2.4. Analysis
Moisture content of potato chips was measured by drying the samples in a convection oven until constant mass at 105 1C. The oilcontent was determined by a simple and rapid method that consists of an initial extraction with a mixture of 1:2:0.8 (v/v/v) in chloroform, methanol, and water, respectively. Then, this mixture is adjusted to 2:2:1.8 (v/v/v) to continue the oil extraction. In this way, the chloroform layer contains the purified oil(Bligh & Dyer, 1959). This method has been used previously for determining oil content in French fries (Bunger et al., 2003; Moyano et al., 2002). Texture measurements of the chips were performed at room temperature (20 1C) by a puncture test performed in a Texture Analyser TA.XT2 (Stable Micro System, Surrey, UK). Force vs. distance curves were generated with the puncture test at different frying times by mounting the sample over a three-point-support, where the distance between points was 15 mm (Segnini et al., 1999). The punch diameter and the cross-head speed was 2 mm and 60 mm/min, respectively. The parameter maximum force (MF) was obtained from the force vs. distance curves using the software Texture Expert (v 6.06) of the Texture Analyser. MF was defined as the force at which the punch penetrates the outer layer of the surface of the fried potato slices.