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

Abstract

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.

Sterol Migration during Rotational Frying of Food Products in Modified Rapeseed and Soybean Oils

“…High temperatures are typically used during frying, resulting in chemical reactions such as oxidation, hydrolysis, polymerization/polycondensation, isomerization, and cyclization [ 18 ]. Many authors have described the changes that occur in vegetable fat and oil quality during heating or frying process of a single product, such as French fries [ 19 , 20 ], fish [ 21 , 22 ], or chicken [ 23 , 24 ], reporting changes in a range of parameters and constituents, including fat content, color, fatty acids, polar compounds, anisidine values, and acid values. Much less information can, however, be found on changes in sterols during frying.…”

“…Information specifically on the changes in fish and fish products upon frying at different frying cycles, times, temperatures, oils, and techniques was reviewed by NurSyahirah and Rozzamri [ 28 ], but changes in sterols are not described there. To decrease the detrimental effect of the frying process on the quality of the oil and chicken nuggets, vacuum frying and using the lowest possible frying temperature has been suggested [ 24 ]. These authors did not examine the oxidative degradation of cholesterol in chicken nuggets and plant sterols in oils.…”