Investigating carotenoid loss after drying and storage of

1.2.3 Sun drying
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1. Literature review
Solar and sun dryers are more environmentally friendly systems and are cheaper to
operate than artificial dryers because they use natural free energy. Consequently sun
drying is one of the lowest-cost preservation methods and is the most commonly used
drying method. However traditional open air sun drying involves a number of risks for
product quality including dust, insects, mammals, rain and provitamin A damaging UV-
sun radiation because of poor control over environmental factors. Improved sun drying
was therefore proposed by FAO (1985) in their “Expert consultation on planning the
development of sun drying techniques in Africa”. Clean smooth raised platforms,
blackened surfaces that absorb solar radiation more efficiently or woven mats and mesh
trays that facilitate the air movement around the product were recommended. An
example of improved sun dryer was a cassava chips dryer (TDRI/CIAT project)
consisting of trays with plastic netting (35 holes/cm) stretched on wooden frames and
supported by chicken wire (Figure 1-6).
Figure 1-6: Improved sun dryer - Cassava Drying Trays (Colombia). FAO (1985).
Trays were mounted on bamboo poles and sloped at the angle of repose to allow to chips
to face the wind (FAO 1985). When the wind was favourable, cassava chips spread in
the late afternoon were mostly dried over-night.