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Processing and Bioavailability (WG2) page 2
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Introduction
The lycopene in tomato products has always been considered very important, although
until the '80s the interest in it was confined to its characteristic as a red pigment and thus
responsible for the red colour of tomato products. The colour has been recognised by
regulatory authorities in establishing standards of quality. A bright red colour, typical of the
mature raw tomato, is taken as evidence of quality by processor and consumer alike.
Millardet in 1875 obtained a crude mixture containing a red pigment, referring to it as
solanorubin. The name was given by Schunck in 1903 after he had shown that the pigment
from tomatoes (Solanum Lycopersicum L.) had a different absorption spectrum than carotenes
from carrots (Nguyen and Schwartz, 1999).
A considerable body of information is available regarding pigment types and levels in a
wide range of tomato genotypes (Zscheile et al., 1996; Davis, 1948; Goodwin, 1952; Liu and
Luh, 1977; Yamaghuci et al., 1960).
During ripening, tomatoes change in colour from green, typical of chlorophylls, through
pink-orange to bright red, due to the development of carotenoids. These are polyenes, in
particular tetraterpenes, which originate from a head-to-tail condensation (with 1,4-bonds) of
several isoprenic units; they are divided into xanthophylls, which are oxygen-containing
carotenoids, and carotenes, consisting solely of hydrogen and carbon atoms. They present a
long chain of double bonds, most of which are conjugated. This chain is responsible for their
typical absorption of light in the visible region.
Of the carotenoids occurring in ripe tomatoes, lycopene, red in colour, is the last to form
and its formation increases especially after the breaker stage (colour change from green to
pink) of the berry. Earlier literature reported that lycopene was found only in the red coloured
strains (Zscheile, 1947). So far, little is known as to the effect of agricultural practices and
soil/climate factors on the oxidant content of tomatoes. It is plain, however, that factors such
as water, fertilisation, temperature and light have a bearing on carotenoid level in tomatoes, as
have variety, degree of maturity, harvest date, fruit growth and post-harvest storage (Sies et
al., 1998b).
Lycopene formation, for example, is inhibited at temperatures above 30°-32°C, whereas
it is favoured at temperatures from 16° to 21°C. The other carotenes occur in concentrations
lower than that of lycopene which, in ripe tomatoes, accounts for 85% of total carotenoids
(Leoni). Within the berry, lycopene level is higher in the outermost part of the mesocarp's