. Three-way analysis of variance showed that treatment durations had a significant effect but there was no significant difference in either static or exchange of both freshwater and 10 ppt brackish water. Exchanged freshwater would be the most suitable method used for reducing off-flavour of Nile tilapia in inland fish culture