Calcium Absorption in Rats Consuming Olive Oil or Sunflower Oil Unused or Used in Frying

Olive and sunflower oils were used in repeated potato‐frying operations without turnover until the oils reached the 25% polar compound limit allowed by law. During a 28‐d period, 5 groups of rats were fed diets containing 8% of unused olive oil, olive oil used in 48 and 69 potato‐frying operations, unused sunflower oil, and sunflower oil used to fry potatoes 48 times. No significant differences in food intake, body weight, and food efficiency was observed. The 2 sunflower oil diets increased calcium absorption efficiency without modifying calcium balance, urinary calcium, blood‐serum calcium, and calcium in the carcasses. Intake of oils used in frying did not induce any significant changes. Sunflower oil enhanced calcium bioavailiability slightly, but oil used for frying did not produce any additional effect.     

Effects of diets containing oils from repeated frying on magnesium absorption

Olive oil, sunflower oil and palm olein were used in repeated potato fryings until the oils reached the limit of 25% of polar compounds allowed by law. Six groups of rats, over 28 days, were fed diets containing 8% of: olive oil; olive oil from 69 fryings; sunflower oil; sunflower oil from 48 frying; palm olein, and palm olein from 80 fryings. Body weight and food intake were monitored weekly, during days 21–28 faeces and urine were collected and finally blood and carcasses were also collected and stored. No significant differences were observed in food intake and body weight among the six groups of animals. The type of oil did not modify magnesium intake, the urinary and faecal excretion of this mineral nor its apparent absorption or retention. The consumption of oils from frying, however, induced an increase in apparent magnesium absorption due to a decrease in faecal magnesium excretion, but magnesium retention did not vary owing to the increase in urinary losses. Serum magnesium and magnesium contents and concentrations in carcasses were unaffected. Therefore, it was concluded that the consumption of used frying oils enhances magnesium absorption, independently from the type of oil, although magnesium retention is not affected due to a an elevation of urinary excretion. © 1999 Society of Chemical Industry     

Some physical changes in Bajo Aragón extra virgin olive oil during the frying process

Changes of viscosity, transmittance spectra and colour of Bajo Aragón extra virgin olive oil, during the frying process, were studied, comparing them to the changes that occur during the frying process of high oleic sunflower oil. The studied oil was obtained from Empeltre variety olives. These changes, due to the deterioration of the oil during this process, were monitored by polar compounds measurement. Polar compounds content increased linearly with the frying cycle in both types of oil; however, the increase was faster in high oleic sunflower oil. The olive oil’s transmittance spectra, after the frying process, proved that, not only do the peaks corresponding to the carotenoids and the chlorophyll disappear but also that transformation of the chlorophyll occured. In high oleic sunflower oil spectra there were no changes. L* and b* colour parameters, measured on the CIELAB colour scale, showed the following behaviour: L* values increased for olive oil after frying while the opposite happened for high oleic sunflower oil. In the case of the b* parameter, the result was the same in both cases: when fried, more green and yellow colours appeared. The viscosity of both oils showed a non-linear increase with number of frying operations, which may correspond to a polynomial relationship. Despite their similar contents of oleic acid, olive oil was more stable to oxidation and there were some physical differences between the two types of oil.     

Copper bioavailability in rats fed unused palm olein and palm olein used in frying

The influence of the consumption of unused and used (in repeated potato frying operations) palm olein on copper bioavailability was investigated. Three diets containing respectively 8% olive oil (O), palm olein (P) and palm olein from 80 repeated potato frying operation without turnover (PF), which nearly reached the limit of 25% polar compounds allowed by law, were given to rats for 28 days. No differences were found in food intake and body weight. The liver mass index was higher in PF than in P rats. No significant differences were observed in copper apparent absorption or in liver, skin, erythrocyte, serum and carcass copper contents. Therefore consumption of palm olein, whether unused or used in frying, does not alter copper bioavailability in growing rats. Copyright © 2004 Society of Chemical Industry     

The influence of oil type and frying temperatures on the texture and oil content of French fries

The purpose of the present study was to determine the effects of the frying medium and temperatures on fat content and texture of French fries. The material taken for the study consisted of seven types of vegetable oil: refined sunflower, rape, soy, olive oil, palm, partially hydrogenated rape oil (modified oil I) and a blend of vegetable oils (modified oil II). The French fries prepared from Asterix potato variety were fried at oils heated to 150, 160, 170, 180 and 190 °C. The length of frying (12, 10, 8, 6.5 and 4.5 min, respectively) depended on oil temperature. Fat content and the texture of French fries were determined. The type of frying medium significantly affects the texture of French fries. Temperature influenced both the fat content and texture of product. The increase of frying temperature decreased fat uptake and hardness of French fries. French fries fried in rape oil exhibited the most delicate texture and the lowest oil absorption when compared with French fries fried in other types of oil under investigation. Copyright © 2005 Society of Chemical Industry     

Suitability of contact angle measurement as an index of overall oil degradation and oil uptake during frying

The aim of the work was to investigate the suitability of contact angle measurement as an index of overall oil degradation phenomena and oil uptake of French fries during frying. In order to measure the contact angle, an image analysis method was developed and applied to four vegetable oils (palm oil, palm super olein, sunflower oil and a blend of hazelnut and high-oleic sunflower oil) in actual frying experiments. With liquid oils, contact angle modification proved to be a sound index of overall oil degradation, being inversely correlated with oil acidity, peroxide value, total carbonyl compounds, K₂₃₂, and viscosity. A significant correlation between contact angle and potato oil uptake was found for sunflower oil. For the other oils, factors such as the structure of food subjected to frying or the oil melting point and viscosity seem to be important in influencing oil uptake.     

French Fries oleuropein content during the successive deep frying in oils enriched with an olive leaf extract

Olive oil, sunflower oil and soybean oil were enriched with an olive (Olea Europaea) leaf extract rich in oleuropein at a supplementation level of 100 mg total phenolics per kg oil. Supplemented oils were used for deep frying of potatoes for eight successive frying sessions without replenishment under domestic frying conditions. Supplemented oils contained oleuropein while deep frying resulted in a gradual decrease in oils oleuropein content. After the eighth successive frying, oleuropein was still detected in oils, its retention being 3.2–12.4%. Deep frying of potatoes in supplemented oils succeeded in preparing French fries containing oleuropein even after eight successive fryings. Contrary to the oil type, the number of frying sessions affected potatoes oleuropein content. Oleuropein intake by consuming French fries deep‐fried in enriched oils was approximately ten times higher in potatoes prepared in the first frying session as compared to the respective intake after the eighth frying.     

Change in colour and rheological behaviour of sunflower seed oil during frying and after adsorbent treatment of used oil

Improvement in colour and viscosity of used sunflower seed oil was studied because the reuse of recovered oil could provide considerable savings to food processors. In this study, 50 consecutive deep-fat fryings were done by using potato samples in sunflower seed oil at 170 °C. Significant changes in sunflower seed oil were observed during frying. Change in viscosity and Hunter colour parameters were investigated. These parameters were determined on oil samples taken periodically during frying, and after adsorbent treatment. A predetermined optimum adsorbent mixture (2% pekmez earth, 3% bentonite and 3% magnesium silicate by weight) was applied for colour and viscosity recovery of used oil. Both the adsorbent-treated and untreated used oils showed Newtonian behaviour. Significant increase in oil viscosity was observed during frying. Frying caused a decrease in Hunter L value and an increase in a, b and TCD values of used oil samples. Adsorbents improved the Hunter L, a and b values significantly as well as TCD values, but not the viscosity of the used oil. All the Hunter parameters and TCD followed zero order reaction kinetics. Good agreement was observed between calculated and measured data (r=0.986–0.996).     

反复煎炸对4种食用植物油品质的影响

以特级初榨橄榄油、混合橄榄油、一级大豆油、一级葵花籽油作为煎炸油,以薯条、鸡翅为煎炸原料,对4种食用植物油在重复煎炸过程中发生的品质变化进行观察。方法 测定酸价、羰基价和极性组分,并进行感官评价。结果 4种食用植物油的酸价、羰基价变化与煎炸次数有关;各种食用植物油的品质变化有差别,且煎炸荤食时的品质变化比煎炸素食时的品质变化大。结论 4种食用植物油在反复煎炸后品质均有劣变趋势,但特级初榨橄榄油总的变化率处于较低水平,可见特级初榨橄榄油是煎炸油的上佳选择。     

煎炸油中极性物质与酸价之间的相关性研究

本实验以油茶籽油、橄榄油和棕榈油为研究对象,研究经过180℃下油炸薯条后三种油的酸价与极性物质的相关性以及主要脂肪酸的变化。发现,三种油随着油炸时间的增加酸价(p<0.05)显著增大。油茶籽油、橄榄油和棕榈油的最终酸价分别为0.32、0.66、0.58mg/g。经过20次油炸,三种油的总极性物质(TPC)显著增加,油茶籽油、橄榄油和棕榈油总极性物质分别为16.01%、20.91%和17.66%。随着油炸时间的增加,三种煎炸油的饱和脂肪酸含量显著增加。不饱和脂肪酸的含量变化较大,C18∶2和C18∶3显著下降,而C18∶1逐渐下降。      

Safety evaluation of individual non‐fried and fried sunflower oil,paraffin oil,jojoba oil and their binary mixtures on rat health

Sunflower, jojoba, paraffin oils and binary oil mixtures of sunflower, jojoba and sunflower–paraffin oils were continuously heated at 180 °C for 12 h. Aliquots of potato chips were fried in the aforementioned oil samples. Organoleptic tests were performed on fried chips and safety limits of the oil samples were measured by certain biochemical tests. Histopathological examinations of rat liver and kidney tissues were microscopically done. Organoleptic results for fried potato chips indicate that all types of chips obtained from heated oils were categorised good. Histopathological examinations indicate changes in rat tissues of liver and kidney paralleled the biochemical data. In general, the results suggest that paraffin oil alone and in mixtures with sunflower oil have to ban its use in frying processes.     

Extra‐virgin and refined olive oils decrease plasma triglyceride,moderately affect lipoprotein oxidation susceptibility and increase bone density in growing pigs

The objective of this study was to determine the health benefits of extra‐virgin and refined olive oils, which are high in mono‐unsaturated fatty acids (MUFAs) and polyphenolic compounds using the pig as a model. Thirty‐two cross‐bred pigs were individually penned, allocated to one of four dietary treatments and fed ad libitum for 28 days. Two of the experimental diets consisted of a basal diet containing 12% tallow and either 7% sunflower oil (TSO) or 7% extra‐virgin olive oil (TEVO) on a w/w basis. The remaining diets contained 19% extra‐virgin olive oil (EVO) or 19% of refined olive oil (RO). On days 7, 14 and 28 fasted and 3‐h post‐prandial blood samples were taken. Body composition was measured at the beginning and end of the study using dual energy X‐ray absorptiometry. Daily gain, feed intake and lean and fat deposition were not significantly different between the treatments. However, the daily increase in bone mineral density was higher in pigs fed diets containing olive oil (1.23 vs 2.54, 6.28, 5.20 mg cm^?2 per day for TSO, TEVO, EVO and RO, respectively, P = 0.050). Both fasting and non‐fasting plasma triglycerides were lower (P = 0.003) in pigs fed MUFA‐rich diets, while the cholesterol profile was not significantly different between the treatments. The results from in vitro copper‐induced lipid peroxidation, expressed in terms of conjugated dienes, showed that low density lipoprotein (LDL) particles in postprandial serum from pigs fed olive oil were moderately more resistant to oxidative modification. In conclusion, these data demonstrate that both extra‐virgin and refined olive oils attenuate postprandial hypertriglyceridaemia, moderately affect oxidation susceptibility and increase bone mineral density in growing pigs. Copyright © 2006 Society of Chemical Industry     

葵花籽油挥发性风味物质研究进展

葵花籽油风味独特,深受大众喜爱。概述了冷、热榨葵花籽油中的主要挥发性风味物质及原料品种、炒籽、精炼、储藏、煎炸等因素对葵花籽油挥发性风味物质的影响。葵花籽油中主要挥发性风味物质包括萜烯类、吡嗪类和醛酮类,赋予葵花籽油独特的清香、坚果香、焙烤香等气味特征。炒籽中通过美拉德反应和脂质氧化反应形成多种风味产物,而脱色和脱酸处理可使大部分挥发性风味物质损失殆尽。储藏和煎炸过程中脂肪酸氧化产生的以醛类和酸类为主的物质导致了油脂异味的产生。高油酸葵花籽油比普通葵花籽油表现出了更好的风味稳定性。今后可利用分子感官科学的手段揭示葵花籽油的香气形成机理和调控机制,为风味品质控制提供理论依据,促进葵花籽油产业的健康发展。     

Enhancement of Shortening Stability by Incorporation of Butteroil

Butteroil, sunflower oil, olive oil, and a blend containing equal portions of the three oils were used for potato frying and examined periodically for oxidative stability. Analysis included measurements of polymers, cyclic monomers, the change in dielectric constant and volatile compounds. The blend exhibited greater stability than expected on the basis of the data obtained from the individual oils. In one frying experiment, for example, the polymers and cyclic monomers formed in the blended oil after 37 hr were 0.6% and 0.2%, respectively, as compared to calculated values of 1.8% and OS%, respectively. The higher stability of the blended shortening against oxidation appeared to reflect the presence in butteroil of a protective agent or agents sufficient to protect other less stable oils.     

Composition, stability and acceptability of different vegetable oils used for frying peanuts

The purpose of this work was to determine the chemical stability of vegetable oils in the frying process and the consumer acceptance of fried-salted peanuts prepared in different vegetable oils. Fatty acids composition was determined in sunflower, corn, soybean, peanut and olive oils. A chemical study (free fatty acid and p-anisidine values) of these oils at frying temperature (170 °C) was developed during 96 h. Consumer test of fresh products was performed on fried-salted peanuts prepared in the different oils. Peanut oil and virgin olive oil presented oleic acid as predominant fatty acid (44.8% and 64.2%, respectively), making it more resistant to lipid oxidation at frying temperature than the other refined vegetable oils (sunflower, corn and soybean oils). Virgin olive and peanut oils showed less increment of free fatty acids and p-anisidine value than the other oils along the heating essay. In addition, fried-salted peanuts prepared with refined peanut oil showed higher consumer acceptance than those prepared with other vegetable oils such as sunflower, corn, soybean and olive oils. Peanut oil could be used to fry peanuts obtaining products with higher consumer acceptance and shelf-life, thus preventing loss of their sensory and nutritional quality.     

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.     

Intake of unused palm olein and palm olein used in frying does not affect calcium and phosphorus bioavailability in rats

Palm oil is widely used as a cooking medium. This study was undertaken to examine whether extensive use leading to the formation of polar compounds has any effect on calcium and phosphorus balances. Three isocaloric diets containing 8% olive oil (O), palm olein (P) and palm olein from 80 repeated potato frying uses (PF) without turnover, and which nearly reached the limit of 25% polar compounds allowed by law, were prepared and given to three groups of growing rats during a study period of 28 days. Body weight and food intake were monitored and faeces and urine were collected to calculate calcium and phosphorus balances during the last week of the study. At the end of the experiment the animals were killed and their livers, serum and carcases stored. No differences were observed between food intake, body weight and food efficiency of rats which consumed palm olein, whether unused or used in frying, and the control group (O). The liver mass index was higher in PF than O rats. No significant differences were observed in apparent absorption and retention of calcium and phosphorus. Faecal calcium (p = 0.065) and the percentage of phosphorus absorbed (p = 0.084) showed a tendency to increase in rats fed diets with both unused and used palm olein and could be due to the known higher affinity of fat for Ca than P. No variations in serum calcium and carcase calcium and phosphorus levels were seen. The conclusion of this study was that consumption of palm olein, whether unused or used in frying, does not alter calcium and phosphorus bioavailability. © 2000 Society of Chemical Industry     

Melatonin is a phytochemical in olive oil

Given the numerous observations regarding the positive effects of olive oil consumption and the presence of melatonin in edible plants, we addressed for the first time the question of melatonin determination in virgin olive oil. All the extra virgin olive oil registered designation of origins from Spain and commercial samples of refined olive and sunflower oil were used. Immunoprecipitation and ELISA were combined for melatonin determination. Melatonin is present in olive oil at higher levels in extra virgin olive oil than in refined olive or sunflower oil samples. We concluded that melatonin is part of the phytochemical profile of the olive oil. Particularly, extra virgin olive oil had almost double the melatonin contents of the other refined oils analysed. Thus, melatonin may account for the healthy effects of the Mediterranean diet in which olive oil is the main source of fat.     

Microfluidic evaluation of some edible oil quality based on viscosity and interfacial tensions

Microfluidic devices were applied to investigate the adulteration of high‐quality olive oil and degradation of edible oil over frying. When the inner water flows through the sheath oil flow inside the microfluidic device at specific rates, the inner water flow will be cut into dispersed droplets by the sheath flow. Lengths of the droplets will be dependent on the viscosity and interfacial tension of the sheath oil. As olive oil is adulterated with other oil, its interfacial tension will generally keep constant while its viscosity decreases. As edible oil is used for frying, its interfacial tension will decrease while viscosity increases. As a result, the droplets’ length generated in adulterated olive oil and frying oil will be dependent on their adulteration ratio and frying grade. Experiments proved that the tiny, low‐cost microfluidic device could be preliminarily implemented to quantitatively evaluate specific oil quality.