Investigating carotenoid loss after drying and storage of

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9. Discussion
Further information about the pattern of degradation of carotenoids during storage of
dried food products was also obtained.
The main findings are discussed below.
9.2 QUANTIFYING CAROTENOID LOSSES DURING DRYING
9.2.1 Levels of carotenoid loss during drying
The effects of drying treatment and chip size on carotenoid losses in OFSP were
investigated. An important finding was that losses after sun drying were relatively low
in comparison with what was expected when starting the research project. This was
relevant because few literature reports had been found on this subject. A report by the
International Center for Potato (CIP) indicated levels of trans-!-carotene loss of 72%
from sun-dried OFSP chips of Jonathan variety and 83% of Kakamega variety in Kenya
(Kósambo 2004). A presentation at the launch meeting of the HarvestPlus Reaching End
Users project (April 2006, Kampala, Uganda) by the program director Howarth Bouis
similarly portrayed losses of carotenoid in sun drying of OFSP between 85 to 91% (van
Jaarsveld unpublished). Moreover farmers in Soroti who were interviewed in December
2006 reported that OFSP or white fleshed-sweet potato dried in the traditional way (on
rocks) could be the same colour after drying, which further indicated that carotenoids
could have been entirely degraded during drying. The first results from a pilot-scale
study in the South of France showed a different picture. Levels of loss in trans-β-
carotene on Rubina® OFSP chips were 34% after sun drying for one day (Chapter 3 or
Bechoff et al. 2009 in Appendix 4a). In the further field studies at the National
Agricultural Research Laboratories, NARO in Uganda, levels of loss in sun-dried chips
on Ejumula and Kakamega varieties were only 9.0% and 8.4% respectively (Chapter 4
or Bechoff et al. 2010a in Appendix 4b) and in Mozambique losses sun-dried chips on
MGCL01 and Resisto were 4.9% and 16.5% respectively (Chapter 5 or Bechoff et al.
2010c) after drying for one day up to three days (with coverage at nights). Hence it was
shown in all the studies (France, Uganda, and Mozambique) that sun drying could retain
most of the carotenoid content. These levels were found consistent with a more recent
study resulting from collaboration between the Chalmers University, Sweden and the
Makerere University, Kampala, and involving the same varieties. The level of trans-β-