Studying the Physicochemical Alterations of Oil after Frying and Cooling Chicken Nugget under Vacuum and Atmospheric Conditions

The present study investigated the effects of frying and cooling of chicken nuggets under vacuum and atmospheric pressure on the qualitative properties of frying oil. For this purpose, first, two cooling treatments were applied to nuggets fried at 170°C under atmospheric pressure. One treatment was subsequently cooled at atmospheric pressure (control) and the other at 10 kPa. Other treatments included frying at temperatures of 115 and 170°C under the pressure of 10 kPa before cooling at pressures of 10 kPa and atmospheric levels. Results indicated that frying and cooling at 170°C increased acid value, polar compounds, viscosity, redness, yellowness, and oil oxidation. Also, this treatment reduced the oil's unsaturated fatty acids. On the other hand, minimum values of acid content, viscosity, and oxidation rate were observed in the oil used to vacuum fry at 115°C and subsequently cooled at 10 kPa pressure. Moreover, these samples exhibited the highest quantities of oleic, linoleic, and linolenic acids due to the lower oxidation taking place in such unsaturated fatty acids under the vacuum rather than the atmospheric pressure. Based on the results obtained, frying and cooling at 115°C under vacuum seems to have the least unfavorable effects on frying oil.