Effect of drying in Solar-Biomass hybrid Tunnel dryer on Biochemical, Microbial and Sensory Properties of Mackerel (Rastrilliger Kangurta)

Drying of mackerel was conducted using solar biomass hybrid tunnel dryer (S-BHTD) and open sun drying (OSD) at air temperatures 32.4–57.7°C, relative humidity of 23.9–85.8% and air flow rate 0.20–0.6 ms⁻¹. Solar radiation ranged between 287–898 Wm⁻² during the experimentation. During the night time, drying was carried out by combusting biomass. The fresh mackerel dried in experimental dryer and in open sun drying achieved the final moisture content <17% (w.b.). The drying time required in S-BHTD was 21 h. The overall drying efficiency of the solar-biomass hybrid tunnel dryer was estimated to be about 5.42 during fish drying. S-BHTD significantly influenced the biochemical properties of dried mackerel. Mackerel dried by using S-BHTD showed very high corresponding coefficients of determination, where all R² were greater than 0.85, except histamine value. In experimental dryer, microbial growth was not found except TPC (<30 cfu/g) which was within the acceptable limit. Contour plots of dried mackerel in S-BHTD dryers also showed that for all the sensory attributes examined, panelists preferred more the fish dried with S-BHTD than OSD. The optimum points for all sensory attributes of dried mackerel evaluated at temperatures ranged from 45–55°C for 20–30 h. Biochemical, microbial analysis and sensory evaluation showed that the dried mackerel remained acceptable after 120 days of storage at ambient temperature. The data showed that the drying in S-BHTD resulted in high quality dried mackerel. The study suggests that the experimental dryer could be used successfully to produce high quality dry fish.