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

Bala and Hossain - Solar Drying of Fishery Products
4.1. INTRODUCTION
Fish is the major source of animal protein and important food item in many Asian
countries. In poor households fish intake is 13 and 83 g raw whole fish per person per
day; the frequency of intake of small fish is high, and made up to 50-80% of all fishes
eaten during the fish production season in rural Bangladesh and Cambodia (Roos et al.,
2007). Dried fish is also popular because of its special taste and flavor. Dried and seasoned
squid products, dried fish such as Bombay duck and pomfret, dried shrimp and
dried shark fin are some of the most popular items consumed in Asian countries.
Drying is the oldest preservation technique of agricultural products and the traditional
method of sun drying is widely practiced to preserve fish and shrimp in many
parts of the world. In developing countries, including Bangladesh, traditional fish-drying
is practiced on the ground, raised bamboo platforms and bamboo made structures
(Figure 4.1). The drying process in the sun takes usually about 1 week depending on the
climatic conditions. The longer duration of drying causes considerable spoilage, blowfly
infestation, broken pieces and contamination with filth and soil particles. Some reports
indicate that losses from insects, animals and weather may be up to 30 to 40% (Hollick,
1999; Wall et al., 2001). To avoid insect infestation, insecticides are applied in Bangladesh
and that creates the risk of health hazards. Besides, considerable postharvest could
occur during processing, storage and during different stages of marketing channel. The
physical and organoleptic qualities of most of the traditional sun-dried products available
in the market are also not satisfactory for human consumption.
Figure 4.1. Drying of fish in bamboo made structures
Solar drying can be considered as an elaboration of sun drying and it is an efficient
system of utilizing solar energy (Bala, 1997a & 1998; Zaman and Bala, 1989;
Mühlbauer, 1986). The tropics and subtropics have abundant solar radiation. Hence, the
obvious option for drying would be natural convection solar driers. Many studies on
natural convection solar drying of agricultural products have been reported (Excell and
Kornsakoo, 1978; Excell, 1980; Oosthuizen, 1995; Bala and Woods, 1994 & 1995; Sharma
et al., 1995). Considerable studies on simulation and optimization have also been
reported (Bala and Woods, 1994 & 1995; Simate, 2003). The success achieved by indirect
natural convection solar driers has been limited, the drying rates achieved to date
are still not very satisfactory (Oosthuizen, 1996). These prompted researchers to devel-
Drying of Foods, Vegetables and Fruits 97