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Processing and Bioavailability (WG2) page 3
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cells; here it builds up in vesicles (aged chloroplasts) which originate from chloroplast
transformation-degeneration and which form, with the carotenoid molecules, the so-called
LHC (light-heaping complexes). These complexes consist of sequences of hydrophobic
membrane-linked proteins containing several pigment molecules coagulated in the form of
elongated needle-shaped crystals (Voet et al., 1991). Laval-Martin (1974) categorized tomato
chromoplasts into two types: globulous chromoplasts, containing mainly β-carotene found in
the jelly part of the pericarp and other chromoplasts found in the outer part of the pericarp
containing voluminous sheets of lycopene. The development and ultrastructure of these sheets
of lycopene were studied by Ben-Shaul et al., and named crystalloids (or coagula, or clots).
In the last decade, the red pigment has also been seen as a possible natural antioxidant
compound, with promising implications for human nutrition and health.
Vegetable products, including tomatoes, contain many substances which may have
beneficial effects on the health, providing protection from certain pathologies correlated to
oxidative processes. These substances have differing functions, such as free radical
scavengers, singlet oxygen quenchers, metal chelants and inhibitors of enzymes involved in
the formation of the active species of oxygen (Di Mascio et al., 1989). Several antioxidants
are present in tomatoes (carotenoids, vitamin C, polyphenols, vitamin E), although, thanks to
its specificity, lycopene has been the main centre of attention. Tomato is the main dietary
source of lycopene, the typically red-coloured carotenoid. Other carotenoids, such as β-,γ- and
ζ-carotene, lutein, phytoene and phytofluene, are present, though in much lower
concentrations. Tomato is an important source of ascorbic acid, which exerts a well-known
antioxidant and nutritional effect. Like other vegetables, the tomato contains a number of
polyphenolic compounds, which can exert antioxidant activity. Finally, tocopherols are also
found in tomatoes, though in low concentrations. The antioxidant composition of the tomato
is complex and rich, and optimisation criteria of processing and storage technologies should
take into account the preservation of the whole antioxidant pool and of its functional
properties.
In most Western diets the majority of carotenoids are derived from green vegetables,
carrots, tomatoes and tomato products (Foreman et al., 1993, Bolton-Smith et al., 1991),
although in some parts of the world other food items may be a major source, e.g. sweet
potatoes. Lycopene concentration in plasma normally ranges from around 50-800 ng/ml (0.1-
1.5 µmol/l) depending upon intake. This lycopene is almost exclusively derived from