Abstract
A study was planned to evaluate the influence of continual heating at $150{\pm}5^{\circ}C$ and $170{\pm}5^{\circ}C$ respectively upon edible oils for frying the several food. Two kinds of domestic edible oils (Sample A and B) were collected by random sampling from market and in order to estimate deterioration degrees at both temperatures previously mentioned, thiobarbituric acid (TBA) value, acid value (AV), peroxide value (POV) and carbonyl value (CV) were measured at intervals due to its optical density. Those values were examined and compared according to the temperatures and times, and it was concluded as follows: 1) TBA value was rapidly increased until 24 hours in both temperatures and after 1 day its value have shown a slower increase as compared with initial rapid reaction. 2) Acid value and peroxide value of both oils (A & B) used for frying were increased continuously during heating and the changes in these values were dependent on the thermal oxidation, and moreover at low temperature $(150{\pm}5^{\circ}C)$ these values were found to be increased more readily than at high temperature $(170{\pm}5^{\circ}C)$. 3) Carbonyl value of both sample A and B show almost the same increasing rate at either $150{\pm}5^{\circ}C$ or $170{\pm}5^{\circ}C$ in proportion to the heating time. 4) It was found that there were differences between the chemical changes caused by heating sample A and B at high and low temperature.