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.     

Effect of fish (Catla catla) frying on the quality characteristics of sunflower oil

The quality of sunflower oil, as affected by fish (Catla catla) frying at 180 °C for 14 h was investigated. The purpose of the study was to find out the quality deterioration of sunflower oil with respect to time as affected by fish frying and to generate equations that can be used for predicting the quality parameters. The physico-chemical characteristics of sunflower oil were evaluated by drawing out the oil samples (75 ml) from the fryer at an interval of 2 h. The parameters evaluated were refractive index, colour, total polar material, free fatty acids, iodine value and peroxide value. There was a gradual increase in refractive index and colour with time of frying which was found to be significant (P < 0.05) in the latter. Iodine value decreased significantly (P < 0.05) with time of frying. Peroxide value first increased up to 12 h of frying and then decreased. After 10 h of frying, the total polar materials were 26.9%, indicating the need for replenishment or refinement of sunflower oil. Total polar material correlated well (r > 0.97) with colour, free fatty acids, peroxide value and time of frying. Free fatty acids correlated well (r > 0.96) with colour, total polar material and duration of frying. Fit of the equations was determined for total polar material and free fatty acids as a function of the respective correlated parameters.     

Consequence of Commercial Fish Frying on Some Quality Parameters of Oil with Special Reference to Trans Fat

In the present study, the quality of frying oil, as affected by commercial pan fish frying, was investigated. The quality of fresh frying oil, null replenishment (NR) oil, and discarded frying oil were evaluated by drawing out the oil samples from the fryer at the initial stage, just before the addition of new frying oil for level make-up and used oil of the last frying cycle, respectively. The parameters used to assess the quality were the fatty acid composition including trans fatty acid (TFA), free fatty acid, and peroxide values of frying oil. Gas chromatography-mass spectroscopy (GC-MS) was used to examine fatty acids profiles of the frying oils. Trans fatty acid in fresh oils varied from 2.5%–3.8% (except oil-6, which contained 13%), whereas NR oils and discarded oils contained 5.6%–14.8% and 7.3%–20.8% trans fatty acids, correspondingly. Free fatty acid in fresh, NR, and discarded oils were 0.12%–0.24%, 0.22%–1.74%, and 0.80%–3.39%, respectively. Peroxide value in fresh, NR, and discarded oils were determined to be 1.15–3.93, 2.71–7.51, and 2.84–14.68 meq of O₂ /kg oil. It was observed that commercial fryers were not using the proper oil for frying. Furthermore, the last frying cycle just before discarding the oil may be dangerous for the health of consumers due to their significant level of TFA, free fatty acid, and peroxide values.     

部分食品煎炸用油的反式脂肪酸比较

为探究不同品种食用油和煎炸食品对反式脂肪酸形成的影响,本文使用5种食用油(葵花油、大豆油、菜籽油、棕榈油、花生油),在一定温度下炸制14批次油条,又依次使用大豆油炸制豆腐、油条和鸡腿,对2种情况下产生的煎炸油进行气相色谱分析,比较反式脂肪酸含量。结果表明:炸油条过程中,食用油中反式脂肪酸的含量均随着煎炸时间的延长而增加,葵花油中反式亚油酸总含量最多(约12 mg/g),花生油中反式油酸含量最低(约0.6 mg/g),在煎炸过程中,大豆油中反式脂肪酸的含量无显著变化,保持在3.5 mg/g左右。比较可知,不同种类食用油在加热过程中产生的反式脂肪酸含量有较大差异,而使用大豆油分别炸制豆腐、油条和鸡腿时,煎炸油中的反式脂肪酸无显著差异,说明油炸过程中的反式脂肪酸主要来源于食用油中不饱和脂肪酸的氧化裂解和异构化,与煎炸食品关系不大。从反式脂肪酸的生成量来看,烹饪过程中长时间煎炸建议使用大豆油,而不适宜使用葵花油。     

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.     

饲用油脂品质初步调查分析

目的以油脂中脂肪酸含量和极性成分为依据,用气相色谱法和快速筛查试剂盒对饲料用油脂品质进行初步分析。方法取自国内饲料企业的280份饲料用油脂样品,包括猪油、鸭油、鸡油、大豆油、大豆磷脂油、玉米油、米糠油、棕榈油等动植物油脂和未知种类的油脂,与自制或采购标准的动物油脂和植物油脂,进行脂肪酸种类、含量和极性成分的测定,对其品质作出初步判定。结果脂肪酸分析结果证明,动物油样品和植物油样品中的部分脂肪酸成分含量均发生不同程度的降低或增高;极性成分检测的83个样品中,其中标准值为0.1,极性成分吸光值在0.147～0.947的样品占55个,阳性率达66.26%。结论未知类型样品超过半数为不合格样品;未知油脂样品脂肪酸组成不符合单一油脂比值范围,推断可能为混合油脂。根据极性成分含量高低不同,判断部分样品可能为复炸油。     

煎炸油在煎炸过程中脂肪酸组成的变化

以大豆油、棉籽油、棕榈液油和氢化油作为煎炸油,分别进行薯条和鸡翅的煎炸实验。结果表明：在煎炸过程中,各种煎炸油的脂肪酸含量均会发生一定的变化。采用C18:2/C16:0比值变化作为研究煎炸油脂肪劣变的指标,氢化油煎炸过程中C18:2/C16:0比值减少的程度最小(P＜0.05),证明其煎炸过程中脂肪酸的稳定性最好。但对于反式脂肪酸含量变化来说,均没有显著增加(P＞0.05),其中氢化油的反式脂肪酸含量从煎炸前的10.39%降低到煎炸后的6.66%,变化显著(P＜0.05),不过高反式脂肪酸含量的煎炸油在煎炸后其反式脂肪酸含量还保持在较高水平。     

Influence of composition on degradation during repeated deep‐fat frying of binary and ternary blends of palm,sunflower and soybean oils with health‐optimised saturated‐to‐unsaturated fatty acid ratios

The American Heart Association recommended the fatty acid balance contributed by all the fats in our diet, suggesting it would be best at approximately 1:1:1 for saturated (SFA), monounsaturated (MUFA) and polyunsaturated fatty acids (PUFA), respectively. Three individual oils: palm oil (PO), soybean oil (SBO) and sunflower oil (SNF) and their binary and ternary blends were prepared and used for repeated deep‐fat frying of French fries. The acid value, peroxide value, p‐anisidine value and Totox values, as well as oxidative stability, contents of total polar compounds, tocochromanols, triacylglycerol dimers and oligomers, were determined in individual and blended oils. The lowest Totox value and highest stability were found for PO, and the opposite data were obtained for SNF and SBO. The degradation of tocochromanols in blends ranged from 91% to 95% after 4 days of frying, while in individual oils, it was 63% in SBO, 71% in SNF and 100% in PO. The lowest formation of dimers and oligomers was observed for the PO: SNF blend. Obtained results showed that only pure PO was a better frying medium than its blends with SBO and SNF. However, a prepared blend had a better fatty acid composition for human health and was more stable than pure SBO and SNF.     

影响煎炸油中极性组分含量的研究

目的为更好地根据不同煎炸时间和煎炸食材选择合适的煎炸油,并确定合理的煎炸油更换频率,以最大程度降低煎炸油的劣化程度,保持煎炸油的良好卫生质量。方法本实验采用食用油品质检测仪对常用植物油中的总极性组分含量进行测定,对影响煎炸油极性组分含量的几点因素进行考察研究。结果不同煎炸时间、不同煎炸食材对总极性组分含量影响不同;不同植物油品种在煎炸过程中极性组分含量变化趋势不同;当已知极性组分含量初始值的油品以一定比例相互混合时,其极性组分含量初始值会发生可预期的改变。结论不同油品在煎炸过程中的极性组分含量与煎炸时间、油品中单不饱和脂肪酸含量、煎炸食品中碳水化合物含量和煎炸数量正相关;选择合适的煎炸油需要综合考虑油品极性组分初始值、极性组分在煎炸过程中的变化情况;根据不同品种食用油极性组分含量初始值的不同,可初步判断油品是否与其声称成分相符。     

Deep fat frying of frozen foods in sunflower oil. Fatty acid composition in fryer oil and frozen prefried potatoes

The fatty acid pattern was used to evaluate the alteration of a sunflower oil that had been used 20 times to fry various frozen foods with frequent replenishment (FR) or without replenishment (NR) of the used oil with fresh oil during frying. Furthermore, the fat extracted from potatoes fried in the sunflower oil from fryings 1, 5, 8, 12, 16 and 20 was also analysed by gas–liquid chromatography to compare its fatty acid profile with that of the corresponding fryer oil. The amount of unaltered fatty acids decreased from 96.2 mg per 100 mg oil in the unused sunflower oil to 89.6 mg per 100 mg oil after 20 fryings in the FR oil and to 88.9 mg per 100 mg oil in the NR oil, following a linear adjustment (r > 0.97; p < 0.001). Linoleic acid also decreased while palmitic and oleic acids increased in the bath oil. Fatty acid variations were more pronounced in NR than FR oil for major fatty acids and not only related to the degradation of unsaturated fatty acids but also to the interactions between the bath oil and the fried food fat. Thus the increase in palmitic acid of the fryer oil could be due to migration of this fatty acid from the prefried frozen potatoes as revealed by the composition of the fat extracted from those potatoes. Although the fatty acid variation (eg myristic, palmitic, oleic, trans–cis isomers of linoleic and linoleic acids) was not equivalent in FR or NR fryer oil and in the fat of the potatoes, the changes in total unaltered fatty acids were not significantly different in oil and potatoes. Present data suggest that frequent addition of fresh oil throughout the frying process minimises the fatty acid changes, contributing to the obtainment of fried foods with a healthy fatty acid profile. © 2000 Society of Chemical Industry     

Frying of potato chips in a blend of canola oil and palm olein: changes in levels of individual fatty acids and tocols

The changes occurring in the levels of nutritionally relevant oil components were assessed during repeated frying of potato chips in a blend of palm olein and canola oil (1:1 w/w). The blend suffered minimal reductions in omega‐3 and omega‐6 polyunsaturated fatty acids. There was no significant difference between the fatty acid composition of the oil extracted from the product and that of the frying medium, in all three cases. The blend also contained a significant amount of tocols which add a nutritional value to the oil. The concentration of the tocols was satisfactorily retained over the period of oil usage, in contrast to the significant loses observed in the case of the individual oils. The blend also performed well when assessed by changes in total polar compounds, free fatty acids, p‐anisidine value. When fried in used oil, the product oil content increased progressively with oil usage time. This study shows that blended frying oils can combine good stability and nutritional quality.     

A study on monitoring of frying performance and oxidative stability of cottonseed and palm oil blends in comparison with original oils

Blending polyunsaturated oils with highly saturated or monounsaturated oils has been studied extensively; however, in literature there is negligible information available on the blending of refined cottonseed oil with palm olein oil. Blending could enhance the stability and quality of cottonseed oil during the frying process. In the present study, the effects of frying conditions on physicochemical properties of the palm olein-cottonseed oil blends (1:0, 3:2, 1:1, 2:3, and 0:1, w/w) were determined and compared to the pure oils. The frying process of frozen French fries was performed in duplicate at 170 ± 5°C for 10 h without interruption. The oil degradations were characterized during deep-frying applications; peroxide, free fatty acid, and iodine value by standardized methods, fatty acid profile by using a gas chromatography-flame ionization detector, polar and polymeric compounds by using the high-performance size exclusion chromatography/evaporative light scattering detector technique. The present study clearly indicated that the oxidative and frying performances of pure palm olein oil and cottonseed oil significantly improved by blending application. Results clearly indicated that the frying performance of cottonseed oil significantly improved by the blending with palm olein oil. Except that free fatty acid content, all the physicochemical variables were significantly influenced by type of pure and blend oils. By increasing the proportion of palm olein oil in cottonseed oil, the levels of polyunsaturated fatty acids decreased, while saturated fatty acid content increased. The progression of oxidation was basically followed by detecting polar and polymeric compounds. The fastest increments for polar and polymeric compounds were found as 6.30% level in pure cottonseed oil and as 7.07% level in 40% cottonseed oil:60% palm olein oil blend. The least increments were detected as 5.40% level in 40% cottonseed oil:60% palm olein oil blend and 2.27% level in 50% cottonseed oil:50% palm olein oil blend. These levels were considerably below the acceptable levels recommended by the official codex. Therefore, the present study suggested that blending of cottonseed oil with palm olein oil provided the oil blends (50% cottonseed oil:50% palm olein oil and 40% cottonseed oil:60% palm olein oil, w/w) with more desirable properties for human nutrition.     

食用植物油煎炸过程中的品质变化北大核心CSCD

利用花生油、大豆油、调和油、棕榈油4种食用植物油作为煎炸油对豆腐、裹粉鸡柳、油条3种食材进行煎炸,研究煎炸时间对煎炸油极性组分含量及羰基值的影响,确定煎炸油时间预警点,同时研究了不同煎炸油品种、不同食材对煎炸油极性组分含量的影响。结果表明:极性组分含量、羰基值均与煎炸时间呈正相关(r_(极性组分)=0.809,r_(羰基值)=0.859,P=0.000);煎炸6~11 h煎炸油极性组分含量均值从初始的11.85%增至20.96%,最大值为34.10%,可作为煎炸油质量不达标的时间预警点;煎炸12 h,极性组分含量从低到高依次为花生油、棕榈油、调和油、大豆油,含量分别为21.1%、24.1%、26.8%、27.8%,豆腐、裹粉鸡柳、油条煎炸油中极性组分含量分别为17.7%、25.0%、32.2%;煎炸18 h,极性组分含量增大程度由低到高为棕榈油/调和油、大豆油、花生油,煎炸食材用油为豆腐煎炸油、裹粉鸡柳煎炸油、油条煎炸油。     

Sunflower oil versus olive oil and iron metabolism in rats. Influence of a frying process

Olive oil and sunflower oil were used in repeated potato‐frying operations without turnover until the oils reached the limit of 25% polar compounds allowed by law. Over a 28 day period, five groups of rats were fed diets containing 8% 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. In the final week, faeces and urine were collected and, on day 28, animals were sacrificed. The type of oil, unused or used in frying, did not modify food intake, body weight, faecal iron and its apparent absorption or retention, but consumption of oils used in frying tended to increase urinary iron excretion. No differences were found in serum iron, total iron‐binding capacity and haemoglobin values. Iron contents and concentrations in liver, spleen and skin did not vary between groups. Iron concentrations in erythrocytes were significantly higher in rats fed sunflower oil, either unused or used in frying. It was concluded that the consumption of sunflower oil compared to olive oil could affect intra‐ and extracellular haematic distribution of iron, probably associated with changes in membrane permeability, and that some alteration products of the oils originated during frying tend to increase urinary iron losses without repercussions on iron metabolism. © 2000 Society of Chemical Industry     

常见食用植物油中特征性脂肪酸的检测及鉴别

目的分析常见市售植物油中特征性脂肪酸构成及含量范围,并探讨在此基础上如何综合利用上述指标对常见植物油进行定性鉴别。方法从6个城市采集9个品种125份样品,每种两个批次。按照GB/T 22223—2008方法测定46种脂肪酸,分析植物油中的特征脂肪酸及其构成。结果菜籽油中的特征脂肪酸为芥酸;花生油中为C20∶0、C24∶0和C22∶0脂肪酸;茶油中的油酸含量高达75.45 g/100 g,是其特征脂肪酸;亚麻籽油的特征脂肪酸为α-亚麻酸;葵花籽油的特征脂肪酸为亚油酸;稻米油中棕榈酸含量范围为15.13～16.37 g/100 g,可以此作为其特征进行鉴别;大豆油中n6/n3比值最接近中国营养学会推荐比值;芝麻油中油酸和亚油酸的总含量及棕榈酸和硬脂酸含量的组成特征比较稳定,可以此作为芝麻油的鉴别依据;玉米油中脂肪酸特征不明显。结论结合单体特征脂肪酸、脂肪酸构成以及n6/n3比值分析可达到常见植物油定性检测的目的。     

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.     

西式快餐条件下煎炸油氧化稳定性及其不饱和脂肪酸氧化动力学研究

为了解煎炸油在煎炸过程中的氧化动力学规律,考察了5种常见煎炸油在西式快餐条件下的氧化稳定性,并对煎炸油中主要不饱和脂肪酸（亚麻酸、亚油酸及油酸）的氧化动力学进行研究。结果表明,煎炸过程中,棕榈油的茴香胺值、全氧化值的生成速率及碘值降低幅度最小,相比其他4种煎炸油具有更好的氧化稳定性。大豆油和菜籽油中亚麻酸的反应规律均同时符合0级和1级反应动力学模型;棕榈油、菜籽油、葵花籽油及稻米油中亚油酸的反应规律均同时符合0级和1级反应动力学模型,大豆油中亚油酸符合1级反应动力学模型;棕榈油、大豆油、菜籽油及葵花籽油中油酸的反应规律均同时符合0级和1级反应动力学模型;模型相应的决定系数R2在0.886~0.987之间,均大于0.85,模型拟合程度均较好。表明所构建煎炸油不饱和脂肪酸氧化动力学模型是可行的。     

Polar compounds: a quantitative indicator for life cycle assessment during protracted semi-continuous deep fat frying simulation

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. TPCs 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.     

煎炸油中反式脂肪酸和极性化合物检测方法及防控措施研究进展

油脂在煎炸过程中会产生反式脂肪酸（TFA）和极性化合物（TPC）等危害因子,长期摄食会在体内蓄积,影响婴幼儿生长发育,引发心脏病、血栓、2型糖尿病、癌症等。对煎炸油中TFA和TPC的分析检测方法、危害及防控措施进行综述,旨在寻找快速有效的分析检测方法,并通过相应措施降低其含量。提出选择合适的煎炸温度,缩短煎炸时间,减少反复煎炸次数,选择饱和程度较高、氢化程度较低的煎炸油,选择合适的煎炸食品,添加适当种类和浓度的抗氧化剂等可降低煎炸油中TFA和TPC的含量。     

Effect of fat-enriched diets on rabbit meat fatty acid composition

The effects of beef tallow-, soya and sunflower olein- and soya bean oil-enriched (3%) diets on the chemical and fatty acid composition of total, a polar and polar lipids of rabbit meat have been studied. No significant differences (P > 0.05) in the meat chemical composition were observed between groups. However, a large effect of the diet on the total and apolar lipid fatty acids was found, with C18:1 and C18:2 the most affected fatty acids. The influence of the diets on the fatty acids of the polar fraction was less marked. It is concluded that the enrichment of the rabbit diet with either soya and sunflower oleins or soya bean oil allows the production of rabbit meat with a higher unsaturation degree than is obtained by using conventional diets, which constitutes an important nutritional benefit to the human being.