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Processing and Bioavailability (WG2) page 45
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(sauces) involving a partial solubilisation of the lycopene and consequently greater reactivity
and degradation.
With regard to other tomato antioxidants, it has been shown that ascorbic acid
concentration decreases during storage in various conditions.
As a final consideration, it seems that more research work is needed to understand the
behaviour of the whole antioxidant pool in processed tomato products. Relationships between
individual components should be studied, in order to reveal mutual protective or pro-oxidative
effects. Researchers usually evaluate the antioxidant power of products in terms of
concentration of the various antioxidant constituents: this kind of determination is useful but
not exhaustive in explaining the antioxidant effectiveness of food. The antioxidant activity of
tomato products should be measured through “functional methods”, that is, methods allowing
for the evaluation of the protective effects against oxidative reactions. These methods should
use model oxidative reactions similar to those occurring in vivo and in food products.
The most stimulating objective of the Concerted Action was to evaluate the presence and
the actual bioavailability of lycopene and other antioxidants (in the forms in which they are
present in processed tomato products) for humans.
Although there are a number of comparative studies on the bioavailability of lycopene
from tomato products, there are no validated methods for the quantitative assessment of
bioavailability of the carotenoids; not even for β-carotene, which is the most well studied.
There are only few studies on the bioavailability of lycopene in man, one indicating that
absorption of lycopene is greater from heat treated tomato juice than from untreated juice and
the other indicating that absorption from tomato paste is greater than from fresh tomatoes.
What is known, however is that the physical state and processing history of food has a very
marked effect on the availability of these compounds for absorption, hence, disruption of the
food matrix and thermal history via processing technique could be the most important factor
determining bioavailability. It is also known that bioavailability of carotenoids is markedly
affected by the fat content of the diet, since the presence of lipid is essential for the extraction
of the carotenoid from the aqueous bulk of the food and the formation of mixed micelles via
which the carotenoids are absorbed by enterocytes and transfer to the tissues (via plasma
lipoproteins). Carotenoids are passively absorbed lipophilic compounds and their
bioavailability is therefore affected by those factors that influence the mass transfer of the
carotenoids from the food into the mixed micelles, which can be absorbed by the gut.
Interestingly, absorption can be improved by cooking and homogenising the food to break
down the cell structure, and by cooking in the presence of oil or fat.