Frying Oil Samples Research Articles

Effect of Adding Vitamin to Cooking Oil on Peroxide Value

The aim of this research is to reduce the number of peroxides in two frying oil samples by using one of the natural antioxidants which is vitamin E, one of the chemical specifications that assess the oil is the peroxide number, which is the number of free radicals formed in the oil and the number of peroxides increases during exposure to heat, moisture, oxygen, bad storage conditions, light or other conditions. These peroxides have a harmful effect on the consumer health (Carcinogenic substances). The vitamin E had a clear impact on the peroxide value, as when conducting the experiment and using oil to fry potato slices, the number of peroxides was high before adding vitamin E which score approximately (Peroxide number is 5.6 for 15 minutes, 9.8 for 30 minutes, and 11.6 for 45 minutes). After using vitamin E in amount of 10 microgram per 100 ml of oil, the effect was clear of vitamin E on the number of peroxide as it decreased significantly. Which scored (5 for 15 minutes, 8.1 for 30 minutes, 8.9 for 45 minutes), When vitamin E added by 20 microgram the result was (4.8 for 15 minutes, 5.5 for 30 minutes, 6.5 for 45 minutes). 50 micrograms per 100 oils shown to have no significant effect on the peroxide value. it was found that the best concentration is 20 micrograms for a sample of 100 ml of oil.

Food safety assessment for fried meat and fish ball in Ninh Kieu district, Can Tho city

The study aims to evaluate the degree of fat oxidation and the reuse of fried oils in fried meat and fish ball products sold in Ninh Kieu District, Can Tho City. The fat content was determined in fried products, as follows: fish balls (15 - 21%), beef balls (11 -14%), and shrimp balls (15 - 23%). Because of the difference in the fat origin of the three types of fried products, the oxidation levels of these products are also different; therefore, this is possible through parameters related to the variation of fat such as acid index, peroxide index, malondialdehyde (MDA) content. The concentration of MDA was the highest in fried fish balls, and the lowest value was in beef balls. After surveying for five consecutive days, the highest concentration of MDA in fried products was obtained in the last days of the cycle (4th day). The acid value in the fried oil samples ranges from 0 - 1 mg, the peroxide index from 2 - 5.78 meq/kg, and the concentration of MDA ranges from 0.22 - 2.98 µmol/L. A combination of results of the degree of fat oxidation in fried meat and fish ball products and frying oils indicates that the sellers reused the oils and tended to renew them every 3 - 4 days.

Quality Assessment of Fried Oils from Different Street Food Vendors and Restaurants in Different Areas of Gilgit, Pakistan

The study was designed to estimate the quality of the frying oils used in northern areas of Pakistan. A cross-sectional analysis was performed to investigate the behavior and common practices of street food vendors (SFVs) regarding oil selection, food preparation, and awareness of rancid oil on human health. Seventy-Eight (78) commercial fried oil samples were evaluated based on the free fatty acid (FFAs), peroxide value (PV), moisture contents (MC), total polar matter (TPM), color, and iodine value (IV). The analysis showed that FFAs, PV, TPM, color, and IV significantly deviated from standard values provided by Pakistan Standard Quality Control Authority, (PSQCA) Pakistan. The SFVs used low-quality oil because of low price and ease of availability over quality, frying oil was changed infrequently and blended with new oil. Furthermore, the majority of SFVs were unaware of the hazards of rancid oil to human health, food handling practices were unsanitary, and cleaning methods were ineffective. Quality control, legislation, and SFVs safety and hygiene training are the most critical requirements to improve the overall quality of fried street foods in Gilgit, Pakistan.

Effect of Microwave Frying on 3-MCPD and Glycidyl Ester Content of Potato Strips

The study aims to investigate the effect of microwave frying power and time on 3-MCPD and glycidyl ester contents of oils absorbed by fried potatoes. For this purpose, potato sticks were fried with three different refined vegetable oils (canola, corn, sunflower) at two power settings (350 W, 700 W) for two time periods (3 and 5 minutes). The fried potato oil samples were evaluated for their 3-MCPD and glycidyl ester content using alkali transesterification with DGF Standard Method C-VI 18 (10). Results have shown that microwave frying with different vegetable oils resulted in the formation of different 3-MCPD ester patterns. Microwave power and time did not change significantly the content of glycidyl ester s of potatoes fried with canola oil.

Quality assessment and degradative changes of deep-fried oils in street fried food chain of Kashmir, India

Repetitive use of same oil for deep-frying over a prolonged time period is a common practice followed by street vendors across various developing countries. This practice usually results in generation of harmful compounds imposing serious health threats to consumers. Frying oil samples (fresh, in-use and discarded) and commonly consumed fried street foods of Kashmir were randomly collected from 16 street food vendors of srinagar town and its adjacent areas for the assessment of their quality changes during repetitive deep frying. Significant increase in total SFA (saturated fatty acids), total MUFA (monounsaturated fatty acids) and total TFA (transfatty acids) content and decrease in total PUFA (polyunsaturated fatty acids) was observed in in-use, discarded oil and street foods as compared to fresh oil, reflecting the higher degree of oxidative degradation on repetitive use of same oil. The extent of oxidative degradation was highly influenced by the type of food fried, with lipid-based products showing higher degradation. High free fatty acid value (FFA˃1%), peroxide value (PV˃10meq/kg), P-anisidine value (P-Av˃6), color (higher ΔE), and TOTOX (Totox value˃19.5 mEq/kg) value revealed that only 20% of the in-use frying oil and 10% food products were safe for consumption. However, TPC test, a widely used measure of oxidative degradation suggested that majority of the in-use frying oil were of acceptable quality, thus greatly underestimating oil degradation.

WITHDRAWN: Quality assessment and degradative changes of deep-fried oils in street fried food chain of Kashmir, India

Repetitive use of the same oil for deep-frying over a prolonged period is a common practice followed by street vendors across various developing countries. This practice usually results in the generation of harmful compounds imposing serious health threats to consumers. Frying oil samples (fresh, in-use, and discarded) and commonly consumed fried street foods of Kashmir were randomly collected from 16 street food vendors of Srinagar town and its adjacent areas for the assessment of their quality changes during repetitive deep frying. Significant increase in ΣSFA, ΣMUFA, and ΣTFA content and decrease in ΣPUFA was observed in in-use, discarded oil and street foods as compared to fresh oil, reflecting the higher degree of oxidative degradation on repetitive use of same oil. The extent of oxidative degradation was highly influenced by the type of food fried, with lipid-based products showing higher degradation. High free fatty acid value (FFA˃1%), peroxide value (PV˃10meq/kg), P-anisidine value(P-Av˃6), color (higher ΔE), and TOTOX (Totox value˃19.5 mEq/kg) value revealed that only 20% of the in-use frying oil and 10% food products were safe for consumption. However, TPC test, a widely used measure of oxidative degradation suggested that majority of the in-use frying oil was of acceptable quality, thus greatly underestimating oil degradation. • Frying practices of 16 commercial street vendors were assessed. • Fresh, inuse, discarded oil samples and commonly consumed street foods were analysed • Fatty acid profile and physico-chemical characteristics of samples were evaluated. • Fat rich products reportedly shows higher oxidative degradation • Majority of the in-use frying oil and street foods were highly degraded.

Monitoring of free fatty acid content in mixed frying oils by means of LF-NMR and NIR combined with BP-ANN

The free fatty acid (FFA) is an essential indicator to determine the discard point of frying oils, however, the current detection method of FFA in oil is laborious. This research established two non-destructive approaches based on low field nuclear magnetic resonance (LF-NMR), near Infrared (NIR) spectra, and back-propagation artificial neural network (BP-ANN) algorithm for monitoring the FFA content of fried oil samples. 105 used frying oils, representing various frying degree, were detected using LF-NMR, NIR and reference method. HCA and PCA were used for natural clustering of LF-NMR parameters (S21, S22, S23, T21, T22, and T23) and NIR spectroscopy. Finally, the value of the correlation coefficient (R 2 ) manifested that the accuracy of LF-NMR model and NIR model reached 0.850, 0.963, respectively. The R 2 value of NIR model was 0.113 higher than that of LF-NMR model, indicating NIR spectroscopy of used frying oil could be a more accurate method for monitoring the FFA content in the oil using the BP-ANN model. • The changes of FFA of frying oil with the increase of frying batch were investigated. • HCA and PCA were used for natural clustering of LF-NMR and NIR parameters. • Both LF-NMR and NIR were applied for monitoring FFA values using the BP-ANN model. • NIR-FFA model was more accurate than LF-NMR-FFA model.

Characterization of key odorants in fried red and green huajiao (Zanthoxylum bungeanum maxim. and Zanthoxylum schinifolium sieb. et Zucc.) oils

Fried huajiao oil (FHO) samples prepared with red or green huajiao are widely applied in different Chinese cuisines due to their own aroma characteristics. To investigate their different aroma profiles, 2 red and 3 green FHOs were analyzed by quantitative descriptive sensory analysis (QDA) and gas chromatography–olfactometry/aroma intensity (GC–O/AI). QDA results showed a distinct difference among FHOs in terms of all sensory attributes. Thirty odorants with high OAVs and AIs were screened from 5 FHOs, among which β-myrcene, (E)-2-heptenal, limonene, α-terpineol and p-cymene were the major characteristic compounds of FHOs. In addition, through orthogonal partial least square discriminate analysis (OPLS-DA), linalool, linalyl acetate, and 1,8-cineole were considered as the volatile markers for classification of FHOs with red and green huajiao. Thereafter, aroma recombination and omission tests were performed to characterize the key aroma compounds of red and green FHOs.

Assessment of potentials of Moringa oleifera seed oil in enhancing the frying quality of soybean oil

Abstract This study investigated the effects of mixing Moringa oleifera seed oil with soybean (Glycine max) seed oil in enhancing the physical and chemical properties of soybean oil during repetitive frying. Different blends (100:0, 50:50, and 70:30) of soybean and M. oleifera seed oils were formulated, while soybean oil served as control. All these oil samples were used for frying potato (Ipomoea batatas) slices. The quality of the fried oil samples was evaluated by determining the smoke point, refractive index (RI), viscosity, colour, peroxide value, iodine value, and free fatty acid (FFA). The range of values obtained were smoke point (158.7–172.3°C), RI (1.46–1.49°C), colour (6.0–9.42), viscosity (0.41–2.13 mm2/s), peroxide value (0.93–5.16 meq/kg), iodine value (87.16–64.71 mg/100 g), and FFA (0.3–1.95%), for different blends of soybean and M. oleifera seed oils and control. In terms of changes in the chemical and physical properties, during frying, soybean/M. oleifera seed oil mix of 70:30 had the lowest reduction in iodine value (87.56–68.73 mg/100 g), lowest increase in peroxide value (0.93–1.86 meq/kg) and FFA value (0.3–0.65%), while no changes in RI (1.47°C) was observed. The study revealed that mixing of soybean seed oil with M. oleifera seed oil at a ratio of 70:30 enhanced the physical and chemical properties of the soybean oil after two repetitive frying.

Analysis of Total Polar Material in Selected Indian Snack’s Fried Oil

The study was envisaged to examine the quality of frying oil used by street food vendors for two of the most popular food items viz. Samosa and Jalebi in India. Changes in the quality of frying oil were analysed by analysing the total polar material (TPM) content in the oil using an oil tester and Attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy. Total 143 oil samples were collected at different frying times, i.e. 0, 2 and 4 h from five different Samosa and Jalebi vendors. In both the fried food oil samples, TPM content increased with increasing frying time. The TPM content in the 4 h fried oil samples of Jalebi was significantly (p< 0.001) higher than the samosa fried oil. Partial Least Square Regression (PLS) model based on the 1st derivative FTIR spectra exhibited good prediction capability for TPM values with a high regression coefficient (R2 ≥ 0.99) and low root mean square error (RMSE).

Quality alert from direct discrimination of polycyclic aromatic hydrocarbons in edible oil by liquid-interfacial surface-enhanced Raman spectroscopy

Edible oil is easy to be polluted by polycyclic aromatic hydrocarbons (PAHs) in production, processing, storage and use. Rapid screening of oil quality and safety is a huge demand in food industry and government regulation. Usually, sample pretreatment is needed for PAHs detection due to the complexity of the oil base but greatly limits the detection speed. Here we develop a liquid-interfacial surface-enhanced Raman spectroscopy (SERS) technology without sample pretreatment to realize the rapid and direct detection of ultra-trace PAHs in edible oil within 3 min. A quantitative analysis curve of benzopyrene (BaP) content in soybean oil is established in the range of 0.1 ppb–100 ppm with a high coefficient correlation (R2) of 0.9959 in curve fitting. It was found that only 4.5 h of frying would make the BaP content exceed the limit of 10 ppb in the Chinese Food Safety National Standard. Four common PAHs can be quickly identified in frying oil samples collected from special snack streets and the SERS profiles of soybean oil with adulteration of refined gutter oil could be well classified. This study paves a reliable method to rapid analyze edible oil with broad application prospects in the field of grain and oil safety.

Intermittent frying effect on French fries in palm olein, sunflower, soybean and canola oils on quality indices, 3-monochloropropane-1,2-diol esters (3-MCPDE), glycidyl esters (GE) and acrylamide contents

This study was carried out to determine the effect of intermittent frying of French fries using four different types of frying media on the media quality as well as 3-monochloropropane-1,2-diol esters (3-MCPDE) and glycidyl esters (GE) in frying oils and acrylamide contents in finished product. A total of 80 h of heating (control) and frying experiments at 180 °C was conducted, from which the heated and frying oil samples, as well as French fries were collected every day for 10 consecutive days. The oil samples were subjected to oil quality assessment as well as 3-MCPDE and GE in oils and acrylamide content in fried foods. A significant reduction of more than 80% in the 3-MCPDE content of palm olein was observed as compared to the other oils. The final 3-MCPDE levels in all oils were below 0.5 mg kg−1; whilst the GE levels were between 0.5 and 2.0 mg kg−1. For acrylamide analysis, oil type and lipid oxidation profile play an important role in the acrylamide concentration in the fried products. As for oil quality parameters, palm olein showed better frying performance due to the fact that it contains balanced proportion of saturated and unsaturated fatty acid composition. Edible oils with high unsaturated fatty acid are more susceptible to oxidation. In general, frying conditions affect the formation of 3-MCPDE and GE in all oils under extended frying time.

Intelligent evaluation of total polar compounds (TPC) content of frying oil based on fluorescence spectroscopy and low-field NMR

The purpose of this study was to construct a fusion model using probe-based and non-probe-based fluorescence spectroscopy and low-field nuclear magnetic resonance spectroscopy (Low-field NMR) for rapid quality evaluation of frying oil. Iron tetraphenylporphyrin (FeTPP) was selected as the probe to detect polar compounds in frying oil samples. Non-probe-based fluorescence spectroscopy and low-field NMR were employed to determine the fluorescence changes of antioxidants, triglycerides and fatty acids in frying oil samples. Compared to the models constructed using non-fusion data, the fusion-data models achieved a better regression prediction performance and correlation coefficients with values of 0.9837 and 0.9823 for the training and test sets, respectively. This study suggested that the multiple data fusion method was capable to construct better regression models to rapidly evaluate the quality of frying oil and other food with high oil contents.

Quality Assessments of the Fried Oils in Fast Food Restaurants of Yazd, Iran

Background: Oils and fats are among the important constituents of foods. Lipid oxidation can cause changes in taste, flavor, smell, color, texture, and nutritional value of the foods. Deep-fat frying (temperatures of 150 to 200 °C) leads to a series of chemical and physical reactions, so that the oil is oxidized, polymerized, and hydrolyzed. Methods: In a current descriptive cross-sectional study, 100 oil samples were obtained from fast food shops in Yazd city during the spring and summer of 2018. A checklist was prepared including the oil type (oil or fat), odor, color, smoke, and duration of use. The peroxide value (PV), p-anisidine value (p-AV), free fatty acid (FFA) levels, and total polar compound (TPC) of the samples were examined. Results: We found that 93% of the oil samples were in form of liquid. In term of color, 45% of the samples had a dark color and about 57% had an undesirable odor during cooking. In 23% of the fast food shops in Yazd, oil is used more than two days. The measurement of peroxide value showed that 73 samples had peroxide values higher than the allowable limits. The allowable average peroxide value was estimated as 2.33 meq/kg. Results showed that 56 samples had allowable FFA level (less than one), while the others were classified as oxidized oils. The p-AV in 55% of the oil samples were higher than 4. According to the results, 46% of the frying oil samples had TPC of higher than 25%, which showed that they should be discarded. Conclusion: The results showed that majority of the fast food shops in Yazd used highly oxidized oils to prepare their food. The absorption of such oils by food can endanger the public health. Therefore, continuous monitoring of fast foods and restaurants as well as training the staff seem necessary.

The Effect of Adding Different Concentration of Vitamin E to Frying Oil on the Peroxide Value

The aim of this research is to reduce the number of peroxide in two frying oil samples (Aldura and altusan) by using one of the natural antioxidants which is vitamin E. one of the chemical specifications that assess the oil is the peroxide number, which is the amount of free radicals formed in the oil and the number of peroxides increases during exposure to heat, moisture, oxygen, bad storage conditions, light or other conditions. These peroxides have a harmful effect on the consumer health (initiation cancer). The vitamin E had a clear impact on the peroxide value, as when conducting the experiment and using oil to fry potato slices, the number of peroxide was high before adding vitamin E which score (Peroxide number is 5.6 for 15 minutes, 9.8 for 30 minutes, and 11.6 for 45 minutes). After using vitamin E in amount of 10 microgram per 100 ml of oil, the effect was clear of vitamin E on the number of peroxide as it decreased significantly. Which scored (5 for 15 minutes, 8.1 for 30 minutes, 8.9 for 45 minutes). When vitamin E added by 20 microgram the result was (4.8 for 15 minutes, 5.5 for 30 minutes, 6.5 for 45 minutes). 50 microgram per 100 oil shown to have no significant effect on the peroxide value. it was found that the best concentration is 20 microgram for a sample of 100 ml of oil.

Effects of different vegetable oils on the aroma characteristics of deep‐fried shallot flavoring evaluated by HS‐SPME/GC‐MS coupled with PLSR

In this study, four fried shallot-flavored oil (FSO) samples prepared with different oil were analyzed by gas chromatography-mass spectrometry (GC-MS), descriptive sensory analysis (DSA), and electronic nose (E-nose). A total of 75 volatile compounds were identified, and 44, 34, 32, and 25 of these compounds were found in the FSOs with rapeseed oil, peanut oil, soybean oil and sunflower oils, respectively, which were conducted for comparison and evaluation of the aroma characteristics of FSOs. Seven sensory attributes (“oily,” “pungent,” “cooked vegetable,” “grease,” “burnt,” “pickled,” and “shallot scent”) were chosen to evaluate FSOs. DSA results showed a significant difference among these FSO samples for “shallot scent” and “grease,” and FSO2 heated by peanut oil presented strong in these two notes, but weaker in “burnt,” FSO3 also has the weaker “burnt” flavor. Moreover, E-nose analysis confirmed the results of GC-MS and DSA. Results of correlation analysis partial least squares regression (PLSR) among 50 volatile compounds and DSA data, indicated that 2-Ethyl-3,5-dimethyl-pyrazine, 2,3-Dihydro-benzofuran, and benzaldehyde contribute to “grease” flavor; 2-Ethyl-3,5-dimethyl-pyrazinemay contribute to “shallot scent” flavor, and further confirmed that peanut oil may be a suitable carrier oil for the sensory characteristics of FSO. Practical applications The unique shallot flavor and rich fat fragrance of FSO play an increasingly important role in the cooking and processing of dishes. However, there is relatively little research on FSO. In this study, FSO prepared by different types of oil can produce different flavor of FSO with dissimilar volatiles and sensory characteristics. We used PLSR to analyze the relationship between sensory attributes and compounds. These research contents will provide a basis for the industrialization of fried shallot oil.

Determination of frying sunflower oil usage time for local potato samples by using microwave transmission line based sensors

Abstract Amount of oil usage time can be determined by microwave measurements instead of using complex laboratory equipments to measure oil parameters such as viscosity, base number, refractive index, acid numbers, density, water substances, etc. Microwave measurements are easy and offer clear results to indicate oil quality and lifetime. In microwave measurements, there are two main parameters: dielectric constant value “e”, and loss tangent value “tanδ” that can be used as indicators for identifying any material or medium which will be oil substances in our case. When the dielectric constant value “e” of frying sunflower oil is measured, changes in the dielectric constant and loss tangent of the used oil relative to the unused pure sunflower oil can specify the presence of contaminant materials such as water and particles, or changes in the chemistry of the oil. In this study, we propose two different sensor structures to determine the usage amount of sunflower oil in frying. Before the sensor design, dielectric constants and loss tangent values of various time fried oil samples were measured in 4–8 GHz band. Each sensor structures designed as two port transmission line and operating in 4–8 GHz band. Designed first sensor has two advantages including the resonance shifts on return loss (S11) at around 5.45 GHz and another resonance shifts on transmission (S21) of 150 MHz, 100 MHz and 200 MHz at 4.4 GHz, at 5.4 GHz and at 7.6 GHz, respectively. The second sensor has a resonance shift only on transmission (S21) characteristic between the frequencies of 4 GHz and 6 GHz with approximately 100 MHz band. Finally, each sensor structures were fabricated and experimental measurements were conducted by using the vector network analyzer in microwave laboratory and accurate results were obtained and well match is observed with simulation results. According to experiment, proposed structures are reliable and also have advantages such as easy fabrication, low cost, high sensing performance and real time measurement. Designed sensors have higher sensing performances than its counterparts and they can be used to determine lifespan of frying oil samples in various applications.

Trans Fatty Acid Analysis of Frying Oil Using ATR-FTIR Spectroscopy: A Study on Indian Traditional Snack Foods

Background: Trans Fatty Acid (TFA) content in oil is an important quality parameter due to its adverse health effect. This study was aimed to examine the TFA content in the frying oil used by street food vendors in India for two traditional snack foods. Methods: Totally, 143 oil samples were collected at different frying times (0, 2, and 4 h) from five different vendors for Samosa and Jalebi. TFA levels of the oil samples were analyzed by Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATRFTIR). Statistical analyses were carried out using SPSS software version 23.0. Results: ATR-FTIR spectra exhibited an increase in peak intensity at 966 cm-1 with different frying time in both frying oil samples, indicating the formation of TFA. The TFA content in oils fried at 4 h was significantly higher than the ones at 0 and 2 intervals. It was found that 3 out of 74 (4%) Samosa fried oils and 12 out of 69 (17.4%) Jalebi fried oils were over the maximum allowed regulatory limit of TFA (5%). Jalebi fried oils had significantly higher TFA content than Samosa fried oils. Conclusion: The increase in frying time decreased the peroxide values and increased saturated fatty acids and TFA values of oils used for both food items. The local vendors and consumers should be educated by national authorities regarding health risk of TFA in street fried snacks.

Determination of Polycyclic Aromatic Hydrocarbons and α,β-Unsaturated Aldehydes in Frying Oils in Jordan

In this study, an efficient gas chromatography with mass-spectrometric detector (GC/MS) method has been developed for extraction and quantitation of 16 carcinogenic polycyclic aromatic hydrocarbons PAH in frying edible oil. The method showed satisfactory linearity (R 2 > 0.995) over the range (1.00–100.0 µg kg−1), the limits of detection were 0.0700 to 1.26 µg kg−1, limits of quantitation ranged from 0.230 to 4.20 µg kg−1, and the recovery ranged from 71.5% to 101. %. Samples of used frying edible oils have been collected from different fast food restaurants in Jordan. The mean of the 16 PAH in the oil samples ranged from 1.49 to 65.7 µg kg−1, while the concentration of Benzo[a]pyrene ranged from 3.08 to 4.09 µg kg−1. In addition, the incremental lifetime cancer risk (ILCR) associated with PAH was estimated, and ranged from 1.01 × 10−9 to 3.33 × 10−6, indicating a slight potential risk. A second objective of this research involved calculation of p-Anisidine values (AVs) in the collected frying oil samples as an indicator for the presence of α,β-unsaturated aldehydes. The AVs in the investigated oil samples ranged from 14.3 to 71.3 and the estimated concentration of α,β-unsaturated aldehydes was 33 μmol g−1 which is higher that the internationally proposed maximum limits. The outcomes of this study show that regulations on PAHs and α,β-unsaturated aldehydes in frying oils must be established in Jordan.

Volatile components of deep-fried soybean oil as indicator indices of lipid oxidation and quality degradation

The present study investigated the lipid oxidation degree of soybean oil during regularly discontinuous 40 h-deep-frying process. Electron spin resonance (ESR) spectroscopy technique was applied to identify and quantify the formed radicals, along with evaluation of physicochemical parameters including acid value (AV), peroxide value (PV), p-anisidine value (p-AnV), polar compounds (PC), fatty acid composition and volatile profile. Results showed the AV, p-AnV, PC and free radical of frying oil samples increased significantly with the increasing frying time. The results of fatty acids showed that unsaturated fatty acid such as C18:1 and C18:2 decreased by 19.98% and 14.58%, respectively, with prolonged frying time, while the content of C16:1, trans C18:1 and C18:2 increased by 20.38%, 425% and 42.86%, respectively, when compared to the fresh oil samples. In contrast, the content of saturated fatty acid had little change. In total, 37 volatile compounds were detected revealing a complex aroma profile of frying soybean oil, composed of 15 aldehydes, 8 alcohols, 4 ketones, 4 acids, 5 alkanes and 1 furan. Principal component analysis and hierarchical clustering analysis indicated that hexanal, heptanal, (E)-2-hexenal, octanal, (E)-2-heptenal, nonanal, (E)-2-octenal, undecanal, (E,E)-2,4-heptadienal, (E)-2-decenal, 2-undecenal, (E,E)-2,4-decadienal, 1-pentanol, 2,2-dimethyl-3-hexanol, (Z)-2-dodecenol, 1-octen-3-ol, pentanoic acid, octanoic acid, nonanoic acid and 2-pentyl-furan may be potential markers for evaluating lipid oxidation of frying soybean oil.