Investigating carotenoid loss after drying and storage of

CHAPTER 8.
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8. Study under controlled conditions
CAROTENOID DEGRADATION AND FORMATION OF
VOLATILE COMPOUNDS IN DRIED SWEET POTATO
CHIPS STORED UNDER CONTROLLED CONDITIONS
OF TEMPERATURE, HUMIDITY AND OXYGEN
8.1 INTRODUCTION
Both field studies in Uganda and Mozambique clearly indicated that storage, rather than
drying, was a critical step for preservation of provitamin A in dried sweet potato
(Chapters 4 and 5). Later pre-treatment studies failed to significantly reduce carotenoid
loss in storage (Chapter 6). It was also demonstrated that carotenoid degradation due to
enzymatic activity was unlikely (Chapter 7). Following these research studies, there was
a further need to measure the separate impact of the main factors, which are temperature;
oxygen concentration and humidity, on carotenoid breakdown in sweet potato flour
during storage. The conditions in the field did not allow evaluation of these factors
separately. In this current chapter, experiments under controlled conditions were carried
out in order to measure more precisely the separate impact of the various factors on
carotenoid degradation. The kinetics of carotenoid degradation were determined and the
production of volatile compounds was tentatively related to the carotenoid breakdown.
The first hypothesis was that the degradation of carotenoid by temperature can be
predicted by a mathematical model. The main objective of this study was therefore to
measure the degradation of !-carotene in sweet potato chips during storage influenced
by temperature taking into account oxygen and water activity and then predict, by
modelling, thermal degradation under a range of conditions found in tropical countries.
The second hypothesis was that the degradation of carotenoids could be observed from
the degradation products formed. A secondary objective of the study was then to relate
the degradation of !-carotene to the formation of volatile compounds. Degradation of
standard !-carotene has already been studied using both High Performance Liquid