Investigating carotenoid loss after drying and storage of
Investigating carotenoid loss after drying and storage of
Investigating carotenoid loss after drying and storage of
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60<br />
2. Assessment <strong>of</strong> Methods<br />
!-carotene st<strong>and</strong>ard curve with five concentration levels (4.38, 15.34, 30.69, 46.08,<br />
61.38 mg.l -1 ) had a coefficient <strong>of</strong> correlation <strong>of</strong> 0.9986 indicating excellent linearity<br />
(y=4.9565.10 -3 x where y is the concentration in mg.l -1 <strong>and</strong> x the area).<br />
2.3.4 Carotenoid analysis by HarvestPlus method (UK <strong>and</strong> Ug<strong>and</strong>a)<br />
Extraction<br />
Total <strong>carotenoid</strong>s extraction <strong>and</strong> analysis were based on Rodriguez Amaya (2001) <strong>and</strong><br />
Rodriguez Amaya <strong>and</strong> Kimura (2004). A portion from the homogeneous representative<br />
sample (fresh or dried) was homogenised with methanol: tetrahydr<strong>of</strong>uran (THF) (1:1)<br />
using a Polytron PT1200E (Kinematica, Switzerl<strong>and</strong>) homogeniser for one minute. The<br />
extract was filtered through a porosity 2-sintered glass funnel by vacuum <strong>and</strong> rinsed with<br />
methanol: THF until there was no colour left in the filtrate. The extracts were combined<br />
<strong>and</strong> poured into a 500 ml-separatory funnel where 40 ml <strong>of</strong> Petroleum ether (PE) had<br />
been added. After washing thrice with desionised water (200 ml) the upper-PE phase<br />
containing the extract was collected in a 100 ml flask. The PE phase was dewatered by<br />
addition <strong>of</strong> anhydrous sodium sulphate until some crystals remain undissolved, then<br />
filtered into a 50 ml volumetric flask through glass wool <strong>and</strong> made up to volume (see<br />
Appendix 3).<br />
Spectrophotometric reading<br />
In Ug<strong>and</strong>a (see Appendix 3), total <strong>carotenoid</strong> content was determined using a Genesys<br />
(Model 10 UV) UV-visible spectrophotometer to measure absorbance at 450 nm in<br />
PMMA cuvettes. Concentrations were determined by comparison to a st<strong>and</strong>ard curve<br />
using pure !-carotene (Purity > 95%; UV synthetic, powder, type I (10g) Sigma-Aldrich,<br />
UK) <strong>and</strong> absorption coefficient <strong>of</strong> !-carotene in PE <strong>of</strong> 2592 (Rodriguez-Amaya 2001,<br />
Rodriguez-Amaya <strong>and</strong> Kimura 2004). Carotenoid content was calculated using<br />
Equation 2-2 given by Rodriguez Amaya <strong>and</strong> Kimura (2004):<br />
4 A<br />
C = 10 (Equation 2-2)<br />
A<br />
1%1 cm<br />
Concentration (C in mg.l -1 ) was calculated by Lambert Beer law from the absorbance<br />
(A). A1%1cm is the absorption coefficient <strong>of</strong> !-carotene in PE (2592) for 1cm -1 -path<br />
length.<br />
A !-carotene st<strong>and</strong>ard curve with seven concentration levels (0.4514, 0.9028, 1.8056,<br />
2.2569, 2.7083, 3.1597, 3.6111 mg.l -1 ) had a coefficient <strong>of</strong> correlation <strong>of</strong> 0.9974
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