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Processing and Bioavailability (WG2) page 23
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Lycopene
(mg/Kg d.w.)
Comments and topics -
2100
2050
2000
1950
o days 30 days 90 days 165 days
Figure 3: Variation in the a/b ratio with time
As long as lycopene remains within the original hydrophilic matrix and, most of all,
within a whole cell, it is considerably stable. The hot break juice extraction technique does not
lessen the initial lycopene, but allows the lycopene concentration to remain almost unchanged
during the storage of finished products, probably because of the more intact tomato cell
structure.
Very few studies concern the fate of tomato antioxidant constituents other than
carotenoids during the storage of tomato products.
Lee et al. (1977) studied ascorbic acid stability in tomato as a function of temperature
(from 10° to 38°C), pH (from 3.53 to 4.36) and copper concentration under anaerobic
conditions. The degradation reaction followed a pseudo-first-order kinetics, with activation
energy of 13.8 kJ/mol at pH 4.06. The rate of ascorbic acid destruction was significantly
influenced by pH, reaching a maximum near the pKa of ascorbic acid (pKa = 4.08). The
presence of copper also increased the rate of ascorbic acid degradation, with a linear
correlation between copper concentration (from 2 to 10 mg/L) and the rate constant.
Mesic et al. (1993) studied the variation in redox potential, ascorbic acid and HMF
concentrations during storage of tomato paste in aluminium tubes. Ascorbic acid degradation
was followed in sample stored in various materials at 4°, 20° and 40°C. In all cases, residual
ascorbic acid after 10 months of storage was approximately 20%-35% of the initial content,