VISCOSITY AND SURFACE-TENSION OF CORN-OIL AT FRYING TEMPERATURES

Surface active properties and viscosity changes of corn oil were deter mined. under controlled frying conditions. Viscosity of corn oil was m easured at a temperature range of 100-200C, Surface-active properties of thermally degraded corn oil were determined by measuring the statio nary contact angle (theta) of oil droplets placed on a low energy surf ace (polystyrene). The viscosity of oil decreased as temperature incre ased, At 200C, the kinematic viscosity had decreased 69% when compared with its initial value of 7.50 mm(2)/s at 100C. Oil was degraded by f rying 400 g of potatoes for 5 min each hour for 36 h (low load frying) . The experiment was repeated with 1200g of potatoes (high load frying ). The viscosity of the oil increased 9.4% and 28.6% for low and high load fryings, respectively. The surface tension of the oil and its deg radation time were inversely proportional (at high load frying) loweri ng the surface tension of the oil by 2.0%. A high correlation (r(2) = 0.90) between the viscosity and surface tension of oil was obtained.