The antioxidant activity of tomato. III. Effects of processing technologies on oxidative and heat damage

Various tomato products (commercial tomato pulp, tomato puree, and tomato paste obtained from the same producer, and pilot plant air-dried tomato halves) were evaluated for their antioxidant content (ascorbic acid, lycopene, polyphenols), antioxidant activity (XOD/xanthine and linoleic acid/CuSO4 test), and 5-hydroxymethyl-2-furfural (HMF) to evaluate the effects of processing technology on oxidative and heat damage. The main conclusions of this study can be summarized as follows: (a) tomato paste had a much lower ascorbic acid concentration and a higher total phenolics concentration than tomato puree. This affected the antioxidant activity of the hydrophilic fraction, which was slightly higher in tomato paste. Lycopene concentration was similar in tomato paste and puree, and, consequently, the antioxidant activity of the lipophilic fraction was almost the same in the two products. (b) Tomato pulp and tomato puree, despite similar HMF contents, showed differences in ascorbic acid concentration and antioxidant activity of the hydrophilic fraction, which were nearly twice as high in tomato pulp. Neither the lycopene content nor the antioxidant activity of the lipophilic fraction differed significantly. Air-drying of tomato halves caused a marked decrease in the ascorbic acid content and antioxidant activity of the hydrophilic fraction. In this product too, lycopene showed great stability as did the antioxidant activity of the lipophilic fraction.