Investigating carotenoid loss after drying and storage of

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1. Literature review
(Rees, NRI, unpublished). Fibrillar structures might be more resistant because of
association between proteins and carotenoids. It is believed that the structure and
association between these three constituents may have an impact on the stability of
carotenoids in processing and their body absorption (bioavailability).
Bioavailability is defined as the fraction of carotenoid that is absorbed and available for
utilisation in normal physiological functions or for storage (Tanumihardjo 2002).
Through the mastication process and through digestion, provitamin A carotenoids are
extracted from the food matrix where they are associated with proteins and lipids (Furr
and Clark 1997). Enzymatic cleavage of provitamin A from plant origin into retinol (by
15,15’-dioxygenase) occurs in the intestinal mucosal cells (Tanumihardjo 2002). Retinol
is incorporated into chylomicra and transported from the lymphatic system, either to the
general circulation (Furr and Clark 1997) or to the liver to be stored (Sommer 1998).
Carotenoid absorption and availability for use in the body is therefore dependent on the
nature of carotenoids, the structure of chromoplasts and the resistance of food matrix
(raw or processed) to mastication and absorption. Although these factors are important
in understanding the context of carotenoid degradation “in vivo”, their influence,
however, was not further studied in this thesis. This present research work is restricted to
the determination of the level of carotenoid degradation during food processing and the
influence of physico-chemical factors on the β-carotene molecule in the sweet potato
during processing.
1.3.3 Factors affecting degradation of β-carotene
Disruption of the food’s cellular matrix by processing makes carotenoids more
vulnerable to oxidative degradation (Kósambo et al. 1998). Factors leading to the
degradation of β-carotene are illustrated in Figure 1-14.