Investigating carotenoid loss after drying and storage of

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9. Discussion
reduce the storage time up to two months and favour drying and/or storage of varieties
with very high initial carotenoid content such as Resisto variety. In summary therefore it
has been demonstrated that drying of OFSP had a limited effect on !-carotene retention
but storage had a major impact. If dried OFSP is to make a major contribution to the
vitamin A requirements of children then storage needs to be limited in time. The shelf
life (typically 1-4 months) will depend on the initial carotenoid content of the dried
OFSP (typically 100-400 µg.g -1 ).
Factors influencing the carotenoid retention during drying, and storage, were examined.
Chip size, variety or pre-treatment (blanching; chemical pre-treatment) showed a limited
effect on carotenoid stability. Therefore the fundamental factors influencing carotenoid
degradation have been investigated in particular during storage. Light has negligible
effect on carotenoid degradation under these conditions. Water activity has an effect but
it was limited. Temperature and oxygen are the main parameters that would need control
for the reduction of carotenoid degradation in particular during storage. Low temperature
storage under nitrogen, under vacuum or with an oxygen absorber should be envisaged
but clearly this would pose great problems for small scale farmers.
Further research work is needed in particular to solve the issue of high carotenoid losses
during storage considering oxygen and temperature as main constraints, and to develop a
deeper understanding of the mechanisms of carotenoid degradation in a dried food
product such as dried orange-fleshed sweet potato. The research questions generated
from this work deal with various research fields. They are as follows:
• How does one reduce carotenoid loss in storage? Could affordable packaging under
vacuum, for instance, be developed and could samples be stored at reduced
temperature? These types of storage conditions may be expensive for the local
farmers or processors in developing countries. Economic feasibility of these
packaging or storage facilities needs to be determined. Storage at low temperatures
or under specific packaging may be valuable when the product is sold into higher
value marketing chains.
• What is the relationship between sweet potato composition and stability? In
particular, what is the relationship between sweet potato genes, dry matter content