Deep fat frying is an important operation that imparts characteristics of flavor, color and texture in the fried products, however oil or fat becomes an ingredient that induces chemical alterations during prolonged heating periods. The performance of refined soybean oil was studied under intermittent deep fat frying conditions at a university cafeteria, at temperatures between 170ºC (338ºF) and 180ºC (356ºF), for a period of 30 hours. During this period, 101 liters of soy oil were used to process 373kg of vegetables (potato, cauliflower, squash and cassava). The oil quality was assessed by means of physical (uv absorptivity A232nm and A270nm, Lovibond color) and chemical (free fatty acids (FFA) and polar compounds (PC)) determinations. Sensorial analysis in the deep fat fried foods was performed through the acceptability test. The limits for alteration of the oils were established at 27% PC, 1% FFA and an average of 7.0 for acceptability. The results obtained at the end of the period were 0.282% FFA, 18.8% PC, 14Y/2R for Lovibond color, 9.213 for A232nm and 2.409 for A270nm and an average of 7.96 for the acceptability test. It can be concluded that the hydrolytic and oxidative alterations induced by the soybean oil under the heating conditions studied did not warrant discarding the oil after 30 hours.
frying; soybean oil; termoxidation; absorptivity; polar compounds
