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Processing and Bioavailability (WG2) page 21
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Also for Zanoni et al. (1998) lycopene appeared to be stable during drying, but not during
the storage of the dried product, and thus storage conditions also require optimisation for
product moisture, time and temp. of storage, and exposure of product to air and light. The
authors observed a marked total lycopene loss (>50% and >70% after 90 days) during storage
of powdered air-dried tomatoes (≅10% moisture) at 37°C in the dark in the presence of air.
In a recent work, Anguelova and Whartesen (2000) affirmed that in tomato powders
lycopene was degraded 30% and 60%, during 6 weeks of storage at 6 °C 45 °C respectively
(Fig.2).
Reviewing available data on the
fate of lycopene during the
production and storage of tomato
powders, Boskovic (1979) proposed
a pathway for all-trans lycopene
degradation. This pathway involves
an initial reversible stage, when alltrans
lycopene isomerises into monocis
and/or poly-cis lycopene. These
isomers are energy-richer and
relatively more reactive than the alltrans
form, which is a fully stretched,
planar molecule. The reversibility of
the isomerisation reaction is
explained by the return from an
unstable, energy-rich state to the
more favoured and stable ground
state. Both cis isomers and all-trans
lycopene can proceed to the reaction
with an irreversible autoxidation, which Fig.2 - (a) All-trans lycopene and total lycopene
Degradation during storage of two tomato powders.
is favoured by low aw and low
temperature. Since cis isomers are more
Anguelova and Whartesen (2000)
readily oxidised than the all-trans forms; the overall extent of oxidative degradation is related
to the isomerisation rate. Even if this pathway was proposed for dehydrated tomato products,
it could be assumed that the same reactions could occur during the processing and storage of
other tomato products, favoured by oxygen availability and by temperature.