Abstract

Aim:
The knowledge of drying kinetics is of paramount importance for predicting and determining the drying behavior of food materials, and optimizing food drying parameters. Hence, the drying kinetics of rock fish cuts using NSPRI Smoking Kiln® (Model B) was evaluated to assess its smoke-drying performance.

Methods:
Rock Fish was procured at Bodija market and was transported to Nigerian Stored Products Research Institute (NSPRI), Ibadan Zonal office for further processing operations to take place. At the Institute Processing Center, Rock Fish were thus washed, sorted and degutted. They were cut into diverse fragments which include head, middle and tail. The source of power for the kiln was charcoal. Moisture loss was monitored, thus experimental data was generated. Drying rate was estimated and experimental moisture ratio was fitted into eight mathematical models to predict the rate at which moisture was lost in the rock fish cuts during the smoke-drying process. Statistical analysis was carried out and the models were evaluated for performance using coefficient of determination, R^2and Root Mean Square Error, RMSE.

Results:
The initial moisture contents of the fresh samples (Head, middle and tail) were 163.7794±0.0108% db, 163.7821±0.0149% db, and 165.0898±2.2709 db% while the final moisture contents of the dried samples (Head, middle and tail) were 2.4432±0.8500% db, 6.5792±2.3989 %db, and 16.1937±3.7415% db respectively. Drying rate of the different parts of the smoke-dried rock fish samples (Head, middle and tail) were 0.0058±0.0001a, 0.0049±0.0005b, and 0.0047±0.0005b kg/h respectively. Drying for all fish samples were completed in 25 hours. Drying predominantly took place at the falling rate for all samples. Middili et al. model gave the best fit to experimental data when compared with other models with highest R^2 and lowest RMSE values.

Conclusion:
NSPRI smoking kiln® (Model B) is efficient in smoke-drying of rock fish to safe moisture content, hence, giving the dried product a longer shelf life. It is therefore recommended, especially for commercial use.

Key words: Sebastes, Drying characteristics, Shelf-life extension, Smoking kiln, Performance evaluation