2.1. Sample Collection: Three freshwater fish species; chapila (Gudusia chapra), kaika (Xenentodon cancila) and Baim (Mastacembelus pancalus) were collected from the Meghna River early in the morning. These experimental fishes were collected from the Meghna River during very early in the morning. They were brought to the laboratory (IFST) in iced condition. Fresh mature fish samples were transported to the research laboratory in sterile polythene bag to avoid any type of microbial contamination.
2.2. Place of experiment: The whole experiment was carried out at the laboratory of Fish Technology and Food Microbiology Section of the Institute of Food Science and Technology (IFST) of Bangladesh Council of Scientific and Industrial Research (BCSIR), Dhanmondi, Dhaka and only mineral work was done in Center for Advanced Research in Science (CARS).
2.3. Preparation of the smoked-dried product: The experimental fish was quickly carried to the laboratory as early as possible to avoid any spoilage during that period. At first, the collected chapila fish was discaled while kaika and baim fish was beheaded. Then three fish samples were gutted and washed properly with clean water. The dressed fish samples were then weighed and prepared for further processing.
2.4. Fish Smoke-drying: The fishes were smoked in improved traditional type of smoking kiln. The fish smoking kiln was operated by first loading tamarind wood chips and rice-husk into the heat chamber, preheating for some minutes and then loading the fish-samples onto removable wire mesh trays in its central chamber for the smoke-drying process. The desired temperature (75-80°C) was maintained manually. Smoking was done approximately for 4 hours. During the smoking fish samples were turned upside down in the middle period, to make the sample smooth and steady in texture and appearance. After completing the smoke-drying process, the smoke-dried fishes showed characteristic attractive golden brown color and acceptable texture with smoky flavor, which was followed by cooling for 20-30 minutes at ambient temperature to make fish muscle compressed and facilitate to prevent breaking of smoked products.
2.5. Storage for shelf life study: The marked, cooled smoked-dried fish samples were then packed in transparent polythene bags. Bags were then sealed by using an electrical sealing machine (PFS-300). After that, three groups of smoke-dried fish product were then kept for storage at room (260C-310C) temperature for further analysis.
2.6. Sample preparation: At first the collected fresh fishes, as well as smoke-dried fish samples, were fairly minced and homogenized in a blender for the analysis.
2.7. Analysis: For quality analysis-Sensory evaluation, biochemical and Microbial analysis were done. Sampling was done on every 2nd month for fish kept at room temperature (260C-310C). Important mineral composition i.e. Ca, Mg, Cu Zn, Fe and Mn were determined in fresh smoke-dried fish products. The analytical methods are given below: Physical changes were assessed by the sensory method as described by Larmond. The moisture, fat, and ash contents of the fish were determined by AOAC method. The crude protein of the fish was determined by Micro-Kjeldhal method. TVB-N was determined by Conway modified micro-diffusion technique. Microbial analysis (TVC) was done according to the Standard methods of [26]. Samples for mineral analysis were prepared according to recommendations of Perkin Elmer’s procedures of Atomic Absorption Spectrometer.