Investigating carotenoid loss after drying and storage of

Transmittance (%)
101
4. Ugandan field study
Figure 4-1: Solar dryers. From left to right: UV-polythene resistant; non-UV
resistant; red-polythene; tunnel dryer and open sun-air dryer
Transmittance of the polythene sheetings of tent-dryers (UV resistant, non-UV resistant
and red) were measured by spectrophotometer measurement between 200-800nm
(Figure 4-2) (see Chapter 2).
100
90
80
70
60
50
40
30
20
10
UV resistant polythene Lumitherm
Red polythene
Simple polythene
0
200 240 280 320 360 400 440 480 520 560 600 640 680 720 760 800
Wavelength (nm)
Figure 4-2: UV/visible spectrum of polythene sheeting used in drying studies
Polythene sheeting had different transmittance toward sun light. Red plastic sheeting
absorbed at wavelengths between 300-600 nm at which provitamin A is reportedly
sensitive (part of UVA and visible). Sattar et al. (1977) and Lennersten and Linghert
(2000) reported that when exposed to sunlight radiation, provitamin A is more sensitive
to ultra-violet (UV) rays, especially at wavelengths close to the maximum absorption of
!-carotene of 450 nm and, in general, short wavelengths less than 470 nm cause the most
!-carotene degradation. UV-resistant plastic reduced transmission of most UV-
wavelengths: between 200-240 nm (UVB and UVC) and between 260-370 nm (UVB,
UVA). Simple polythene was not wavelength selective.