Kinetics of crust color changes during deep-fat frying of impregnated french fries

Abstract

The objective of this work was to study the kinetics of crust browning during deep-fat frying of impregnated and control potato strips ( Solanum tuberosum L., Desiree variety) by using a dynamic method and, with the obtained kinetics parameters, to predict the color change during frying. Blanched potato strips were impregnated at 25 °C by soaking in solutions of corn syrup DE 42-NaCl, 50–3% by weight, and NaCl 3% by weight. After rinsing and air drying, the strips were deep fried in sunflower oil at 160, 170 and 180 °C. A control treatment, consisting of potato strips blanched but not soaked was also conducted. Experimental data of surface temperature, mean moisture content of potato strips and crust color changes during frying were fit to empirical relationships, with correlation coefficients greater than 99.0%. A first-order rate equation was used to model the kinetics of color change. In all cases, the Arrhenius activation energy decreased alongside with decreasing mean moisture content, suggesting a possible color development rate control from a chemical step to a diffusional one. The kinetic parameters were employed to predict the color change during the deep-fat frying with RMS's values in the range of 5.1–10.5%.