Solar Drying: Fundamentals,Applications and Innovations - National ...

Bala and Hossain - Solar Drying of Fishery Products
za et al. (2009) conducted organoleptic tests of different type of sea fish available in
Bangladesh. The organoleptic characteristics of dried fish were determined to find the
suitable drying temperature. The quality of the dried fish products was assessed on the
basis of color, odor, texture, insect infestation, presence of broken pieces and overall
quality. The color of solar tunnel dried silver Jew fish, Bombay duck, big-eye tuna and
ribbon fish were from whitish to light brown color, whereas the Chinese pomfret was
light-intense orange. Odor was very much natural in all samples. No insect infestation or
broken pieces were found around the products. All these results were not significantly
different (P < 0.05) for two different temperature ranges for production of dried fish.
The overall quality of the products produced in the drier was of excellent to good quality
for all five marine fish species. It was observed that the flavor and color are important
factors influencing the overall consumer acceptance.
4.5. SOLAR DRYING PERFORMANCES OF SELECTED FISHERY
PRODUCTS
Large scale field studies were conducted at Bangladesh Agricultural University, Mymensingh,
Bangladesh and Silpakorn University at Nakhon Pathom, Thailand to demonstrate
the potentiality of the solar driers for production of high quality dried fruits, vegetables,
spices, medicinal plants and fish. Packages of technology for solar drying of fish
have also been developed at Bangladesh Agricultural University, Mymensingh, Bangladesh.
The drying air temperature can be set easily in the solar tunnel drier while the temperature
profile is regulated by solar radiation. Of course, the design should be such that
the drying air temperature must not exceed the maximum permissible drying air temperature
for a long period so that the cooking of the fish is avoided.
Figure 4.6 shows the variations of the ambient air temperature and relative humidity
of a typical drying run during solar drying of Bombay duck at Cox’s Bazar in Bangladesh.
The ambient relative humidity decreases with the increase in the ambient temperature.
The second day of the experiment was bright in the morning and cloudy in the
afternoon which resulted in the sharp fall and rise in the relative humidity.
The patterns of temperature changes of the drying air at the collector outlet and airflow
rate of a typical drying run are shown in Figure 4.7. The variation of the airflow rate
helped to regulate the drying temperature. During high insolation period more energy
was received by the collector which was intended to increase the drying air temperature,
but it was compensated by the increase of the air flow rate. While during low solar insolation
period less energy was received by the collector and airflow rate was low. Hence
the decrease in temperature due to low solar insolation was compensated by the increase
in temperature due to low airflow rate. This resulted in minimum variation of the
drying air temperature throughout the drying period and saved the product from overheating/partial
cooking of fish due to excess temperature.
102 Drying of Foods, Vegetables and Fruits