Abstract

The kinetics of the thermal degradation of color (L*, a*, and b* coordinates), lycopene (L), and L-ascorbic acid (AA) in crushed tomato were studied over a temperature range of 70 to 100 degrees C. These results showed that the changes in a*, L, and AA followed a first-order kinetic model (R-2 > 0.91), while those for L* and b* did not fit any suitable kinetic models. The temperature effects on degradation rates were adequately compatible with the Arrhenius equation (R-2 > 0.96) with the following activation energy values (E-a, kJ mol(-1)): a* (64.54), L (45.96) and AA (25.69). These E-a values indicated that a* was the most sensitive parameter towards temperature changes, while the reaction rate constants (k) showed that L had the highest degradation rate compared with the other parameters studied. A linear relationship between a* and L content was found, suggesting that a* measured instantaneously by tristimulus colorimeters can be used for the online determination of L degradation in crushed tomatoes during heat treatment. The knowledge gained from this study could be useful for improving the design and optimization of the thermal process of crushed tomato in order to preserve its nutritional value and sensory quality.