Oil distribution in potato slices during frying

The objective of this research was to study the kinetics of oil absorption and distribution in the structure of potato slices during frying, considering the effects of three oil temperatures and a blanching pre-treatment. Either raw or blanched potato slices (Desirée variety, diameter: 30 mm, thickness: 3.0 mm) were fried at three constant (±1 °C) oil temperatures: 120, 150 and 180 °C. The blanching pre-treatment was accomplished in hot water at 85 °C for 3.5 min. Raw potato slices were used as the control for the experiments. The amount of oil absorbed was quantified during frying at four time intervals. The following fractions of the total oil (TO) content of potato slices were determined: (i) structural oil (STO); (ii) penetrated surface oil (PSO); and (iii) surface oil (SO). PSO constituted the highest fraction of the total oil content and this was the case for the control as well as the blanched slices, confirming that oil absorption in potato chips is mainly a surface phenomenon. Contrary to expectation, the blanched potato chips absorbed more oil than the control chips. The higher the frying temperature, the lower the oil absorbed by chips. Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) allowed studying the surface topography of potato chips, and in some cases, the location of oil on the surface.