Effect of equivalent thermal treatments on the color and the antioxidant activity of tomato purees

The influence of different heat treatments on color and antioxidant properties of tomato purees was investigated. The treatments were designed to produce the same total thermal effect against spoilage microorganisms. Although the development of nonenzymatic browning reactions occurred by increasing process temperature, no changes in redness were observed in the heated samples, due to the "masking" effect of lycopene. Also, the heat treatments had equivalent effect on the chain-breaking activity of the aqueous and lycopene tomato fractions. However the redox potential values increased as the heating temperature increased. All data together showed that the thermal resistance constant z values for color and chain-breaking activity were close to 10 degreesC, but lower than 10 degreesC for reducing properties.