Investigating carotenoid loss after drying and storage of

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9. Discussion
Absence of cis-isomerisation was further observed during the storage of dried sweet
potato chips. During the storage of dried samples at ambient temperature in the dark (ca.
25ºC) in Mozambique for four months (Chapter 5), trans-!-carotene, 9-cis and 13-cis all
degraded following first order kinetics.
As opposed to light, temperature during storage was shown to have a very significant
impact on carotenoid catabolism of dried sweet potato in accordance with literature
(Cinar 2004; Kósambo 2004; Koca et al. 2007; Hidalgo and Brandolini 2008) (Chapter
8). It was also shown that carotenoid content of samples of dried OFSP stored in the
freezer (-20ºC) for four months remained constant (Chapter 2).
The effect of temperature (10-40ºC) that can be found in tropical and sub-Saharan
climates such as those of developing countries was evaluated during storage.
Carotenoids degraded following a first order kinetics of degradation in accordance with
many authors including Koca et al. (2007); Lavelli et al. (2007) working on dehydrated
carrots; Hidalgo and Brandolini (2008) working on wheat flour. A predictive model
(Arrhenius model) developed in laboratory was further assessed with data from the field
in Uganda (Chapter 8). This model was able to successfully predict the carotenoid
degradation as affected by temperature and storage time and could be used as a tool to
evaluate sweet potato dried chips shelf life.
9.5.3 Water activity
The lowest degradation of carotenoids occurred at the highest water activity level in
accordance with the studies on food model and on dehydrated sweet potato (Haralampu
and Karel 1983) and was explained by the protective effect of water against air oxidation
(Chou and Breene 1972). Water activity is an important parameter for the measurement
of food quality and preservation. Moreover water activity was proved to influence
carotenoid content in the storage of foodstuff (carrots (Arya et al. 1979; Lavelli et al.
2007); sweet potato (Haralampu and Karel 1983)) and β-carotene food model systems
(Chou and Breene 1972; Goldman et al. 1983) (Chapter 8). As compared with water
activity, temperature and oxygen had a stronger effect on carotenoid degradation
(Chapter 8).