Thermal Oxidation of Olive Oil, Sunflower Oil and a Mix of Both Oils during Forty Discontinuous Domestic Fryings of Different Foods

Investigating the role of adsorbent type and ratio in mitigating 3-MCPD and GE formation during the inhibition of palm oil chemical interesterification via earth treatment

This study examined the potential to mitigate 3-monochloropropane-1,2-diol esters (3-MCPDE) and glycidyl esters (GE) during the inhibition phase of chemical interesterification in refined, bleached, and deodorized (RBD) palm olein oil. Two types of bleaching earth, natural and acid-activated, were used at concentrations ranging from 3% to 6%, and their impact on ester formation was evaluated. Chemical interesterification and adsorption treatments significantly improved oil quality and reduced ester levels (p < 0.05). Specifically, using 6% bleaching earth led to a 98.5% reduction in 3-MCPDE and a 98.3% reduction in GE. The type of bleaching earth did not significantly affect the reduction of these contaminants, while the amount of bleaching earth used played a crucial role in the mitigation.

Vegetable Oils and Their Use for Frying: A Review of Their Compositional Differences and Degradation

This review provides an overview of the main vegetable oils of different botanical origin and composition that can be used for frying worldwide (olive and extra-virgin olive oil, high-oleic sunflower oil, rapeseed oil, peanut oil, rice bran oil, sunflower oil, corn oil, soybean oil, cottonseed oil, palm oil, palm kernel oil and coconut oil) and their degradation during this process. It is well known that during this culinary technique, oil's major and minor components degrade throughout different reactions, mainly thermoxidation, polymerization and, to a lesser extent, hydrolysis. If severe high temperatures are employed, isomerization to trans fatty acyl chains and cyclization are also possible. The factors conditioning frying medium degradation are addressed, including oil composition (unsaturation degree, fatty acyl chain length and "free" fatty acid content, and presence of beneficial and detrimental minor components), together with frying conditions and food characteristics. Likewise, this review also tackles how the frying oil and other processing conditions may impact on fried food quality (oil absorption, texture, flavor and color). Finally, potential health implications of fried food consumption are briefly reviewed.

Particulate matters, aldehydes, and polycyclic aromatic hydrocarbons produced from deep-frying emissions: comparisons of three cooking oils with distinct fatty acid profiles

It is recognized that hazardous emissions produced from frying oils may be related to oil properties, particularly the fatty acid composition. However, investigations have been limited and partial. In this work, the emissions from deep-frying foods with three oils (palm, olive, and soybean oils) with distinct fatty acid profiles were comprehensively examined in a simulated kitchen, and the interrelationship among emitted substances, oil quality parameters, and fatty acids profiles was explored. Firstly, palm oil emitted the highest number concentration of total particle matters ((3895 ± 1796) × 103 #/cm3), mainly in the Aitken mode (20-100 nm). We observed a positive correlation between particle number concentration and levels of palmitic acid, a major saturated fatty acid (SAFA) (rs = 0.73, p < 0.05), and total polar compounds (TPC) (rs = 0.68, p < 0.05) in the fried oil, a degradation marker which was also positively correlated with that of black carbon (BC) (rs = 0.68, p < 0.05). Secondly, soybean oil emitted the highest level of gaseous aldehydes (3636 ± 607 μg/m3), including acrolein, propinoaldehyde, crotonaldehyde, hexanal, and trans-2-heptenal; the total aldehyde concentration were positively correlated with α-linolenic acid (ALA) percentage (rs = 0.78, p < 0.01), while hexanal and trans-2-heptenal were with linoleic acid (LA) (rs = 0.73 and 0.67, p < 0.05). LA and ALA were two major polyunsaturated fatty acids in non-tropical plant oils. Thirdly, palm oil emitted the most particle-bound polycyclic aromatic hydrocarbons (PAHs), and a positive association was discovered between two PAHs and SAFA percentage. Olive oil seems superior to soybean and palm oils with regards to toxic emissions during deep-frying.

EFFECT OF LIGHT ON THE KINETICS OF OXIDATION REACTIONS IN VEGETABLE OILS

The article deals with the effect the lighting conditions of storage have on the oxidation stability of vegetable oils of various unsaturation degrees and made by different technologies (raw-pressed and unrefined sunflower oil and flaxseed oil) according to the main oxidation parameters: peroxide value (PV), acid value (AV), and colour value. It has been experimentally established that in natural lighting, at the end of the shelf life, the PV of flaxseed oil increased most significantly, from 0.55·10-3 to 11.2·10-3 mmolO2/kg (20 times). The PV of sunflower oils varied less: in unrefined oil, it changed from 0.48·10-3 to 4.5·10-3 mmolO2/kg (9 times), in raw-pressed, from 0.3·10-3 to 4.4·10‑3 mmolO2/kg (14.7 times). Under artificial UV radiation, the PV of sunflower oil increased from 0.3 to 0.55 mmol O2/kg after 2 hours of the experiment, and remained practically unchanged. In the case of flaxseed oil, after a slight increase from 0.55 to 0.7 mmol O2/kg, within the same period of time, there was then a decrease in the PV to 0.45 mmol O2/kg, which may indicate a relative instability of hydroperoxides that, due to their degradation, converted into more stable secondary compounds. The analysis of the oil oxidation kinetics by the PV has shown that the average rates of peroxide compounds accumulation in unrefined, raw-pressed, and flaxseed oils was 47·10-4, 48·10-4, 127·10-4 mmol ½О/kg·hour, respectively. At the same time, under natural light, the true rate of change of the AV in the oils studied was uneven over time. At the beginning of the experiment, it increased (especially noticeably in the case of flaxseed oil), at the end of the shelf life (the 5th week), it was slowed down significantly, decreasing to negative values, and in flaxseed oil, it had zero value, which indicates a constant value of AV in the experimental setting.

Consumers' knowledge, attitude and behavioural patterns towards the liquid wastes (cooking oil) in Istanbul, Turkey

This study was carried out to reveal the people's knowledge level about the harmful effects of waste oils, especially waste cooking oil, on the environment. It also aims to understand the attitude and behavioural patterns related to the safe disposal of them. Istanbul is chosen because it represents the entire country with its diverse socio-demographic and socio-cultural structure. A total of 408 respondents were randomly chosen and interviewed in the designated regions. The research data were obtained by using a structured survey consisting demographic and Likert scale questions. SPSS 23.0 statistical software was used to analyse the survey data. Results suggest that despite the high educational level, participants did not know that household liquid waste has a negative impact on the environment. They disagreed on the statement that liquid waste can damage water resources. Public spots, and formal and informal education were not found effective and failed to make the desired impact. Majority of participants did not know their duties in the disposal of waste. They also did not know where the liquid waste collection units were and what projects were being implemented in their neighbourhood. Fewer participants were concerned at what point and how the hazardous liquid wastes collected by municipalities were disposed of after leaving their habitat and whether these methods were reliable or acceptable. This research concludes that user behaviour was disappointing in cooking oil usage and waste oil disposal. The collection of waste cooking oils remains far below the developed countries.

Thermally Abused Frying Oil Potentiates Metastasis to Lung in a Murine Model of Late-Stage Breast Cancer

Deep-frying is a popular form of food preparation used globally and throughout in the United States. Each time dietary oils are heated to deep-frying temperatures, they undergo chemical alterations that result in a new matrix of lipid structures. These lipid products include triglyceride dimers, polymers, oxidized triglycerides, and cyclic monomers, which raises nutritional concerns about associations between these lipid products and heightened health risks. Reports of associations between thermally abused frying oil and deleterious health outcomes currently exist, yet there is little information concerning the effects of thermally abused frying oil consumption and the progression of breast cancer. This study used a late-stage breast cancer murine model and in vivo bioluminescent imaging to monitor progression of metastasis of 4T1 tumor cells in animals consuming fresh soybean oil (SBO) and a thermally abused frying oil (TAFO). Bioluminescent and histologic examinations demonstrated that TAFO consumption resulted in a marked increase of metastatic lung tumor formation compared to SBO consumption. Further, in animals consuming the TAFO treatment diet, metastatic tumors in the lung displayed a 1.4-fold increase in the Ki-67 marker of cellular proliferation and RNA-sequencing analysis of the hepatic tissue revealed a dietary-induced modulation of gene expression in the liver.

Frying performance of two virgin oils from <em>Cornicabra</em> olives with different ripeness indices

The frying performance of two virgin olive oils (VOO) from Cornicabra olives of different ripeness indices, 2.08 for VOO1 and 4.13 for VOO2, was evaluated. Thermal, oxidative and hydrolytic alterations were determined throughout 40 frying operations with potatoes. The initial oils showed similar fatty acid compositions and oxidative stability indices as determined by Rancimat, but VOO1 presented higher amounts of total polyphenols and tocopherols. The oils showed high and similar frying performance. No significant differences in the levels of polar compounds (PC) were found between the two oils during frying. Therefore, the frying stability of Cornicabra VOOs appears to be unconnected with olive fruit ripeness. The limit of degradation at 25% PC as established in different countries was calculated to occur at 55 frying operations in the two oils. As oil toxicity is related to the levels of compounds formed, the use of Cornicabra VOOs for frying is highly recommended.

Deep fried edible oils disturb hepatic redox equilibrium and heightens lipotoxicity and hepatosteatosis in male Wistar rats

Hepatosteatosis is a complex disorder, in which insulin resistance and associated dyslipidemic and inflammatory conditions are fundamental. Dietary habit, especially regular consumption of fat and sugar-rich diet, is an important risk factor. Coconut and mustard oils (CO and MO) are medium-chain saturated and monounsaturated fats that are common dietary ingredients among the Indian populations. Present study analyzed the effect of prolonged consumption of the fresh and thermally oxidized forms of these oils on glucose tolerance and hepatosteatosis in male Wistar rats. Thermally oxidized CO (TCO) and MO (TMO) possessed higher amount of lipid peroxidation products and elevated p-anisidine values than their fresh forms. Dietary administration of TCO and TMO along with fructose altered glucose tolerance and increased hyperglycemia in rats. Dyslipidemia was evident by elevated levels of triglycerides and reduced high density lipoprotein cholesterol (HDLc) levels in fructose and edible oil-fed group ( p < 0.05). Additionally, hepatic antioxidant status was diminished and oxidative stress markers were elevated in TCO- and TMO-fed rats. Substantiating these, hike in liver function marker enzyme activities were also observed in these animals. Supporting this, histological analysis revealed higher incidence of microvesicles and hepatocellular ballooning. Results thus suggest that consumption of thermally oxidized fats may cause hepatic damage.

Oxidized dietary oils enhance immediate- and/or delayed-type allergic reactions in BALB/c mice

BACKGROUND

The consumption of cooking oils may exacerbate some allergic diseases. In the present study, the effects of naturally oxidized olive oil on immediate- and/or delayed-type allergic reactions were investigated in BALB/c mice.

METHODS

Mouse models of 3 types of allergic reactions: contact hypersensitivity (CHS), active cutaneous anaphylaxis (ACA), and DNFB-induced hypersensitivity, were orally administered naturally oxidized olive oil that was obtained by keeping the oil at room temperature for more than 3 years. The effects of ultraviolet ray (UV)-irradiated olive oil and other dietary oils as well as their possible oxidation products on CHS were also investigated.

RESULTS

Naturally oxidized olive oil had a high peroxide value (POV) and exacerbated CHS, ACA, and DNFB-induced hypersensitivity in a POV-dependent manner. UV-irradiated olive oil, corn oil, sesame oil and triolein had high POVs, but almost the same acid value (AV) and thiobarbituric acid-reactive substance (TBARS) level as fresh oils. Fresh olive oil and the representative oxidation product with a high AV or TBARS level had no effect on CHS, whereas all UV-irradiated oils and naturally oxidized olive oil exacerbated it.

CONCLUSIONS

Oxidized dietary oils that have high POVs exacerbated immediate- and/or delayed-type allergic reactions regardless of the different oil constituents or oxidation processes.

Changes in chemical composition of frozen coated fish products during deep-frying

This work evaluates the influence of deep-frying coated fish products on total fat, fatty acid (FA) and amino acid profile, and on the formation of volatile compounds, with special attention on furan and its derivatives due to their potential harmful characteristics. As expected, deep-frying in sunflower oil increased linoleic acid content, but total fat amount increased only by 2% on a dry basis. Eicosapentanoic and docosahexanoic acids were preserved while γ- and α-linoleic acids were oxidised. Deep-frying also induces proteolysis, releasing free AA, and the formation of volatile compounds, particularly aldehydes and ketones arising from polyunsaturated FA. In addition, high quantities of furanic compounds, particularly furan and furfuryl alcohol, are generated during deep-frying coated fish. The breaded crust formed could contribute simultaneously for the low uptake of fat, preservation of long chain n-3 FA, and for the high amounts of furanic compounds formed during the deep-frying process.

Consumption of fried foods and weight gain in a Mediterranean cohort: the SUN project

BACKGROUND AND AIMS

The consumption of fried foods is believed to be linked with obesity and higher weight gain, however, the evidence from long-term randomized trials or prospective epidemiological studies is scarce. Therefore, the aim of our study was to prospectively evaluate the association between the consumption of fried foods and weight change and the incidence of overweight/obesity in a Mediterranean cohort.

METHODS AND RESULTS

Prospective cohort study of 9850 men and women with a mean age of 38.1 years (SD 11.4) were followed-up for a median of 6.1 years to assess average yearly change in body weight, and incidence of overweight/obesity. The consumption of fried foods was associated with higher weight gain, but the differences were of small magnitude and statistically non-significant. The incidence of overweight/obesity during follow-up was also assessed in the subset of 6821 participants with initial body mass index <25 kg/m(2) (initially free of overweight/obesity), after adjusting for potential confounders, the odds ratio for developing overweight/obesity among participants who consumed fried foods >4 times/week was 1.37 (95% confidence interval: 1.08 to 1.73) in comparison with those who consumed fried foods <2 times/week (p for trend = 0.02).

CONCLUSION

In this Mediterranean prospective cohort, a more frequent consumption of fried foods at baseline was associated with a higher risk of subsequently developing overweight/obesity during follow-up.

Impact of cooking and handling conditions on furanic compounds in breaded fish products

This study evaluates the influence of cooking and handling conditions on the quantity of furanic compounds (furan, 2-furfural, furfuryl alcohol, 2-pentylfuran, 5-hydroxymethylfurfural) in breaded fish products. Oven-baking and reheating in the microwave lead to low furanic compounds formation in comparison with deep-frying. The use of olive oil for deep-frying promoted higher levels of furanic compounds than sunflower oil. The amounts of these compounds diminished as the temperature and time of deep-frying decreased as well as after a delay after deep-frying. Thus, the generation of furanic compounds can be minimized by adjusting the cooking method and conditions, such as using an electric oven, deep-frying in sunflower oil at 160°C during 4min, or waiting 10min after cooking. However, these conditions that reduce furanic compounds levels also reduce the content of volatile compounds related to the aroma and flavour of fried foods. In this sense, new efforts should be done to reduce the formation of furanic compounds without being detrimental to the volatile profile.

Endogenous lipase catalyzed transesterification of olive oil fats. The formation of isomeric and oligomeric triacyleglycerols

The role of lipase to catalyze hydrolysis and transesterification of triacylglycerols (TAGs) was evaluated in model systems as well as in virgin olive oil. Tandem mass spectrometry was applied in the identification of modified TAGs, ionized by electrospray, formed during the incubation of selected TAGs with mono and di carboxylic acids. The oligomerization of TAGs was observed in authentic olive oil samples and verified in model systems under catalysis exerted by lipase, whose presence in olive oil was already documented. The hydrolytic pathways taken under enzymatic treatment is balanced by the formation of TAG oligomers that should not alter the nutritional value of the aliment.

Fatty acids profile and alteration of lemon seeds extract (Citrus limon) added to soybean oil under thermoxidation

This paper aimed at evaluating fatty acids profile and the total alteration of lemon seeds extract added to soybean oil under thermoxidation, verifying the isolated and synergistic effect of these antioxidants. Therefore, Control treatments, LSE (2,400 mg/kg Lemon Seeds Extract), TBHQ (mg/kg), Mixture 1 (LSE + 50 mg/kg TBHQ) and Mixture 2 (LSE + 25 mg/kg TBHQ) were subjected to 180°C for 20 h. Samples were taken at 0, 5, 10, 15 and 20 h intervals and analyzed as for fatty acid profile and total polar compounds. Results were subjected to variance analyses and Tukey tests at a 5% significance level. An increase in the percentage of saturated fatty acids and mono-unsaturated, and decrease in polyunsaturated fatty acids was observed, regardless of the treatments studied. For total polar compounds, it was verified that Mixtures 1 and 2 presented values lower than 25% with 20 h of heating, not surpassing the limits established in many countries for disposal of oils and fats under high temperatures, thus proving the synergistic effect of antioxidants.

Chemistry of deep-fat frying oils

Deep-fat frying produces desirable or undesirable flavor compounds and changes the flavor stability and quality of the oil by hydrolysis, oxidation, and polymerization. Tocopherols, essential amino acids, and fatty acids in foods are degraded during deep-fat frying. The reactions in deep-fat frying depend on factors such as replenishment of fresh oil, frying conditions, original quality of frying oil, food materials, type of fryer, antioxidants, and oxygen concentration. High frying temperature, the number of fryings, the contents of free fatty acids, polyvalent metals, and unsaturated fatty acids of oil decrease the oxidative stability and flavor quality of oil. Antioxidant decreases the frying oil oxidation, but the effectiveness of antioxidant decreases with high frying temperature. Lignan compounds in sesame oil are effective antioxidants in deep-fat frying.

Effect of the type of frying culinary fat on volatile compounds isolated in fried pork loin chops by using SPME-GC-MS

The effect of the type of frying culinary fat (olive oil, sunflower oil, butter, and pig lard) on volatile compounds isolated from fried pork loin chops (m. Longissimus dorsi) was measured by SPME-GC-MS. Frying modified the fatty acid composition of lipids from pork loin chops, which tended to be similar to that of the culinary fat used to fry. Volatile compounds formed from the oxidation of fatty acids increased, such as aldehydes, ketones, alcohols, and hydrocarbons. Besides, each culinary fat used modified the volatile profiles in fried meat differently. Sunflower oil-fried pork loin chops presented the highest aldehyde aliphatic content, probably due to their highest content of polyunsaturated acids. Hexanal, the most abundant aldehyde in fried samples, presented the most elevated content in sunflower oil-fried pork loin chops. In addition, these samples presented more heterocyclic compounds from the Maillard reaction than other fried samples. Volatiles detected in olive oil-fried pork loin chops were mainly lipid-derived compounds such as pentan-1-ol, hexanal, hept-2-enal, nonanal, decanal, benzaldehyde, and nonan-2-one. Butter-fried pork loins were abundant in ketones with a high number of carbons (heptan-2-one, nonan-2-one, undecan-2-one, tridecanone, and heptadecan-2-one). Pig lard-fried pork loin chops presented some Strecker aldehydes isolated in only these samples, such as 2-methylbutanal and 3-(methylthio)propanal, and a sulfur compound (dimethyl disulfide) related to Strecker aldehydes.

Comparison of the radical scavenging potential of polar and lipidic fractions of olive oil and other vegetable oils under normal conditions and after thermal treatment

The antioxidant activity (IC(50)) of extra virgin olive oil (EVOO), commercial olive oil, and other vegetable oils (soybean, sunflower, and corn oil) was determined by UV-vis and by electron paramagnetic resonance (EPR) spectroscopy of the stable radical 2,2-diphenyl-1-picrylhydrazyl (DPPH). Also, we studied the antioxidant activity of the methanol soluble phase (methanolic, MF) and the nonsoluble phase (lipidic, LF) of oils by the same methods. Similarly, we studied the effect of heating on the antioxidant activity at 160 and 190 degrees C. Also, the MF, containing the polyphenolic substances, was used for measurements of the radical scavenging capacity toward the most important oxygen free radicals, superoxide anion (O(2)(*)(-)) and hydroxyl (HO(*)) radicals. Results showed that soybean oil and EVOO had the highest antioxidant potential and thermal stability. In the case of soybean oil, the antioxidant capacity is the result of its high content of gamma- and delta-tocopherols (with the highest antioxidant capacity and thermostabilities), whereas in EVOO, the antioxidant potential is the result of the combination of specific antioxidant polyphenols, which are acting additionally as effective stabilizers of alpha-tocopherol. The high content of EVOO in tyrosol, hydrotyrosol, and oleuropein and other polyphenolics with radical scavenging abilities toward superoxide anion and hydroxyl radical suggests that olive oil possesses biological properties that could partially account for the observed beneficial health effects of the Mediterranean diet.

Influence of thermal treatments simulating cooking processes on the polyphenol content in virgin olive oil

Virgin olive oils were subjected to simulated common domestic processing, including frying, microwave heating, and boiling with water in a pressure cooker. The impact of these processes on polyphenol content and physicochemical characteristics of oils was assessed. Thermal oxidation of oils at 180 degrees C caused a significant decrease in hydroxytyrosol- and tyrosol-like substances. In contrast, oils heated for 25 h still retained a high proportion of the lignans 1-acetoxypinoresinol and pinoresinol. Thermal oxidation also resulted in a rapid degradation of alpha-tocopherol and the glyceridic fraction of oils. Microwave heating of oils for 10 min caused only minor losses in polyphenols, and the oil degradation was lower than that in thermoxidation assays. Again, lignans were the least affected polyphenols and did not change during microwave heating. Boiling a mixture of virgin olive oil and water in a pressure cooker for 30 min provoked the hydrolysis of the secoiridoid aglycons and the diffusion of the free phenolics hydroxytyrosol and tyrosol from the oil to the water phase. Losses of polyphenols were detected only at pH lower than 6. Moreover, alpha-tocopherol and the glyceridic fraction of oils were not modified during this process. It is worth noting that all the heating methods assayed resulted in more severe polyphenols losses and oil degradation for Arbequina than for Picual oil, which could be related to the lower content in polyunsaturated fatty acids of the latter olive cultivar. These findings may be relevant to the choice of cooking method and olive oil cultivar to increase the intake of olive polyphenols.

Ultrasonic assessment of oil quality during frying

In this paper, changes in ultrasonic properties during thermoxidation of virgin olive oil were studied. Samples of virgin olive oil were heated over different periods of time from 2 to 16 h at 200 degrees C. Oil degradation was characterized by means of physical and chemical changes, i.e., viscosity, color, polar compounds, polymers, and polar fatty acids. Ultrasonic measurements were carried out while the oil sample was cooled from 35 to 25 degrees C. It was found that velocity and attenuation measurements were related to viscosity measurements through a classical equation for viscous liquids. The ultrasonic measurements were also related to the percentages of polar compounds and polymers, which shows the feasibility of using ultrasonic properties to monitor oil quality. Nevertheless, as long as the ultrasonic measurements are temperature dependent, this variable must be controlled in order to obtain repetitive and reliable measurements.