Formation of trans fatty acids in chicken legs during frying

The formation of trans fatty acids in chicken legs during frying in unhydrogenated and hydrogenated soybean oil was studied. Frying was conducted at 160°C, 180°C and 200°C for 15, 30, 45, 60 and 75 min, with the various cis and trans fatty acids being analyzed in unhydrogenated and hydrogenated soybean oil, as well as chicken leg meat and chicken leg skin, using a gas chromatography–mass spectrometry technique. Results showed that the amounts of most fatty acids decreased along with increasing frying temperature and frying time when fried in unhydrogenated or hydrogenated soybean oil. No trans fatty acids were formed in chicken leg meat fried in unhydrogenated or hydrogenated soybean oil. Instead, the formation of trans fatty acids was observed in chicken leg skin fried in hydrogenated soybean oil, probably because of oil absorption. A maximum level of trans fatty acids occurred 15 min after frying and then declined thereafter.     

Formation of trans fatty acids in chicken legs during frying

The formation of trans fatty acids in chicken legs during frying in unhydrogenated and hydrogenated soybean oil was studied. Frying was conducted at 160 degrees C, 180 degrees C and 200 degrees C for 15, 30, 45, 60 and 75 min, with the various cis and trans fatty acids being analyzed in unhydrogenated and hydrogenated soybean oil, as well as chicken leg meat and chicken leg skin, using a gas chromatography-mass spectrometry technique. Results showed that the amounts of most fatty acids decreased along with increasing frying temperature and frying time when fried in unhydrogenated or hydrogenated soybean oil. No trans fatty acids were formed in chicken leg meat fried in unhydrogenated or hydrogenated soybean oil. Instead, the formation of trans fatty acids was observed in chicken leg skin fried in hydrogenated soybean oil, probably because of oil absorption. A maximum level of trans fatty acids occurred 15 min after frying and then declined thereafter.     

Stability During Frying of Moringa oleifera Seed Oil Variety “Periyakulam 1”

The frying performance of the Moringa oleifera seed oil variety Periyakulam 1 (PKM 1) from India, extracted using cold press (CP) and n -hexane (H), during frying of potatoes and cod was studied especially as regards repeated frying operations. The oils were used for intermittent frying of potato slices and cod filets at a temperature of 175±5°C for 5 consecutive days. The chemical changes occurring in the oils were evaluated. Free fatty acid content, peroxide value, specific extinction at 232 nm, polar compounds colour and viscosity of the oils all increased, whereas the iodine values, smoke points, polyunsaturated fatty acid content, induction period and tocopherol concentration decreased. The effect of the oils on the organoleptic quality of these fried foods was also determined by expert panellists. The analytical and sensory data showed that the lowest deterioration occurred in cold pressure produced oil and the highest in n -hexane extracted oil. Therefore, cold pressure oil appears to be the most appropriate for frying. Potatoes and cod were also fried in virgin olive oil in order to have a direct comparison between the different oils. The results clearly indicated that virgin olive oil has the highest resistance to thermal deterioration during frying compared with the other two oils.     

Deterioration of natural antioxidant species of vegetable edible oils during the domestic deep-frying and pan-frying of potatoes

In the present work, virgin olive oil, sunflower oil and a vegetable shortening were used as cooking oils for the deep-frying and pan-frying of potatoes, for eight successive sessions, under the usual domestic practice. Several chemical and physicochemical parameters (acidic value, peroxide value, total polar artefacts, total phenol content and triglyceride fatty acyl moiety composition) were assayed during frying operations in order to evaluate the status of the frying oils, which were found within expected ranges similar to those previously reported. The oil fatty acids were effectively protected from oxidation by the natural antioxidants. The frying oil absorption by the potatoes was quantitated within 6.1-12.8%, depending on the oil type and the frying process. The retention of alpha- and (beta + gamma)-tocopherols during the eight fryings ranged from 85-90% (first frying) to 15-40% (eighth frying), except for the (beta + gamma)-tocopherols of sunflower oil, which almost disappeared after the sixth frying. The deterioration during the successive frying of several phenolic species present in virgin olive oil is reported for the first time. The retention of total phenolics ranged from 70-80% (first frying) to 20-30% (eighth frying). Tannic acid, oleuropein and hydroxytyrosol-elenolic acid dialdeydic form showed remarkable resistance in all frying sessions in both frying methods, while hydroxytyrosol and hydroxytyrosol-elenolic acid were the faster eliminated. The deterioration of the other phenolic species account for 40-50% and 20-30% for deep-frying and pan-frying, respectively, after three to four frying sessions, which are the most usual in the household kitchen. Deep-frying resulted in better recoveries of all the parameters examined. The correlation of the deterioration rate of the phenolic compounds and tocopherols during frying is discussed and the nutritional aspects of the natural antioxidant intake, through the oil absorbed by the potatoes, are evaluated.     

Deterioration of natural antioxidant species of vegetable edible oils during the domestic deep-frying and pan-frying of potatoes

In the present work, virgin olive oil, sunflower oil and a vegetable shortening were used as cooking oils for the deep-frying and pan-frying of potatoes, for eight successive sessions, under the usual domestic practice. Several chemical and physicochemical parameters (acidic value, peroxide value, total polar artefacts, total phenol content and triglyceride fatty acyl moiety composition) were assayed during frying operations in order to evaluate the status of the frying oils, which were found within expected ranges similar to those previously reported. The oil fatty acids were effectively protected from oxidation by the natural antioxidants. The frying oil absorption by the potatoes was quantitated within 6.1-12.8%, depending on the oil type and the frying process. The retention of α - and (β + γ)-tocopherols during the eight fryings ranged from 85-90% (first frying) to 15-40% (eighth frying), except for the (β + γ)-tocopherols of sunflower oil, which almost disappeared after the sixth frying. The deterioration during the successive frying of several phenolic species present in virgin olive oil is reported for the first time. The retention of total phenolics ranged from 70-80% (first frying) to 20-30% (eighth frying). Tannic acid, oleuropein and hydroxytyrosol-elenolic acid dialdeydic form showed remarkable resistance in all frying sessions in both frying methods, while hydroxytyrosol and hydroxytyrosol-elenolic acid were the faster eliminated. The deterioration of the other phenolic species account for 40-50% and 20-30% for deep-frying and pan-frying, respectively, after three to four frying sessions, which are the most usual in the household kitchen. Deep-frying resulted in better recoveries of all the parameters examined. The correlation of the deterioration rate of the phenolic compounds and tocopherols during frying is discussed and the nutritional aspects of the natural antioxidant intake, through the oil absorbed by the potatoes, are evaluated.     

Decrease in essential fatty acid content of edible fats during the frying process

Degradation of sunflower oil, rapeseed oil, and lard during the frying operation was investigated by studying the loss of essential fatty acids compared to the accumulation of decomposition products. Linoleic and/or linolenic acid concentration was measured by GLC, and for detecting decomposition products determination of polymer content by GPC was chosen. Twelve laboratory experiments with different heating or frying conditions were run aimed at modelling practice and studying the effects of certain factors. The results indicated that loss of essential fatty acids being a parallel process to the accumulation of breakdown products is suitable both for detecting the decrease in nutritive value and for quality assessment of used frying fats. It was also found that the rate of deterioration is considerably affected by the nature of fat and the frying parameters. Study of the relationship between polymer content and the decrease in essential fatty acid concentration (using data from 110 samples) showed that high, linear correlation depending on the nature of fat can be found. Correlation coefficients and equations of regression lines were calculated.     

Optimization of the omega-3 extraction as a functional food from flaxseed

The fatty acid content, total lipid, refractive index, peroxide, iodine, acid and saponification values of Iranian linseed oil (Linum usitatissimum) were studied. For optimization of extraction conditions, this oil was extracted by solvents (petroleum benzene and methanol-water-petroleum benzene) in 1:2, 1:3 and 1:4 ratios at 2, 5 and 8 h. Then its fatty acid content, omega-3 content and extraction yield were determined. According to the statistical analysis, petroleum benzene in a ratio of 1:3 at 5 h was chosen for the higher fatty acid, extraction yield, and economical feasibility. For preservation of omega-3 ingredients, oil with specified characters containing 46.8% omega-3 was kept under a nitrogen atmosphere at -30 degrees C during 0, 7, 30, 60 and 90 days and its peroxide value was determined. Statistical analysis showed a significant difference in the average amount of peroxide value only on the first 7 days of storage, and its increase (8.30%) conformed to the international standard.     

Optimization of the ω-3 extraction as a functional food from flaxseed

The fatty acid content, total lipid, refractive index, peroxide, iodine, acid and saponification values of Iranian linseed oil (Linum usitatissimum) were studied. For optimization of extraction conditions, this oil was extracted by solvents (petroleum benzene and methanol–water–petroleum benzene) in 1:2, 1:3 and 1:4 ratios at 2, 5 and 8 h. Then its fatty acid content, omega-3 content and extraction yield were determined. According to the statistical analysis, petroleum benzene in a ratio of 1:3 at 5 h was chosen for the higher fatty acid, extraction yield, and economical feasibility. For preservation of ω-3 ingredients, oil with specified characters containing 46.8% ω-3 was kept under a nitrogen atmosphere at ?30°C during 0, 7, 30, 60 and 90 days and its peroxide value was determined. Statistical analysis showed a significant difference in the average amount of peroxide value only on the first 7 days of storage, and its increase (8.30%) conformed to the international standard.     

Nonhydrogenated cottonseed oil can be used as a deep fat frying medium to reduce trans-fatty acid content in french fries

OBJECTIVE: The purpose of this research study was to evaluate the fatty acid profile, in particular trans-fatty acids, of french fries fried in nonhydrogenated cottonseed oil as compared with french fries fried in partially hydrogenated canola oil and french fries fried in partially hydrogenated soybean oil. DESIGN: Cottonseed oil, partially hydrogenated canola oil, and partially hydrogenated soybean oil were subjected to a temperature of 177 degrees C for 8 hours per day, and six batches of french fries were fried per day for 5 consecutive days. French fries were weighed before frying, cooked for 5 minutes, allowed to drain, and reweighed. Oil was not replenished and was filtered once per day. Both the oil and the french fries were evaluated to determine fatty acid profiles, trans-fatty acids, and crude fat. STATISTICAL ANALYSIS: A randomized block design with split plot was used to analyze the data collected. Least-squares difference was used as the means separation test. RESULTS: No significant differences were found between fries prepared in the three oil types for crude fat. Fatty acid profiles for the french fries remained stable. The french fries prepared in cottonseed oil were significantly lower in trans-fatty acids. The combined total of the trans-fatty acid content and saturated fatty acid content were lower in french fries prepared in cottonseed oil. CONCLUSIONS: Because deep fat frying remains a popular cooking technique, health professionals should educate the public and the food service industry on the benefits of using nonhydrogenated cottonseed oil as an alternative to the commonly used hydrogenated oils.     

Phenolic compounds from Andean mashua (Tropaeolum tuberosum) tubers display protection against soybean oil oxidation

Phenolic compounds from mashua tuber were evaluated as potential antioxidants to retard the oxidation of crude soybean oil submitted to accelerated storage and frying. During the accelerated storage, an ethanolic crude extract, a purified extract, an aqueous fraction and an ethyl acetate fraction from mashua containing different gallic acid equivalent concentrations (100, 300 and 600?ppm) in oil were evaluated at 55?°C. After 15 days of storage, better effects were evidenced against soybean oil oxidation at 300 and 600?ppm of ethyl acetate fraction in comparison to 200?ppm butylated hydroxytoluene and the control (no antioxidant added). During the frying process at ～180?°C, principal component analysis revealed that the content of trienes and dienes were strongly correlated with the frying batch. Ethyl acetate fraction at 200?ppm showed the highest efficacy against oil oxidation in terms of polar compound values, free fatty acids and conjugated dienes and trienes in comparison to the oil containing 200?ppm tert-butylhydroquinone and control. Differential scanning calorimetry corroborated the efficacy of ethyl acetate fraction phenolic and it is strongly recommended as method for validation of results. This study provides strong evidence related to the excellent protective effects against soybean oil oxidation of mashua phenolics. This crop could be utilized as an alternative source of natural antioxidants by the oil industry.     

油炸食品及其煎炸油卫生质量检测与关系探讨

目的调查油炸食品及其煎炸油卫生质量,探讨两者间卫生指标的关系。方法在广州市64个煎炸点采取油炸食品及其相应的煎炸油,按国家标准方法分别测定羰基价(CGV)、酸价(AV)、过氧化值(POV),并进行模拟实验,对不同煎炸时间的油炸食品及其煎炸油三个指标进行检测。结果油炸食品及其煎炸油的CGV及AV与油炸时间正相关(P<0.05),POV随油炸时间变化无规律(P>0.1);油炸米面制品及臭豆腐CGV显著高于与相应煎炸油CGV,且分别正相关(P<0.001)。油炸米面制品、臭豆腐及动物性食品AV显著高于与相应煎炸油AV(P<0.001),米面制品、臭豆腐的AV分别与相应煎炸油AV正相关(P<0.05)。三类油炸食品POV与相应煎炸油间POV关系无规律(P>0.1)。结论对油炸米面制品及臭豆腐等食品不仅进行AV及POV的检测,还应增加CGV的检测及限量探讨,加强对煎炸点的卫生监督及管理。     

合成油的营养评价 (一)合成油饲料对正常大鼠的生长、血脂水平、肝脂与体脂脂肪酸组成的影响

本文研究了由石油副产品尿素蜡中提炼出辛酸(8:0)和癸酸(10:0),酯化后作为日常食用油的可能性。 (1)用含12％不同油酯(合成油,豆汕,不同比例配合的合成油与豆油,和奇数碳脂肪酸的合成油等)的饲料,分别饲养断乳大鼠12周,每组16只大鼠,雌雄各半,观察其生长、脏体比、血脂与肝脂水平、肝脂与体脂的脂肪酸组成、和体脂碘价的改变。 (2)用12％合成油饲料喂养大鼠的12周内,动物生长良好,未见必需脂肪酸缺乏的典型症状。在饲养期的前8周内,各组动物的体重增长近似,在后4周内,凡掺有含偶数碳脂肪酸的合成油饲料组动物,其体重增加值皆显著较少。 (3)合成油饲料和豆油饲料比较,对大鼠血清胆固醇水平无影响,但显著使血清甘油三酯含量增高。 (4)合成油饲料不影响动物的体成分(水份、蛋白质、脂肪),其体脂含量较豆油饲料组的略低(0.05相似文献   

不同食用油和烹调方式的油烟成分分析

目的:分析不同食用油和不同烹调方式的油烟成分及其对健康危害。方法:应用粉尘采样器(15 L/min×20 min)和大气采样器(0.1 L/min×30 min)采集不同的食用油(菜籽油、花生油、大豆油、玉米油)及不同烹调方式(炸上排、炸蔬菜、炸鱼、煎鱼、炒菜)的油烟样品并分析。结果:菜籽油、大豆油及煎鱼、炒菜的油烟浓度均较高;烷烃类的含量以大豆油、炸蔬菜较高,炒菜较低;抗氧化剂存在不同油与食物中。结论:在本实验条件下,单纯食用油烹调比加入食物烹调的油烟浓度大;大豆油的油烟浓度及有机物含量均较高,炒菜的油烟浓度较大但有机物的含量最小。     

The intake of fried virgin olive or sunflower oils differentially induces oxidative stress in rat liver microsomes

The effects of non-fried and fried virgin olive and sunflower oils on rat liver microsomal compositional features have been investigated. In addition, plasma antioxidants (alpha-tocopherol and ubiquinone 9) were investigated as well as the possible oxidative modifications suffered by virgin olive and sunflower oils during the frying process. The frying process decreased the content of alpha-tocopherol and phenolics in the oils and increased total polar materials. Sunflower oil was affected to a greater extent than olive oil. In rats, the intake of fried oil led to higher levels of lipid peroxidation and a lower concentration of plasma antioxidants. Microsomal fatty acid and antioxidant profiles were also altered. It seems that a strong relationship exists between the loss of antioxidants and the production of toxic compounds in the oils after frying and the extent of the peroxidative events in microsomes, which were also different depending on the fat source. The highly unsaturated sunflower oil was less resistant to the oxidative stress produced by frying and led to a higher degree of lipid peroxidation in liver microsomes in vivo than virgin olive oil.     

Chemical composition and characteristic profiles of seed oils from three Tunisian Acacia species

In this paper, physicochemical properties, fatty acid and phenolic compositions of Acacia cyclops, Acacia cyanophylla and Acacia mollissima oils were studied. These oils were compared in terms of physicochemical properties and fatty acid composition to soybean oil. The oil content of Acacia seeds is 8.85%,11.13% and 7.16%, respectively. A small difference was observed in the acid and saponification value. However, no differences were observed for refractive index, iodine value and fatty acid composition. This latter was essentially dominated by linoleic acid (56.66–60.52%), oleic acid (19.45–22.74%) and palmitic acid (9.36–12.25%). This study compares also the phenolic composition in Acacia seed oils. Syringic and ferulic acids were the dominant phenolic compounds observed in the studied oils. Minor amounts of phenolic acids as o-coumaric, p-coumaric and protocatechuic are also detected. The results of this preliminary study showed that Acacia samples are promising oilseed crops and the high level of unsaturated fatty acids makes them desirable in terms of nutrition and could be used as a potential oil in the human diet.     

Palm oil and palm olein frying applications

Several million tones of palm oil and palm olein are used annually in the world for frying. This paper will discuss their frying performances in three major applications - industrial production of potato chips/crisps, industrial production of pre-fried frozen French fries and in fast food outlets. In the first study, about four tones of potato chips were continuously fried 8 hours a day and five days a week. The palm olein used (with proper management) performed well and was still in excellent condition and usable at the end of the trial. This was reflected in its low free fatty acid (FFA) content of around 0.23%, peroxide value of 4 meq/kg, anisidine value of 16, low polar and polymer contents of 10% and 2%, respectively, induction period (OSI) of 21 hours and high content of tocopehrols and tocotrienols of 530 ppm even after >1900 hours. In the second study in which an average 12 tones pre-fried frozen French fries were continuously fried a day for 5 days a week, palm oil performed excellently as reflected by its low FFA of 0.34%, food oil sensor reading of 1.1, low polar and polymer contents of 17% and 2.8%, respectively, over the 12 days of trial. In the third study in which palm shortening, palm oil and palm olein were simultaneously used to intermittently fry chicken parts in the laboratory simulating the conditions in fast food outlets, the three frying oils also performed very satisfactorily as reflected by their reasonably low FFA of <1%, smoke points of >180 degrees C, and polar and polymer contents of <25% and <6%, respectively, after 5 days of consecutive frying. All the quality indicators did not exceed the maximum discard points for frying oils/fats in the three applications, while the fried food product was well accepted by the in-house train sensory panel using a-nine point hedonic score.     

Total parenteral nutrition decreases liver oxidative metabolism and antioxidant defenses in healthy rats: comparative effect of dietary olive and soybean oil

BACKGROUND: Total parenteral nutrition (TPN) is used for critically ill patients undergoing surgery, after trauma, or during disease conditions that favor oxidative stress. We studied the effect of TPN on liver oxidative metabolism and antioxidant defenses in rats, and we compared the effect of soybean oil- and olive oil-based diets. METHODS: Seven-week-old rats (n = 28) were divided into four groups. Two experimental groups received a TPN solution containing soybean oil (TPN-S) or a mixture of olive/soybean oil, 80/20 (TPN-O), IV for 6 days. Orally fed animals received a solid diet including soybean oil (Oral-S) or olive/soybean oil, 80/20 (Oral-O). The following parameters were measured: DL-alpha-tocopherol, vitamin A, malondialdehyde and thiobarbituric acid reactive substances (MDA-TBARS), and total radical-trapping antioxidant parameter (TRAP) in serum; DL-alpha-tocopherol, vitamin A, glutathione (GSH), and catalase (Cat) activity in liver homogenate; fatty acids from phospholipid, cytochrome P-450 content, NADPH-cytochrome c2 reductase activity in liver microsomes; superoxide dismutase (SOD), glutathione peroxidase (Gpx), glutathione reductase (GR), glutathione transferase (GST), and glucose-6-phosphate dehydrogenase (G6PD) in liver cytosol. RESULTS: The soybean or olive oil diets modified the liver microsomal fatty acid phospholipid composition, but the unsaturation index remained unchanged. TPN specifically increased the saturation of the membrane. The cytochrome P-450 level and the NADPH-cytochrome c2 reductase, SOD, Gpx, Cat, and GST activities were unchanged by soybean oil or olive oil diet but decreased receiving TPN. CONCLUSIONS: In rats, TPN decreased the liver oxidative metabolism and enzymatic antioxidant defenses. This may be related to saturation of the liver microsomal fatty acids.     

Lipids and fatty acids composition in Bolti (Tilapia nilotica) fish flesh as affected by environment

Bolti (Tilapia nilotica) fish and water samples were taken from three different locations in Kafr El-Sheikh governorate. Water quality and oil characteristics in fish flesh were studied. The obtained results showed that crude lipid and phospholipid contents of fish fillet were increased by increasing total solids and total hardness of fish environment. Peroxide, iodine and acid values of fish oil influenced by water quality. Fatty acids composition in fish oil showed a wide variation due to differences in water-head. Total unsaturated fatty acids in drainage fish oil were higher than that found in farm's fish oil, while the lowest percentage of unsaturated fatty acids was recorded by Nile's fish oil. Generally, palmitic was the main saturated fatty acid in fish oil, whereas it constituted about 66-68% of the total saturated fatty acids. Nile's fish oil contained higher amounts of omega-3 fatty acids than those of drainage and farm's fish oils. In contrast, odd and branched fatty acids content in drainage and farm's fish oils were higher than those found in Nile's fish oil. Concentrations of arachidonic and erucic acids in oil extracted from drainage fish were higher than oil extracted from farm's fish, while the lowest concentration for these fatty acids were found in oil extracted from Nile's fish. Although the acid value and peroxide value of drainage and farm's fish oils were slightly high, it is still accepted for human consumption according to The Association of Fish Meal Manufacturers.     

Squalene in oils and fats from domestic and commercial fryings of potatoes

Squalene was determined in commercial frying oils and fats (sunflower oil, cottonseed oil, corn oil, soybean oil, palm kernel oil, palm oil, vegetable shortening oil, and cooking fats) sampled during deep-frying of potatoes from 21 restaurants in Athens, Greece, and in domestic frying oils [virgin olive oil (VOO), vegetable shortening and sunflower oil] used during the domestic pan-frying and deep-frying of potatoes. The analyses were carried out after cold saponification of the oils followed by gas chromatography-mass spectrometry of the hexane extract. Quantification was carried out by reference curve, using standard squalene solutions. Fresh vegetable oils and fats were found to contain small amounts of squalene (10.2-49.3 mg/100 g oil or fat), with the exception of fresh VOO, which contained 454 mg/100 g. The squalene content of the frying oils was reduced during frying, its lower concentration found in cooked fats (5.9 mg/100 g fat) and its higher in fried VOO (428 mg/100 g oil) after the first frying session. Squalene appeared to be rather stable during frying. Its retention in used restaurant seed oils and fats remained over 50% even after 30 h of frying while a high recovery of 84-96% was observed during the domestic deep-frying of potatoes in VOO. It seems that by using VOO as frying medium a considerable amount of squalene is absorbed by the fried potatoes, thus becoming part of our diet.     

市售大豆油中“地沟油”调查

目的:了解市售食用植物油是否掺入"地沟油"。方法:应用国标法对省内市场销售的68个大豆油的酸价、过氧化值、羰基价、冷冻试验、苯并芘和胆固醇等项目进行检测。结果:3个预包装样品酸价不符合GB 1535《大豆油》相应等级指标要求。4个散装样品酸价检出值较高,均超过1.0 mg/g。过氧化值在0.9 mmol/kg～4.1 mmol/kg范围间,羰基价检测值在1 meq/kg～13 meq/kg之间,8个一级大豆油冷冻试验结果为"澄清、透明",均符合GB 1535要求。25个预包装样品和有产品等级标识的17个散装样品苯并芘检测结果在1μg/kg～7μg/kg之间,符合GB 2716限量要求。胆固醇均未检出。结论:抽查的68个大豆油样品大部分检测值符合相关标准要求,但有部分样品检测值超标或检测值较高,尤其是散装样品和无企业标识样品需要进一步关注。