Investigating carotenoid loss after drying and storage of

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1. Literature review
Centenial) has identified carotenoids from the biosynthesis chain being "-carotene
(86%), phytoene (3%), phytofluene (2%), $-(zeta) carotene (2%), #-carotene (1%),
violaxanthin (0.06%) (Purcell and Walter 1968).
Because of their hydrophobic (lipophilic) nature, carotenoids are associated with lipid-
protein complexes (Vishnevetsky et al. 1999). In plant cells, carotenoids are
incorporated in semi-autonomous organelle structures. In leaves, carotenoids are situated
in the chloroplast although in fruits or other parts of the plant, roots for example,
carotenoids are located in chromoplasts (Figure 1-13).
Figure 1-13: A parenchyma cell containing chromoplasts. Each red dot is a
chromoplast that contains carotenoids. Webb (2009).
In leaves and raw green vegetables, where carotenoids are present in the chloroplasts,
they are linked to protein and chlorophylls that are green in colour and mask the orange
colour of the carotenoids (Bartley and Scolnik 1995; Rodriguez-Amaya 1997;
Vishnevetsky et al. 1999). Chromoplasts usually derive from chloroplasts. During the
transformation of chloroplasts into chromoplasts, the photosynthetic apparatus
disintegrate and carotenoids accumulate in the novel plastid. This transformation can be
observed, for instance, in autumn leaves or during fruit ripening. Microscopic
observation of chromoplasts has revealed differential accumulation of carotenoids that
led to five different classes: globular, crystalline, membranous, tubular, and fibrillar
(Vishnevetsky et al. 1999). This classification is on the basis of carotenoid-containing
structures: polar lipids, carotenoids, proteins (Vishnevetsky et al. 1999). For instance
globular chromoplasts are characterised by a very high ratio of apolar to polar
components (10:1) (where carotenoids represent about 15-25% of apolar components).
Fibrillar structures, however, are characterised by a low ratio of apolar to polar
components (1:1) with xanthophylls and equal contents of proteins and lipids
(Vishnevetsky et al. 1999). In sweet potato, the structure of chromoplasts is not known