The antioxidants in oils heated at frying temperature,whether natural or added,could protect against postprandial oxidative stress in obese people

We have investigated the effects of the intake of oils heated at frying temperature in order to find an oil model for deep-frying that prevents postprandial oxidative stress. Twenty obese people received four breakfasts following a randomised crossover design consisting of different oils (virgin olive oil (VOO), sunflower oil (SFO), and a mixed seed oil (SFO/canola oil) with added dimethylpolysiloxane (SOX) or natural antioxidants from olives (SOP)), which were subjected to 20 heating cycles. The intake of SFO-breakfast reduced plasma GSH levels and the GSH/GSSG ratio, increased protein carbonyl levels, and induced a higher gene expression of the different NADPH-oxidase subunits, Nrf2-Keap1 activation, gene expression of the antioxidant enzymes in peripheral blood mononuclear cells and antioxidant plasma activities than the intake of the breakfasts prepared with VOO, SOP and SOX. Oils with phenolic compounds, whether natural (VOO) or artificially added (SOP), or with artificial antioxidant (SOX), could reduce postprandial oxidative stress compared with sunflower oil.     

The postprandial inflammatory response after ingestion of heated oils in obese persons is reduced by the presence of phenol compounds

Scope Heating during the process of cooking alters the chemical properties of foods and may affect subsequent postprandial inflammation. We tested the effects of four meals rich in different oils subjected to heating on the postprandial inflammatory metabolism of peripheral blood mononuclear cells (PBMCs). Methods and results Twenty obese participants received four breakfasts following a randomized crossover design, consisting of milk and muffins made with different oils (virgin olive oil (VOO), sunflower oil (SFO), and a mixture of seeds oil (SFO/canola oil) with added either dimethylpolysiloxane (SOD), or natural antioxidants from olive mill wastewater alperujo (phenols; SOP)), previously subjected to 20 heating cycles. Postprandial inflammatory status in PBMCs was assessed by the activation of nuclear NF‐κB, the concentration in cytoplasm of the NF‐κB inhibitor (IκB‐α), the mRNA levels of NF‐κB subunits and activators (p65, IKKβ, and IKKα) and other inflammatory molecules (TNF‐α, IL‐1β, IL‐6, MIF, and JNK), and lipopolysaccharide (LPS) levels. VOO and SOP breakfasts reduced NF‐κB activation, increased IκB‐α, and decreased LPS plasma concentration. SFO increased IKKα, IKKβ, p65, IL‐1b, IL‐6, MIF, and JNK mRNA levels, and plasma LPS Conclusion Oils rich in phenols, whether natural (VOO) or artificially added (SOP), reduce postprandial inflammation, compared with seed oil (sunflower).     

Effects of deep frying vegetable oils rich in PUFAs on gut microbiota in rats

Vegetable oils rich in PUFAs are widely used in daily cooking and food industry, and PUFAs could be utilised by gut microbiota and present prebiotic effects. However, PUFAs are unstable in high-temperature cooking like frying. In the current study, we aimed to explore the influence of thermally oxidised oils rich in PUFA on gut microbiota. Two vegetable oils: omega-3 alpha-linolenic acid (ALA)-rich perilla oil or omega-6 linoleic acid-rich sunflower oil were heated at 180 °C for 10 h, and then fed to male SD rats for 14 weeks. Administration of heated perilla oil dramatically increased the relative abundance of Akkermansia muciniphila, a recent identified probiotics which may weaken intestinal mucus barrier, and inhibited the expression of several tight junction-related genes including occludin and claudin-1 in colon. Consumption of thermally oxidised sunflower oil stimulated the proliferation of Bifidobacterium. Our findings suggested that thermally processing has complicated effects on the prebiotic effects of vegetable oils rich in PUFAs, and perilla oil fried foods may be potential sources to stimulate Akkermansia proliferation in gut.     

Rapid determination of polar compounds in frying fats and oils using image analysis

Fats and oils were exposed to high temperature at 145°C for 80 h with frying steamed noodles, and the polar compounds were determined using a standard column chromatography and a novel image analysis method. The image was separated into polar and nonpolar component on TLC plate, and recorded with a camera. When the original image was transformed into 3 monochrome components of red, green and blue, respectively, pseudo-mass (the intensity-weighted area) ratio of image processed with a red-frame was highly correlated with real mass determined by column chromatography. The content of polar compounds for respective frying oils was calculated with the standard curves of first order regression that showed the determination coefficients of R²>0.8 (P<0.001). Consequently, it seemed that image analysis on polar compound could replace the extremely time and chemical consuming standard method for estimating the quality of frying fats and oils.     

Distribution and retention of phytosterols in frying oils and fried potatoes during repeated deep and pan frying

The retention and distribution of phytosterols in fried oils and French-fries during eight successive pan- and deep-frying sessions of pre-fried potatoes in sunflower oil, palm oil, cottonseed oil, virgin olive oil and a vegetable shortening were evaluated. Phytosterols (β-sitosterol, campesterol, stigmasterol, Δ⁵-avenasterol) were determined in the unsaponifiable fraction of frying oils and lipids extracted from French-fries by GC/FID after derivatization to trimethylsilyl ethers. French-fries were enriched with phytosterols due to the absorption of frying oil, with β-sitosterol predominating in both fried oils and potatoes. The amount of phytosterols decreased during frying, their overall retentions reaching 9.5–22.8% and 29.4–51.2% after eight successive pan- and deep-frying sessions, respectively, while their deterioration was found to be affected by frying time, frying technique, being more prolonged during pan-frying, and by the oils’ unsaturation, being more extended in polyunsaturated oils. Phytosterols were more or less uniformly distributed between the fried oil and the fried potatoes. The phytosterols dietary intake by consuming potatoes fried in the oils tested is discussed.     

The effects of oils and frying temperatures on the texture and fat content of potato crisps

The purpose of the study was to determine the effects of oils and frying temperatures on fat content and texture of potato crisps.     

Formation of trans fatty acids in edible oils during the frying and heating process

To assess an impact of heated edible oils on intake of trans fat, the formations of trans fatty acids (TFAs) in cooking conditions was estimated by a frying and heating model system. For the frying model, sliced raw potatoes (10% of the frying oil (w/w)) were fried in commercially available canola oil at 160, 180 and 200 °C, and the 10 frying cycles were performed. The TFAs contained both in fried potatoes and in frying oils were measured by gas chromatography (GC). Lipids content of raw potatoes was about 0.1% (w/w) and TFAs in the raw potatoes were negligible. On the other hand, fried potatoes contained lipids at the level of 8.8%–9.2% and their fatty acid composition was mostly in correspondence with that of the frying oil. The TFAs amount of potatoes fried by the tenth frying operation was at the level of 0.99–1.05 g/100 g lipids. When 100 g potatoes fried in this process were consumed, the TFAs intake was estimated at less than 0.1 g. After 10 frying operations, TFAs content, acid values and peroxide values of the frying oils were measured and compared with those of corresponding heated canola oils without food. The amounts of trans 18:1 FAs contained both in the frying oil and in heated oil were less than the quantitative limit (0.047 g/100 g oil). The increases of trans 18:2 FAs and trans 18:3 FAs of the used frying oil were 0.02 g/100 and 0.05 g/100 g, respectively, compared with those of the fresh oil. trans 18:2 FAs accumulation in the heated oil was slightly less than that in the frying oil. To elucidate TFAs accumulation in various edible oils during cooking, six kinds of commercially available edible vegetable oils were heated to 180 °C in glass test tubes. Small changes in TFAs amounts were observed after four hours heating. These results suggested that an ordinary frying process using unhydrogenated edible oils has little impact on TFAs intake from edible oils.     

煎炸对茶油品质指标及挥发组分的影响

目的：研究煎炸对茶油品质指标及挥发组分的影响，了解油脂的氧化情况；方法：通过顶空固相微萃取技术与GC／MS相结合，对煎炸加工导致的茶油理化指标和挥发组分的变化进行研究；结果：随着煎炸次数的增多，茶油的过氧化值及酸价均逐渐上升，同样K232值和K270值也随之变大，茶油挥发组分的总峰面积及出峰数也随着煎炸次数的增加而增大，大部分挥发物质的含量随着煎炸次数的增加而明显变大。可见煎炸强烈地影响着油脂的理化指标及挥发组分。     

真空低温煎炸对油稳定性影响的研究

主要探讨了真空低温煎炸胡萝卜片后3种煎炸油的稳定性,研究了3种煎炸油的酸值、过氧化值、羰基值随煎炸时间的变化规律,并分析了它们之间的相关性.结果显示,与大豆色拉油相比,棕榈油和猪油有更高的煎炸稳定性;3种油的酸值、过氧化值、羰基值与煎炸时间存在着显著的相关性.     

Influence of fatty acid composition on chemical changes in blends of sunflower oils during thermoxidation and frying

The influence of fatty acid composition on formation of new compounds at frying temperatures has been studied in seven samples of sunflower oils widely differing in their fatty acid composition. Thermal oxidation assays as well as frying experiments were carried out and samples were evaluated by measuring the new compounds formed, i.e. polymers, polar compounds and their distribution by molecular weight, and polar fatty acids and their distribution by molecular weight. The levels of all the new compounds analysed strongly depended on the degree of oil unsaturation; the two least unsaturated oils with low content of linoleic acid and high content of palmitic acid behaved exceptionally well. When considering polar compounds or polar fatty acids, the polymers/oxidised monomers ratio increased significantly as the level of degradation increased. The new compounds formed are practically identical when analysed in the used frying oils or in the lipids extracted from the counterpart fried potatoes, independently of the level of degradation.     

Characterisation of phenolic compounds of Inca muña (Clinopodium bolivianum) leaves and the feasibility of their application to improve the oxidative stability of soybean oil during frying

Phenolic compounds from Inca muña leaves were, for the first time, qualitatively and quantitatively characterised. The main phenolic compounds encountered corresponded to flavanones, followed by flavones and hydroxycinnamic acid derivatives. Fractionation of Inca muña phenolic compounds revealed an ethyl acetate fraction (EaF) rich in phenolics and antioxidant activity. This EaF proved to be an efficient source of natural antioxidants for use against soybean oil oxidation during frying. Differential scanning calorimetry revealed higher induction periods for 600 ppm of EaF compared to 200 ppm of TBHQ and a negative control (no antioxidant added). During frying at ∼180 °C, 600 ppm of EaF showed the highest efficacy against oil oxidation in terms of p-anisidine values, conjugated dienes and trienes and polar compounds compared to 200 ppm of TBHQ and negative control. This study provides strong evidence for the antioxidant potential of Inca muña EaF phenolics against soybean oil oxidation. It suggests the possibility of incorporating these natural antioxidants from Inca muña leaves for use by the food industry.     

Effect of repeated frying on the viscosity, density and dynamic interfacial tension of palm and olive oil

The effect of deep-fat frying on the viscosity, density and dynamic interfacial tension (against air and water) of palm oil and olive oil was investigated. Repeated frying (up to 40 batches) at two different potato-to-oil ratios (1/7, 1/35 kg_potatoes/L_oil) was examined. Results were compared to those from simple heating the oils at the same temperatures. Viscosity increased during repeated frying for both oils. However, only palm oil viscosity was sensitive to potato-to-oil ratio. Due to the novelty of dynamic interfacial characterization of such systems a discussion was made about the appropriate timescales and deformation types for interfacial measurements. Significant effects of repeated frying on the dynamic interfacial tension at the oil/water interface were observed. Contrarily, changes in density were not significant. Results were assessed with respect to the evolving chemical profile of the oils determined in previous works. Possible implications of the determined properties on the frying process were discussed.     

Effect of endoplasmic reticulum stress on metabolic and stress signaling and kidney-specific functions in Madin-Darby bovine kidney cells

Recent studies demonstrated induction of endoplasmic reticulum (ER) stress in tissues of cows after parturition, but knowledge about the effect of ER stress on important cellular processes, such as critical signaling and metabolic pathways, in cattle is scarce. Thus, the present study aimed to investigate the effect of ER stress induction on nuclear factor-κB (NF-κB), nuclear factor E2-related factor 2 (Nrf2), and sterol regulatory element-binding protein (SREBF1) pathway in Madin-Darby bovine kidney (MDBK) cells, a widely used in vitro model in ruminant research. To consider the kidney origin of MDBK cells, the effect on renal distal tubular cell-specific functions, such as transport processes and regulation of 1,25(OH)₂D₃ levels, was also studied. Treatment of MDBK cells with 2 different ER stress inducers, thapsigargin (TG) and tunicamycin (TM), strongly induced ER stress as evident from induction of ER stress target genes, increased phosphorylation of PKR-like ER kinase, and enhanced splicing of X-box binding protein 1. The TM decreased the protein concentration of NF-κB p50 and the mRNA levels of the NF-κB target genes. Likewise, TG decreased the mRNA concentration of tumor necrosis factor and tended to decrease NF-κB p50 protein and mRNA levels of NF-κB target genes. The mRNA levels of most of the Nrf2 target genes investigated were reduced by TG and TM in MDBK cells. Both ER stress inducers reduced the mRNA levels of SREBF1 and its target genes in MDBK cells. Interestingly, TG decreased, but TM increased the mRNA level of the Ca²⁺ binding protein calbindin 1, whereas the mRNA level of the plasma membrane Ca²⁺-transporting ATPase 1 remained unchained. The mRNA level of the cytochrome P450 component 24A1 involved in 1α-hydroxylation of 25(OH)D₃ was strongly elevated, whereas the mRNA level of the cytochrome P450 component 27A1 catalyzing the breakdown of 1,25(OH)₂D₃ was markedly reduced by both ER stress inducers. The concentration of 1,25(OH)₂D₃ in the supernatant of MDBK cells was increased by approximately 15% by both TG and TM. The present study indicates that under conditions of ER stress, critical signaling pathways, such as NF-κB, Nrf2, and SREBF1, are inhibited, whereas the formation of 1,25(OH)₂D₃ is stimulated in bovine MDBK cells. Future studies are necessary to clarify the physiological relevance of these findings.     

介电常数在煎炸油极性组分快速检测中的应用

介电常数与煎炸油中极性组分含量有较好相关性,用于评价煎炸油品质,具有快速、便捷、安全等优点。本文分析了液体介电特性的测试原理和煎炸油介电特性机制,列出极性组分和介电常数的相关性拟合模型。以商业化应用广泛的FOS、FOM 310、Testo 270三类快速检测仪器为对象,对其内部构造、仪器操作和数据可靠性进行评价,结合餐饮业实践经验总结了影响其检测准确度的主要因素,包括煎炸油品种、校准体系、悬浮物、操作规范性。最后,提出此快速检测技术未来的两大发展方向:对信号处理参数的特异性优化和对数据处理技术或红外在线检测技术的引入结合。     

Phenolic compounds in virgin olive oils: influence of the degree of olive ripeness on organoleptic characteristics and shelf-life

 An experimental investigation was performed on virgin olive oils from Coratina and Ogliarola salentina cultivars extracted from green, partially blackened and totally blackened olives in order to evaluate changes in the organoleptic properties and in the shelf-life of the oil. The aim of the investigation was to identify the optimal stage of olive maturation for each cultivar to produce higher quality oils. Routine analyses in accordance with EC regulation no. 2568/91, the determination of phenols by HPLC and induction times were carried out. On the whole, the simple phenolic compounds increased as darker olives were used whereas the hydrolysable phenolic compounds decreased. In both the cultivars, total phenols and induction times were significantly higher in the oils obtained from green olives than in oils from totally blackened olives. Hence, it seems advisable to delay olive harvesting for cultivars usually yielding bitter to pungent oils (e.g. Coratina), but to anticipate harvesting for olives producing sweet tasting oils (e.g. O. Salentina). This would produce less bitter Coratina oils, with organoleptic features which may better fulfil consumers' expectations, and O. Salentina oils more resistant to oxidation. Received: 5 June 2000