Investigating carotenoid loss after drying and storage of

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1. Literature review
drying retained more provitamin A carotenoids than open-sun drying (Mulokozi and
Svanberg 2003) (24% against 47% losses); in another study on leafy vegetables by Negi
and Roy (2000) carotenoid losses in solar and sun drying were similar though slightly
lower in solar drying (respectively 65% and 70%). When comparing shade and sun
drying, which are equivalent in terms of cost and drying technology, it was shown that
there was a significant improvement with shade drying of leaves compared to sun drying
(74% against 94% loss) (Mosha et al. 1994). An improved retention in shade drying than
in sun drying of cassava was also observed by Chavez et al. (2007). Kidmose et al.
(2007) corroborated this by demonstrating that shade drying OFSP variety Zappalo for
five hours generated a loss of only 21%. Better retention in shade drying in different
crops including sweet potato can be explained by minimal exposure to UV sun
radiations and lower temperatures than in sun drying (Chavez et al. 2007). However
there was an exception in the study by Negi et al. (2000) working on various tropical
plant leaves: the improvement of shade drying as compared to sun drying was not
significant. In this study, lower retention in shade drying may be explained by longer
drying times in shade drying as compared to sun drying.
From the literature, the levels of carotenoid loss varied greatly between the authors for
solar, shade and sun drying. The level of carotenoid loss also varied with the different
food products analysed using the same dryer. In a study on carotenoid retention of
OFSP, carrot, collard greens in solar drying levels of loss were found to be significantly
different being 10%, 59% and 22% respectively (Mdziniso et al. 2006). The author
suggested that the difference in initial moisture contents of these food products
(respectively 75.8%, 90.5% and 89.1%) would have influenced the level of carotenoid
lost after drying.
Effect of variety
The effect of variety was also investigated. It was found that carotenoid retention was
very variable between varieties. Thirteen Kenyan OFSP varieties, from 1.64µg.g -1 to
422µg.g -1 trans-β-carotene content on a dry basis (db), presented losses on chips varying
between 6 and 57% after electric cabinet drying at 58 o C for 4 hours (Kósambo 2004).
Twenty three varieties with a total carotenoid content of between 2 and 632 µg.g -1 db
had losses ranging from 0 to 80% (Hagenimana et al. 1999). In both studies, reductions