MOHAMMAD YOUNIS

Abstract

Consequences of discontinuous chicken frying on some important parameters of soybean (SBO), sunflower (SFO) and canola oil (CLO) at constant temperature of 190 o C for 12 h were examined. The quality parameters such as fatty acid composition (FAC) with special emphasis on trans fatty acids (TFAs), free fatty acids (FFAs), iodine value (IV) and peroxide value (PV) of SBO, SFO and CLO were evaluated by taking out the oil samples from the fryer at an interval of 2 h. The total TFAs increased during frying of chicken in the range of 0.77- 1.67, 1.02- 2.62 and 1.29-3.14% in SFO, SBO and CLO. Other chemical parameters such as FFAs was 0.03-0.78, 0.05-0.49 and 0.19- 1.47%, PV was 1.51-3.04, 2.11-6.07 and 2.90- 8.02 meqO 2 /kg of oil increased whereas IV at 154.21- 140.69, 134.50 and 116.10-99.70 g/100g was decreased with respect to time of frying in SFO, SBO and CLO, respectively. The effect of commercial fish frying on the stability of FOs was examined at different intervals of time. The FO samples were collected into two phases; one before frying (unused) and other after frying (used; null replenishment, discarded). The main indicators of FOs determined during frying procedure were FAC, TFAs, FFA and PV. The FAC and TFAs in the FO samples were analyzed using the GC-MS. The TFAs were present in the range of 2.5-3.8, 5.6-14.8 and 7.3-20.8% in the fresh, null replenishment and discarded FO samples, respectively during the different frying periods. FFAs in fresh, NR, and discarded oils were 0.12%–0.24%, 0.22%–1.74%, and 0.80%–3.39%, respectively. PV in fresh, NR, and discarded oils were determined to be 1.15–3.93, 2.71– 7.51, and 2.84–14.68 meqO 2 /kg of oil. It was observed that commercial fryers were notusing the proper oil for frying. Furthermore, the last frying cycle just before discarding the oil may be dangerous for the health of consumers due to their significant level of TFAs, FFAs and PV. An easy UV spectrometric methodology was developed to assay PV of the FO samples. The assay of PV was based on the stoichiometric reaction of triphenylphosphine (TPP) with hydroperoxides available in FO samples to yield oxide of TPP, which indicates a reasonable absorption at 240 nm in UV region. The level of PV was found in the range 0.15-11.66 meqO 2 /Kg of oil in heated CLO samples for 1-12 h at frying temperature (180 0 C). Present methodology was compared with official procedure. The correlation of coefficient (R 2 ) was observed as 0.99525 which found in good agreement with official procedure. The present methodology may be used as a disjunctive to the official procedure, for the analysis of PV in FO samples. In another study the changes in main fat groups like saturated, monoene, trans and polyunsaturated FAs and their key fatty acid ratios (SFA/UFA, cis PUFA/SFA, C18:2/C16:0 and C18:3/C16:0) were investigated during potato chips frying in CLO. Single bounce attenuated total reflectance Fourier transform infrared (SB-ATR-FT-IR) spectroscopy was used for rapid analysis. The data obtained from gas chromatography- flame ionization detector (GC-FID) used as reference. The calibration of main fat groups and their key fatty acid ratios were developed by partial least square (PLS) regression coefficients using 4000 to 650 cm -1 spectral range. FT-IR PLS regression for the predicted SFAs, MUFAs, TFAs and PUFAs were found 0.999, 0.998, 0.998 and 0.999, respectively. Whereas for SFA/UFA, cis PUFA/SFA, C18:2/C16:0 and C18:3/C16:0 the regression coefficients were 0.991, 0.997, 0.996 and 0.994, respectively. We concludedthat FT-IR-PLS could be used for rapid and accurate assessment of changes in the main fat groups and their key fatty acid ratios ratio during frying process. The quantity of total polar compounds (TPC), carbonyl value (CV), conjugated diene (CD) and conjugated triene (CT) were monitored during potato chips frying in canola oil. Transmission Fourier transform infrared (FT-IR) spectroscopy was applied to attain improved sensitivity using 100 μm KCl cell. Partial least square (PLS) regression was applied to assess spectral regions correlating with known value of TPC, CV, CD and CT. Excellent coefficient of determinations were obtained as 0.997, 0.997, 0.999 and 0.999 for TPC, CV, CD and CT, respectively. The calibration models obtained were applied to analyze samples of canola oil drawn during potato chips frying from 1 to 7 h with wide ranges of 1.33 to 19.55% for TPC, 7.12 to 31.06 μmol/g for CV, 3.17 to 26.96 mmol/l for CD and 0.01 to 6.67 mmol/l for CT. A linear relationship was obtained between CD and TPC with a good correlation of coefficient (R 2 = 0.936). Results were compared with values obtained by their standard methods and found to be comparable. Outcomes of the present study revealed that transmission FTIR-PLS method could be used for quick and precise evaluation of oxidative changes occurred during frying process without using any organic solvent.