Nutritional Variation in Five Indigenous Fish Species Processed with Traditional, Improved, and Institutional Kiln Technologies in Northern Nigeria

Fish constitutes a vital source of animal protein and essential nutrients for many households in Northern Nigeria, where traditional smoking remains a dominant preservation method despite its limitations in retaining nutritional quality. This study investigated the effects of three smoking kiln technologies—traditional market kiln, modified drum kiln, and institutional FUTY kiln—on the proximate composition of five native freshwater fish species: Bagrus bayad, Clarias gariepinus, Heterotis niloticus, Mormyrus rume, and Oreochromis niloticus. A total of 150 fish samples (30 per species) were smoked and analyzed for crude protein, lipid, ash, moisture, fibre, and dry matter contents using standard AOAC procedures. Results showed that the modified drum kiln consistently preserved the highest protein values, with Heterotis niloticus reaching 61.72%, compared to 50.12% and 57.00% in market and FUTY smoked samples respectively. Moisture content was lowest in samples smoked using the modified kiln (as low as 3.33%) and highest in FUTY samples (up to 27.41%). Lipid content peaked in Heterotis niloticus smoked with the FUTY kiln (11.20%), while ash content varied slightly across all treatments. The study concludes that the modified drum kiln offers superior drying efficiency and nutrient preservation, particularly for protein and moisture, while the FUTY kiln retained more lipids in some species. The findings underscore the importance of kiln type in postharvest fish processing and recommend the widespread adoption of improved smoking technologies to enhance nutritional quality and shelf life.