Kinetic Modeling of Color Changes in French Fries During Frying Process

Color development during frying process is a surface phenomenon that depends on the processing temperature and time and might concern other aspects. The aim of this research was explanation of color changes and behavior of French fries during the process as a mathematical model at various temperatures.
Blanched potato stripes were fried using a fryer equipped with thermo controller where the sunflower oil was used as a frying media at the temperature of 145, 160 and 175 ºC for 60, 120, 180 and 240 seconds. Surface temperature of the product was measured using T type thermocouple that was located about 1mm below the surface of the strip and recorded using data logger by 2 seconds intervals during process. Color parameters as brightness (L), redness (a) and yellowness (b) were achieved using Lovibond apparatus and kinetic model was fitted on their changes versus time using MATLAB software version of 2009. Finally, critical temperature of color changes during frying was specified by carrying out statistical analysis of equivalent values of color change intensity (∆E∞) as completely randomized design and Duncan mean comparison with 95% confidence level using SPSS software version of 19.
The results of this experiment showed that the main part of color parameter changes occurred during early stages of frying process. Higher temperature caused less brightness (L), more redness (a) and more yellowness (b) (more acceptable). The temperature of 160 ºC can be defined as the critical temperature for significant changes (P≤0.05) in the color intensity.
Kinetic of crust color changes in French fries follows the raising exponential equation of R2=0.99. Applying high temperature and short time process can be suitable for the control of color quality and therefore food safety.