Evaluation of heat and oxidative damage during storage of processed tomato products. II. Study of oxidative damage indices
2003
Lavelli, Vera | Giovanelli, Gabriella
Tomato products (pulp, puree and paste) submitted to accelerated aging (30, 40 and 50 °C for 3 months) were studied to evaluate variations in the kinetics of the degradation of antioxidants and antioxidant activity. The carotenoids lycopene and β-carotene, ascorbic acid, rutin and total phenolics were analysed. The antioxidant activity was measured using (a) the xanthine oxidase (XOD)/xanthine system, which generates superoxide radicals and hydrogen peroxide, and (b) the linoleic acid/CuSO4 system, which promotes lipid peroxidation. The ascorbic acid content decreased even at 30 °C, following pseudo-first-order kinetics, with an activation energy of 105 200 J mol(-1) for tomato pulp and 23 600 J mol(-1) for tomato paste. The lower the initial ascorbic acid content, the higher was the degradation rate. Variations in phenolic compounds occurred at 40 °C and higher, following pseudo-zero order kinetics. The antioxidant activity of the hydrophilic fraction of the tomato products depended on both antioxidant degradation and the Maillard reaction and could not be described by a kinetic model. The β-carotene content decreased even at 30 °C, whereas the lycopene content was stable in all samples. The antioxidant activity of the lipophilic fraction of the tomato products decreased following pseudo-first order kinetics, with an activation energy of 22 200 J mol(-1) for tomato pulp and 20 200 J mol(-1) for tomato paste. It is concluded that significant 'oxidative damage' can occur in tomato products during their commercial shelf-life.
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