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

Hii and Law - Solar Drying of Major Commodity Products
heat extraction fluid. Air was heated through dimpled vertical tubes in a water reservoir
and the whole unit was connected to a solar water collector. Considerable reduction in
drying time, as much as 30%, can be achieved based on the simulated results with energy
storage. The proposed drying configuration also enables the control over the quality
of the finished product without increasing the drying time.
3.3. PRODUCT QUALITY CONSIDERATION
The quality aspect of dried product is important in any drying system especially
in solar and sun drying. This is mainly due to the possible extended drying duration as
the source of solar radiation depends on the weather condition. The prolonged drying
duration, coupled with unfavorable drying condition could contribute to product spoilage
i.e. mould growth. Typically, the product quality of any dried products can be classified
into the physical, chemical, biological and nutritional parameters (Perera, 2005;
Sablani, 2006); whichever is applicable to both edible and non-edible products.
Not all commodities can be benefited from the use of solar drying in terms of quality
improvement i.e. no significant effect on quality, especially when compared against sun
drying. However, certain products are better when dried under mild drying condition as
compared to hot air drying. Cocoa is one such commodity where fast drying using hot air
will give a detrimental effect to the flavour of the dried product (Bravo and Mc Gaw,
1974). Certain products need to be cured for reasons related to physical and chemical
changes, and this cannot be accelerated via high temperature drying. This is especially
true for product that undergoes flavour development process. A specific chapter has
been included in this e-book which further explains the product quality aspects during
solar and sun drying.
3.4. REASONS FOR LIMITED USE OF SOLAR DRYING TECHNOLO-
GY
The adaptation of solar drying technology is relatively scarce especially in developing
countries. Most of these countries are producing some of the major commodities
for export worldwide i.e. chilli, herbs, spices, timber, cotton. Technology transfer activities
involved highly intensive extension activities and services in order to disseminate
the correct information and advice to the farmers especially those at the remote areas.
Government and non-governmental organization have to educate the right target groups
and promote the use of solar drying technology. In this regard, the level of adaptation is
still low due to several reasons which can be summarized as follow:
• High capital cost of installation i.e. solar panels, insulation, building.
• Lack of government incentive to encourage the use of new technology.
• No premium price is given for better quality product dried using solar drying.
• Farmers are reluctant to learn new technique and replace the conventional one
that has been used for decades.
• Difficulties in getting spare parts and lack of skilled personnel for periodic maintenance
job.
• Limited funding to carry out continuous and follow up extension work to promote
the use of solar dryers.
90 Drying of Foods, Vegetables and Fruits