Oil partition in pre-treated potato slices during frying and cooling

The objective of this research was to study the effect of some pre-treatments and oil temperatures in the kinetics of oil absorption and distribution in the structure of potato chips not only during the frying process but also during the posterior cooling. Pre-treated potato slices (Desirée variety, diameter: 30 mm, thickness: 3.0 mm) were fried at four constant oil temperatures (±1 °C): 120, 140, 160 and 180 °C. The tested pre-treatments were: (i) blanching in hot water at 85 °C per 3.5 min (control); (ii) blanching as in (i) and then immersion in a NaCl solution of 20 g/L per 5 min and at 200 rpm of agitation and 25 °C (salt impregnation); (iii) blanching as in (i) and then covering with an edible film solution of hydroxypropylmethylcellulose – HPMC – (16 g/L per 20 min at 70 °C). The partition of the oil absorbed was quantified during frying and the post-frying stage. Oil could penetrate in chip microstructure either during frying or during cooling when the oil wetting the potato chip surface at the end of the frying process, penetrates into the chip microstructure by vacuum forces created by evaporative cooling. Potato chips absorbed during frying at 180 °C nearly 38% of the total oil content, and almost 62% of the total oil content remained at the chip surface without penetrating into the microstructure (average values for the three pre-treatments tested). This situation reverses during the cooling stage and ∼65% of the total oil content was absorbed by potato chips and only 35% remained at the chip surface. Contrary to expected, potato chips coated with the edible film HPMC absorbed more oil than control and salt impregnated potato chips (P<0.05).