Kinetics of tofu color changes during deep-fat frying

Kinetics of color changes of a tofu (extra firm variety) was studied during deep-fat frying at 147-172degreesC. Lightness (L*) decreased exponentially from 85.5 to 68.0 with frying time, while redness (a*) and total color change (DeltaE) increased from -1.17 to 6.72 and from 0 to 26.7, respectively. Yellowness (b*) increased from 18.8 to 34.5 then decreased exponentially to another minimum of 29.4. All the color parameters followed first-order reaction kinetics. Temperature dependency of the reaction rate constant was modeled using Arrhenius equation. The activation energy for color parameters was 76.0-165 kJ/mol. Good agreement was observed between calculated and measured data (R-2 = 0.968-0.996). (C) 2002 Swiss Society of Food Science and Technology. Published by Elsevier Science Ltd. All rights reserved.