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J. Food Qual. Hazards Control 2026, 13(1): 16-24 |
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Adu O, Ogun S, Ogunrinola O, Fajana O, Olaitan S, Akinola O, et al . Quality Changes in Fresh and Recycled Frying Oil in Nigeria. J. Food Qual. Hazards Control 2026; 13 (1) :16-24
URL: http://jfqhc.ssu.ac.ir/article-1-1334-en.html
URL: http://jfqhc.ssu.ac.ir/article-1-1334-en.html
O.B. Adu * 
, S.O. Ogun , O. Ogunrinola , O. Fajana , S. Olaitan , O. Akinola , A. Yusuf , Q. Malik , B.O. Elemo
, S.O. Ogun , O. Ogunrinola , O. Fajana , S. Olaitan , O. Akinola , A. Yusuf , Q. Malik , B.O. Elemo
Department of Biochemistry, Lagos State University, Ojo, Lagos, PMB 0001, LASU Post Office, Ojo, Lagos, Nigeria , oluwatosin.adu@lasu.edu.ng
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Quality Changes in Fresh and Recycled Frying Oil in Nigeria
O.B. Adu ** , S.O. Ogun, O. Ogunrinola, O. Fajana, S. Olaitan, O. Akinola, A. Yusuf, Q. Malik, B.O. Elemo
Department of Biochemistry, Lagos State University, Ojo, Lagos, PMB 0001, LASU Post Office, Ojo, Lagos, Nigeria
HIGHLIGHTS:
Figure 1: Physicochemical properties of oils sampled
Bars represent mean values ± Standard Error of Mean (SEM). Bars with different letters (a, b, c) indicate significant difference.
a=Peroxide value; b=Iodine value; c=Acid value; d=Free fatty acid content, e=Color intensity (red); f=Color intensity (yellow); g=Viscosity, h=refractive index
Figure 2: Acrylamide concentration of fresh oil and recycled oil samples.
Figure 3: The effect of continuous usage on various Polycyclic Aromatic Hydrocarbon (PAH) content in fresh oil and recycled oil samples from rural street vendors in Morogbo
Author contributions
O.B.A., B.O.E., O.F., S.O and O.O. conceptualized the study; O.B.A. and B.O.E supervised the research. Q.M., A.Y., O.A and S.O.O. performed the experiments and collected data; S.O.O. and O.B.A. analyzed and interpreted the data; O.B.A., O.O, O.F., Q.M., B.O.E., S.O., A.Y., O.A., and S.O.O wrote the manuscript. All authors reviewed the results and approved the final version of the manuscript.
Acknowledgements
The authors are grateful to the Department of Biochemistry, Lagos State University, Lagos, Nigeria, for the permission to use the Departmental laboratory.
Conflicts of interest
The authors declare that there is no conflict of interest.
Funding
This research received no specific grant from any funding agency in the public, commercial, or non-profit sectors.
Ethical consideration
Not applicable.
O.B. Adu **
Department of Biochemistry, Lagos State University, Ojo, Lagos, PMB 0001, LASU Post Office, Ojo, Lagos, Nigeria
- Prolonged reuse of frying oil by street vendors in Morogbo, Lagos State, Nigeria resulted in significant deterioration of oil quality.
- High levels of Polycyclic Aromatic Hydrocarbons (PAHs) and acrylamide were detected in all oil samples.
- Vendors routinely reused and recycled frying oil without proper regulation or awareness of the associated toxicological risks.
| Article type Original article |
ABSTRACT Background: Fried food business is common among street vendors in Nigeria, many of whom reuse frying oils repeatedly due to economic constraints and limited regulatory oversight. Repeated use of frying oil results in physical and chemical degradation, which introduces toxic compounds into the food. This work aimed to determine the physicochemical changes occurring in vegetable oils used by roadside food vendors in Morogbo, a rural area of Lagos state, Nigeria. Methods: The safety and quality of these oils were assessed by analyzing samples collected from three street vendors on the first and fifth days of the week. Physical and chemical parameters- color intensity, viscosity, refractive index, acid value, Free Fatty Acid (FFA) content, iodine value, and peroxide value (PV)- were measured. Additionally, acrylamide and polycyclic aromatic hydrocarbons (PAHs) concentrations were quantified using High Performance Liquid Chromatography (HPLC). Fresh oils from the vendors served as controls. Results were expressed as the mean ± Standard Error of Mean (SEM) and analyzed using one-way analysis of variance (ANOVA) followed by Tukey’s Honestly Significant Difference (HSD) post-hoc test. Values of p<0.05 were considered statistically significant. Statistical analyses were performed using GraphPad Prism version 10.4.1 Results: There was significant difference (p<0.05) in the refractive index, viscosity, Peroxide Value (PV), and Free Fatty Acid (FFA) content between the control and the recycled oil. However, there was no significant difference in iodine value and color intensity between the fresh and recycled oil. All the oil samples, including the control, had high acrylamide while the recycled oil had elevated concentrations of some Polycyclic Aromatic Hydrocarbons (PAHs) like benzo[a]pyrene. Conclusion: This study highlights the significant deterioration in the safety and quality of frying oils used by street vendors in the Morogbo rural area of Lagos State. © 2026, Shahid Sadoughi University of Medical Sciences. This is an open access article under the Creative Commons Attribution 4.0 International License. |
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| Keywords Acrylamide Polycyclic Aromatic Hydrocarbons Fatty Acids |
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| Article history Received: 09 Feb 2025 Revised: 24 Feb 2026 Accepted: 26 Feb 2026 |
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| Abbreviations FFA=Free Fatty Acid HPLC=High Performance Liquid Chromatography KOH=Potassium Hydroxide PAHs=Polycyclic Aromatic Hydrocarbons ppb=parts per billion PV=Peroxide Value |
To cite: Adu, O.B., Ogun, S.O., Ogunrinola, O., Fajana, O., Olaitan, S., Akinola, O., Yusuf, A., Malik, Q. and Elemo B.O. (2026) 'Quality Changes in Fresh and Recycled Frying Oil in Nigeria', Journal of Food Quality and Hazards Control, 13(1), pp. 16-24.
Introduction
Frying is a popular cooking method used both domestically and industrially to enhance texture, flavor, and appearance of foods (Rani et al., 2023) . Fried foods are popular and widely consumed all over the world due to their crispness, crunchiness, flavor, taste, and color (Rani et al., 2023) . During deep fat frying at temperatures between 170 °C – 200 °C, steam formed from moisture in the food and oxygen induces hydrolysis of triacylglycerols to produce di- and monoacylglycerols, glycerol, and Free Fatty Acids (FFA), while the present oxygen results in the thermal oxidation of oil (Oke et al., 2018) . Deep fat frying generates volatile compounds that contribute to the flavor of fried foods as well as decomposition products such as nonvolatile polar compounds, dimers, and polymers (Oke et al., 2018) . These non-volatile compounds accumulate in the oil and get absorbed into fried foods as the oil is repeatedly used (Nayak et al., 2016) resulting in rancid taste and accumulation of toxic oxidation products (Bekdeşer et al., 2024) which eventually ends up in our body system.
During frying, physicochemical reactions such as starch gelatinization, protein denaturing, and browning through Maillard reactions occur. The Maillard reactions responsible for the browning result in the formation of acrylamide, a carcinogenic and neurotoxic substance that poses a potential health risk when consumed in significant amounts (Rani et al., 2023) . Additionally, these reactions produce toxic substances such as Polycyclic Aromatic Hydrocarbons (PAHs), trans fatty acids, heterocyclic amines (Xin et al., 2022) . Thermal oxidation of oil further produces free radicals, peroxides, and other substances, thus decreasing oil quality (Liu et al., 2019) . Therefore, monitoring oil quality and the concentration of decomposition products is essential for the safety and quality of fried foods. Several analytical indices like color, odor, Peroxide Value (PV), acid value, FFA, iodine value, and pH value are used to determine the quality of oil (Bekdeşer et al., 2024) .
The type of fried food significantly influences oil degradation (Adu et al., 2019), and practices for oil reuse vary among food vendors. For instance, in a survey conducted in Malawi on oil used for preparing potato chips, most vendors (59.4%) reported discarding the oil after 1 day of use, whereas 12.5% discarded the oil after three days and only 3.1% after four days(Phiri, Mumba and Mangwera, 2006) . A survey on the repetitive use of oil in Ilishan-Remo Nigeria revealed that degraded oil is constantly mixed with fresh oil while frying (Ngozi et al., 2019) . In Japan, restaurant frying oils are typically used for approximately 3 h per day at 180 °C and are discarded after 9 days, corresponding to a total frying time of about 27 h (Wai, 2007) .
Frying foods is a lucrative business among low-income earners especially in rural areas. The practice is widespread among street vendors in Nigeria, who rely on frying to prepare popular and affordable foods and snacks such as yam fries, plantain chips, akara (bean cakes), and puff-puff (fried dough)(Adu et al., 2019) . However, due to the high cost of vegetable oil, it is common for vendors to use unbranded vegetable oils and reuse frying oil repeatedly, often continuing until the color visibly changes (Adelagun et al., 2023; Adu et al., 2019; Fekadu, Abera and Weldemichael, 2024; Oladunjoye and Aluko, 2024) . This repeated use of oil can lead to its degradation, resulting in the accumulation of non-volatile polar compounds, free radicals, and other toxic oxidation products (Liu et al., 2019; Xin et al., 2022) . These substances not only compromise the taste and safety of the fried food but also pose potential health risks to consumers (Adelagun et al., 2023) . The lack of awareness and enforcement of food safety regulations in rural areas exacerbates the problem, making it critical to assess the quality of oils used in such settings (Adelagun et al., 2023) . Therefore, the aim of this study was to analyze the physiochemical properties and biochemical products formed in vegetable oil used in frying foods by road-side food vendors in a rural area, Morogbo, in Lagos State.
Materials and methods
Collection of oil samples and experimental design
Oil samples were obtained from three street vendors in Morogbo, Lagos State, Nigeria using amber glass bottles. Sampling was conducted twice a week (Monday and Friday) from three different roadside food outlets in Morogbo. During the second round of sampling, oil was collected only if the vendor continued using the same type. Approximately 200 ml of hot oil was drawn directly from the fryer, passed through a filter paper with the aid of an aspirator to remove food residues and stored in a bottle flushed with nitrogen gas prior to sealing to limit oxidative changes. The samples were labeled and stored at −20 °C until analyzed. All physical and chemical assessments were conducted in duplicate. A structured researcher-developed questionnaire adapted from Yilmaz and Aydeniz, (2011), was used to obtain information on frying practices, oil handling, fryer cleaning, and food types prepared by street vendors.
Determination of physicochemical properties
PV, iodine value, acid value, and FFA content of the oil samples were determined according to the American Oil Chemists' Society ([AOCS], 1998) method.
Determination of color
Oil color was measured using a Lovibond tintometer (Model F, England). Oil samples were melted and filtered using a filter paper. The filtered oil was transferred into a clean glass cell, which was then placed in the tintometer. The yellow and red slides were matched with the color shade of the oil in a tintometer. To minimize errors, a composite color factor was used, calculated as the yellow (Y) units plus 5 or 10 times the total red units, following the standard method(I.S.I., 1984) .
Determination of viscosity
The viscosity of the oil was measured using a Lamy Viscometer RM100 (Lamy, France). A 25 ml oil sample was placed in the Tube’s outer cylinder, and the bob was inserted (tube radius: 16.25 mm; bob radius: 15.5 mm; bob length: 54 mm). Measurements were conducted in mode MS 19 with a measurement time of 60 s. A circulatory water bath maintained temperatures of 26, 30, 38, 40, 50, 70, and 90 °C. Torque values were recorded across shear rates ranging from 64.5 to 4835 s⁻¹. Each sample was measured in triplicate, with each replicate run twice: first increasing and then decreasing the shear rate. The mean torque value at each shear rate was recorded(Diamante and Lan, 2014) .
Determination of refractive index
The refractive index of the oil samples was measured using an Abbe 60 Refractometer (Bellingham + Stanley, UK). A drop of oil was placed on the open prism and the cover was secured by tightening the screws. Water was circulated through the instrument and allowed to equilibrate for several minutes to ensure that the sample and instrument reached the same temperature. Between readings, the prism was cleaned with a cotton pad moistened with ethyl alcohol and allowed to dry. The lighting and instrument settings were adjusted to obtain optimal readings. The refractometer temperature was carefully maintained within ±0.1 °C in a water bath. When temperature correction was necessary, the refractive index was calculated using the following formula:(Bureau of Indian Standards, 2005; Nova analytics, 2008) .
R= R1 + K1 (T1 –T)
Where R = Reading of the refractometer reduced to the specified temperature T oC
R1 = Reading at T1 oC
K = constant 0.000365 for fats and 0.000385
T1 = temperature at which the reading R1 is taken
T = specified temperature (generally 40 oC)
Acrylamide analysis by High Performance Liquid Chromatography (HPLC)
One g of oil was poured in a 50 ml centrifuge tube, spiked with 1000 µl of 20 ng/ml internal standard and 1000 ng/ml spiking solution, then shaken vigorously for 1 min. Five ml of n-hexane was then added, and shaken for another minute. This was followed by the addition of 9 ml of water and 10 ml of acetonitrile, accompanied by vigorous vortexing for 1 min. A Bond QuEChERS salt packet was added for acrylamide extraction, and the mixture was shaken for another minute, followed by centrifuging for 5 min at 4000 rpm, and the upper hexane layer discarded(Kostopolou et al., 2007) .
Dispersive SPE cleanup
A 6 ml aliquot of the acetonitrile layer was applied to a Bond ElutQuEChERS dispersive SPE 15 ml tube and centrifuged for 5 min at 4000 rpm. The supernatant was transferred into an autosampler vial for analysis by HPLC-DAD (Agilent Technologies, USA)(Pule and Torto, 2009) .
Chromatographic analysis
This was done on an Agilent ZORBAX HILIC Plus column (4.6mm x 50mm x 3.5um, p/n 959943-901) using isocratic elution with 3% 5 mm acetic acid and 97% acetonitrile as the mobile phase. The column temperature was 30 oC and the flow rate was 0.2ml/min.
PAHs analysis by HPLC
The method employed utilized an internal standard approach with Benzo(b)Chrysene at a concentration of 250 parts per billion (ppb) serving as the internal standard. This procedure was adapted from ISO 15753: 2006 and further refined. The technique involved gradual enrichment of PAHs in the oil phase, followed by a two-step solid-phase extraction cleanup to isolate the PAHs. A total of 15 PAHs were analyzed.
Liquid–liquid extraction
A 2.5 g sample was spiked with 100 μl of internal standard, Benzo(b)Chrysene, at a concentration of 250 ppb. Extraction of PAHs was done using 10 ml of a 60/40 acetonitrile/acetone mixture by vortexing and ultra-sonication. The mixture was centrifuged and the supernatant collected into a 100 ml conical flask. The procedure was repeated twice, and the extracts concentrated at 35 °C using a rotary evaporator.
Clean up
The oil residue was extracted with 21 ml of a 60:40 (v/v) acetonitrile/acetone solution in a centrifuge tube. The mixture was vortexed and centrifuged, after which the supernatant was carefully decanted. The supernatant was poured onto a C18 solid-phase extraction cartridge that had been preconditioned sequentially with 24 ml each of methanol and acetonitrile. The extraction procedure was carried out twice to ensure optimal recovery. The PAH was then eluted with 5 ml of 60:40 acetone/acetonitrile, and the eluate was collected in a 50 ml conical flask and concentrated at 35 oC using a rotary evaporator. The concentrate was then dissolved in 1 ml of hexane and applied to a Florisil bonded-phase cartridge. The conical flask was rinsed with 1 ml of 25:75 dichloromethane/ hexane three times and each rinse was transferred onto the cartridge. The eluate was collected in a 50 ml conical flask, concentrated at 35 oC using a rotary evaporator and brought to dryness under a nitrogen stream. The residue was reconstituted in 1 ml of acetonitrile, followed by agitation, filtration and then prepared for HPLC injection.
Statistical analysis
The results were expressed as the means ± Standard Error of Mean (SEM). The data were analyzed using one-way analysis of variance (ANOVA) followed by Tukey’s Honestly Significant Difference (HSD) post-hoc test. Values of p<0.05 were considered statistically significant. All statistical analyses were performed using Graph Pad Prism version 10.4.1
Results and discussion
Deep frying is one of the oldest and frequently used methods of food preparation globally(Nayak et al., 2016) . In Nigeria, deep frying is common among street vendors. To reduce expenses, the oil is recycled and topped off repeatedly as confirmed by the interview of the rural vendors in Morogbo area of Lagos State (Table 1). This practice is common due to the low level of awareness among the public about its possible adverse effects. In a study on the perception of food vendors in Lagos Nigeria, 99% repeatedly used the same frying oil for cooking till depletion (Oladunjoye and Aluko, 2024) . Repeated use of oil degrades oil and releases toxic compounds that can be transferred into food (Adelagun et al., 2023) . Therefore, we analyzed the quality of oil used by street vendors in Morogbo area of Lagos by investigating the physicochemical parameters, acrylamide, and PAH concentration in the frying oil.
From the questionnaires administered to the food vendors all respondents used Kings Oil as their preferred brand due to its perceived quality. The first vendor, Morogbo 1, engaged in frying for the longest duration, operating for 9 h per day. This vendor frequently topped up the oil, never changed oil and fried a variety of foods like akara, chicken, potato, and yam. The second respondent, Morogbo 2, had the shortest frying duration, operating for 3 h per day. This vendor regularly topped up and filtered the oil but never replaced it. All products, primarily pastries, were fried in the same oil. The third vendor, Morogbo 3, performed frying for 6 h per day, topped up oil and never changed oil. The vendor fried a variety of foods like akara, fish, potato, yam, and plantain. The vendor did not use the same oil for frying all the products.
Physicochemical properties
The physicochemical properties of the frying oil samples collected from street vendors in Morogbo, a rural area in Lagos, Nigeria were analyzed to assess oil quality. Parameters analyzed include PV, iodine value, acid value, FFA content, color intensity (red and yellow), viscosity, and refractive index.
The PV is an indicator of the peroxides or hydroperoxides formed during primary oxidation of hydroxyl groups of unsaturated oils(Al-Khusaibi and Rahman, 2021; Gilbraith et al., 2021; Zhang et al., 2012) . The PV quantifies the amount of chemically bound oxygen in the oil (Al-Khusaibi and Rahman, 2021) . The PV of the oil samples ranged from 5 meq/kg to 18 meq/kg (Figure 1a). The PV was lowest in oil samples from Morogbo 1 and highest in samples from Morogbo 2. Notably, the PV of oil samples from Morogbo 2 was significantly higher (p<0.05) than the fresh oil samples. Auto oxidation of oils transforms peroxides or hydroperoxides into alcohols, ketones, and aldehydes, which impart rancid flavors and odors in oils. (Gilbraith et al., 2021) . A high PV in freshly processed oil indicates a shorter shelf life. The PV analysis showed that the fresh oil and samples from Morogbo 1 had a PV lower than the Codex standards for refined oils (10 mEq/kg), while the samples from Morogbo 2 and 3 had a PV higher than the Codex standard (Codex Alimentarius Commission, 1999) . This indicates a faster primary oxidation due to prolonged frying practices and oil reuse by the food vendors. These vendors typically top off the oil during continuous frying sessions lasting between 3 to 6 h per day but do not change the oil.
The PV for the Morogbo 2 samples was significantly higher (p<0.05) than the fresh oil but this was not the case for Morogbo 1 and 3. This variation could be an indication of differences in oil handling and storage practices among the vendors. Continuous exposure of oil to factors such as temperature, light, and storage time can negatively affect PV and oil quality(Idun-Acquah, Obeng and Mensah, 2016; Kaleem, Aziz and Iqtedar, 2015) . It is worthy of note that although the Morogbo 1 and 3 samples were used to fry fish and chicken, which are foods typically associated with faster oil oxidation, while Morogbo 2 was used primarily for pastries, the Morogbo 2 samples still exhibited a higher PV. This indicates that factors other than the type of fried food contributed to the elevated PV observed in Morogbo 2.
The Iodine value is a measure of the degree of unsaturation in oils with higher values indicating a higher number of double bonds in the fatty acids. Prolonged heating during frying can promote oxidation and polymerization, which can break double bonds and subsequently reduce the iodine value(Al-Khusaibi and Rahman, 2021) . The iodine value of the oil samples ranged from 23.84 I2/100 g of fat for the Morogbo 3 samples to 46.04 I2/100 g of fat for the Morogbo 2 samples (Figure 1b). The iodine value of oils from Morogbo 1 and Morogbo 3 were statistically significant from the fresh oil. The oil used by the vendors is produced from refined palm olein. All the samples, including the fresh sample, had an iodine value less than the Codex standard of 56 or greater (Codex Alimentarius Commission, 1999) . The observed iodine value suggests that the oil used may have been adulterated with high saturated fat (Kalia and Mishra, 2019) . The observed reduction in iodine value for Morogbo1 and 3 samples indicates a deterioration of the frying oil. In the study by Chebet, Kinyanjui and Cheplogoi (2016), the highest decrease in iodine value of vegetable oil was observed after a 5-day storage at room temperature compared to those stored at 4 oC.
The acid value measures the amount of FFA in the oil, serving as an indicator of hydrolysis caused by oxidation and lipolytic enzymes. A lower acid value indicates a higher oil stability over a long period(Ekpe et al., 2018) . Acid value (Figure 1c) of the oil samples ranged from 15.6 mg Potassium Hydroxide (KOH) in Morogbo 2 samples to 22.40 mg in fresh oil. Acid value was lower in all the recycled oil samples compared to the control. However, only the samples from Morogbo 1 and Morogbo 2 were significantly lower (p<0.05) than the fresh control. The acid value of both fresh and frying oils were extremely higher (15.6-22.4 mg KOH) than the Codex standard of 0.6 mg KOH/g oil, indicating the poor stability of the frying oil (Codex Alimentarius Commission, 1999) . The acid value of the fresh vegetable oil was significantly higher than those of the Morogbo 1 and Morogbo 2 samples. This indicates that, contrary to the expected increase during repeated use, the acid value was actually decreased in the recycled oils compared to the fresh sample. This unexpected pattern may be attributed either to poor storage conditions of the fresh oil, which could have promoted hydrolysis, or to the periodic replenishing and topping-up of oil during frying, which can dilute accumulated FFA.
The type of fried food significantly influences oil degradation (Adu et al., 2019), and practices for oil reuse vary among food vendors. For instance, in a survey conducted in Malawi on oil used for preparing potato chips, most vendors (59.4%) reported discarding the oil after 1 day of use, whereas 12.5% discarded the oil after three days and only 3.1% after four days
Frying foods is a lucrative business among low-income earners especially in rural areas. The practice is widespread among street vendors in Nigeria, who rely on frying to prepare popular and affordable foods and snacks such as yam fries, plantain chips, akara (bean cakes), and puff-puff (fried dough)
Materials and methods
Collection of oil samples and experimental design
Oil samples were obtained from three street vendors in Morogbo, Lagos State, Nigeria using amber glass bottles. Sampling was conducted twice a week (Monday and Friday) from three different roadside food outlets in Morogbo. During the second round of sampling, oil was collected only if the vendor continued using the same type. Approximately 200 ml of hot oil was drawn directly from the fryer, passed through a filter paper with the aid of an aspirator to remove food residues and stored in a bottle flushed with nitrogen gas prior to sealing to limit oxidative changes. The samples were labeled and stored at −20 °C until analyzed. All physical and chemical assessments were conducted in duplicate. A structured researcher-developed questionnaire adapted from Yilmaz and Aydeniz, (2011), was used to obtain information on frying practices, oil handling, fryer cleaning, and food types prepared by street vendors.
Determination of physicochemical properties
PV, iodine value, acid value, and FFA content of the oil samples were determined according to the American Oil Chemists' Society ([AOCS], 1998) method.
Determination of color
Oil color was measured using a Lovibond tintometer (Model F, England). Oil samples were melted and filtered using a filter paper. The filtered oil was transferred into a clean glass cell, which was then placed in the tintometer. The yellow and red slides were matched with the color shade of the oil in a tintometer. To minimize errors, a composite color factor was used, calculated as the yellow (Y) units plus 5 or 10 times the total red units, following the standard method
Determination of viscosity
The viscosity of the oil was measured using a Lamy Viscometer RM100 (Lamy, France). A 25 ml oil sample was placed in the Tube’s outer cylinder, and the bob was inserted (tube radius: 16.25 mm; bob radius: 15.5 mm; bob length: 54 mm). Measurements were conducted in mode MS 19 with a measurement time of 60 s. A circulatory water bath maintained temperatures of 26, 30, 38, 40, 50, 70, and 90 °C. Torque values were recorded across shear rates ranging from 64.5 to 4835 s⁻¹. Each sample was measured in triplicate, with each replicate run twice: first increasing and then decreasing the shear rate. The mean torque value at each shear rate was recorded
Determination of refractive index
The refractive index of the oil samples was measured using an Abbe 60 Refractometer (Bellingham + Stanley, UK). A drop of oil was placed on the open prism and the cover was secured by tightening the screws. Water was circulated through the instrument and allowed to equilibrate for several minutes to ensure that the sample and instrument reached the same temperature. Between readings, the prism was cleaned with a cotton pad moistened with ethyl alcohol and allowed to dry. The lighting and instrument settings were adjusted to obtain optimal readings. The refractometer temperature was carefully maintained within ±0.1 °C in a water bath. When temperature correction was necessary, the refractive index was calculated using the following formula:
R= R1 + K1 (T1 –T)
Where R = Reading of the refractometer reduced to the specified temperature T oC
R1 = Reading at T1 oC
K = constant 0.000365 for fats and 0.000385
T1 = temperature at which the reading R1 is taken
T = specified temperature (generally 40 oC)
Acrylamide analysis by High Performance Liquid Chromatography (HPLC)
One g of oil was poured in a 50 ml centrifuge tube, spiked with 1000 µl of 20 ng/ml internal standard and 1000 ng/ml spiking solution, then shaken vigorously for 1 min. Five ml of n-hexane was then added, and shaken for another minute. This was followed by the addition of 9 ml of water and 10 ml of acetonitrile, accompanied by vigorous vortexing for 1 min. A Bond QuEChERS salt packet was added for acrylamide extraction, and the mixture was shaken for another minute, followed by centrifuging for 5 min at 4000 rpm, and the upper hexane layer discarded
Dispersive SPE cleanup
A 6 ml aliquot of the acetonitrile layer was applied to a Bond ElutQuEChERS dispersive SPE 15 ml tube and centrifuged for 5 min at 4000 rpm. The supernatant was transferred into an autosampler vial for analysis by HPLC-DAD (Agilent Technologies, USA)
Chromatographic analysis
This was done on an Agilent ZORBAX HILIC Plus column (4.6mm x 50mm x 3.5um, p/n 959943-901) using isocratic elution with 3% 5 mm acetic acid and 97% acetonitrile as the mobile phase. The column temperature was 30 oC and the flow rate was 0.2ml/min.
PAHs analysis by HPLC
The method employed utilized an internal standard approach with Benzo(b)Chrysene at a concentration of 250 parts per billion (ppb) serving as the internal standard. This procedure was adapted from ISO 15753: 2006 and further refined. The technique involved gradual enrichment of PAHs in the oil phase, followed by a two-step solid-phase extraction cleanup to isolate the PAHs. A total of 15 PAHs were analyzed.
Liquid–liquid extraction
A 2.5 g sample was spiked with 100 μl of internal standard, Benzo(b)Chrysene, at a concentration of 250 ppb. Extraction of PAHs was done using 10 ml of a 60/40 acetonitrile/acetone mixture by vortexing and ultra-sonication. The mixture was centrifuged and the supernatant collected into a 100 ml conical flask. The procedure was repeated twice, and the extracts concentrated at 35 °C using a rotary evaporator.
Clean up
The oil residue was extracted with 21 ml of a 60:40 (v/v) acetonitrile/acetone solution in a centrifuge tube. The mixture was vortexed and centrifuged, after which the supernatant was carefully decanted. The supernatant was poured onto a C18 solid-phase extraction cartridge that had been preconditioned sequentially with 24 ml each of methanol and acetonitrile. The extraction procedure was carried out twice to ensure optimal recovery. The PAH was then eluted with 5 ml of 60:40 acetone/acetonitrile, and the eluate was collected in a 50 ml conical flask and concentrated at 35 oC using a rotary evaporator. The concentrate was then dissolved in 1 ml of hexane and applied to a Florisil bonded-phase cartridge. The conical flask was rinsed with 1 ml of 25:75 dichloromethane/ hexane three times and each rinse was transferred onto the cartridge. The eluate was collected in a 50 ml conical flask, concentrated at 35 oC using a rotary evaporator and brought to dryness under a nitrogen stream. The residue was reconstituted in 1 ml of acetonitrile, followed by agitation, filtration and then prepared for HPLC injection.
Statistical analysis
The results were expressed as the means ± Standard Error of Mean (SEM). The data were analyzed using one-way analysis of variance (ANOVA) followed by Tukey’s Honestly Significant Difference (HSD) post-hoc test. Values of p<0.05 were considered statistically significant. All statistical analyses were performed using Graph Pad Prism version 10.4.1
Results and discussion
Deep frying is one of the oldest and frequently used methods of food preparation globally
From the questionnaires administered to the food vendors all respondents used Kings Oil as their preferred brand due to its perceived quality. The first vendor, Morogbo 1, engaged in frying for the longest duration, operating for 9 h per day. This vendor frequently topped up the oil, never changed oil and fried a variety of foods like akara, chicken, potato, and yam. The second respondent, Morogbo 2, had the shortest frying duration, operating for 3 h per day. This vendor regularly topped up and filtered the oil but never replaced it. All products, primarily pastries, were fried in the same oil. The third vendor, Morogbo 3, performed frying for 6 h per day, topped up oil and never changed oil. The vendor fried a variety of foods like akara, fish, potato, yam, and plantain. The vendor did not use the same oil for frying all the products.
Physicochemical properties
The physicochemical properties of the frying oil samples collected from street vendors in Morogbo, a rural area in Lagos, Nigeria were analyzed to assess oil quality. Parameters analyzed include PV, iodine value, acid value, FFA content, color intensity (red and yellow), viscosity, and refractive index.
The PV is an indicator of the peroxides or hydroperoxides formed during primary oxidation of hydroxyl groups of unsaturated oils
The PV for the Morogbo 2 samples was significantly higher (p<0.05) than the fresh oil but this was not the case for Morogbo 1 and 3. This variation could be an indication of differences in oil handling and storage practices among the vendors. Continuous exposure of oil to factors such as temperature, light, and storage time can negatively affect PV and oil quality
The Iodine value is a measure of the degree of unsaturation in oils with higher values indicating a higher number of double bonds in the fatty acids. Prolonged heating during frying can promote oxidation and polymerization, which can break double bonds and subsequently reduce the iodine value
The acid value measures the amount of FFA in the oil, serving as an indicator of hydrolysis caused by oxidation and lipolytic enzymes. A lower acid value indicates a higher oil stability over a long period
Figure 1: Physicochemical properties of oils sampled
Bars represent mean values ± Standard Error of Mean (SEM). Bars with different letters (a, b, c) indicate significant difference.
a=Peroxide value; b=Iodine value; c=Acid value; d=Free fatty acid content, e=Color intensity (red); f=Color intensity (yellow); g=Viscosity, h=refractive index
FFAs, which result from oil hydrolysis, increased with repeated frying cycles. FFAs are commonly used for monitoring oil quality as their accumulation along with their oxidized compounds can create off flavors in frying oil (Karimi, Wawire and Mathooko,, 2017) . The recommended Codex FFA value should not exceed 0.3%. The FFA value (Figure 1d) ranged from 7.840 /100 g of fat in Morogbo 2 samples to 11.26/100 g of fat in the fresh oil samples. The FFA values of the recycled oil were lower than the fresh oil; however, only the Morogbo 2 samples was significantly lower (p<0.05). All the oil samples had higher FFA content than the recommended value (Codex Alimentarius Commission, 1999) . The FFA content also followed similar trend as the acid value. In the study by Emelike, Ujong and Achinewu (2020), on oils used by local food vendors in Port Harcourt, Nigeria, the frying oils, except for the branded oils, had FFA contents higher than the reference. Notably, the lowest FFA values were observed in oil samples used for 3 h per day, indicating that both frying time and cycles play a role in the accumulation of FFA.
The change and deepening in the color intensity of frying oil is a reflection of oil deterioration and accumulation of degradation products(Manzoor et al., 2022; Zhang et al., 2012) . The color intensity (red) ranged from 0.13 lovibond unit in both fresh oil and Morogbo 2 samples to 0.58 lovibond unit in Morogbo 3 samples (Figure 1e). The color intensity (red) was higher in Morogbo 1 and Morogbo 3 compared to the fresh oil, though not significantly. Fresh oil showed the lowest colour intensity (red) but did not differ significantly from any other sample. The sample from Morogbo 2 matched the fresh oil in colour intensity, likely due to its shorter frying time (3 h/day) compared to Morogbo 3 (6 h/day) and Morogbo 1 (9 h/day), which exhibited higher color intensities.
The color intensity (yellow) ranged from 0.43 lovibond unit in fresh oil to 1.23 lovibond unit for Morogbo 2 (Figure 1f). The color intensity (yellow) was higher in all samples compared to fresh oil, but the difference was not statistically significant. This suggests an increase in color intensity (both yellow and red) due to the continuous heating of the oil. The increase in the color intensity of frying oil is similar to the study of Manzoor et al. (2022) where deep frying caused a pronounced change in color of oil. Most of the time, vendors repeatedly use the same frying oil and discard it when it smokes or becomes too dark(Fekadu et al., 2024) .
Viscosity is an indicator of oil degradation. Polymerization generates high-molecular-weight compounds that enhance oil resistance to flow(Pambou-Tobi et al., 2010) . An increase in viscosity indicates a decline in oil quality (Mariana et al., 2020) . Viscosities (Figure 7) of the oils ranged from 1.090 mPa.s in Morogbo 3 to 1.312 mPa.s in Morogbo 2. The viscosity of Morogbo 2 was significantly higher (p<0.05) than in the fresh oil. Similar finding was reported by Fekadu, Abera and Weldemichael (2024), where the viscosity of discarded oil was highest, followed by the used oil, compared to the fresh oil. The viscosity results in our study showed that there was deterioration in the quality of oil, which may be attributed to continuous heating and accumulation of the degradation products in oil (Fekadu et al., 2024) .
Refractive index is used to assess hydrogenation, isomerization, and purity of materials andit is influenced by factors like wavelength, degree of unsaturation, and the type of fatty acids. (Ichu and Nwakanma, 2019) . According to the Codex standard, the recommended refractive index for palm olein ranges from 1.458–1.460 but all our samples had a refractive index above this range. Samples from Morogbo 3 had a significantly lower refractive index compared to the fresh oil, while samples from Morogbo 1 and 2 had similar refractive index compared to the fresh oil. In the study of Fekadu, Abera and Weldemichael (2024) the highest refractive index occurred in discarded oil, followed by used oil, relative to fresh oil. This is not the case in our study as the refractive index was similar in both the recycled and fresh oils with the exception of samples from Morogbo 3. The lack of difference between recycled and fresh oil may result from oil replenishment (“topping up”) and storage conditions.
The change and deepening in the color intensity of frying oil is a reflection of oil deterioration and accumulation of degradation products
The color intensity (yellow) ranged from 0.43 lovibond unit in fresh oil to 1.23 lovibond unit for Morogbo 2 (Figure 1f). The color intensity (yellow) was higher in all samples compared to fresh oil, but the difference was not statistically significant. This suggests an increase in color intensity (both yellow and red) due to the continuous heating of the oil. The increase in the color intensity of frying oil is similar to the study of Manzoor et al. (2022) where deep frying caused a pronounced change in color of oil. Most of the time, vendors repeatedly use the same frying oil and discard it when it smokes or becomes too dark
Viscosity is an indicator of oil degradation. Polymerization generates high-molecular-weight compounds that enhance oil resistance to flow
Refractive index is used to assess hydrogenation, isomerization, and purity of materials and
Figure 2: Acrylamide concentration of fresh oil and recycled oil samples.
Bars represent mean values ± Standard Error of Mean (SEM). Bars with different letters (a, b, c) indicate significant difference.
Acrylamide forms at high temperatures in foods, typically above 120 °C, due to Maillard reaction (Başaran and Turk, 2021) . Exposure to acrylamide is associated with some cancer risk (Adani et al., 2020; Başaran and Turk, 2021; Liu et al., 2017) . Acrylamide formation depends on factors such as oil, food type, pretreatment of food, frying temperature, and time (Başaran and Turk, 2021).
Acrylamide forms at high temperatures in foods, typically above 120 °C, due to Maillard reaction
Figure 3: The effect of continuous usage on various Polycyclic Aromatic Hydrocarbon (PAH) content in fresh oil and recycled oil samples from rural street vendors in Morogbo
PAHs have been shown to have carcinogenic and mutagenic properties (Li et al., 2016) . Humans are exposed to PAH from environmental contamination and food processing involving high temperatures such as frying, smoking, and grilling (Li et al., 2016) . The PAH content varied between the various oil samples (Figure 3). Phenanthrene was highest in fresh oil whereas benzo(b)fluoranthene and benzo(a)pyrene was highest in oil samples from Morogbo 3. Benzo(g,h,i)pyrene, indeno(1,2,3 -cd)pyrene, and fluoranthrene were the lowest in the oil samples including the fresh control. The concentrations of most of the PAHs detected exceeded the standard safety limit of 10 ppb, raising concerns about potential health risks. According to the European Food Safety Authority (EFSA), in addition to benzo[a]pyrene the sum of 4 or 8 PAH serves as a more reliable indicator of the presence and associated toxicity of the genotoxic and carcinogenic PAHs. The PAH4 includes benzo[a]pyrene, chrysene, benz[a]anthracene and benzo[b]fluoranthene while the PAH8 includes benzo[a]pyrene, benz[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[ghi]perylene, chrysene, dibenz[a,h]anthracene and indeno[1,2,3-cd]pyrene (EFSA, 2008).
The European :union: (EU) has set the maximum permissible level of PAH4 in palm oil at 10 μg/kg, equivalent to 10 ppb(Ingenbleek et al., 2019) . In this study, all the oil samples including the fresh oil had both PAH4 and PAH8 levels above the limit. Some of the PAHs, like Benzo (g,h,i) pyrene, lndeno (1,2,3-cd) pyrene, and Fluoranthrene, were not present in the fresh oil. Anthracene and Benzo (g,h,i) pyrene was also not detectable in Morogbo 2 samples. Oil samples from Morogbo 3 had the highest levels of benzo[a]pyrene (4391.73 ppb), followed by Morogbo 2 (345.9) and Morogbo 1 (53.12) as compared to the fresh oil of (7.48). Overall, oil samples from Morogbo 3 had the highest PAH content. The frying time and the type of fried product may have played a role in the high PAH levels observed in Morogbo 3.
The European :union: (EU) has set the maximum permissible level of PAH4 in palm oil at 10 μg/kg, equivalent to 10 ppb
Conclusion
The findings of this study highlight the significant deterioration in the quality of oil used by street vendors in the Morogbo, a rural community in Lagos State. The oil's physicochemical properties, including increased PVs, viscosity, and color intensity, indicate the harmful effects of repeated oil usage. The presence of high levels of PAH in frying oil is alarming as these compounds are well known for their carcinogenic and mutagenic potentials. This highlights the urgent need for the implementation of stronger regulations and enforcement measures to ensure that oils used in food preparation meet established safety standards. The current lack of awareness among food vendors about the potential risks of oil reuse and improper storage practices exacerbates the problem, as evidenced by the vendors’ practices of continuously topping up and never changing the oil. There is also a need for adequate training and education of food vendors on hygienic practices, oil reusability, and storage.
The findings of this study highlight the significant deterioration in the quality of oil used by street vendors in the Morogbo, a rural community in Lagos State. The oil's physicochemical properties, including increased PVs, viscosity, and color intensity, indicate the harmful effects of repeated oil usage. The presence of high levels of PAH in frying oil is alarming as these compounds are well known for their carcinogenic and mutagenic potentials. This highlights the urgent need for the implementation of stronger regulations and enforcement measures to ensure that oils used in food preparation meet established safety standards. The current lack of awareness among food vendors about the potential risks of oil reuse and improper storage practices exacerbates the problem, as evidenced by the vendors’ practices of continuously topping up and never changing the oil. There is also a need for adequate training and education of food vendors on hygienic practices, oil reusability, and storage.
Author contributions
O.B.A., B.O.E., O.F., S.O and O.O. conceptualized the study; O.B.A. and B.O.E supervised the research. Q.M., A.Y., O.A and S.O.O. performed the experiments and collected data; S.O.O. and O.B.A. analyzed and interpreted the data; O.B.A., O.O, O.F., Q.M., B.O.E., S.O., A.Y., O.A., and S.O.O wrote the manuscript. All authors reviewed the results and approved the final version of the manuscript.
Acknowledgements
The authors are grateful to the Department of Biochemistry, Lagos State University, Lagos, Nigeria, for the permission to use the Departmental laboratory.
Conflicts of interest
The authors declare that there is no conflict of interest.
Funding
This research received no specific grant from any funding agency in the public, commercial, or non-profit sectors.
Ethical consideration
Not applicable.
References
Adani, G., Filippini, T., Wise, L.A., Halldorsson, T.I., Blaha, L. and Vinceti, M. (2020) 'Dietary intake of acrylamide and risk of breast, endometrial, and ovarian cancers: a systematic review and dose–response meta-analysis', Cancer Epidemiology, Biomarkers and Prevention, 29, pp. 1095–1106. Available at: https://doi.org/10.1158/1055-9965.EPI-19-1628
Adelagun, R.O., Berezi, E.P., Fagbemi, J.O., Igbaro, O.J., Aihkoje, F.E., Ngana, O., Osondu, G. and Garba, M.S. (2023) 'Evaluation of level of rancidity of edible oil in some fried snacks food', Journal of Chemical Society of Nigeria, 48(1). Available at: https://doi.org/10.46602/jcsn.v48i1.853
Adu, O.B., Fajana, O.O., Ogunrinola, O.O., Okonkwo, U.V., Evuarherhe, P. and Elemo, B.O. (2019) 'Effect of continuous usage on the natural antioxidants of vegetable oils during deep-fat frying', Scientific African, 5, p. e00144. Available at: https://doi.org/10.1016/J.SCIAF.2019.E00144
Al-Khusaibi, M. and Rahman, M.S. (2021) 'Quality assessment of frying oil degradation'. In: Khan, M.S. and Rahman, M.S. (eds.) Techniques to Measure Food Safety and Quality: Microbial, Chemical, and Sensory, Cham: Springer International Publishing, pp. 329–344. Available at: https://doi.org/10.1007/ 978-3-030-68636-9_14
American Oil Chemists' Society (AOCS) (1998) Official Methods and Recommended Practices of the AOCS. Champaign: American Oil Chemists' Society. Available at: https://library.aocs.org/ (Accessed: 3 January 2025).
Başaran, B. and Turk, H. (2021) 'The influence of consecutive use of different oil types and frying oil in French fries on the acrylamide level', Journal of Food Composition and Analysis, 104, p. 104177. Available at: https://doi.org/10.1016/J.JFCA.2021.104177
Bekdeşer, B., Esin Çelik, S., Bener, M., Dondurmacıoğlu, F., Yıldırım, E., Nida Yavuz, E. and Apak, R. (2024) 'Determination of primary and secondary oxidation products in vegetable oils with gold nanoparticle based fluorometric turn-on nanosensor: A new total oxidation value', Food Chemistry, 434, p. 137426. Available at: https://doi.org/10.1016/J.FOODCHEM.2023.137426
Bureau of Indian Standards (2005) Manual of Methods of Analysis of Food, Oil, and Fat. FAD 10: Food and Agriculture Standard IS: 548 (Part 2). New Delhi: Bureau of Indian Standards.
Chebet, J., Kinyanjui, T. and Cheplogoi, P.K. (2016) 'Impact of frying on iodine value of vegetable oils before and after deep frying in different types of food in Kenya', Journal of Scientific and Innovative Research, 5(5), pp. 193–196.
Codex Alimentarius Commission (1999) Codex Standard for Named Vegetable Oils (Codex Stan 210-1999). Available at: https://www.fao.org/fao-who-codexalimentarius/sh-proxy/en/?lnk=1&url=https%253A%252F%252Fworkspace.fao.org%252Fsites%252Fcodex%252FStandards%252FCXS%2B210-1999%252FCXS_210e.pdf (Accessed: 5 January 2025).
Diamante, L.M. and Lan, T. (2014) 'Absolute viscosities of vegetable oils at different temperatures and shear rate range of 64.5 to 4835 s-1', Journal of Food Processing, 2014(1), p. 234583. Available at: https://doi.org/10.1155/2014/234583
European Food Safety Authority (EFSA) (2008) 'Polycyclic aromatic hydrocarbons in food: Scientific opinion of the panel on contaminants in the food chain', EFSA Journal, 6(8), p. 724. Available at: https://doi.org/10.2903/j.efsa.2008.724
Ekpe, O.O., Bassey, S.O., Udefa, A.L. and Essien, N.M. (2018) 'Physicochemical properties and fatty acid profile of Irvingia gabonensis (Kuwing) seed oil', International Journal of Food Science and Nutrition, 3(5), pp. 153–156.
Emelike, N.J., Ujong, A.E. and Achinewu, S.C. (2020) 'Physicochemical and antioxidant properties of oils used by local fried food vendors in D/line-Port Harcourt, Rivers State', Agriculture and Food Sciences Research, 7(1), pp. 89–96. Available at: https://doi.org/10.20448/journal.512. 2020.71.89.96
Fekadu, D., Abera, S. and Weldemichael, H. (2024) 'The influences of street food vendor frying equipment on the quality of frying oil', Heliyon, 10(7), p. e28293. Available at: https://doi.org/10.1016/j.heliyon.2024.e28293
Gilbraith, W.E., Carter, J.C., Adams, K.L., Booksh, K.S. and Ottaway, J.M. (2021) 'Improving prediction of peroxide value of edible oils using regularized regression models', Molecules, 26(23), p. 7281. Available at: https://doi.org/10.3390/molecules26237281
Ichu, C.B. and Nwakanma, H.O. (2019) 'Comparative study of the physicochemical characterization and quality of edible vegetable oils', International Journal of Research in Informative Science Application and Techniques (IJRISAT), 3(2), pp. 1–9. Available at: https://doi.org/10.46828/ijrisat.v3i2.56
Idun-Acquah, N., Obeng, G.Y. and Mensah, E. (2016) 'Repetitive use of vegetable cooking oil and effects on physico-chemical properties – Case of frying with redfish (Lutjanus fulgens)', Science and Technology, 6(1), pp. 8–14. Available at: https://doi.org/10.5923/j.scit.20160601.02
Ingenbleek, L., Veyrand, B., Adegboye, A., Hossou, S.E., Koné, A.Z., Oyedele, A.D., Kisito, C.S., Dembélé, Y.K., Eyangoh, S. and Verger, P. (2019) 'Polycyclic aromatic hydrocarbons in foods from the first regional total diet study in Sub-Saharan Africa: Contamination profile and occurrence data', Food Control, 103, pp. 133–144. Available at: https://doi.org/10.1016/j.foodcont.2019.04.006
Indian Standards Institution (ISI) (1984) 'Unsaponifiable matter, RI, Specific gravity, Colour, IV, SV'. In: Handbook of Food Analysis (Part XIII), pp. 62–90. Indian Institution of Standards.
ISO 15753 (2006) Animal and Vegetable Fats and Oils – Determination of Polycyclic Aromatic Hydrocarbons. Available at: https://www.iso.org/standard/36703.html (Accessed: 3 January 2025).
Kaleem, A., Aziz, S. and Iqtedar, M. (2015) 'Investigating changes and effect of peroxide values in cooking oils subject to light and heat', FUUAST Journal of Biology, 5(2), pp. 191–196.
Kalia, J. and Mishra, M. (2019) 'Quality and safety of the frying oils used in small-or medium-sized food enterprises', International Journal of Engineering, Management, Humanities and Social Sciences Paradigms, 31.
Karimi, S., Wawire, M. and Mathooko, F.M. (2017) 'Impact of frying practices and frying conditions on the quality and safety of frying oils used by street vendors and restaurants in Nairobi, Kenya', Journal of Food Composition and Analysis, 62, pp. 239–244. Available at: https://doi.org/10.1016/J.JFCA.2017.07.004
Kostopolou, M., Mylona, A., Nikolaou, A., Lofrano, G., Meric, S. and Belgiorno, V. (2007) 'Determination of polycyclic aromatic hydrocarbons in the harbour sediments of Mytilene, Greece'. In: Proceedings of 10th International Conference on Environmental Science and Technology, pp. A723–A729.
Li, G., Wu, S., Wang, L. and Akoh, C.C. (2016) 'Concentration, dietary exposure and health risk estimation of polycyclic aromatic hydrocarbons (PAHs) in youtiao, a Chinese traditional fried food', Food Control, 59, pp. 328–336. Available at: https://doi.org/10.1016/J.FOODCONT.2015.06.003
Liu, Y., Li, J., Cheng, Y. and Liu, Y. (2019) 'Effect of frying oils' fatty acid profile on quality, free radical and volatiles over deep-frying process: A comparative study using chemometrics', LWT, 101, pp. 331–341. Available at: https://doi.org/10.1016/ j.lwt.2018.11.033
Liu, Z., Tse, L.A., Ho, S.C., Wu, S., Chen, B., Chan, D. and Wong, S.Y. (2017) 'Dietary acrylamide exposure was associated with increased cancer mortality in Chinese elderly men and women: a 11-year prospective study of Mr. and Ms. OS Hong Kong', Journal of Cancer Research and Clinical Oncology, 143, pp. 2317–2326. Available at: https://doi.org/10.1007/s00432-017-2477-4
Manzoor, S., Masoodi, F.A., Rashid, R., Ahmad, M. and Kousar, M. (2022) 'Quality assessment and degradative changes of deep-fried oils in street fried food chain of Kashmir, India', Food Control, 141, p. 109184. Available at: https://doi.org/10.1016/j.foodcont.2022.109184
Mariana, R.R., Susanti, E., Hidayati, L. and Wahab, R.A. (2020) 'Analysis of peroxide value, free fatty acid, and water content changes in used cooking oil from street vendors in Malang'. In: AIP Conference Proceedings, 2231. Available at: https://doi.org/10.1063/5.0002656
Nayak, P.K., Dash, U.M.A., Rayaguru, K. and Krishnan, K.R. (2016) 'Physio-chemical changes during repeated frying of cooked oil: A Review', Journal of Food Biochemistry, 40(3), pp. 371–390. Available at: https://doi.org/10.1111/jfbc.12215
Ngozi, E.O., Giwa, O.H., Adeoye, B.K., Ani, I.F., Ajuzie, N.C. and Olutayo, T.I. (2019) 'Quality effect of repetitive use of frying oil by street food vendors on quality of the oil', Nigerian Journal of Nutritional Sciences, 40(1), pp. 73–78. Available at: https://doi.org/10.4314/njns.v40i1
Nova Analytics (2008) Abbe 60 Refractometer User Guide (Issue 4B). Available at: https://img.daihan-sci.com/allforlab/pdf/ Refractometer_Abbe60_man_en.pdf (Accessed: 3 January 2025).
Oke, E.K., Idowu, M.A., Sobukola, O.P., Adeyeye, S.A.O. and Akinsola, A.O. (2018) 'Frying of food: a critical review', Journal of Culinary Science and Technology, 16(2), pp. 107–127. Available at: https://doi.org/10.1080/15428052.2017.1333936
Oladunjoye, O.M. and Aluko, O.O. (2024) 'The perception of food vendors on the associated effects of used cooking oil in Lagos State, Nigeria', International Journal of Environmental Health Research, pp. 1–14. Available at: https://doi.org/10.1080/09603123.2024.2338888
Pambou-Tobi, N.P., Nzikou, J.M., Matos, L., Ndangui, C.B., Kimbonguila, A., Abena, A.A., Silou, T., Scher, J. and Desobry, S. (2010) 'Comparative study of stability measurements for two frying oils: soybean oil and refined palm oil', Advance Journal of Food Science and Technology, 2(1), pp. 22–27.
Phiri, G., Mumba, P. and Mangwera, A. (2006) 'The quality of cooking oil used in informal food processing in Malawi: a preliminary study', International Journal of Consumer Studies, 30(5), pp. 527–532. Available at: https://doi.org/10.1111/j.1470-6431.2006.00513.x
Pule, O.B. and Torto, N. (2009) Determination of Acrylamide in Cooking Oil by Agilent Bond Elut QuEChERS Acrylamide Kit and HPLC-DAD. Agilent Technologies.
Rani, L., Kumar, M., Kaushik, D., Kaur, J., Kumar, A., Oz, F., Proestos, C. and Oz, E. (2023) 'A review on the frying process: Methods, models and their mechanism and application in the food industry', Food Research International, 172, p. 113176. Available at: https://doi.org/10.1016/J.FOODRES.2023.113176
Wai, T. (2007) 'Local repeatedly used deep-frying oils are generally safe', International Journal of Science and Medical Education, 1, pp. 55–60.
Xin, L., Hu, M., Ma, X., Wu, S., Yoong, J.H., Chen, S., Tarmizi, A.H.A. and Zhang, G. (2022) 'Selection of 12 vegetable oils influences the prevalence of polycyclic aromatic hydrocarbons, fatty acids, tocol homologs and total polar components during deep frying', Journal of Food Composition and Analysis, 114, p. 104840. Available at: https://doi.org/10.1016/j.jfca.2022.104840
Yılmaz, E. and Aydeniz, B. (2011) 'Quantitative assessment of frying oil quality in fast food restaurants', GIDA: The Journal of Food, 36(3).
Adani, G., Filippini, T., Wise, L.A., Halldorsson, T.I., Blaha, L. and Vinceti, M. (2020) 'Dietary intake of acrylamide and risk of breast, endometrial, and ovarian cancers: a systematic review and dose–response meta-analysis', Cancer Epidemiology, Biomarkers and Prevention, 29, pp. 1095–1106. Available at: https://doi.org/10.1158/1055-9965.EPI-19-1628
Adelagun, R.O., Berezi, E.P., Fagbemi, J.O., Igbaro, O.J., Aihkoje, F.E., Ngana, O., Osondu, G. and Garba, M.S. (2023) 'Evaluation of level of rancidity of edible oil in some fried snacks food', Journal of Chemical Society of Nigeria, 48(1). Available at: https://doi.org/10.46602/jcsn.v48i1.853
Adu, O.B., Fajana, O.O., Ogunrinola, O.O., Okonkwo, U.V., Evuarherhe, P. and Elemo, B.O. (2019) 'Effect of continuous usage on the natural antioxidants of vegetable oils during deep-fat frying', Scientific African, 5, p. e00144. Available at: https://doi.org/10.1016/J.SCIAF.2019.E00144
Al-Khusaibi, M. and Rahman, M.S. (2021) 'Quality assessment of frying oil degradation'. In: Khan, M.S. and Rahman, M.S. (eds.) Techniques to Measure Food Safety and Quality: Microbial, Chemical, and Sensory, Cham: Springer International Publishing, pp. 329–344. Available at: https://doi.org/10.1007/ 978-3-030-68636-9_14
American Oil Chemists' Society (AOCS) (1998) Official Methods and Recommended Practices of the AOCS. Champaign: American Oil Chemists' Society. Available at: https://library.aocs.org/ (Accessed: 3 January 2025).
Başaran, B. and Turk, H. (2021) 'The influence of consecutive use of different oil types and frying oil in French fries on the acrylamide level', Journal of Food Composition and Analysis, 104, p. 104177. Available at: https://doi.org/10.1016/J.JFCA.2021.104177
Bekdeşer, B., Esin Çelik, S., Bener, M., Dondurmacıoğlu, F., Yıldırım, E., Nida Yavuz, E. and Apak, R. (2024) 'Determination of primary and secondary oxidation products in vegetable oils with gold nanoparticle based fluorometric turn-on nanosensor: A new total oxidation value', Food Chemistry, 434, p. 137426. Available at: https://doi.org/10.1016/J.FOODCHEM.2023.137426
Bureau of Indian Standards (2005) Manual of Methods of Analysis of Food, Oil, and Fat. FAD 10: Food and Agriculture Standard IS: 548 (Part 2). New Delhi: Bureau of Indian Standards.
Chebet, J., Kinyanjui, T. and Cheplogoi, P.K. (2016) 'Impact of frying on iodine value of vegetable oils before and after deep frying in different types of food in Kenya', Journal of Scientific and Innovative Research, 5(5), pp. 193–196.
Codex Alimentarius Commission (1999) Codex Standard for Named Vegetable Oils (Codex Stan 210-1999). Available at: https://www.fao.org/fao-who-codexalimentarius/sh-proxy/en/?lnk=1&url=https%253A%252F%252Fworkspace.fao.org%252Fsites%252Fcodex%252FStandards%252FCXS%2B210-1999%252FCXS_210e.pdf (Accessed: 5 January 2025).
Diamante, L.M. and Lan, T. (2014) 'Absolute viscosities of vegetable oils at different temperatures and shear rate range of 64.5 to 4835 s-1', Journal of Food Processing, 2014(1), p. 234583. Available at: https://doi.org/10.1155/2014/234583
European Food Safety Authority (EFSA) (2008) 'Polycyclic aromatic hydrocarbons in food: Scientific opinion of the panel on contaminants in the food chain', EFSA Journal, 6(8), p. 724. Available at: https://doi.org/10.2903/j.efsa.2008.724
Ekpe, O.O., Bassey, S.O., Udefa, A.L. and Essien, N.M. (2018) 'Physicochemical properties and fatty acid profile of Irvingia gabonensis (Kuwing) seed oil', International Journal of Food Science and Nutrition, 3(5), pp. 153–156.
Emelike, N.J., Ujong, A.E. and Achinewu, S.C. (2020) 'Physicochemical and antioxidant properties of oils used by local fried food vendors in D/line-Port Harcourt, Rivers State', Agriculture and Food Sciences Research, 7(1), pp. 89–96. Available at: https://doi.org/10.20448/journal.512. 2020.71.89.96
Fekadu, D., Abera, S. and Weldemichael, H. (2024) 'The influences of street food vendor frying equipment on the quality of frying oil', Heliyon, 10(7), p. e28293. Available at: https://doi.org/10.1016/j.heliyon.2024.e28293
Gilbraith, W.E., Carter, J.C., Adams, K.L., Booksh, K.S. and Ottaway, J.M. (2021) 'Improving prediction of peroxide value of edible oils using regularized regression models', Molecules, 26(23), p. 7281. Available at: https://doi.org/10.3390/molecules26237281
Ichu, C.B. and Nwakanma, H.O. (2019) 'Comparative study of the physicochemical characterization and quality of edible vegetable oils', International Journal of Research in Informative Science Application and Techniques (IJRISAT), 3(2), pp. 1–9. Available at: https://doi.org/10.46828/ijrisat.v3i2.56
Idun-Acquah, N., Obeng, G.Y. and Mensah, E. (2016) 'Repetitive use of vegetable cooking oil and effects on physico-chemical properties – Case of frying with redfish (Lutjanus fulgens)', Science and Technology, 6(1), pp. 8–14. Available at: https://doi.org/10.5923/j.scit.20160601.02
Ingenbleek, L., Veyrand, B., Adegboye, A., Hossou, S.E., Koné, A.Z., Oyedele, A.D., Kisito, C.S., Dembélé, Y.K., Eyangoh, S. and Verger, P. (2019) 'Polycyclic aromatic hydrocarbons in foods from the first regional total diet study in Sub-Saharan Africa: Contamination profile and occurrence data', Food Control, 103, pp. 133–144. Available at: https://doi.org/10.1016/j.foodcont.2019.04.006
Indian Standards Institution (ISI) (1984) 'Unsaponifiable matter, RI, Specific gravity, Colour, IV, SV'. In: Handbook of Food Analysis (Part XIII), pp. 62–90. Indian Institution of Standards.
ISO 15753 (2006) Animal and Vegetable Fats and Oils – Determination of Polycyclic Aromatic Hydrocarbons. Available at: https://www.iso.org/standard/36703.html (Accessed: 3 January 2025).
Kaleem, A., Aziz, S. and Iqtedar, M. (2015) 'Investigating changes and effect of peroxide values in cooking oils subject to light and heat', FUUAST Journal of Biology, 5(2), pp. 191–196.
Kalia, J. and Mishra, M. (2019) 'Quality and safety of the frying oils used in small-or medium-sized food enterprises', International Journal of Engineering, Management, Humanities and Social Sciences Paradigms, 31.
Karimi, S., Wawire, M. and Mathooko, F.M. (2017) 'Impact of frying practices and frying conditions on the quality and safety of frying oils used by street vendors and restaurants in Nairobi, Kenya', Journal of Food Composition and Analysis, 62, pp. 239–244. Available at: https://doi.org/10.1016/J.JFCA.2017.07.004
Kostopolou, M., Mylona, A., Nikolaou, A., Lofrano, G., Meric, S. and Belgiorno, V. (2007) 'Determination of polycyclic aromatic hydrocarbons in the harbour sediments of Mytilene, Greece'. In: Proceedings of 10th International Conference on Environmental Science and Technology, pp. A723–A729.
Li, G., Wu, S., Wang, L. and Akoh, C.C. (2016) 'Concentration, dietary exposure and health risk estimation of polycyclic aromatic hydrocarbons (PAHs) in youtiao, a Chinese traditional fried food', Food Control, 59, pp. 328–336. Available at: https://doi.org/10.1016/J.FOODCONT.2015.06.003
Liu, Y., Li, J., Cheng, Y. and Liu, Y. (2019) 'Effect of frying oils' fatty acid profile on quality, free radical and volatiles over deep-frying process: A comparative study using chemometrics', LWT, 101, pp. 331–341. Available at: https://doi.org/10.1016/ j.lwt.2018.11.033
Liu, Z., Tse, L.A., Ho, S.C., Wu, S., Chen, B., Chan, D. and Wong, S.Y. (2017) 'Dietary acrylamide exposure was associated with increased cancer mortality in Chinese elderly men and women: a 11-year prospective study of Mr. and Ms. OS Hong Kong', Journal of Cancer Research and Clinical Oncology, 143, pp. 2317–2326. Available at: https://doi.org/10.1007/s00432-017-2477-4
Manzoor, S., Masoodi, F.A., Rashid, R., Ahmad, M. and Kousar, M. (2022) 'Quality assessment and degradative changes of deep-fried oils in street fried food chain of Kashmir, India', Food Control, 141, p. 109184. Available at: https://doi.org/10.1016/j.foodcont.2022.109184
Mariana, R.R., Susanti, E., Hidayati, L. and Wahab, R.A. (2020) 'Analysis of peroxide value, free fatty acid, and water content changes in used cooking oil from street vendors in Malang'. In: AIP Conference Proceedings, 2231. Available at: https://doi.org/10.1063/5.0002656
Nayak, P.K., Dash, U.M.A., Rayaguru, K. and Krishnan, K.R. (2016) 'Physio-chemical changes during repeated frying of cooked oil: A Review', Journal of Food Biochemistry, 40(3), pp. 371–390. Available at: https://doi.org/10.1111/jfbc.12215
Ngozi, E.O., Giwa, O.H., Adeoye, B.K., Ani, I.F., Ajuzie, N.C. and Olutayo, T.I. (2019) 'Quality effect of repetitive use of frying oil by street food vendors on quality of the oil', Nigerian Journal of Nutritional Sciences, 40(1), pp. 73–78. Available at: https://doi.org/10.4314/njns.v40i1
Nova Analytics (2008) Abbe 60 Refractometer User Guide (Issue 4B). Available at: https://img.daihan-sci.com/allforlab/pdf/ Refractometer_Abbe60_man_en.pdf (Accessed: 3 January 2025).
Oke, E.K., Idowu, M.A., Sobukola, O.P., Adeyeye, S.A.O. and Akinsola, A.O. (2018) 'Frying of food: a critical review', Journal of Culinary Science and Technology, 16(2), pp. 107–127. Available at: https://doi.org/10.1080/15428052.2017.1333936
Oladunjoye, O.M. and Aluko, O.O. (2024) 'The perception of food vendors on the associated effects of used cooking oil in Lagos State, Nigeria', International Journal of Environmental Health Research, pp. 1–14. Available at: https://doi.org/10.1080/09603123.2024.2338888
Pambou-Tobi, N.P., Nzikou, J.M., Matos, L., Ndangui, C.B., Kimbonguila, A., Abena, A.A., Silou, T., Scher, J. and Desobry, S. (2010) 'Comparative study of stability measurements for two frying oils: soybean oil and refined palm oil', Advance Journal of Food Science and Technology, 2(1), pp. 22–27.
Phiri, G., Mumba, P. and Mangwera, A. (2006) 'The quality of cooking oil used in informal food processing in Malawi: a preliminary study', International Journal of Consumer Studies, 30(5), pp. 527–532. Available at: https://doi.org/10.1111/j.1470-6431.2006.00513.x
Pule, O.B. and Torto, N. (2009) Determination of Acrylamide in Cooking Oil by Agilent Bond Elut QuEChERS Acrylamide Kit and HPLC-DAD. Agilent Technologies.
Rani, L., Kumar, M., Kaushik, D., Kaur, J., Kumar, A., Oz, F., Proestos, C. and Oz, E. (2023) 'A review on the frying process: Methods, models and their mechanism and application in the food industry', Food Research International, 172, p. 113176. Available at: https://doi.org/10.1016/J.FOODRES.2023.113176
Wai, T. (2007) 'Local repeatedly used deep-frying oils are generally safe', International Journal of Science and Medical Education, 1, pp. 55–60.
Xin, L., Hu, M., Ma, X., Wu, S., Yoong, J.H., Chen, S., Tarmizi, A.H.A. and Zhang, G. (2022) 'Selection of 12 vegetable oils influences the prevalence of polycyclic aromatic hydrocarbons, fatty acids, tocol homologs and total polar components during deep frying', Journal of Food Composition and Analysis, 114, p. 104840. Available at: https://doi.org/10.1016/j.jfca.2022.104840
Yılmaz, E. and Aydeniz, B. (2011) 'Quantitative assessment of frying oil quality in fast food restaurants', GIDA: The Journal of Food, 36(3).
*Corresponding author (O.B. Adu)
E-mail: oluwatosin.adu@lasu.edu.ng
ORCID ID: https://orcid.org/0000-0002-4216-165X
E-mail: oluwatosin.adu@lasu.edu.ng
ORCID ID: https://orcid.org/0000-0002-4216-165X
Type of Study: Original article |
Subject:
Special
Received: 25/02/09 | Accepted: 26/02/26 | Published: 26/03/20
Received: 25/02/09 | Accepted: 26/02/26 | Published: 26/03/20
References
1. Adani, G., Filippini, T., Wise, L.A., Halldorsson, T.I., Blaha, L. and Vinceti, M. (2020) 'Dietary intake of acrylamide and risk of breast, endometrial, and ovarian cancers: a systematic review and dose–response meta-analysis', Cancer Epidemiology, Biomarkers and Prevention, 29, pp. 1095–1106. Available at: [DOI:10.1158/1055-9965.EPI-19-1628]
2. Adelagun, R.O., Berezi, E.P., Fagbemi, J.O., Igbaro, O.J., Aihkoje, F.E., Ngana, O., Osondu, G. and Garba, M.S. (2023) 'Evaluation of level of rancidity of edible oil in some fried snacks food', Journal of Chemical Society of Nigeria, 48(1). Available at: [DOI:10.46602/jcsn.v48i1.853]
3. Adu, O.B., Fajana, O.O., Ogunrinola, O.O., Okonkwo, U.V., Evuarherhe, P. and Elemo, B.O. (2019) 'Effect of continuous usage on the natural antioxidants of vegetable oils during deep-fat frying', Scientific African, 5, p. e00144. Available at: [DOI:10.1016/J.SCIAF.2019.E00144]
4. Al-Khusaibi, M. and Rahman, M.S. (2021) 'Quality assessment of frying oil degradation'. In: Khan, M.S. and Rahman, M.S. (eds.) Techniques to Measure Food Safety and Quality: Microbial, Chemical, and Sensory, Cham: Springer International Publishing, pp. 329–344. Available at: [DOI:10.1007/ 978-3-030-68636-9_14]
5. American Oil Chemists' Society (AOCS) (1998) Official Methods and Recommended Practices of the AOCS. Champaign: American Oil Chemists' Society. Available at: https://library.aocs.org/ (Accessed: 3 January 2025).
6. Başaran, B. and Turk, H. (2021) 'The influence of consecutive use of different oil types and frying oil in French fries on the acrylamide level', Journal of Food Composition and Analysis, 104, p. 104177. Available at: [DOI:10.1016/J.JFCA.2021.104177]
7. Bekdeşer, B., Esin Çelik, S., Bener, M., Dondurmacıoğlu, F., Yıldırım, E., Nida Yavuz, E. and Apak, R. (2024) 'Determination of primary and secondary oxidation products in vegetable oils with gold nanoparticle based fluorometric turn-on nanosensor: A new total oxidation value', Food Chemistry, 434, p. 137426. Available at: [DOI:10.1016/J.FOODCHEM.2023.137426]
8. Bureau of Indian Standards (2005) Manual of Methods of Analysis of Food, Oil, and Fat. FAD 10: Food and Agriculture Standard IS: 548 (Part 2). New Delhi: Bureau of Indian Standards.
9. Chebet, J., Kinyanjui, T. and Cheplogoi, P.K. (2016) 'Impact of frying on iodine value of vegetable oils before and after deep frying in different types of food in Kenya', Journal of Scientific and Innovative Research, 5(5), pp. 193–196.
10. Codex Alimentarius Commission (1999) Codex Standard for Named Vegetable Oils (Codex Stan 210-1999). Available at: https://www.fao.org/fao-who-codexalimentarius/sh-proxy/en/?lnk=1&url=https%253A%252F%252Fworkspace.fao.org%252Fsites%252Fcodex%252FStandards%252FCXS%2B210-1999%252FCXS_210e.pdf (Accessed: 5 January 2025).
11. Diamante, L.M. and Lan, T. (2014) 'Absolute viscosities of vegetable oils at different temperatures and shear rate range of 64.5 to 4835 s-1', Journal of Food Processing, 2014(1), p. 234583. Available at: [DOI:10.1155/2014/234583]
12. European Food Safety Authority (EFSA) (2008) 'Polycyclic aromatic hydrocarbons in food: Scientific opinion of the panel on contaminants in the food chain', EFSA Journal, 6(8), p. 724. Available at: [DOI:10.2903/j.efsa.2008.724]
13. Ekpe, O.O., Bassey, S.O., Udefa, A.L. and Essien, N.M. (2018) 'Physicochemical properties and fatty acid profile of Irvingia gabonensis (Kuwing) seed oil', International Journal of Food Science and Nutrition, 3(5), pp. 153–156.
14. Emelike, N.J., Ujong, A.E. and Achinewu, S.C. (2020) 'Physicochemical and antioxidant properties of oils used by local fried food vendors in D/line-Port Harcourt, Rivers State', Agriculture and Food Sciences Research, 7(1), pp. 89–96. Available at: [DOI:10.20448/journal.512.2020.71. 89.96]
15. Fekadu, D., Abera, S. and Weldemichael, H. (2024) 'The influences of street food vendor frying equipment on the quality of frying oil', Heliyon, 10(7), p. e28293. Available at: [DOI:10.1016/j.heliyon.2024.e28293]
16. Gilbraith, W.E., Carter, J.C., Adams, K.L., Booksh, K.S. and Ottaway, J.M. (2021) 'Improving prediction of peroxide value of edible oils using regularized regression models', Molecules, 26(23), p. 7281. Available at: [DOI:10.3390/molecules26237281]
17. Ichu, C.B. and Nwakanma, H.O. (2019) 'Comparative study of the physicochemical characterization and quality of edible vegetable oils', International Journal of Research in Informative Science Application and Techniques (IJRISAT), 3(2), pp. 1–9. Available at: [DOI:10.46828/ijrisat.v3i2.56]
18. Idun-Acquah, N., Obeng, G.Y. and Mensah, E. (2016) 'Repetitive use of vegetable cooking oil and effects on physico-chemical properties – Case of frying with redfish (Lutjanus fulgens)', Science and Technology, 6(1), pp. 8–14. Available at: [DOI:10.5923/j.scit.20160601.02]
19. Ingenbleek, L., Veyrand, B., Adegboye, A., Hossou, S.E., Koné, A.Z., Oyedele, A.D., Kisito, C.S., Dembélé, Y.K., Eyangoh, S. and Verger, P. (2019) 'Polycyclic aromatic hydrocarbons in foods from the first regional total diet study in Sub-Saharan Africa: Contamination profile and occurrence data', Food Control, 103, pp. 133–144. Available at: [DOI:10.1016/j.foodcont.2019.04.006]
20. Indian Standards Institution (ISI) (1984) 'Unsaponifiable matter, RI, Specific gravity, Colour, IV, SV'. In: Handbook of Food Analysis (Part XIII), pp. 62–90. Indian Institution of Standards.
21. ISO 15753 (2006) Animal and Vegetable Fats and Oils – Determination of Polycyclic Aromatic Hydrocarbons. Available at: https://www.iso.org/standard/36703.html (Accessed: 3 January 2025).
22. Kaleem, A., Aziz, S. and Iqtedar, M. (2015) 'Investigating changes and effect of peroxide values in cooking oils subject to light and heat', FUUAST Journal of Biology, 5(2), pp. 191–196.
23. Kalia, J. and Mishra, M. (2019) 'Quality and safety of the frying oils used in small-or medium-sized food enterprises', International Journal of Engineering, Management, Humanities and Social Sciences Paradigms, 31.
24. Karimi, S., Wawire, M. and Mathooko, F.M. (2017) 'Impact of frying practices and frying conditions on the quality and safety of frying oils used by street vendors and restaurants in Nairobi, Kenya', Journal of Food Composition and Analysis, 62, pp. 239–244. Available at: [DOI:10.1016/J.JFCA.2017.07.004]
25. Kostopolou, M., Mylona, A., Nikolaou, A., Lofrano, G., Meric, S. and Belgiorno, V. (2007) 'Determination of polycyclic aromatic hydrocarbons in the harbour sediments of Mytilene, Greece'. In: Proceedings of 10th International Conference on Environmental Science and Technology, pp. A723–A729.
26. Li, G., Wu, S., Wang, L. and Akoh, C.C. (2016) 'Concentration, dietary exposure and health risk estimation of polycyclic aromatic hydrocarbons (PAHs) in youtiao, a Chinese traditional fried food', Food Control, 59, pp. 328–336. Available at: [DOI:10.1016/J.FOODCONT.2015.06.003]
27. Liu, Y., Li, J., Cheng, Y. and Liu, Y. (2019) 'Effect of frying oils' fatty acid profile on quality, free radical and volatiles over deep-frying process: A comparative study using chemometrics', LWT, 101, pp. 331–341. Available at: [DOI:10.1016/j.lwt.2018.11.033]
28. Liu, Z., Tse, L.A., Ho, S.C., Wu, S., Chen, B., Chan, D. and Wong, S.Y. (2017) 'Dietary acrylamide exposure was associated with increased cancer mortality in Chinese elderly men and women: a 11-year prospective study of Mr. and Ms. OS Hong Kong', Journal of Cancer Research and Clinical Oncology, 143, pp. 2317–2326. Available at: [DOI:10.1007/s00432-017-2477-4]
29. Manzoor, S., Masoodi, F.A., Rashid, R., Ahmad, M. and Kousar, M. (2022) 'Quality assessment and degradative changes of deep-fried oils in street fried food chain of Kashmir, India', Food Control, 141, p. 109184. Available at: [DOI:10.1016/j.foodcont.2022.109184]
30. Mariana, R.R., Susanti, E., Hidayati, L. and Wahab, R.A. (2020) 'Analysis of peroxide value, free fatty acid, and water content changes in used cooking oil from street vendors in Malang'. In: AIP Conference Proceedings, 2231. Available at: [DOI:10.1063/5.0002656]
31. Nayak, P.K., Dash, U.M.A., Rayaguru, K. and Krishnan, K.R. (2016) 'Physio-chemical changes during repeated frying of cooked oil: A Review', Journal of Food Biochemistry, 40(3), pp. 371–390. Available at: [DOI:10.1111/jfbc.12215]
32. Ngozi, E.O., Giwa, O.H., Adeoye, B.K., Ani, I.F., Ajuzie, N.C. and Olutayo, T.I. (2019) 'Quality effect of repetitive use of frying oil by street food vendors on quality of the oil', Nigerian Journal of Nutritional Sciences, 40(1), pp. 73–78. Available at: [DOI:10.4314/njns.v40i1]
33. Nova Analytics (2008) Abbe 60 Refractometer User Guide (Issue 4B). Available at: https://img.daihan-sci.com/allforlab/pdf/ Refractometer_Abbe60_man_en.pdf (Accessed: 3 January 2025).
34. Oke, E.K., Idowu, M.A., Sobukola, O.P., Adeyeye, S.A.O. and Akinsola, A.O. (2018) 'Frying of food: a critical review', Journal of Culinary Science and Technology, 16(2), pp. 107–127. Available at: [DOI:10.1080/15428052.2017.1333936]
35. Oladunjoye, O.M. and Aluko, O.O. (2024) 'The perception of food vendors on the associated effects of used cooking oil in Lagos State, Nigeria', International Journal of Environmental Health Research, pp. 1–14. Available at: [DOI:10.1080/09603123.2024.2338888]
36. Pambou-Tobi, N.P., Nzikou, J.M., Matos, L., Ndangui, C.B., Kimbonguila, A., Abena, A.A., Silou, T., Scher, J. and Desobry, S. (2010) 'Comparative study of stability measurements for two frying oils: soybean oil and refined palm oil', Advance Journal of Food Science and Technology, 2(1), pp. 22–27.
37. Phiri, G., Mumba, P. and Mangwera, A. (2006) 'The quality of cooking oil used in informal food processing in Malawi: a preliminary study', International Journal of Consumer Studies, 30(5), pp. 527–532. Available at: [DOI:10.1111/j.1470-6431.2006.00513.x]
38. Pule, O.B. and Torto, N. (2009) Determination of Acrylamide in Cooking Oil by Agilent Bond Elut QuEChERS Acrylamide Kit and HPLC-DAD. Agilent Technologies.
39. Rani, L., Kumar, M., Kaushik, D., Kaur, J., Kumar, A., Oz, F., Proestos, C. and Oz, E. (2023) 'A review on the frying process: Methods, models and their mechanism and application in the food industry', Food Research International, 172, p. 113176. Available at: [DOI:10.1016/J.FOODRES.2023.113176]
40. Wai, T. (2007) 'Local repeatedly used deep-frying oils are generally safe', International Journal of Science and Medical Education, 1, pp. 55–60.
41. Xin, L., Hu, M., Ma, X., Wu, S., Yoong, J.H., Chen, S., Tarmizi, A.H.A. and Zhang, G. (2022) 'Selection of 12 vegetable oils influences the prevalence of polycyclic aromatic hydrocarbons, fatty acids, tocol homologs and total polar components during deep frying', Journal of Food Composition and Analysis, 114, p. 104840. Available at: [DOI:10.1016/j.jfca.2022.104840]
42. Yılmaz, E. and Aydeniz, B. (2011) 'Quantitative assessment of frying oil quality in fast food restaurants', GIDA: The Journal of Food, 36(3).
43. Zhang, Q., Saleh, A.S., Chen, J. and Shen, Q. (2012) 'Chemical alterations taken place during deep-fat frying based on certain reaction products: A review', Chemistry and Physics of Lipids, 165(6), pp. 662–681. Available at:
10.1016/ j.chemphyslip.2012.07.002 [DOI:10.1016/j.chemphyslip.2012.07.002]
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