Investigating carotenoid loss after drying and storage of

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4. Ugandan field study
Table 4-1: Source, flesh colour and yield of selected orange fleshed and yellow
fleshed sweet potato cultivars. Source: Mwanga et al. (2003); Mwanga et al. (2007).
Cultivar Original source Flesh colour
Typical reported
fresh root yield
(tonnes per ha)
Ejumula Eastern Uganda Deep orange 36.6
Kakamega (SPK004) Western Kenya Yellow/light orange 31
SPK004/1
Yellow/light orange 7.4-59.7
SPK004/1/1 Bred from SPK004- Yellow/light orange 7.0-43.2
SPK004/6 Uganda
Orange 4.6-50.4
SPK004/6/6 Orange 7.9-38.3
4.2.2 Handling and processing prior to drying
Sweet potato roots were trimmed, weighed, washed, and drained in the open air for
about 30 minutes. Unpeeled roots were chipped using a rotary disc type chipper (Tonnet
Company, Kampala, Uganda). Exposure to light was minimised by using black
polythene bags to cover the samples. Chips (thickness 2 mm; width 5 mm; length 69
mm on average) were thoroughly mixed before drying.
4.2.3 Drying of sweet potato chips
Sweet potato chips were dried using dryers that varied in design. Different types of
coverage were selected to have different screening effects on UV-radiation for the tent
dryers since it was hypothesised that screens, which filter selected UV wavelengths, can
reduce losses of carotenoids during drying and that dryer design can influence
carotenoid losses during drying. Details of the dryers are given below (Figure 4-1):
• Open air sun dryer
• Tent dryer with UV resistant polythene (Lumitherm BPI-Visqueen®, Herfordshire,
UK)
• Tent dryer with non-UV resistant polythene (locally bought in the market in Uganda)
• Tent dryer with red resistant polythene (Allplass®, Hertfordshire, UK)
• Tunnel dryer (UV-resistant polythene sheeting of unknown origin).
The chips were spread over black plastic sheeting that absorbed the sun heat apart from
the tunnel dryer where they were spread of cloth netting (mosquito mesh).