Investigating carotenoid loss after drying and storage of

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5. Mozambican field study
good as the use of a mechanical chipper on the retention of carotenoids. On the other
hand, the effect of variety was significant in drying and storage. More carotenoid losses
were obtained with the variety having the highest moisture content immediately after
drying but less carotenoid losses were obtained with this variety during subsequent
storage. These observations require investigation on more varieties as this was noted in
the research station based study (Chapter 4).
Provitamin A losses during storage were high and those were considered to be slightly
greater than the losses determined on-station in Uganda (results after four month-
storage). Higher losses in the on farm-study in Mozambique may be explained by higher
temperatures and lower relative humidity especially in the day. Moreover the samples in
the research station in Uganda were stored in a room and therefore protected from
outside elements such as wind, dust whilst the samples stored on-farm were stored in
jute bags hung inside a mud house and not protected from these elements. In both cases,
however, the conclusions were similar in that the levels of losses were high and some
quality issues (smell and insects) were associated with longer storage durations (though
their impact was not specifically evaluated). In order to meet a significant part of daily
nutritional requirements (see Chapter 4), provitamin A chip samples should not be stored
for more than two months for MGCL and three months for Resisto.
For the rapid determination of carotenoid bleaching in sweet potato flour, a colorimetric
method was recommended as a non-destructive technique compared to
spectrophotometric or HPLC techniques. This could be used without requiring to any
equipment other than a colorimeter and therefore adapted for on-farm studies.
Changes in the main carotenoids mainly fitted a first order kinetics degradation during
storage in accordance with literature. There were few qualitative differences in
carotenoids between un-stored and stored samples by HPLC. An increase in the
concentration of products of degradation of #-carotene was not observed by HPLC; but
when analysed by SPME/GC/MS production of volatile degradation products (#-ionone;
#-ionone 5,6 epoxide and dihydroactinidiolide (DHA)), was observed in relation with
the quantity of #-carotene degraded. This helped understand the degradation of
provitamin A in dried sweet potato but further investigation is required to measure
volatile production with storage time and further understand pathways of degradation.