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Olive oil stability under deep-frying conditions

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Abstract

The suitability of different commercial olive oil categories for domestic frying was investigated. Oil samples were taken every 3h of frying and evaluated for free acidity, peroxide and p-anisidine values, specific extinction coefficients, oxidative stability, fatty acids, vitamin E, β-carotene and total phenols, until the total polar compounds achieved the maximum legal value (25%). All olive oils were fried during more time than the commercial vegetable oil blend taken for comparison (from 24 to 27 h, against 15 h). The extra-virgin Protected Designation of Origin (PDO) olive oil was characterized by reduced levels of oxidation and hydrolysis, and superior amounts of minor antioxidant compounds. The "olive oil" commercial category behaves similarly, but "Cobrançosa" olive oils performance was slightly worse, and clearly different between years, highlighting the importance of blending different cultivars. The vegetable oil, despite containing significantly higher amounts of vitamin E, was highly susceptible to oxidation under frying conditions when compared to all olive oils. The results also show that the chemical composition of olive oils, particularly the amount of natural antioxidants, are important parameters in their predictive behavior along the frying process, but mostly that olive oil is clearly resistant to frying conditions, independently to the commercial category chosen.

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... The p-anisidine value (AnV) refers to the formation of more stable secondary products of lipid oxidation. This relates the susceptibility to the oxidation of fatty acids differently from that analyzed by the peroxide value (Casal et al., 2010). AnV values below 10 indicate low concentrations of degradation compounds (Casal et al., 2010;Silva et al., 1999). ...
... This relates the susceptibility to the oxidation of fatty acids differently from that analyzed by the peroxide value (Casal et al., 2010). AnV values below 10 indicate low concentrations of degradation compounds (Casal et al., 2010;Silva et al., 1999). Values above those recommended for this index were found for bacaba oil only when the samples were subjected to microwave heating for 15 min (AnV = 11.49 ...
... The maximum amount allowed for K 270 is 0.90 for common vegetable oils, and the K 232 values are required to be lower than 2.5 or even not evaluated. The ΔK is also a measure of lipid secondary oxidation, with maximum amounts of 0.15 for oil blends (Casal et al., 2010;Gharby et al., 2016;Pannico et al., 2015;Paraskevopoulou et al., 2007). There is a significant rise in K 232 and K 270 values with an increase in microwave heating time, as can be observed in Table 1. ...
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Background. Bacaba (Oenocarpus bacaba Mart.) has a high yield of oil, with the potential to produce biologically active natural products and can be considered a new "superfruit" with high value added. Materials and methods. Acid value, peroxide value, refractive index, saponification value, p-anisidine value, relative density, iodine value, total oxidation value, specific extinction coefficients at 232 and 270 nm (K 232 and K 270), ΔK, and color were determined. Results. The most significant changes in the quality values, such as peroxide (26.25 mEq kg-1), p-anisidine (11.41), acidity (14.66 mg KOH g-1 oil), and total oxidation (63.92) were determined for 15 min of microwave heating. Conclusions. The microwave heating promoted the acceleration of oxidative processes showing that, overall, much care should be taken when heating the bacaba oil by microwave to avoid oil degradation.
... The p-anisidine value (AnV) refers to the formation of more stable secondary products of lipid oxidation. This relates the susceptibility to the oxidation of fatty acids differently from that analyzed by the peroxide value (Casal et al., 2010). AnV values below 10 indicate low concentrations of degradation compounds (Casal et al., 2010;Silva et al., 1999). ...
... This relates the susceptibility to the oxidation of fatty acids differently from that analyzed by the peroxide value (Casal et al., 2010). AnV values below 10 indicate low concentrations of degradation compounds (Casal et al., 2010;Silva et al., 1999). Values above those recommended for this index were found for bacaba oil only when the samples were subjected to microwave heating for 15 min (AnV = 11.49 ...
... The maximum amount allowed for K 270 is 0.90 for common vegetable oils, and the K 232 values are required to be lower than 2.5 or even not evaluated. The ΔK is also a measure of lipid secondary oxidation, with maximum amounts of 0.15 for oil blends (Casal et al., 2010;Gharby et al., 2016;Pannico et al., 2015;Paraskevopoulou et al., 2007). There is a significant rise in K 232 and K 270 values with an increase in microwave heating time, as can be observed in Table 1. ...
Article
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Background: Bacaba (Oenocarpus bacaba Mart.) has a high yield of oil, with the potential to produce biologically active natural products and can be considered a new "superfruit" with high value added. Methods: Acid value, peroxide value, refractive index, saponification value, p-anisidine value, relative density, iodine value, total oxidation value, specific extinction coefficients at 232 and 270 nm (K232 and K270), ΔK, and color were determined. Results: The most significant changes in the quality values, such as peroxide (26.25 mEq·kg-1), p-anisidine (11.41), acidity (14.66 mg KOH·g-1 oil), and total oxidation (63.92) were determined for 15 min of microwave heating. Conclusions: The microwave heating promoted the acceleration of oxidative processes showing that, overall, much care should be taken when heating the bacaba oil by microwave to avoid oil degradation.
... Furthermore, oil quality and stability are also affected by variations in fatty acid compositions and antioxidant contents [6,7]. Despite their nutritional benefits, LA and ALA are more prone to oxidative deterioration during storage and high heat application [8]. ...
... Peroxide Value (PV). Peroxide value was analyzed as described by Casal et al. [6] where 5 g of samples was measured in an Erlenmeyer flask and dissolved the sample by adding 25 mL of the 3 volumes of glacial acetic acid and 2 volumes of chloroform solvent mixture. Then, 0.5 mL of the saturated potassium iodide solution was pipetted to the sample and swirled on a magnetic mixer for precisely 60 seconds. ...
... Analysis of variance (ANOVA) was used to compare oyster nut oil's fatty acid contents, PV, p-AV, and FFA to flaxseed oil, refined, and unrefined sunflower oils [8]. Pearson's correlation was used to establish the effects of storage time on the peroxide value (PV), panisidine value, and free fatty acid (FFA) contents in the four oil samples [6]. Post hoc tests using Tukey's multiple comparison tests were done to compare means. ...
Article
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The selection of healthy fats for consumption is important. Linoleic acid (LA) (omega-6) and alpha-linolenic acid (ALA) (omega-3) are essential polyunsaturated fatty acids required for the maintenance of good health; however, LA derivatives such as arachidonic acid (AA) are associated with the onset of inflammatory diseases, and both are prone to oxidation and deterioration. This study compared the fatty acid contents, peroxide value (PV), p-anisidine value (p-AV), and free fatty acids (FFA) of the oyster nut oil with refined sunflower, nonrefined sunflower, and flaxseed oil stored at 27°C for 40 days. Flaxseed oil had significantly high ALA content (59.8%) compared to 0.1-0.5% for oyster nut and sunflower oil brands. The LA content was high in sunflower brands (50.3-52.8%) compared to the oyster nut (48%) and flaxseed oil 14.7%. Oleic acid was lower in oyster nut oil (8.6%) and flaxseed oil 15.8% compared to sunflower brands (35.7-38.2%). As a consequence, oyster nut and flaxseed recorded higher PV of 4.35-2.88 mEq O2/kg and FFA 0.26-0.47% compared to sunflower brands. The p-AV recorded small values which were not significantly different in all samples. Although oyster nut is widely consumed by pregnant and lactating women across Africa, its keeping quality in nonrefined form is low compared to flaxseed and sunflower oil as shown in this study. Hence, the fatty acid contents in oyster nuts should be consumed in other alternative forms such as flour and roasted kernels rather than its oil when in nonrefined form. This study will enable the consumption balance of omega-6/omega-3 fatty acids and the keeping quality of oils which is key to health.
... In fresh form, there were substantial differences between the fatty acid compositions of the investigated oils. The present data were consistent with the literature by showing that palm oil is mainly composed of palmitic acid (C16:0) and OA [47], whereas the main fatty acids in soybean oil are OA and LA [36,[48][49][50][51][52][53][54], in rapeseed oil OA, LA and ALA [36,48,52] and in sunflower oil [36,48,[54][55][56] and olive oil [37,48,52,[54][55][56] LA and OA. ...
... Similarly, neither heating nor frying induced significant formation of TFAs in corn oil at 170 • C [58]. In contrast, Casal et al. [37] found increasing TFA values during the heating process in EV olive oil as well as in the blend of refined and virgin olive oil and sunflower oil. Although the TFA content of these oils after a longer time of frying (15 to 27 h) did not reach 0.5% of total fatty acids (except for commercially blended refined and virgin olive oil: 0.58% after 27 h), there was a highly significant positive correlation between TFA values and frying time in case of each oil. ...
... The type of the frying process also influences TFA formation in vegetable oil: deep-frying can lead to higher TFA formation than stir-frying or pan-frying [48]. As a summary, studies showed that the TFA formation can depend on several factors, like the type of oil [23,31,34,37,48,50,60], temperature [23,34,49,50] and time of heating [23,31,34,37,48,50,[58][59][60], as well as the mode of cooking (e.g., heating, frying, stir-frying) [23,48,52,58]. Results of the present study also showed that cis-trans isomerization occurs even at a lower temperature and with a shorter exposure to frying. ...
Article
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Several polyunsaturated fatty acids are considered to have beneficial health effects, while saturated fatty acids and industrial trans fatty acids (TFAs) are linked to negative health consequences. Given the increased formation of TFAs during heating, many studies already investigated compositional changes in oils after prolonged heating or at extremely high temperatures. In contrast, our aim was to measure changes in fatty acid composition and in some health-related indices in edible oils after short-time heating that resembles the conventional household use. Potatoes were fried in palm, rapeseed, soybean, sunflower and extra virgin olive oils at 180 °C for 5 min, and samples were collected from fresh oils and after 1, 5 and 10 consecutive heating sequences. Regardless of the type of oil, the highest linoleic acid and alpha-linolenic acid values were measured in the fresh samples, whereas significantly lower values were detected in almost all samples following the heating sequences. In contrast, the lowest levels of TFAs were detected in the fresh oils, while their values significantly increased in almost all samples during heating. Indices of atherogenicity and thrombogenicity were also significantly higher in these oils after heating. The present data indicate that prolonged or repeated heating of vegetable oils should be avoided; however, the type of oil has a greater effect on the changes of health-related indices than the number of heating sequences.
... In the presence of food, the loss of TPC was complete following the deep frying (3 h at 170 • C) of fresh potatoes with a refined vegetable oil blend, consisting mostly of sunflower oil [46]. However, differently from the above publication, the loss of TPC was lower (by 42%) for EVOO than for a blend of refined and VOOs (53% loss) [46]. ...
... In the presence of food, the loss of TPC was complete following the deep frying (3 h at 170 • C) of fresh potatoes with a refined vegetable oil blend, consisting mostly of sunflower oil [46]. However, differently from the above publication, the loss of TPC was lower (by 42%) for EVOO than for a blend of refined and VOOs (53% loss) [46]. Some authors used the technique of spiking vegetable oils with defined amounts of PC (see also Section 4.3.1). ...
... Later, Casal and co-workers reported that domestic deep frying of fresh potatoes at 170 • C for 3 h induced a loss of almost 50% of TPC of EVOO oil, measured by the Folin-Ciocalteu method [46]. This is actually not surprising, if we consider that heating can result in the loss of original PC in EVOO already after 30 min at 180 • C, as reported above (Section 4.2), rather it seems that the vegetable protects oil PC. ...
Article
The fate of phenolic compounds in oil and food during cooking vary according to the type of cooking. From a nutritional point of view, reviews largely suggest a preference for using extra-virgin olive oil at a low temperature for a short time, except for frying and microwaving, for which there appears to be no significant advantages compared to olive oil. However, due to the poorly pertinent use of terminology, the different protocols adopted in studies aimed at the same objective, the different type and quality of oils used in experiments, and the different quality and quantity of PC present in the used oils and in the studied vegetables, the evidence available is mainly contradictory. This review tries to reanalyse the main experimental reports on the fate, accessibility and bioavailability of phenolic compounds in cooking oils and cooked vegetables, by considering different cooking techniques and types of oil and foods, and distinguishing experimental findings obtained using oil alone from those in combination with vegetables. The re-analysis indicates that incomplete and contradictory observations have been published in the last few years and suggests that further research is necessary to clarify the impact of cooking techniques on the phenolic compounds in oil and vegetables during cooking, especially when considering their nutritional properties.
... Of the 234 studies identified by our search, 33 were included in this review ( Figure 1 and Supplementary Table S1). Collectively, the studies analysed 21 different cooking oils, with corn [11,13,[16][17][18][19][20][21][22][23], soybean [15,20,21,[23][24][25][26][27][28][29], sunflower [11,16,20,21,[30][31][32][33][34], and hydrogenated vegetable fat [15,24,27,29,31,[35][36][37] being the most commonly assessed; fewer studies investigated other oils including Aleppo pine seed [38], blend [16,17,23,33,39,40], canola [17,41], coconut [42], cottonseed [35], groundnut [24], linseed [20], olive [11,12,16,20,24,32,34], palm [33,36,39,42,43], peanut [20,28,36], peony seed [20], rapeseed [20,24,44], rice bran [17,20,40], safflower [17,23], and sesame [17,20] oil; or solid fats such as ghee [24] and lard [16]. The relatively high baseline (preheating) levels of TFA in hydrogenated vegetable fats compared to the two most commonly studied cooking oils (corn and soybean) are shown in Supplementary Table S2. ...
... Of the 234 studies identified by our search, 33 were included in this review ( Figure 1 and Supplementary Table S1). Collectively, the studies analysed 21 different cooking oils, with corn [11,13,[16][17][18][19][20][21][22][23], soybean [15,20,21,[23][24][25][26][27][28][29], sunflower [11,16,20,21,[30][31][32][33][34], and hydrogenated vegetable fat [15,24,27,29,31,[35][36][37] being the most commonly assessed; fewer studies investigated other oils including Aleppo pine seed [38], blend [16,17,23,33,39,40], canola [17,41], coconut [42], cottonseed [35], groundnut [24], linseed [20], olive [11,12,16,20,24,32,34], palm [33,36,39,42,43], peanut [20,28,36], peony seed [20], rapeseed [20,24,44], rice bran [17,20,40], safflower [17,23], and sesame [17,20] oil; or solid fats such as ghee [24] and lard [16]. The relatively high baseline (preheating) levels of TFA in hydrogenated vegetable fats compared to the two most commonly studied cooking oils (corn and soybean) are shown in Supplementary Table S2. ...
... The median TFA level at baseline was 0.23% of total fatty acids [0.04% to 0.70%]. Five different cooking methods were employed: baking [13], heating [19,24,30,33,36,38], deep-frying [11,13,17,18,20,21,23,24,[27][28][29][32][33][34][35]37,[39][40][41][42][43], pan-frying [11,13,20], and stirfrying [13,20]. Heating temperatures, heating times, and heating cycles corresponding to the various cooking methods and for the various TFA studied are summarised in Supplementary Tables S4 and S5 ...
Article
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Consumption of trans fatty acids (TFA) is associated with adverse health outcomes and is a considerable burden on morbidity and mortality globally. TFA may be generated by common cooking practices and hence contribute to daily dietary intake. We performed a systematic review and meta- analysis to investigate the relationship between heating edible oils and change in their TFA content. A systematic search of experimental studies investigating the effect of various methods of heating on TFA content of edible oils was conducted in Medline and Embase since their inception up to 1 October 2020 without language restrictions. Comparable data were analysed using mixed multilevel linear models taking into account individual study variation. Thirty-three studies encompassing twenty-one different oils were included in this review. Overall, heating to temperatures <200 ◦C had no appreciable impact on different TFA levels. Between 200 and 240 ◦C, levels of C18:2 t (0.05% increase per 10 ◦C rise in temperature, 95% CI: 0.02 to 0.05%), C18:3t (0.18%, 95% CI: 0.14 to 0.21%), and total TFA (0.38%, 95% CI: 0.20 to 0.55%) increased with temperature. A further increase in total TFA was observed with prolonged heating between 200 and 240 ◦C. Our findings suggest that heating edible oils to common cooking temperatures (≤200 ◦C) has minimal effect on TFA generation whereas heating to higher temperatures can increase TFA level. This provides further evidence in favour of public health advice that heating oils to very high temperatures and prolonged heating of oils should be avoided.
... Ultraviyole bölgede yapılan spektrofotometrik ölçümler, yağların kalitesi ve işleme sırasında yapılarında meydana gelen değişimler hakkında fikir verebilmektedir [25]. 232 nm'de gerçekleştirilen spektrofotometrik ölçüm sonuçları çoklu doymamış yağ asitlerinin yani konjuge dienlerin oluşumu ile ilişkilendirilirken, 270 nm'de elde edilen sonuçlar aldehit ve keton gibi ikincil oksidasyon ürünlerinin oluşumuyla paralellik göstermektedir [26]. Normal atmosferde, vakum ve N2 gazı altında paketlenen ve farklı sıcaklıklarda depolanan bütün, kırık ve öğütülmüş ceviz örneklerinin konjuge dien ve konjuge trien değerleri sırasıyla Şekil 4 ve Şekil 5'te verilmiştir. ...
... İkincil oksidasyon ürünleri, hidroperoksitlerden çok daha kararlı ürünlerdir. Bu nedenle, oksidasyon durumunun doğru bir şekilde belirlenebilmesi için, birincil ve ikincil oksidasyon ürünleri birlikte değerlendirilmelidir [26]. Normal atmosferde, vakum ve N2 gazı altında paketlenen ve farklı sıcaklıklarda depolanan bütün, kırık ve öğütülmüş ceviz örneklerinin p-anisidin değerleri Şekil 6'da verilmiştir. ...
... It was indicated by some researchers (e.g., Shahidi and Zhong (2020)) that the presence of a wide range of natural antioxidants in vegetable oils can protect the oil against thermal degradation, transfer their health benefits and reduce the incidence of various cancers and oxidation stresses. However, during the heat treatment of vegetable oils, their physical and chemical properties are subjected to some deteriorations such as increasing the acid number and peroxide value, reducing the oxidative stability, changing the type or amount of pigments, and eventually forming dimers and polymers that increase the viscosity of the oil (Casal et al., 2010). ...
... Therefore, in terms of raw material costs, grapeseed oil is the economical raw material (Negro et al., 2003). On the other hand, since the combination of sesame oil with some edible oils improves the nutritional value and stability of the mixture oil during frying and cooking process, so the combination of oils is the most cost-effective process for oil modification (Casal et al., 2010). ...
Article
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Abstract In spite of grapeseed oil high contents of linoleic acid, its oxidative stability is relatively low, and mixing with more stable oils such as sesame oil can be a good way to improve the oxidative stability of this oil. The aim of this study was to increase the oil oxidative stability by producing an optimum formulation due to the combination of grapeseed and sesame oil. For this purpose, some of the qualitative properties of the optimum formulation were investigated during frying process. For finding the best formulation, the quantities of 0%, 25%, 50%, 75%, and 100% of sesame oil were blended with 100, 75%, 50%, 25%, and 0% of grapeseed oil. The results show that the highest percentage of fatty acid in various samples (sesame oil, grapeseed oil, and mixed formulations) is related to the linoleic acid, followed by oleic, palmitic, and stearic acid. In conclusion the addition of sesame oil to grapeseed oil increased the number of phenolic compounds, antioxidant strength, and oxidative stability of the mixed oil samples. Considering the price of the product and the importance of the nutritional quality and stability of the oil, combining 75% sesame oil and 25% grapeseed oil has the best nutritional quality and lower cost than pure sesame oil formula. After frying process, comparison of sesame and grapeseed oil different factors with national Iranian standard limits showed that the parameters of acid number and peroxide value were more than Iran’s national standard, but the content of polar compounds was within the permissible content. Finally, the mixture of sesame and grapeseed oil is not suitable for long‐term heating and frying.
... 2. The presence of natural antioxidants in EVOO, such as biophenols and Vitamin E, enhance the oil's stability and resistance to oxidative degradation. Besides adding health benefits to the oil, these minor constituents boost EVOO's stability reducing oxidative processes when the oil is heated [31,32]. ...
... Frying with EVOO using a lower food:oil ratio presents lower total polar compound amounts than more unsaturated vegetable oils, and with apparently no interference by the presence of food [32,48,49]. Within olive oils, the higher the degree of polyunsaturation the higher the tendency for the formation of total polar compounds [50]. ...
Chapter
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Mediterranean cultures have used Extra Virgin Olive Oil (EVOO) as the only source of cooking oil for centuries, with their diet showing the highest amount of scientifically proven health benefits. However, there is a common misconception that EVOO is not suitable for cooking given its relatively lower smoke point, despite no scientific evidence that support this. This chapter aims to provide an overview of how EVOO is healthier, safer, and more stable to cook with than other common edible oils. Furthermore, this chapter aims to present EVOO’s suitability for use on Teflon coated pans, which is another common myth.
... Extra Virgin Olive Oil (EVOO) is the main source of fat in the Mediterranean diet, well appreciated due to its flavor and known health effects. EVOO is consumed both raw and cooked; however, during thermal processes, its components can undergo transformations, oxidations, and/or degradations (Casal, Malheiro, Sendas, Oliveira, & Pereira, 2010). EVOO is mainly composed of triglycerides, with a high content of monounsaturated fatty acid (MUFA) and relatively low polyunsaturated fatty acid (PUFA) amounts, which makes it more stable than other edible oils richer in PUFAs (Aşkın & Kaya, 2020;Cui, Hao, Liu, & Meng, 2017). ...
Article
In this work, the major changes in extra-virgin olive oil (EVOO) composition during cooking were assessed. A foodomics approach based on both metabolomics and lipidomics was used to evaluate the impact of six different cooking techniques, three traditional and three more innovative (Crock-pot®, Roner® and Gastrovac®), and the effect of temperature and cooking time. The lipophilic and hydrophilic fractions of EVOO that underwent different cooking processes were characterized by untargeted high-resolution mass spectrometry approaches. Multivariate statistics were used to unravel the differences in chemical signatures. The different cooking methods resulted in broadly different phytochemical profiles, arising from thermally driven reactions accounting for hydrolysis, synthesis, and oxidation processes. The innovative cooking techniques marginally altered the phytochemical profile of EVOO, whereas sauteing was the cooking method determining the most distinctive profile. Conventional cooking methods (oven, pan-frying, and deep-frying) produced more oxidation products (epoxy- and hydroxy-derivatives of lipids) and markedly induced degradation processes.
... As shown in Table 3, the fatty acids composition of the three oils under heating at 180°C showed obvious differences with an extended heating time; the content of saturated fatty acids and trans fatty acids increased, while the content of unsaturated fatty acids decreased with the elongation of heating time. The fatty acid content change tendency of this study was nearly similar to the findings of Casal et al. [37] and Xu et al. [36]. The letters a-e indicate significant differences (p < 0.05) in the same oil at different heating times under the same heating method, while the letters x and y indicate significant differences (p < 0.05) at the same heating time between ordinary heating and HVEF heating. ...
Article
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High-voltage electrostatic field (HVEF) as an emerging green technology is just at the beginning of its use in meat products and by-products processing. In this study, we employed duck oil to produce duck-oil-based diacylglycerol (DAG), termed DDAG. Three different DDAG volume concentrations (0, 20%, and 100%) of hybrid duck oils, named 0%DDAG, 20%DDAG, and 100%DDAG, respectively, were used to investigate their thermal oxidation stability in high-voltage electrostatic field heating and ordinary heating at 180 ± 1 ℃. The results show that the content of saturated fatty acids and trans fatty acids of the three kinds of duck oils increased (p < 0.05), while that of polyunsaturated fatty acids decreased (p < 0.05) from 0 h to 8 h. After heating for 8 h, the low-field nuclear magnetic resonance showed that the transverse relaxation time (T21) of the three oils decreased (p < 0.05), while the peak area ratio (S21) was increased significantly (p < 0.05). The above results indicate that more oxidation products were generated with heating time. The peroxide value, the content of saturated fatty acids, and the S21 increased with more DAG in the duck oil, which suggested that the oxidation stability was likely negatively correlated with the DAG content. Moreover, the peroxide value, the content of saturated fatty acids and trans fatty acids, and the S21 of the three concentrations of duck oils were higher (p < 0.05) under ordinary heating than HVEF heating. It was concluded that HVEF could restrain the speed of the thermal oxidation reaction occurring in the duck oil heating and be applied in heating conditions.
... Our results in deep-fried AVO did not agree with the multiple reports of net decreases in phenol concentration that ranges from 40 to 80% after heat treatment with or without food [68,69]. But, coincidences with other oil reports showed mixed tendencies in the phenols depending on the compound analyzed and the vegetable processed. ...
Article
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Avocado virgin oil (AVO) was used during eggplant deep-frying, boil, and boil in a water-oil mixture (W/O). There were measured the contents of moisture, dry matter, fat, total (TPC) and ten individual phenols, antioxidant activity (ABTS and DPPH), and total sterols; as well as the profiles of eight fatty acids and fourteen sterols/stanols. The values of raw and processed foods were compared and studied with multivariate analysis. The antioxidant capacity of AVO lowered after deep frying but augmented in eggplant and water after all treatments. The TPC was steady in AVO and raised in fried eggplant. Thermal treatments added to the initial profiles of the AVO, eggplant and water, nine, eight, and four phenols, respectively. Percentages of the main fatty acids (oleic, palmitic and linoleic), and sterols (β-sitosterol, campesterol, and Δ5-avenasterol), remained unchanged between the raw and treated AVO; and the lipidic fractions from processed eggplant. Cooking leads to the movement of hydrophilic and lipophilic functional compounds between AVO, eggplant and water. Migration of sterols and unsaturated fatty acids from AVO to eggplant during deep frying and W/O boiling improved the functional properties of eggplant by adding the high biological value lipophilic fraction to the naturally occurring polyphenols.
... These two types of oils are the most frequently used in food service establishments in Spain (Mesias et al., 2019), although olive oil is typically the main source of lipids in the Mediterranean diet. Fundamentally, economic reasons have led this sector to use other types of oils for frying, such as sunflower oil or mixtures of refined vegetable oils, soybean oils and high oleic acid content (Casal et al., 2010), while olive oil is used to dress salads. With regard to the information collected on the visits to the selected food services (Table 2), we found that the information they provide us regarding the type of oil used did not coincide with that observed in situ in three establishments. ...
Article
Deep frying is one of the most used worldwide methods in food preparation, but controlling the oil quality (temperature and formation of polar compounds) is crucial. The main objective of this work was to assess the practices of food handlers with regard to the frying processes in social food services located in Navarra (a region of northern Spain). The study was performed in two phases: in the first one, a self-administrable questionnaire regarding the usual practices on food deep-frying processes was sent to the food services through the main social catering companies of Navarra participating in the study. In the second one, in situ monitoring of the frying practices was performed as verification tools of frying practices reported by food services and to check the oil quality. Almost half of the fryers exceeded the maximum recommended temperature to avoid the formation of toxic compounds (175 °C). Despite only one the fryers exceeded the maximum limit of polar compounds established by current Spanish regulation, the obtained values indicated that the oil had begun to degrade in 20% of the fryers. Oil temperature is an important factor that affects the quality of the oil. In addition, significant differences were found between the different frequencies of change or types of oils. We have noticed a lack of knowledge in relation to the risks associated to the bad management of frying oil. Therefore, it would be desirable to improve food handlers training in relation to this matter. Defining a periodic frequency of oil change according to its use and periodic controls of temperature and polar compounds (as part of the Hazard Analysis and Critical Control Point system), could be adequate tools to improve management of frying oil in food services.
... The higher the PV the lower the OS. Oxidation is the primary unwanted process that leads to the formation of hydroperoxides as primary oxidation products, which degrade into secondary oxidation products, such as aliphatic aldehydes, ketones, lactones, alcohols, acids, and hydrocarbons (Casal et al. 2010). These secondary products are more stable during heat exposure and can negatively impact oil flavor, shelf life, and nutrition (Vlachos et al. 2006). ...
Article
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Authenticity and adulteration detection are primary concerns of various stakeholders, such as researchers, consumers, manufacturers, traders, and regulatory agencies. Traditional approaches for authenticity and adulteration detection in edible oils are time-consuming, complicated, laborious, and expensive; they require technical skills when interpreting the data. Over the last several years, much effort has been spent in academia and industry on developing vibrational spectroscopic techniques for quality, authenticity, and adulteration detection in edible oils. Among them, Fourier transforms infrared (FT-IR) spectroscopy has gained enormous attention as a green analytical technique for the rapid monitoring quality of edible oils at all stages of production and for detecting and quantifying adulteration and authenticity in edible oils. The technique has several benefits such as rapid, precise, inexpensive, and multi-analytical; hence, several parameters can be predicted simultaneously from the same spectrum. Associated with chemometrics, the technique has been successfully implemented for the rapid detection of adulteration and authenticity in edible oils. After presenting the fundamentals, the latest research outcomes in the last 10 years on quality, authenticity, and adulteration detection in edible oils using FT-IR spectroscopy will be highlighted and described in this review. Additionally, opportunities, challenges, and future trends of FT-IR spectroscopy will also be discussed.
... Additionally, oxidative stability was estimated by measuring the oxidation induction time on a Rancimat equipment (Metrohm CH series 679). In this process, air was bubbled (20 L/h) through the OMSS (3.0 g) heated at 110 ± 0.2 • C, and the volatile compounds produced were trapped in water, and the changes in the electrical conductivity of this water were recorded, until reaching the conductivity inflection [97]. Each measurement was performed in triplicate, and the results were presented as the mean values ± SD. ...
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In this study, aqueous enzymatic extraction (AEE) was evaluated during the process of obtaining oil from mamey sapote seed (OMSS). Viscozyme L enzyme complex was used at pH 4 and 50 °C during the optimization of the extraction process by central composite design and response surface methodology. Optimal conditions were: 3.5% (w/w) of enzyme (regarding the seed weight), 5.5 h of incubation time, 235 rpm of agitation rate, and 1:3.5 of solid-to-liquid ratio. These conditions enabled us to obtain an OMSS yield of 66%. No statistically significant differences were found in the fatty acid profile and physicochemical properties, such as the acid and iodine values and the percentage of free fatty acids, between the oil obtained by AEE or by the conventional solvent extraction (SE). However, the oxidative stability of the oil obtained by AEE (11 h) was higher than that obtained by SE (9.33 h), therefore, AEE, in addition to being an environmentally friendly method, produces a superior quality oil in terms of oxidative stability. Finally, the high oil content in mamey sapote seed, and the high percentage of oleic acid (around 50% of the total fatty acid) found in this oil, make it a useful edible vegetable oil.
... Then, phenolphthalein was added as an indicator and the resulting solution was titrated with 0.01 N NaOH for neutralization. Free fatty acid (FFA) content was given in percent oleic acid (Casal et al., 2010). ...
Article
Deep‐fat frying process is a commonly used procedure for food preparation, and the oxidative stability is an important quality issue for frying oils. In this study, the effect of citrus peel extracts (orange, lemon, mandarin) and BHT (Butylated hydroxytoluene; a synthetic antioxidant) on oxidative stability of sunflower oil during deep‐fat frying process were investigated. For this purpose; classic chemical wet methods (free fatty acid (FFA), peroxide, p‐anisidine, conjugated diene) and a spectroscopic method (Electron Paramagnetic Resonance (EPR) spectroscopy, spin trapping technique) were used. According to both chemical data and EPR spin trapping results, antioxidant effects of citrus peel extracts were found to be comparable to BHT. Moreover, the antioxidant effect of lemon peel extract was higher than other citrus peel extracts. EPR spin trapping technique can be used as an earlier and more accurate detection method in determining lipid oxidation during repetitive deep‐fat frying.
... Regarding PV, a similar behavior was observed for roasted and fried samples, presenting a high initial PV value (47 ± 1 and 41 ± 1 meq O 2 kg −1 sunflower seed oil, respectively, Table 3), which may be explained by their high linoleic fatty acid content, being highly susceptible to oxidation during processing conditions. These results are in accordance with those reported in other studies for different vegetable oils, including almond and olive oils [41,42]. Under accelerated conditions (100 • C), PV analysis was conducted only at day 0, as no change in color during the titration of samples, corresponding to the formation of peroxides, was observed for three, five, and 10 days of oxidative treatment. ...
Article
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The effect of different cooking processes such as frying and roasting on the oxidative stability of sunflower seeds was evaluated under accelerated oxidation and normal storage conditions. The fatty acid composition by GC-MS showed a higher amount of linoleic acid in fried samples due to the replacement of the seed moisture by the frying oil. On the other hand, roasted samples presented a higher oleic acid content. DSC and TGA results showed some decrease in the thermal stability of sunflower seed samples, whereas PV and AV showed the formation of primary and secondary products, with increasing oxidation time. Roasted sunflower seeds showed seven main volatile compounds characteristic of the roasting process by HS-SPME-GC-MS: 2-pentylfuran, 2,3-dimethyl-pyrazine, methyl-pyrazine, 2-octanone, 2-ethyl-6-methylpyrazine, trimethyl-pyrazine, and trans,cis-2,4-decadienal, whereas fried samples showed six volatile characteristic compounds of the frying process: butanal, 2-methyl-butanal, 3-methyl-butanal, heptanal, 1-hexanol, and trans,trans-2,4-decadienal. The generation of hydroperoxides, their degradation, and the formation of secondary oxidation products were also investigated by ATR-FTIR analysis. The proposed methodologies in this work could be suitable for monitoring the quality and shelf-life of commercial processed sunflower seeds with storage time.
... The specific extinction coefficients are used as indicators of oil oxidation, providing information about its quality and preservation state [40]. The parameter K 232 is indicator of primary oxidation during oxidation processes and it is correlated with the formation of conjugated dienes of polyunsaturated fatty acids [37,[41][42][43][44]. Conversely, K 270 indicates the level of conjugated trienes that is representative of the secondary oxidation [45]. ...
Article
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Hazelnuts are one of the most appreciated nuts worldwide due to their unique organoleptic and nutritional characteristics. The present work intended to analyse several physical and chemical properties of different hazelnut varieties grown in Portugal, namely Tonda de Giffoni, Grada de Viseu, Segorbe, Longa de Espanha, Butler, Gunslebert, and Negreta. In general, the results revealed statistically significant differences between the varieties under study. The Gunslebert had more elongated hazelnuts and with heavier shelled fruits, while the kernels of the Grada de Viseu revealed to be heavier. Grada de Viseu was harder in the shell, Gunslebert had a harder core, and Segorbe was more resistant to fracture. Fat was the more representative component for all varieties and in some cases the values of moisture and water activity were over the recommended amount (≥0.62). Tonda de Giffoni was the variety with the highest induction time, indicating the highest oxidation stability. Moreover, discriminant analysis revealed that the variables more important to distinguish the varieties were protein (λ = 0.007) and water activity (λ = 0.010). The results of this study help to better understand the differences between some hazelnut varieties that are cultivated in Portugal, which gives important hints for all players in the hazelnut sector.
... In terms of the maximum threshold, the p-Anisidine value of vegetable oils has no known values. However, several authors have admitted a value of 10 units not to be exceeded (Gan et al., 2005;Casal et al. 2010;Cerretani et al., 2008). According to Plard (2014), the content of conjugated dienals is useful to assess the quality of a highly oxidized oil, case of frying oils. ...
Article
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Edible oils produced and consumed in Burkina Faso often do not meet established standards. The objective of this study was to evaluate the total gossypol level of refined cottonseeds oils and the oxidation state of crude peanut oils and refined cottonseeds oils in Burkina Faso to determine the impact on consumer health. A total of 61 samples including crude peanut oils and refined cottonseeds oils were collected in Ouagadougou, Bobo Dioulasso and surrounding areas. Total Gossypol and p-Anisidine value were determined by spectrophotometry. Peroxide value, acid value, soap residual value and mineral oils were determined by chemical methods. Total oxidation (Totox) value was determined by mathematical prediction. Overall, Gossypol total average of cottonseeds oils analyzed in this study was 0.032%. The p-Anisidine value average was 1.80 for refined cottonseeds oils and 11.65 for crude peanut oils. The Totox averages were respectively 19.37 and 28.36 for refined cottonseeds and crude peanut oils. The average peroxide values for refined cottonseeds oils and peanut crude oils were 8.52 and 8.33 mEq O2/Kg, respectively (p<0.05). The average acid values were 0.27 and 1.95 mg KOH/g for refined cottonseeds oils and crude peanut oils, respectively (p<0.05). None of the oils showed any mineral oil trace. The average residual soap values were respectively 1.47 and 8.32 ppm for peanut oils and cottonseeds oils (p<0.05). The majority values determined conformed to the Codex Alimentarius standard despite some cases of non-compliance. It is essential to improve the processes of oils production and conservation in order to have quality oils to guarantee the health of the consumer.
... The volatile compounds produced by this treatment were captured in water, and the changes in this water conductivity were recorded. The time taken to reach the conductivity inflection point was used as estimation of the oil oxidative stability (Casal et al., 2010). Each of the reported data is the result of three independent experiments, and the results are shown as the mean values ± SD. ...
Article
In this study, the extraction of oil from seeds of castor (Ricinus communis) was intended using aqueous enzymatic extraction (AEE). After evaluating several enzymes (cellulase, pectinase, hemicellulase and Viscozyme L), the enzymatic cocktail Viscozyme L gave the best oil extraction yield (64 %) at pH 4 and 50 • C, and it was chosen for the optimization of the extraction process using a response surface methodology and a central composite design. Under optimal conditions (2% of Viscozyme L, 4 h of incubation time, 200 rpm and a solid to liquid ratio of 1:5), an oil yield extraction of 80 % was achieved using AEE. Compared with oil extracted using solvent extraction, AEE produced an oil with a higher acid and iodine values, but a similar fatty acid composition. Additionally, oxidative stability was higher in oil extracted using AEE, so it can be said that in terms of this parameter, AEE produces a higher quality oil compared to the SE. Scanning Electron Micrographs (SEM) imagines showed that Viscozyme L causes a destruction of cell walls and liposome membranes structure of castor seeds, causing the oil release. The results showed that AEE is a no contaminant extraction technology that can be employed in the industrial extraction of oil from castor seed.
... In a study on the emission of low molecular weight aldehydes from the oils heated at 180°C and 240°C, there was found very similar results for the extra virgin and refined olive oils (Fullana et al., 2004). There was observed no significant difference between the different commercial categories of olive oil fried at 170°C by monitoring a range of oxidation products (Casal et al., 2010). ...
Preprint
Frying stability of two virgin (VSO) and refined (RSO) sesame oils was compared with that of a refined olive oil (ROO). The oils were used to fry potato stripes at 180 °C and conjugated dienes (CDV), total carbonyls (CV), and thermo-oxidative and hydrolytic polar components were monitored over time. The rate of change in CDV (mmol l–1 h–1) was significantly lower for ROO (0.72) than for VSO (1.00) and RSO (1.84). The change in CV for ROO (2.31 μmol g–1 h–1) was significantly much faster than those for RSO (1.89) and VSO (1.17). Based on the thermo-oxidative polar components, the calculated frying times for VSO, RSO, and ROO were on the order of 32.1, 13.9, and 15.4 h. However, VSO contained significantly the highest contents of hydrolytic polar components over time and RSO exhibited more resistance than ROO on this basis.
... The Rancimat method is commonly used to evaluate the oxidation stability under heating conditions, and it measures the induction time. Moreover, a longer induction time corresponds to a higher oxidation stability [39,40]. The induction time varied between 19.54 ± 0.80 h for the sample GV-Faia-17 and 28.51 ± 2.74 h for the sample GV-Faia-18, meaning that the fruits of GV-Faia-18 showed a higher oxidation stability ( Table 9). ...
Article
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“Grada de Viseu” is an indigenous hazelnut variety from Portugal, and it is considered by the producers as the most important variety in terms of production and productivity. Therefore, the aim of this study was to assess the influence of harvest year (2017/2018/2019) and location of production (Viseu/Faia) on some physical and chemical properties of the variety “Grada de Viseu,” namely biometric parameters, colour, true and bulk densities, texture parameters (hardness and friability), and chemical composition. The results showed that the fruits of the samples harvested in 2019 had higher values of height, width, and thickness. Hazelnuts from 2018 had a clearer shell, independently of the location of production, but only the samples from Faia harvested in 2018 had a clearer kernel. As for the texture, the fruits grown in Viseu harvested in 2018 had a harder shell and was more resistant to fracture, whereas the sample from 2019 had a harder kernel. In all cases, fat was the major chemical component. The sample from 2019 had a water activity greater than 0.62, meaning that its stability was not guaranteed. “Grada de Viseu” from Faia in 2018 presented a higher induction period and, therefore, was the one with the highest oxidation stability. The year of production showed to be the best predictor for almost every chemical and biometric characteristics. In general, it was possible to verify that harvesting year and geographical location influence hazelnut characteristics.
... Peroxide values shown in Figure 1 show fresh virgin oils are within a threshold of 10 meq kg À1 (Casal et al., 2010). Beyond this, the oil is considered rancid when the PV is more elevated (Gunstone, 2008). ...
Article
Total Polar Compound (TPC) analysis was used to evaluate fry life cycle of oils and shortenings with differing fatty acids compositions, and to understand if longer trisaturated material (Tribehenin), could influence total fry life, during protracted, semi‐continuous deep frying simulations. Results showed, when TPC reached 25% max, the TOTOX and FFA revealed correlated values. However, both FFA and Totox were deemed unreliable indicators of oil quality. TPC’s were more acutely accurate, especially during oil filtration and top‐up procedures, where peak TPC onset showed stronger correlation for assessing oil degradation. Unsaturated frying oil, SBO (PUFA based), resulted with the shortest fry life of 132 fry‐cycles; POL (MUFA based) 138 fry‐cycles and MPS (MUFA based + Tribehenin) achieving up to 146 fry‐cycles, suggesting Tribehenin may apparently extend fry life longevity.
... Some theoretical explanations could be proposed. Regarding the peroxide values quantification, it was already stated that the hydroperoxides formed due to fatty acids oxidation during the frying process, are not very stable and, for that reason, they could not be correlated with the sample oxidation (Casal, Malheiro, Sendas, Oliveira, & Pereira, 2010). Moreover, the used reference procedures are laborious, time-consuming and produce a huge quantity of toxic residues. ...
Article
When edible oils are exposed to high temperatures, this leads to several chemical changes. Therefore, it is important to have an analytical method (rapid, reliable, multi-parametric, cost-effective and environmentally friendly) capable of monitoring the quality of edible oils at real time. In this sense, the herein presented work focused on the application of Raman spectroscopy for in situ and real-time monitoring of the quality of four different edible oils (vegetable, corn, peanut and sunflower oil) during a 16-h heating at 180 °C. The quality of the edible oils was assessed through the determination of the peroxide and acid values and total polar compounds (TPC). A total of 68 samples were assessed (17 samples for each edible oil type) and the collected analytical data were processed by means of principal component analysis (PCA) and partial least squares (PLS) regression chemometric tools. The accuracy of the developed PLS models was evaluated in terms of coefficient of determination of prediction (R²P), range error ratio (RER) and residual predictive deviation (RPD). RER values of 12.8, 9.3 and 16.5 and RPD values of 3.4, 2.5 and 5.0 were obtained for the determination of acidity values, peroxide values and TPC, respectively. The reliability of the obtained results indicates that the PLS models developed for the determination of acidity and TPC can be used for quality control while the PLS model implemented for the determination of the peroxide values can only be used for screening purposes.
... Selain itu, jenis minyak yang digunakan juga menjadi faktor yang mempengaruhi jumlah minyak yang terserap pada makanan. Jenis minyak zaitun tidak rentan terhadap oksidasi 16 . Minyak zaitun memberikan efek baik terhadap kesehatan jantung ketika digunakan untuk menggoreng 17 . ...
Article
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Background: Cardiovascular disease occurred by many factors, one of them is because of consuming high saturated fat intake from fried food. Previous studies have shown that there are inconsistent results from the research related to the correlation between fried food intake and cardiovascular disease. This literature study is important to be done to explain the problem of different results for each previous study.Objective: To examine the correlation between fried food intake and cardiovascular disease from various previous studies also to analyze the correlation between fried food intake people with polymorphisms of ALDH2 and ABCA1 genes and cardiovascular disease occurrence.Methods: Exploring literature material was done by Pubmed and Science Direct databases. Article research methods were sought by observational studies (cross-sectional, case-control, and cohort). Eight articles were selected based on the inclusion criteria that have been determined.Results: Fried food intake is associated with cardiovascular diseases such as coronary heart disease, ischemic heart disease, and heart failure. However, the EPIC-Spanish cohort study shows that fried food intake is not associated with cardiovascular disease. People with polymorphisms carrier in the ALDH2 gene rs671 genotypes A/A and A/G has a higher risk of increase CHD compared to a person who is a GG genotype carrier. People with polymorphism carrier in the ABCA1 gene rs4149339 genotype CC also has a higher risk of developing CHD compared with people who carry a TT genotype.Conclusion: Fried food intake has a positive correlation with the risk of cardiovascular disease in adulthood and the elderly. Fried food intake with people who have a certain gene variations is associated with cardiovascular disease occurrence.
... The addition of antioxidants to food could enhance the stability of vitamin D 3 during heating process. Natural antioxidant such as phenolic and vitamin E in olive oil were shown to delay the oxidative reaction during deep frying [15]. The natural antioxidants from Beijing grass extract showed a great potential to protect edible oil from lipid oxidation [16]. ...
Article
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Vitamin D insufficiency is widespread in the northern and partly equatorial hemisphere countries. Fortification of vitamin D in commonly consumed vegetable oils can prevent rickets in children, osteoporosis and bone fractures in adults. Avoiding the loss of vitamin D3 fortification in oils during cooking is beneficial for consumer’s health. The aim of this work was to investigate the stability of cholecalciferol (vitamin D3) fortification in canola oil during baking at 80 to 230°C for 10 to 40 min. The natural antioxidants (β-carotene and α-tocopherol) and the synthetic ones (butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ)) were used to prevent the degradation of vitamin D3. The kinetic degradation of vitamin D3, oxidative status of canola oil and the bioaccessibility in in vitro digestion were assessed. Vitamin D3 was relatively stable at 80 and 130°C for 10 to 40 min. High temperatures of 180 and 230°C caused the highest loss of vitamin D3 being up to 90%. Reaction rate of vitamin D3 degradation ranged from 2.01 to 6.80 × 10–2 sec–1. BHT and TBHQ had the highest antioxidant activity (> 50 %) to decrease the degradation of vitamin D3 at 230°C. The oxidative status (peroxide value, malondialdehyde content) of canola oil was improved after incorporating antioxidant agents. The vitamin D3 bioaccessibility was increased 1.5 fold after in vitro digestion. The consumption of 5 g brownie containing vitamin D3 100 μg/L and antioxidant agents 180 mg/L in 1 mL of canola oil would cover the daily intake.
... reducing of oil stability (Casal et al., 2010), changing of the physical characteristics of oil (Sahasrabudhe et al., 2017), reducing of the quality of food (Bou et al., 2012), and compromising the safety of food (Moumtaz et al., 2019). They can also lead to issues such as an increase in foaming and reducing the smoking point of the frying oil (Bansal et al., 2010;Das et al., 2013). ...
Article
Oil degradation occurs rapidly in the deep‐frying process, which compromises food quality and food safety. Oil blending can be used to improve stability. An experiment using a Rancimat at 190°C with 10 L/h airflow for 30 min followed with total polar material content (TPM) and free fatty acid content (FFA) tests were conducted to select blend candidates for full‐scale production trials. Rapeseed oil (RO) blended with 25% rice bran oil (RBO), hazelnut oil (HO), and red palm oil (RPO), respectively, and high oleic sunflower oil (HOSO) blended with 25% RO, RBO, respectively, were tested. In a crisp production trial using an industrial continuous fryer, HOSO‐RO blended with 15% RO had no negative impact on the oil stability and product quality. In a hand‐cooked crisp production trial using industrial batch fryers, regular sunflower oil (RSO) blended with 15% RBO reduced free fatty acid (FFA) accumulation in oil with no negative impacts on product quality. Food manufacturers in the UK producing fried products often have to use high oleic sunflower oil (HOSO) for its high oxidation stability. However, HOSO is expensive and its supply relies on imports. In this work, we have demonstrated the feasibility of using rapeseed oil (RO) as a blending ingredient in HOSO in the production of crisps to reduce cost and improve supply chain resilience, without compromising processing stability and product quality. We also found rice bran oil has considerable potential to be used as a blending ingredient to improve the processing stability of frying oils.
Article
Black sesame seeds (BSS) were processed by nine cycles of steaming and sun-drying, and the chemistry of their resulting products studied. That is, the shell color and structure, proximate composition, oil properties and volatile compounds of raw BSS were determined and compared with processed BSS. Various levels of shell color change and structure damage were observed. The proximate composition also differed, whereas the relative proportion of fatty acids and oil properties were unchanged. SPME-GCMS analysis revealed that aldehydes, hydrocarbons and alcohols were the main volatile compounds. And compared with raw BSS, four volatile substances were newly detected in the processed BSS. Principal component analysis (PCA) displayed the overall difference between samples and showed that repeated steaming and sun-drying process had a significant impact on the chemical composition of BSS.
Article
In this study, oxidation kinetics of refined hazelnut oil heated at the temperature range from 80 to 180 °C was evaluated. The changes in peroxide value, p‐anisidine value, polymer triglyceride content, α‐tocopherol content, and color values during oxidation were best fitted to zero‐order kinetic model. The rate constants for the p‐anisidine value, polymer triglyceride content, and degradation of α‐tocopherol of hazelnut oil increased at the temperatures between 80 and 160 °C, while the rate constant for peroxide value decreased at the temperatures between 80 and 140 °C. The activation energies for the formation of peroxides (at 80–140 °C), secondary oxidation products such as alkenals, the polymer triglycerides, and degradation of α‐tocopherol were found as 47.49, 29.95, 52.65, and 14.22 kJ mol⁻¹, respectively. The induction period of hazelnut oil was observed to reduce with increasing oxidation times. The increase in the b* value with the oxidation time and temperature was attributed to the fact that the heating process intensified the yellow color of the oil.
Chapter
Essential oils-(EOs) are organic compounds derived from aromatic plant sources such as roots, bark, flowers, leaves and seeds. Essential oils were obtained via two different methods of extraction: steam distillation (SD) and water distillation (WD). EOs-therapy, refers to a range of traditional, alternative or complementary therapies that use essential oils from natural products and other aromatic plant compounds. The chemical components composition of EOs depends on the place of origin, climatic conditions, plant species, plant part extracted, and harvesting time. Essential oils are constituted by diversified bioactive constituents, lipophilic and volatile, and in most cases derivatives of terpene compounds and in lower occurrence phenylpropanoids. They have been long recognized for their medicinal uses: antiviral, antibacterial, insecticidal, antifungal, and antioxidant properties. This chapter provides studies on chemical composition, medicinal uses, and benefits of essential oils.
Chapter
The fat consumption in the human diet is based on the intake of two types of fatty acids, namely, saturated (SFA) and unsaturated (UFA) fatty acids. Unsaturated fatty acids, which are grouped into monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA), have been scientifically proven to positively contribute to human health when consumed in a regular diet. However, one of the isomers occurring in the carbon chain, which are called trans fatty acids (commonly “trans fats”), gained specific interest due to their adverse health effects. Trans fatty acids either occur naturally or are the components derived during oil processing such as partial hydrogenation, refining, and deep-fat frying. Since the physicochemical attributes of the fatty acids change when shifting from cis to trans isomerization, trans fats have been widely studied to reveal their impacts on humans. Even though naturally occurring trans fats are considered less harmful than artificial trans fats, the risk of being negatively affected by trans fatty acids in regard to issues such as cardiovascular diseases, diabetes, obesity, several cancers, asthma, allergic reactions, and increased LDL cholesterol is a worldwide medical concern in general. In the last two or three decades, there was a great interest in processed foods such as shortenings, potato chips, margarine, fast food, snacks, and fried foods due to their desirabilities by consumers, but their trans-fat contents made these products to be questioned soon. Today, many countries and organizations have been conducting investigations to limit the maximum amount of trans fats in such processed foods with a high content of fat. This chapter aims to provide further information about the nature, occurrence, and global regulations of trans fatty acids.
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Background and objectives: Olive (Olea europaea L.) belongs to the Oleaceae family and is an evergreen tree. The olive oil has been an important source of nutrition and medicine for centuries. Olive oil is of highly important due to presence of significant amount of mono-unsaturated Fatty Acid namely Oleic Acid and natural antioxidants. Different geographical regions with different natural conditions have been different effects on growth of plants and climate conditions can be affected synthesis of chemical matter or secondary metabolites in plants. Therefore, in this study, fatty acids of olive fruit cultivars in three regions of the Lorestan province were investigated by Gas Chromatography (GC). Materials and Methods: This research was conducted in factorial test in based on completely randomized design with two factors, Factor A was four cultivars of olive (including cultivars of Konservolia, Sevillana, Manzanilla and Rowghani) and factor B was three regions of Lorestan province (including Kouhdasht, Khorramabad and Veysian) that were studied in four replicate and each replicate include three trees. In this study, fruit fatty acids of four olive cultivars in three regions of the Lorestan province were identified using gas chromatography (GC). For each cultivar, selected 30 healthy olive trees from different parts of the garden and about five kilograms of fruit-manually in each repeat randomly picked from different directions trees healthy fruits in separate envelopes were placed. Analysis of variance and mean comparison of traits was performed with Duncan test (P Results: The analysis of variance showed that all fatty acids in different regions had significant differences between cultivars (P Conclusions: The results showed that the quantity and quality of fatty acids in olive cultivars influenced by environmental factors and fatty acid values for each cultivar in each region were different. Finally, among the olive cultivars studied in different regions, the Sevillana in Khorramabad in terms of Linoleic, Palmitoleic and Myristic acid, the Manzanilla in Veysian in terms of Arachidic and Linolenic acid and the Konservolia in Kouhdasht in terms of Gadoleic, Stearic and Palmitic acid and finally the Rowghani cultivars in the Kouhdasht region in terms of Oleic acid had a highest values. Rowghani cultivar in Kouhdasht region had a highest quantity and quality of oil and fatty acid in this research, therefore it can be recommended as ideal cultivar.
Article
New sources of bioactive compounds are constantly explored for reformulating healthier foods. This work aimed to explore and characterize the fatty acid profile and sterol content of three non‐conventional oils used in functional food products (hempseed oil, moringa oil, and echium oil) and to compare them with two conventional ones (extra virgin olive oil [EVOO] and linseed oil). Oxidative stability was assessed by determining their acidity value and peroxide content. All oils showed adequate values for acidity and oxidation status. Echium and hempseed oils showed a high content of polyunsaturated fatty acids (>70%), especially omega‐3 fatty acids, while moringa oil was rich in oleic acid. Echium oil, hempseed oil, and moringa oil presented higher sterol content than EVOO, but lower than that of linseed oil. Sitosterol was the most abundant sterol in all samples (97.88–275.36 mg/100 g oil), except in echium oil, where campesterol (170.62 mg/100 g oil) was the major sterol. Squalene was only found in significant amounts in EVOO. In conclusion, non‐conventional oils seem to be interesting sources of bioactive compounds and have great potential for the food industry. Non‐conventional vegetable oils can be used as alternative sources of lipids in a variety of food products. Additionally, these oils have great potential to be included in the formulation of functional ingredients for the delivery of omega‐3 fatty acids, antioxidants, fiber, among others.
Article
Deep‐frying oil featuring total polar compound (TPC) has been found to be unhealthy. However, little information is available regarding the impact of TPC on the lipid digestion behaviour. In this study, three typical edible oils (palm oil, PO; high oleic acid peanut oil, HOA; and high linoleic acid sunflower oil, HLA) were selected to investigate the effect of deep‐frying on the lipid digestion. Digestion behaviour was monitored by pH‐Stat method in vitro. Digestibility rate analysis showed that free fatty acids release rate of all TPC groups was the slowest among corresponding fresh oils and deep‐frying oils, indicating deep‐frying decreased lipid digestion rate. Lipid droplet analysis uncovered that deep‐frying could increase lipid particle size. Correlation analysis showed the polymers in TPC are negatively correlated with digestion rate and particle size, suggesting the digestion behaviour of deep‐frying oil is related to TPC constitution. In conclusion, this study highlights that deep‐frying weaken the lipid digestion capacity, and the multiplicity of TPC distribution which vary in terms of FAs type contribute to differences of digestion behaviour in deep‐frying oils. Deep‐frying changes the lipid digestion behaviors.
Article
Vegetable oils with different unsaturated degrees (corn > peanut > olive > palm > coconut) and corresponding enzymatic hydrolysis-thermal oxidation (ENTH) oils were added into D-xylose and L-cysteine Maillard reaction (MR) system, respectively, for potential meaty aroma production. Results indicated that coconut oil and palm oil had lower peroxide, p-anisidine, total antioxidant values, and malondialdehyde content after ENTH and MR. Corn, peanut, and olive oils after ENTH could significantly promote MR because they caused the lower pH, higher reactants depletion, and higher browning degree in the water phase separated from the oil-Maillard reaction system. Additionally, the volatiles were mainly formed from oil phase. Corn, peanut, and olive oils were beneficial to volatiles formation in the oil-MR system due to fatty acid oxidation, especially oleic acid and linoleic acid. Meanwhile, compared to raw oils, adding ENTH oils to the MR system could reduce the content of oxygen, nitrogen, and sulfur-containing heterocycles.
Article
Background Extra virgin olive oil (EVOO), the main fat in the Mediterranean diet, is consumed both raw and cooked. During the cooking process, its major and minor fractions are transformed, degraded, and oxidized due to exposure to heat and oxygen. Scope and approach This review examines the effect of cooking on EVOO, including the modification of its fatty acids and minor compounds; the interaction between EVOO and food matrices; the migration of components from the oil to food and vice versa; and how EVOO may enhance the stability and health properties of the cooked food. Key findings and conclusions EVOO has several advantages over other vegetable oils used in cooking. Its fatty acid profile and minor constituents keep the oil stable under high temperatures. By absorbing the oil, the cooked food is likewise protected from oxidation and enriched with EVOO health-promoting bioactive compounds. Finally, food bioactive compounds become more bioavailable upon migration to the oil.
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Tripleurospermum limosum (TL) has been used in folk medicine to treat gastritis. Toward the further development and use of TL, we report the phytochemical profiling, determination of active components, and antioxidant and enzyme inhibitory activities of TL. Nineteen compounds were identified by ultra-performance liquid chromatography-electrospray ionization-orbitrap-mass spectrometry for the first time in this plant. Phytochemical studies indicated that TL contained 11 types of phytochemicals. The active components [total carbohydrate content (TCC), total protein content (TProC), total triterpenoid content (TTC), total phenolic content (TPheC), total flavonoid content (TFC), total phenolic acid content (TPAC), condensed tannin content (CTC), and gallotannin content (GC)] of eight different solvent extracts were determined by ultraviolet-visible spectrophotometry. Aqueous extract had highest TProC, TPheC, and GC values. Methanol extract exhibited highest TCC and TFC values. Ethanol extract showed highest TPAC and CTC values and dichloromethane extract exhibited highest TTC value. Methanol extract showed strongest ability to scavenge 2,2-diphenyl-1-picrylhydrazyl radicals, 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt cation radicals, and hydroxyl radicals, and also exhibited highest antioxidant activity in ferric-reducing antioxidant power and cupric ion-reducing antioxidant capacity assays. Best iron and copper chelating activity and H2O2 scavenging ability were shown by aqueous extract. Ethanol extract showed strongest ability to scavenge superoxide radicals and effectively prevent β-carotene bleaching. Acetone extract had highest inhibitory activity toward α-glucosidase, α-amylase, and xanthine oxidase. Ethyl ether extract had highest inhibitory activity towards urease and angiotensin converting enzyme. Aqueous and ethanol extracts had strongest inhibitory activity toward acetylcholinesterase. Methanol extract showed highest inhibitory activity toward tyrosinase. Methanol extract showed good stability and antioxidant capacity during heating, at different pH values, and after in vitro digestion and had low toxicity. The efficacy of methanol extract in stabilizing olive and sunflower oils was studied, the results suggested that methanol extract had a protective effect on the primary oxidation of the two oils. TL may be useful as a source of active components for application in human nutrition and/or phytomedicine and methanol extract of TL could be used as a natural oil stabiliser.
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The objective of this study was to investigate the antioxidant activity of trehalose in vegetable oils after 16 h deep-frying at 180 °C by using nuclear magnetic resonance (NMR) spectroscopy. ¹H-NMR spectroscopy is a useful technique for determining structure which requires small sample volumes and short processing time. The results of this study indicate the oxidation stability of vegetable oils can be improved with the addition of trehalose at 0.05% (w/w) concentration. The antioxidant activity of trehalose positively affected all vegetable oils studied with notable differences when used in conjunction with soybean oil. For example, the measured percent loss of olefinic protons in soybean oil (oil-0 control) changed from 6.17 to 2.52 (integral value) in sample soybean oil-1 with the addition of trehalose. Similarly, the percent loss of bisallylic protons changed from 8.19 to 3.32. Further, with respect to the percent loss of allylic protons changing from 3.02 to 0, the oxidation of an allylic proton was greatly depressed. Trehalose improved the oxidation stability of soybean oil much better than that of corn oil, canola oil, cottonseed oil and peanut oil. In summary, trehalose can be used as a safe and effective antioxidant for these edible oils.
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Background and objectives: Deep frying is one of the most frequently used methods of food preparation. It is important to note that despite the beneficial effects of frying on the sensory properties of foods, frequent use of frying oil with hydrolysis and the oxidation of oil in the presence of heat and water leads to oil decomposition. Many of the edible oil degradation products are harmful to human health as they destroy vitamins, inhibit enzymes and can cause gastrointestinal mutations or irritation. Therefore, it is important to evaluate the thermal stability of edible oils. In recent years, the use of thermal analysis methods to determine the stability of edible oils has increased, and differential scanning calorimetery (DSC) is one of the most critical methods. It may also be used to determine melting and crystallization profile andvidentify lipids adulterations. Materials and methods: In this study, fatty acid composition, peroxide value, anisidine value, totox, acidity, and total polar compounds were evaluated on peanut oil, rice bran oil and their blends (5, 10, and 15 % (w/w)) for 8 hours with 2 h interval. Results: By increasing heating time, all chemical parameters were increased. However, peroxide value was increased initially and then decreased. The results of the DSC showed that with increasing the frying time, the peak temperature and enthalpy of single crystallization peak decreased. The regression equations were presented to predict each chemical parameters using DSC thermogram. Investigation of the correlation between the results of DSC and chemical parameters of Pearson correlation showed a reverse trend between them (Pearson correlation coefficient is close to -1). As the frying time increased, the chemical parameters increased and DSC parameters decreased. Each of the peanut and rice bran oils showed excellent resistance to heat after 8 h. However, the oil blends, especially in the high mixing ratio showed lower heat stability. Conclusion: It should be noted that using DSC to detect the thermal stability of vegetable oils is a faster, easier, and cheaper method in comparison to the determination of chemical parameters, which may be hazardous to the environment and require trained people. Therefore, depending on thermal decomposition methods and their ease of preparation, the low sample size for tests, accurate results, reproducibility and smooth operation in the food industry, it is recommended especially for edible oils stability studies.
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Frying process was repeatedly carried out 12 times in a deep fryer at 180°C using palm olein oil with potatoes. The effect of deep frying on the chemical and physical properties of the oil has been investigated. Free fatty acidity (0.35%–1.39%), peroxide value (0.64–11.49 meqO2/kg), p‐anisidine value (5.06–67.52), total oxidation value (7.66–91.11), conjugated diene (2.84–11.09) and triene (1.07–5.65), total polar matter, and viscosity (17.64–140 mPa s) analyses were performed in oil samples. In addition, uckun (Rheum ribes L.), quinoa (Chenopodium quinoa Willd.), and propolis extracts were obtained and added to the oils at the level of 1,000–1,500 ppm determined by preliminary studies. Beside that a kind of synthetic antioxidant (BHT as 200 ppm) was added to the oil samples. The results of the present study showed that the propolis extract (1,500 ppm) had the best results on the thermal‐oxidative stability and closest values to BHT. İt was understood that propolis and quinoa extracts could be used in the oil industry. And also especially 1,500 ppm level of propolis extract may affect as much as BHT on the oxidation stability. By adding these extracts into oil, it was seen that oil can be used 12 times for deep frying.
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BACKGROUND Deep-frying oil has been found to cause inflammatory bowel diseases (IBD). However, the molecular mechanism of the effect of deep-frying palm oil on IBD is still indetermination. RESULTS In this study, bioinformatics and cell biology were used to investigate the functions and signal pathway enrichments of differentially expressed genes. The bioinformatics analysis of three original microarray datasets (GSE73661, GSE75214, and GSE126124) in NCBI-Gene Expression Omnibus database showed 17 down-regulated genes (logFC< 0) and 2 up-regulated genes (logFC> 0) are existed in the enteritis tissue. Meanwhile, pathway enrichment and protein–protein interaction network analysis suggested IBD is relevant to cytotoxicity, inflammation, and apoptosis. Furthermore, Caco-2 cell was treated with the main oxidation products of deep-frying oil-total polar compounds (TPC) and its components (polymerized triglyceride, oxidized triglycerides and triglyceride degradation products) isolated from deep-frying oil. The flow cytometry experiment revealed that TPC and its components could induce apoptosis, especially for oxidized triglyceride. The quantitative polymerase chain reaction analysis demonstrated that TPC and its component could induce Caco-2 cell apoptosis through AQP8/CXCL1/TNIP3/IL1. CONCLUSION This study provided fundamental knowledge in the understanding of the effects of deep-frying oils on the cytotoxic and inflammatory of Caco-2 cells, in turn assisting in clarifying the molecular function mechanism of deep-frying oil in IBD. This article is protected by copyright. All rights reserved.
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The digestion behavior of epoxy triglyceride, the main cytotoxic product of deep-frying oil, remains unknow, which may affect its biosafety. In this study, epoxy triglyceride (EGT) and triglyceride (GT) were used to reveal the effect of epoxy group on digestion. Digestibility rate analysis showed that the free fatty acids release rate of EGT was slower. To clarify this phenomenon, binding ability with salt ions in digestive juice and particle size were also been studied. Cluster size analysis indicated that epoxy group increased triglyceride particle size, resulting in smaller contact area between EGT and lipase. Interface behaviors displayed EGT decreased binding ability with salt ions in digestive juice. Spectroscopic analysis showed EGT caused the red shift of lipase peak, indicating that epoxy group changed lipase structure. Molecular dynamics simulation suggested EGT leads to loosen lipase structure. In conclusion, this study highlights that epoxy group could weaken the triglyceride digestion.
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This research investigated the influence of post‐frying vacuum application on thermal resistance, and fate of 3‐monochloropropane‐1,2‐diol esters (3‐MCPDE) and glycidol esters (GE) in palm olein when products of different surface‐to‐volume ratio (SVR) underwent intermittent frying. Pre‐fried shoestring (higher SVR) and straight‐cut French fries (lower SVR) were first conventionally fried prior to vacuum drainage (VD) namely Protocol VD. Meanwhile, control experiments involved atmospheric frying and atmospheric drainage (AD) (Protocol AD). Protocol VD was more prominent in minimising free fatty acids (FFA) for product with higher SVR (63%) compared to lower SVR (41%). Oil acidity was coincided with diacylglycerols (DAG) depreciation and marginal higher smoke point (SP). Protocol VD seemed not effective in minimising oil oxidation and polymerisation as reflected by p‐anisidine value (AnV) and polar compound fractions, and hence, delayed 3‐MCPDE and GE fragmentation.
Chapter
Deep-fat frying is a quick method of cooking that produces a product with attractive organoleptic properties. However, the degradation of frying oil that occurs thr ough series of reactions and the transfer of a substantial amount of oil to the product raises health concerns. The main oil degradation reactions are oxidation, hydrolysis, and polymerization. Each reaction produces specific compounds that negatively affect health, reduce the foods, and oil quality. Hence, frying oil must be discarded when it reaches a certain level of degradation. There are several methods to detect the degradation of oil, such as the peroxide value, free fatty acids, p-anisidine value, and total polar compounds. The fatty acid profile (FAP) of frying oils is a good indicator of their stability. FAP changes with the degradation of oil by the breakdown of unsaturated fatty acids because of their susceptibility to oxidation. According to the American Oil Chemists Society, official methods, rapid methods, and test kits are being developed to reduce time, chemicals, and/or subjectivity of the test methods.
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Virgin olive oil has a high resistance to oxidative deterioration due to both a triacylglycerol composition low in polyunsaturated fatty acids and a group of phenolic antioxidants composed mainly of polyphenols and tocopherols. Polyphenols are of greater importance to virgin olive oil stability as compared with other refined oils which are eliminated or drastically reduced during the refining process. This paper covers the main aspects related to the oxidative stability of virgin olive oil during storage as well as at the high temperatures of the main processes of food preparation, i.e., frying and baking. Differences between oxidation pathways at low and high temperature are explained and the general methods for the measurement of stability are commented on. The compounds contributing to the oxidative stability of virgin olive oils are defined with special emphasis on the antioxidative activity of phenolic compounds. Finally, the variables and parameters influencing the composition of virgin olive oils before, during and after extraction are discussed.
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Deep fat frying is an important, ubiquitous and highly versatile process, which has been used since antiquity to cook a wide spectrum of products. Its unique contribution to sensory characteristics, together with the relatively low cost of large-scale frying, has made fried foods the staples of the ever growing late 20th century fast food industry. Despite its considerable fat content and intensified consumers’ awareness of the relationships between food, nutrition and health, frying remains a principal cooking method. Oil consumption especially saturated fat is considered a major factor increasing health risks such as coronary heart disease (CHD), cancer, diabetes and hypertension, and even linked to increased causes of deaths. Fried foods contribute a significant proportion of the total fat consumed in the Western world. Yet, aside from their high caloric value, fried foods can be nutritious and favourably compared with other cooking methods such as baking and boiling. Fried foods are popular due to their taste, distinctive flavour, aroma and crunchy texture. Misconceptions about frying extend beyond nutrition to the fundamental aspects of the process, such as the role of water and oil quality during frying. The water released during frying enhances heat transfer, may cause oil deterioration, and also can prevent oxidation. Improving oil quality, the mechanism of oil, coating, engineering considerations of residence time and design, are typical examples of frying technology that is still evolving. To provide quality products that meet consumers’ expectations and satisfaction, and simultaneously improve their quality characteristics, a new paradigm is required. These topics are discussed and data presented to suggest that fried foods do not have to be a health risk in a balanced diet, when frying technology and oil quality are carefully maintained. Future research needs are also highlighted.
Chapter
The Mediterranean Diet (MeD) can be considered an example of how ideas about eating habits are changing. Until recently, the diet of Mediterranean Europe did not enjoy much prestige. At a time when height was considered to equate with optimal health, the average height of the Mediterranean people was believed to be indicative of poor diet. Some staple foods in that diet, such as olive oil, did not have a good reputation either, although the MeD originated in the countries that were the cradle of civilization. Nor were some of the cooking methods properly understood—deep-frying, for instance, one of the characteristics of the MeD (Varela & Ruiz-Roso 1992).
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Discussions on the various health promoting and disease preventing properties of olive oils and its components are presented, with focus on cardiovascular diseases, neoplasms and diabetes and other metabolic disorders. Also, chapters on the chemical composition and physicochemical properties of olive oils, including the various methods used to analyse them, are presented.
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Virgin olive oil has a high resistance to oxidative deterioration due to both a triacylglycerol composition low in polyunsaturated fatty acids and a group of phenolic antioxidants composed mainly of polyphenols and tocopherols. Polyphenols are of greater importance to virgin olive oil stability as compared with other refined oils which are eliminated or drastically reduced during the refining process.This paper covers the main aspects related to the oxidative stability of virgin olive oil during storage as well as at the high temperatures of the main processes of food preparation, i.e., frying and baking. Differences between oxidation pathways at low and high temperature are explained and the general methods for the measurement of stability are commented on. The compounds contributing to the oxidative stability of virgin olive oils are defined with special emphasis on the antioxidative activity of phenolic compounds. Finally, the variables and parameters influencing the composition of virgin olive oils before, during and after extraction are discussed.
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A micromethod was developed and validated for the quantification of lutein and β‐carotene in olive oils. The compounds are liquid‐liquid extracted with n‐hexane and n,n–dimethylformamide (DMF), by vortex mixing and centrifugation. The n‐hexane phase retains β‐carotene, whereas the DMF phase retains lutein. This last fraction is concentrated and analyzed by RP‐HPLC/diode‐array, with a gradient of acetonitrile, water, and ethyl acetate, using β‐apo‐8′‐carotenal as I.S. β‐carotene is quantified by UV/Vis measurements at 454 nm, by the external standard method. The method shows appropriate inter‐ and intra‐day reproducibility, accuracy, and linearity for both compounds, allowing fast analysis of several samples simultaneously, with a relatively small consumption of organic solvents. The analytical methodology was applied to several samples of commercial Portuguese PDO olive oils.
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The performance of virgin olive oil and a commercial vegetable shortening was investigated during 10 successive pan-fryings of potatoes at 180 °C for a total period of 60 min and during 10 successive deep-fryings at 170 °C for a total period of 120 min. These are typical conditions of Greek domestic cooking. For both the oils tested the effect of pan-frying on K232, K268, K316, α-tocopherol, total polar artefacts, Rancimat induction times, octanoic acid formation and linoleic acid decomposition was worse than the effect of deep-frying on the same variables. The same was true for visible spectrum and total phenols in virgin olive oil. No systematic variations of oleic acid, refractive index and trans-isomers of fatty acids were detected. None of the oils reached the limit of 25–27% total polar artefacts. Both oils performed similarly during pan-frying, while virgin olive oil performed better during deep-frying. A very strong correlation between octanoic acid formation and total polar artefacts in the whole data set was observed.
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Monovarietal extra virgin olive oils extracted from six dominant and economically important Turkish olive cultivars (memecik, erkence, domat, nizip-yaglik, gemlik, ayvalik) were examined for their simple phenolics, phenolic acids and flavonoid compounds over 2005 and 2006 harvest years. Total phenol contents, oxidative stabilities and chromatic ordinates as colour parameters were also measured. The most typical phenolic compounds that were identified in both years are hydroxytyrosol, tyrosol, vanillic acid, p-coumaric acid, cinnamic acid, luteolin, and apigenin. Multivariate data were analysed by principal component and partial least square-discriminant analyses. It was observed that phenolic profiles of olive oils depended highly on harvest season. In addition, oils of different olive cultivars have different distribution of phenols. No significant correlation was observed between oxidative stability and phenolic compounds. Increase in peroxide value over an accelerated oxidation period of 11 days showed weak correlations with total phenol content, vanillin, syringic acid and colour parameter a∗, as 0.56, 0.55, −0.42, and 0.51, respectively, in terms of correlation coefficient r.
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During frying, the degradation of oil produces harmful compounds. Improper monitoring of oil-discard times in restaurants either risks the public health or causes financial losses to industries. Measuring the oil quality is a complex problem and an online sensor is needed. The process of frying reviewed includes moisture, heat and fat/oil transfer, crust formation and various structural, textural and chemical changes in the product, and degradation of frying medium. Some of the European nations and the U.S. have specific regulations against the use of deteriorated frying oils. Due to the absence of a suitable online frying oil quality sensor for restaurant situations, it is difficult to implement any regulation against the use of deteriorated frying oil. Based on various regulations, a model regulation to increase the safety and quality of fried foods is discussed. Background and requirements for developing an online sensor to measure frying oil quality are discussed. Other related areas reviewed in this article are factors affecting oil penetration and absorption by the food, surfactant theory of frying, analytical indices, quick tests and acceptability of frying oil.
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Recent consumer interest in 'healthy eating' has raised awareness to limit the consumption of fat and fatty foods. What are the relative nutritional advantages and disadvantages of consuming fried foods? Are all fried foods bad for you? A review on macro- and micronutrients losses and gains during frying is presented here. Frying has little or no impact on the protein or mineral content of fried food, whereas the dietary fibre content of potatoes is increased after frying due to the formation of resistant starch. Moreover, the high temperature and short transit time of the frying process cause less loss of heat labile vitamins than other types of cooking. For example, vitamin C concentrations of French fried potatoes are as high as in raw potatoes, and thiamine is well retained in fried potato products as well as in fried pork meat. The nutritive value of the frying media is also important to take into consideration and therefore losses of nutrients from the frying oil are also discussed. Although some unsaturated fatty acids and antioxidant vitamins are lost due to oxidation, fried foods are generally a good source of vitamin E. It is true that some fat is inevitably taken up by the food being fried, contributing to an increased energy density. However, this also results in highly palatable foods with a high nutritional content. It is concluded that fried foods certainly have a place in our diets.
Article
The concentration of hydroxytyrosol (3,4-DHPEA) and its secoiridoid derivatives (3,4-DHPEA-EDA and 3,4-DHPEA-EA) in virgin olive oil decreased rapidly when the oil was repeatedly used for preparing french fries in deep-fat frying operations. At the end of the first frying process (10 min at 180 degrees C), the concentration of the dihydroxyphenol components was reduced to 50-60% of the original value, and after six frying operations only about 10% of the initial components remained. However, tyrosol (p-HPEA) and its derivatives (p-HPEA-EDA and p-HPEA-EA) in the oil were much more stable during 12 frying operations. The reduction in their original concentration was much smaller than that for hydroxytyrosol and its derivatives and showed a roughly linear relationship with the number of frying operations. The antioxidant activity of the phenolic extract measured using the DPPH test rapidly diminished during the first six frying processes, from a total antioxidant activity higher than 740 micromol of Trolox/kg down to less than 250 micromol/kg. On the other hand, the concentration of polar compounds, oxidized triacylglycerol monomers (oxTGs), dimeric TGs, and polymerized TGs rapidly increased from the sixth frying operation onward, when the antioxidant activity of the phenolic extract was very low, and as a consequence the oil was much more susceptible to oxidation. The loss of antioxidant activity in the phenolic fraction due to deep-fat frying was confirmed by the storage oil and oil-in-water emulsions containing added extracts from olive oil used for 12 frying operations.
Article
Olive oil is the primary source of fat in the Mediterranean diet which is associated with a low mortality for cardiovascular disease. In spite of this, data concerning olive oil consumption and primary end points for cardiovascular disease are scarce. However, a large body of knowledge exists providing evidence of the benefits of olive oil consumption on secondary end points for cardiovascular disease. The benefits of olive oil consumption are beyond a mere reduction of the low density lipoprotein cholesterol. Here, we review the state of the art concerning the knowledge of the most important biological and clinical effects related to the intake of olive oil rich diets on lipoprotein metabolism, oxidative damage, inflammation, endothelial dysfunction, blood pressure, thrombosis, and carbohydrate metabolism. The extent to which we possess evidence of the health benefits of olive oil minor components is also assessed. The wide range of anti-atherogenic effects associated with olive oil consumption could contribute to explain the low rate of cardiovascular mortality found in Southern European Mediterranean countries, in comparison with other western countries, despite a high prevalence of coronary heart disease risk factors.
The chemistry of edible fats In: The Chemistry and Technology of Edible Oils and Fats and their High Fat Products
  • G Hoffman
Hoffman, G., 1989. The chemistry of edible fats. In: The Chemistry and Technology of Edible Oils and Fats and their High Fat Products. Academic Press, London, pp. 1–28.
Some nutritional aspects of olive oil Handbook of Olive Oil. Analysis and Properties
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Olive Oil: From the Tree to the Table
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Animal and Vegetable Fats and Oils – Determination of Tocopherol and Tocotrienol Contents by High-Performance Liquid Chromatography
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