The time of frying at each temperature was specially related to the moisture content of the finished product (below 2%). Frying was conducted in 30 min cycles for eight hours daily
for five days. At the end of each day of frying, the fryers were shut off and the oils were filtered to remove solid debris. Then, the oils were left to cool overnight. The oil was replenished before the frying process, to complete losses caused by collection of samples and absorbing fat by potato chips, adding additional fresh oil which volume was less than 5% of the total oil volume.100 mL samples of oil from each fryer were taken daily (after 8,16, 24, 32 and 40 h) and were kept frozen at 20 C until analysed.The fresh and degraded oils were analysed for acid and anisidine values, colour, refractive index, fatty acid composition by GC, content and composition of polar fraction by HPSEC and of GE by LC–MS.