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Composition of tomatoes and tomato products in antioxidants (WG1) page 73
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When tissues are analyzed, depending on the lipid and the collagen levels, digestive
enzymes such as lipase and collagenase must be added to improve further homogenisation
and extraction (Nierenberg and Nann 1992).
In tomato, the antioxidants are not distributed homogeneously. Seeds contained most
of the vitamin E in the fruit and skin and pericarp contained about five times more lycopene
than the whole tomato pulp (Le Maguer et al.1998) indicating that probably most of the
lycopene is bound to the insoluble fraction of tomatoes. Thus it seems necessary to
homogenize all the fruit and to use accurate seed and skin treatments to extract efficiently
both vitamin E and lycopene.
8.2 Storage of the samples
Stablity studies showed that at –20°C plasma β-carotene was only stable for 6 months
whereas tocopherol and vitamin A levels remained unchanged for 2 years, (Fig 14)
(Aebischer et al. 1999). However all carotenoids and vitamin E were shown to be stable in
plasma stored at –70°C for 28 months (Craft et al. 1988). At –80°C plasma β-carotene and α-
tocopherol levels were not affected up to 5 years (Aebisher et al. 1999). When plasma were
protected from light during processing and stored under nitrogen, vitamins A and E, and
carotenoids did not undergo any significant degradation after repeated freezing and thawing
cycles (Hsing et al. 1989, Zaman et al. 1993).