Deep-fat frying process produces desirable and undesirable compounds that can cause impairments to the quality of frying of different oils and the fried foods produced. The quality and stability of frying oils are therefore of concern to food technologists, nutritionists, and consumers. The present study was performed to investigate performance of canola oil (CO) and its blends with either sunflower oil (CO+SF) or palm olein (CO+PO) blended at 1:1( w: w) by using different frying cycles of potato chips up to consecutive 10 frying cycle/ 3 day for each oil /days. Significant chemical changes in the frying oil quality have been occurred during frying process. Different chemical deterioration parameters: Iodine value (IV), Free fatty acid (FFA), Peroxide value (PV), Ansidine value (An.v), Totox value, conjugated
dienes , total polar compounds (TPC), fatty acids composition (FAs) and Fourier transform infrared (FTIR) of these frying canola oil and blends were investigated .
The conjugated dienes at 232nm throughout the frying periods were the lowest (3.12) in CO+PO with the highest
(43.04) value in CO+SF after 30 frying cycles. At the end of frying period, CO+SF had the lowest ratio of TPC 2.15 than found in CO+SF F30 and CO F30 (23.88 and 18.2), respectively. Generally, all blends did not exceed the 25% cut-off point for rejecting used frying oil. The blend of CO+PO was the superior in regard to frying stability and lowering TPC after deep-fat frying process.
The results of 30 potatoes deep-frying cycles in CO and its blends due to higher saturation, which can be seen from the chemical parameters and (FTIR) data. FTIR provides very useful information about the chemical composition
and impaired in oil quality during thermal oxidation, which is equivalent to that used in the ordinary food preparation.
Furthermore FTIR method predicting a modification in the oil's nutritional value. The results showed that FAs of blends, that contain PO had oxidative stability for the most of fatty acids with lower values than those occurred in frying of CO or CO+SF oils after 30 frying cycles. Furthermore, these results showed evidence that, the oxidation rate for PO in monounsaturated fatty acids (ƩMUSFAs) is much slower than that of the polyunsaturated fatty acids (ƩPUFAs). The ƩMUSFAs, were oxidized, and lower adverse contributed to the improvement of CO stability. Oil blends and frying process caused modifications in the FAs compositions and ω-3/ω-6 ratio.
These results indicated that frying may be hazardous due to the formation of lipid oxidation products as a result of thermal degradation of lipids during deep- fat frying process. Therefore in the CO+PO oil blend provided a frying oil alternative for the production deep–fried food, delivering low proportions of trans and saturated fatty acids.