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.     

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.     

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.     

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...     

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。     

The effects of industrial pre-frying and domestic cooking methods on the nutritional compositions and fatty acid profiles of two different frozen breaded foods

This study was carried out to determine the effects of manufacturer pre-frying in olive and sunflower oil, as well as domestic cooking methods (deep-frying in olive and sunflower oil and baking) on the proximate compositions and fatty acid profiles of tuna pasties and ham nuggets. The pre-frying processes reduced moisture and carbohydrates and increased ash, fat and protein content in both pre-fried products. During cooking, the frying processes caused a reduction in moisture content and an increase in fat content in relation to pre-fried samples, while baking did not modify the proximate composition. The fatty acid profiles of products during both the pre-frying and frying processes became similar to those of the culinary fat used. Thus, the frying processes reduced the proportion of saturated fatty acids (SFA) and increased the proportion of monounsaturated fatty acids (MUFA) in the foods when olive oil was used, whereas increased the proportion of polyunsaturated fatty acids (PUFA) in products fried in sunflower oil. The fatty acid profiles of fried samples tended to be more similar to the frying fat than to the pre-frying fat, whereas the fatty acid profiles identified during the pre-frying process for baked products were not significantly modified. Thus, samples pre-fried in olive oil and subsequently baked showed the best proportion of fat content and PUFA/SFA, MUFA + PUFA/SFA and n-6/n-3 ratios of the tested products.     

The evaluation of oil and fatty acid composition in seed of cotton accessions from various countries

Cottonseed oil has a 2:1 ratio of polyunsaturated to saturated fatty acid. Linoleic acid is an essential fatty acid, but in large amounts it contributes to a short shelf‐life due to rancidity. The aim of this study was to screen germplasm from various countries for oil and fatty acid content, to identify parents that can be used in hybridisation to increase stearic and oleic acids and reduce palmitic fatty acids. Oil content varied from 13.6% to 24.7%. Linoleic acid ranged from 51.5% to 63%, palmitic from 19.2% to 25.6%, oleic from 14.2% to 18.5% and stearic from 2.1% to 2.8%. Stearic and palmitic acids were positively correlated, and stearic and linoleic acids were negatively correlated; therefore breeding for increased stearic acid and reduced palmitic acid as well as breeding for increased stearic and linoleic acids at the same time might be difficult through conventional breeding. CIM70 and Cyto 12/74 had high values for stearic and oleic acids and Stoneville had high values of stearic and oleic acids and low palmitic acid. These can be used as parents to improve these two fractions. Copyright © 2006 Society of Chemical Industry     

气相色谱法测定脂肪酸含量判定山茶油纯度

利用气相色谱法,对山茶油掺入大豆油、菜籽油、玉米油和葵花籽油的掺伪油进行脂肪酸组成分析。结果表明:油酸、亚油酸和亚麻酸可作为鉴别山茶油中掺伪大豆油和菜籽油的特征脂肪酸,棕榈酸、油酸和亚油酸可作为鉴别山茶油中掺伪玉米油和葵花籽油的特征脂肪酸;回归预测模型相关系数(R^2)较高(> 0. 99),可分别检出掺伪量4%的大豆油和菜籽油,掺伪量8%的玉米油和葵花籽油,回收率在96. 56%~112. 88%之间。该方法灵敏度高,定量准确,可为掺伪山茶油纯度鉴别及调和山茶油配比的定量分析提供科学依据。     

油酸与亚油酸比例对煎炸油中单环氧 脂肪酸单体含量的影响

油脂煎炸过程中,脂肪酸会氧化形成具有高吸收率和潜在毒性的单环氧脂肪酸。通过对薯条间歇式煎炸,研究煎炸油的油酸与亚油酸比例对单环氧硬脂酸含量、单环氧油酸含量以及顺、反式单环氧脂肪酸相对含量的影响。结果表明:单环氧脂肪酸含量随煎炸时间的延长呈现增长趋势;油酸含量高的煎炸油倾向于生成更多的单环氧硬脂酸,亚油酸含量高的煎炸油倾向于生成更多的单环氧油酸;煎炸过程逐渐积累更多的反式单环氧脂肪酸,顺式单环氧脂肪酸可能会转化为反式单环氧脂肪酸。     

GC/MS法测定葵花籽油中脂肪酸的甲酯化条件研究

研究气相色谱—质谱联用法(GC-MS)测定葵花籽油中脂肪酸的甲酯化条件,以峰面积为考察指标,采用单因素试验与正交试验设计,对葵花籽油氢氧化钾-甲醇法甲酯化条件进行优化,同时分析葵花籽油中各脂肪酸的种类及相对含量.结果表明:GC/MS测定葵花籽油中脂肪酸的最佳甲酯化条件为催化剂用量2.0mL,超声时间9min,超声温度3...     

Genetic and environmental variability in protein,oil and fatty acid composition in high-alkaloid hite lupin (Lupinus albus)

Protein, oil and fatty acid composition ere determined on seed samples of Lupinus albus L cultivars gron in to different locations, Villafranca and Córdoba. Seeds planted in the latter location ere inoculated ith Rhizobium leguminosarum f lupini as soil pH as 7·5-7·9. Locations clearly caused differences in both protein and oil contents. Interactions beteen localities and genotypes ere not significant. Environmental effects ere much greater than the genotypic factors except for oleic and linoleic acids. Both locality and genotype effects ere clearly significant for all fatty acids studied except for palmitic acid. A negative correlation as found beteen protein and oil content. Oil and oleic acid contents ere positively correlated to each other. Linoleic acid content seemed not to be correlated ith any other fatty acid except oleic. Linolenic acid content as also negatively correlated ith that of oleic acid. Covariance analysis shoed a strong positive genetic correlation beteen oil and oleic acid contents; the genetic correlation as higher than the environmental one. Oil content is strongly negatively correlated ith both linoleic and linolenic acid contents at the genotypic level.     

Effect of cooking method on the fatty acid profile of New Zealand King Salmon (Oncorhynchus tshawytscha)

Farmed New Zealand King Salmon (Oncorhynchus tshawytscha) was prepared according to common consumer techniques; raw, poached, steamed, microwaved, pan fried (no added oil), oven baked (no added oil) and deep fried (in sunflower oil). The fatty acid profile was investigated to determine the optimal preparation techniques to achieve both optimal sensory and nutritional qualities, in particular the levels of long chain polyunsaturated omega-3 fatty acids. The modified Bligh and Dyer method was used for lipid extraction and the Hartman and Lago method for FAMES preparation. Fatty acid composition was determined by gas chromatography. There were moisture and lipid losses during cooking amongst the different methods. The fatty acid profile showed only minor differences between the methods apart from an increase in PUFA in the deep fried salmon due to linoleic acid uptake from the frying oil. In all the cooking methods the omega-3 fatty acids were well preserved. However, deep fried showed the lowest amounts of omega-3 fatty acids. As the results showed good preservation of omega-3 fatty acids regardless of cooking method, there may be possible “internal protection” of omega-3 fatty acids in King Salmon that warrants future research.     

Chemistry of deep-fat frying oils

ABSTRACT:  Deep-fat frying produces desirable or undesirable flavor compounds and changes the flavor stability and quality of the oil by hydrolysis, oxidation, and polymerization. Tocopherols, essential amino acids, and fatty acids in foods are degraded during deep-fat frying. The reactions in deep-fat frying depend on factors such as replenishment of fresh oil, frying conditions, original quality of frying oil, food materials, type of fryer, antioxidants, and oxygen concentration. High frying temperature, the number of fryings, the contents of free fatty acids, polyvalent metals, and unsaturated fatty acids of oil decrease the oxidative stability and flavor quality of oil. Antioxidant decreases the frying oil oxidation, but the effectiveness of antioxidant decreases with high frying temperature. Lignan compounds in sesame oil are effective antioxidants in deep-fat frying.     

鸵鸟油理化性质及脂肪酸组成分析

采用索氏提取法提取了在陕西养殖的鸵鸟油,室温分离得到液体油和固体脂.采用化学方法和气相色谱仪测定了两者常规理化指标和脂肪酸组成.结果表明,鸵鸟液体油和固体脂除碘值外其他理化指标稍有不同,其中脂肪酸组成及含量也有差异.液体油主要含有棕榈酸、油酸和亚油酸等,不饱和脂肪酸含量为63.96%,其中油酸含量最高,达到42.23%;固体脂主要含有棕榈酸、硬脂酸和油酸等,饱和脂肪酸含量为55.93%,其中棕榈酸含量最高,为45.23%.     

Effects of egg yolk powder addition to the flour dough on the lipid oxidation development during frying

Effects of egg yolk powder added to the dough on the oxidation of frying oil and lipid of fried products were studied. Flour dough containing egg yolk at 0, 3.53, 6.73, and 9.66/100 g was fried in 180 °C sunflower oil for 1.5 min, and 55 fryings were performed. Lipid damage was determined by free fatty acids (FFA), conjugated dienoic acids (CDA), and polar compounds contents, and p-anisidine values (PAV). Phospholipid (PL) classes were determined by high performance liquid chromatography. PL was not detected in frying oil and fried products without egg yolk, while the first batch of fried products added with egg yolk at 3.53, 6.73, and 9.66 in 100 g of the dough contained total PL at 3.73, 7.93, and 8.98 mg/g, respectively. Contents of PL classes tended to increase in the products fried in the oil performing more fryings. As the number of fryings of oil increased, FFA, CDA, and polar compounds contents and PAV of frying oil increased. Addition of egg yolk to the dough significantly decreased CDA and polar compounds contents and PAV of frying oil, but it increased FFA values. Lipid of fried products showed the same tendency in CDA contents and PAV. The results clearly indicate that egg yolk powder improved the oxidative stability of frying oil during frying, possibly due to PL.     

Dietary evaluation of Mediterranean fish and molluscs pan‐fried in virgin olive oil

The effect of domestic pan‐frying in virgin olive oil (VOO) on the proximate composition, energy content, cholesterol, squalene and fatty acids in the edible portion of six species of finfish, common squid and mussels just caught from several regions of the Aegean Sea (Mediterranean Sea) was investigated. The species selected are traditionally consumed pan‐fried in VOO by the Greeks. On a fresh weight basis, pan‐frying caused significant water loss and increase of total fat, crude protein and energy content. The amount of VOO absorbed during frying ranged from 4.5 to 14.2% of fresh matter, showing a non‐linear negative correlation with initial fat, fish length and fish weight. Cholesterol content increased from 25 to 106 mg 100 g^?1 fresh weight (fw) to 33–130 mg 100 g^?1 fw after frying. VOO absorbed during frying resulted in a 20–78 times increase of squalene content and in significant alteration of fatty acid composition, the major change being the increase of monounsaturated fatty acids which became predominant in all fried samples. The intakes of fat and major fatty acid classes by consuming the pan‐fried seafood were comparable with the respective average Greek values. Frying in VOO resulted in a two to three times decrease of the atherogenic index and a slightly less decrease of the thrombogenic index. Both indices remained lower than 0.45 in all fried samples. The cholesterol‐saturated fat index and the cholesterol index increased up to twice after frying, ranging between 3.4–9.9 and 2.9–9.3, respectively. From the results obtained it is concluded that fish and shellfish pan‐fried in VOO present a healthy lipid profile in terms of the n‐6/n‐3 ratio, major fatty acid classes and total fat content. Copyright © 2004 Society of Chemical Industry     

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.     

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。     

Chemical characteristics of Pandanus conoideus fruit lipid

Pandanus conoideus fruit contained 19.4% by dry weight of red fat. Major fatty acids contained in the fat were oleic (67.6% of the total fatty acids), palmitic (18.7%) and linoleic (7.6%) acids. The fat had an unusually high level of free fatty acid (90.0%) which may have resulted from the action of fat splitting enzymes.     

Frying stability of high oleic sunflower oils as affected by composition of tocopherol isomers and linoleic acid content

The influence of linoleic acid content and tocopherol isomeric composition on the frying performance of high oleic sunflower oil was evaluated during a 14-day restaurant style frying operation. At equal linoleic acid content, no significant difference was observed between high oleic sunflower oil containing only α-tocopherol and the sample containing a mixture of α-, γ-, and δ-isomers as measured by the amount of total polar components, oligomers, anisidine value, and free fatty acids. On the contrary, at similar tocopherol isomeric composition, high oleic sunflower oil containing lower amount of linoleic acid showed superior frying stability compared to the sample with a higher content of linoleic acid, suggesting that the frying performance of high oleic sunflower oil is dictated primarily by the level of linoleic acid, with the tocopherol isomeric composition of the oil having no significant influence. In all oil samples, the loss of γ-tocopherol was higher than the corresponding loss of α-tocopherol.