The use of chromic oxide as a food marker —a warning

Four mixtures of ground barley and soya bean meal were prepared; the first had no further additive, the second had 10% soya bean oil, the third 0.05% chromic oxide and the fourth both 10% soya bean oil and 0.05% chromic oxide. Each of these mixtures was then dried in three ways: at 30°C in vacuo and at 60 and 100°C in a forceddraught oven. The total fatty acid content and the fatty acid composition of each sample was determined either by direct esterification of the fatty acids with methanolsulphuric acid or by extraction into chloroform-methanol followed by esterification with sodium methoxide. When the mixture containing both oil and chromic oxide was heated at 100°C, about 25% of the polyunsaturated fatty acids were lost when they were directly esterified and about 50% when the fat was first extracted from the mixture. It is concluded that this loss is probably due to oxidation of the polyunsaturated fatty acids by the chromic oxide and that the additional loss observed when the extraction method was used is due to partial insolubilisation of the triglyceride by these oxidised fatty acids.     

Oxidative changes during ice storage of rainbow trout (Oncorhynchus mykiss) fed different ratios of marine and vegetable feed ingredients

Recently fish meal and oil have increasingly been replaced with proteins and oils from vegetable sources in the diets of farmed salmonids, but the consequences for the oxidative stability of the resulting fish products have not been investigated. The aim of the present study was to evaluate the influence of feeding regime on composition of rainbow trout fillets, as well as on lipid and protein oxidation during storage on ice. Rainbow trout were fed six different diets, which differed in their levels of marine oil and proteins vs. vegetable oil and protein. Fish fillets were characterised by measurement of fatty acid and amino acid composition, primary and secondary lipid oxidation products, astaxanthin and tocopherol content. Protein oxidation was assessed by measuring protein carbonyl content, oxidised amino acids, sulfhydryl groups and immuno-blotting against carbonyl groups. Feeding regimes significantly influenced fatty acid composition. Replacement of fish oil with vegetable oil reduced formation of primary oxidation products, but the effect on secondary oxidation products differed between different types of volatiles. The differences in protein and amino acid composition were not significant, and there were no clear effects of diets on protein oxidation, but data indicated that compounds present in the marine ingredients might have had an effect on protein oxidation.     

Lipid stability in powdered infant formula stored at ambient temperatures

Lipid stability of standard infant formula was evaluated at ambient temperatures, namely 25, 30 and 37 °C, during 3 months. Lipids were thoroughly analysed to evaluate changes in fatty acid composition and trans fatty acid isomers, non‐volatile oxidation compounds including oxidised, dimeric and polymeric triacylglycerols, and tocopherol. No significant changes in either of the parameters examined were found in total lipids extracted from infant formula along the storage period. However, the minor free oil fractions (about 7.5% of total lipids) showed a significant increase in oxidation compounds and marked decrease in tocopherol levels during storage at all temperatures. Samples stored at 37 °C for 3 months were rancid and, accordingly, contained the highest oxidation level in the free oil fraction, whereas total lipids extracted were apparently not oxidised. Results showed the necessity of analysing separately the free oil fraction in infant formulae to obtain a clear picture of the oxidation status.     

Application of triacylglycerol and fatty acid analyses to discriminate blended sesame oil with soybean oil

Triacylglycerols (TAGs) and fatty acids in the mixture of sesame oil (SO) with soybean oil were analysed using high performance liquid chromatography (HPLC)–an evaporative light scattering detector (ELSD) and gas chromatography (GC)–a flame ionisation detector (FID). Relative percentage of linolenic acid increased rapidly compared to those of oleic and linoleic acids as the ratio of soybean oil increased in the blended SO. Peak responses of trilinolein (LLL) and trilinolenin (LnLnLn) by HPLC–ELSD was higher than those by GC–FID from the same concentration of TAGs. The presence of LLLn peak, the contents of linolenic acid, and the relative ratio of L/S, O/Ln, and L/Ln from fatty acids or LLL/OOO from TAGs could be useful indicators to detect the blended SO with soybean oil. TAG analysis by HPLC–ELSD coupled with fatty acids by GC–FID can be useful methods to discriminate blended SO with soybean oil.     

Determination of thermal oxidation and oxidation products of β-carotene in corn oil triacylglycerols

A reversed phase HPLC-DAD coupled to APCI-MS method is reported for the determination of the degradation of β-carotene and characterization of the oxidation products in corn oil. Corn oil containing β-carotene was oxidized in the Rancimat at 110 °C from 1 to 14 h. A significant degradation of β-carotene was observed in corn oil during accelerated thermal oxidation. A total of eight different oxidized products of β-carotene were identified, which includes 8′-apo-β-carotenal, 6′-apo-β-carotenal, 5,6-epoxy-8′-apo-β-carotenal, β-carotene-2,2′-dione, 13-Z-5,6,5′,6′-diepoxy-β-carotene, all-E-5,8-epoxy-β-carotene, all-E-5,6-epoxy-β-carotene, and 15-Z-5,6-epoxy-β-carotene. Corn oil triacylglycerols (TAGs) oxidation products were also identified using isocratic HPLC–ESI-MS. It was found that β-carotene promoted oxidation of TAGs especially at longer exposure times. For the first time two new classes of oxidized TAGs have been identified in corn oil, which were epidioxy bis-hydroperoxides and hydroxy bis-hydroperoxides. Other oxidation products of TAGs were mono-epoxides, mono-hydroperoxides, and epoxy hydroperoxides. It was found that complementing the HPLC-DAD method for β-carotene with ESI-MS method for TAGs oxidation provides a comprehensive set of analytical tools to characterize carotenoids and triacylglycerols oxidation and degradation in edible oils.     

西兰花种子油中甘油三酯和脂肪酸组成分析

分别使用超高效超临界流体色谱-四极杆飞行时间质谱联用仪和气相色谱-质谱联用仪鉴定西兰花种子油中甘油三酯(TAG)与脂肪酸组成.根据高分辨质谱一级质谱的母离子和二级质谱的碎片离子信息从西兰花种子油中鉴定出43种甘油三酯,采用峰面积归一化法对其在种子油中的相对含量进行表征.结果表明:鉴定的43种甘油三酯中含有13对同分异构...     

Use of some agricultural waste hull ashes for the regeneration of fried sunflower oil

The present study was aimed at improving the quality of fried sunflower oil. Synthetic (Magnesol XL), natural (diatomaceous earth) and hull ashes of rice, wheat and barley (agriculture plant wastes) were used to adsorb the oxidation products of fried sunflower oil. The mineral pattern (Si, Mg, Ca, Fe, Al, Mn and Cu) of the aforementioned substances were determined. The physico-chemical properties [refractive index, viscosity, colour, smoke point, acid value, peroxide value, thiobarbituric acid (TBA) value, conjugated dienes and trienes, polar content, polymer content and oxidised fatty acids] of non-fried, fried and fried-treated sunflower oil were determined. The frying process was carried out at 180 °C ± 5 °C for 20 h, 4 h heating cycle per day for five consecutive days. The fried sunflower oil was treated with synthetic, natural and agricultural hull ashes at 105 °C for 15 min. The results indicate that Magnesol XL, diatomaceous earth, rice hull ash, wheat hull ash and barley hull ash contained Si + Mg + Mn, Si + Mn + Ca, Si + Mn, Si +Mn and Mn + Si as the basic metals, respectively. Frying of sunflower oil led to significant increase in refractive index, viscosity, colour, smoke point, acid value, peroxide value, TBA value, conjugated dienes and trienes, polar content, polymer content, and oxidised fatty acids and decrease in iodine value. Treatments of fried sunflower oil with the aforementioned substances greatly improved the quality of fried oil. Under the present experimental conditions all adsorbing substances performed similarly in removing the fried sunflower oil oxidation products.     

Effects of Sesame Oil Addition to Soybean Oil During Frying on the Lipid Oxidative Stability and Antioxidants Contents of the Fried Products During Storage in the Dark

ABSTRACT: Effects of sesame oil addition to soybean oil during frying on the lipid oxidative stability and antioxidants contents of fried products during storage in the dark were studied. Flour dough pieces (2 cm × 2 cm × 0.1 cm) were fried at 160 °C for 1 min in sesame oil-added soybean oil. Concentrations of sesame oil in the frying oil were 0%, 10%, and 20% by volume. Fried products were put into a glass bottle, and the bottles were tightly sealed and stored at 60 °C in the dark for 18 d. Lipid oxidation of fried products was determined by fatty acid composition changes and conjugated dienoic acid (CDA) and p -anisidine (PA) values. Tocopherols and lignan compounds in the fried products were determined by high-performance liquid chromatography. Relative content of linolenic acid decreased, and CDA and PA values increased during storage of the fried products in the dark. Fatty acid composition change and CDA and PA values during storage were lower in the products fried in sesame oil-added soybean oil than in the products fried in soybean oil without sesame oil. The results clearly showed that addition of roasted sesame oil to soybean oil at 10% and 20% during frying decreased the lipid oxidation of fried products during storage in the dark for 18 d by extension of induction period and decrease in decomposition of oxidized lipids. Fried products contained 134 to 267 ppm tocopherols and 0 to 148 ppm lignans before storage; however, their contents decreased during storage in the dark. Lignan compounds were more stable than tocopherols, and the rate of tocopherols degradation was lower in the products fried in sesame oil-added soybean oil than in the products fried in soybean oil without sesame oil, which could be because of protection of tocopherols from degradation by lignan compounds.     

鸡油加工过程中产品品质的变化

为研究鸡油加工过程中理化指标的变化情况,以酸价、过氧化值、碘值、丙二醛含量、脂肪酸组成和香气成分为指标,对鸡油加工过程进行品质控制。结果表明:鸡油中不饱和脂肪酸含量达60%以上,油酸含量最高,含量为39.79%;加工过程中酸价和过氧化值呈先下降后上升的趋势;碘值呈下降趋势。加工过程未对鸡油的脂肪酸组成造成影响,但鸡油产品香气成分差异较大,其中空气介质中气味最强的物质为2,3-戊二酮。     

巴氏灭菌对不同油脂体乳液氧化稳定性的影响

为探究巴氏灭菌对大豆、葵花、花生、芝麻和核桃油脂体乳液氧化稳定性的影响,本研究测定不同油脂体的基本组成、相关蛋白组成、脂肪酸组成和相对含量,然后利用动态光散射、激光共聚焦显微镜等研究巴氏灭菌（85 ℃加热10 min）对油脂体乳液物理稳定性和氧化稳定性的影响。结果表明：不同油脂体的基本组成、相关蛋白组成和脂肪酸组成存在明显差异,油脂体相关蛋白由内源膜蛋白和外源蛋白组成,油脂体脂肪酸以不饱和脂肪酸为主,其中油酸、亚油酸和α-亚麻酸是主要的不饱和脂肪酸。5 种不同原料油脂体中,大豆油脂体蛋白质量分数和水分质量分数最高,而油脂质量分数最低;花生油脂体总饱和脂肪酸相对含量（21.27%）最高,核桃油脂体总不饱和脂肪酸相对含量（90.10%）最高。巴氏灭菌可显著改善大豆和花生油脂体乳液氧化稳定性,而对葵花、芝麻和核桃油脂体乳液起促进氧化作用。本研究可为油脂体在沙拉酱、植物奶等产品应用提供参考。     

Measurement of oxidation of polyunsaturated fatty acids by spectrophotometric assay of conjugated derivatives

A procedure has been developed for measuring the extent of oxidative deterioration of polyunsaturated fatty acids. The method is based on the conversion of fatty acid hydroperoxides and compounds derived from them, oxodienes and hydroxydienes, to conjugated fatty acids with strongly chromophoric triene and tetraene structures. This is done in two steps in which reduction with sodium borohydride is followed by dehydration under acid conditions; the chromophores produced are measured by absorbance in the ultraviolet. The method has been investigated using methyl linoleate and methyl linolenate as model compounds. Dienoic fatty acid oxidation products give rise to a conjugated triene chromophore whilst the more polyunsaturated fatty acids form a conjugated tetraene chromophore. The sum of absorbance changes at 268 and 301 nm measure the degree of oxidation. The ratio of absorbance change at 301 nm divided by that at 268 nm varies from zero for a pure triene to 2.8 for a pure tetraene and is a measure of the type of polyunsaturated fatty acid being oxidised. The concentration of oxodiene component present in the original mixture may be estimated separately by the decrease in the 275 nm region during the reduction step.     

Effect of lipid oxidation products on the formation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in model systems

Ternary mixtures of creatinine, phenylalanine and lipids (or carbohydrates) were heated at 200 °C for 1 h to determine the potential contribution of lipids to the formation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). Although unoxidised lipids did not contribute to PhIP formation, their oxidation produced many compounds that significantly increased the formation of PhIP. Among the different lipid oxidation products (LOPs) studied, which included ω-6 and ω-3 derived lipid hydroperoxides, 2,4-alkadienals, 2-alkenals, 4,5-epoxy-2-alkenals, 4-oxo-2-alkenals, and 4-hydroxy-2-nonenal, 4-oxo-2-nonenal was the most reactive compound. It produced 32.48 pmol of PhIP/μmol of creatinine in comparison with the 7.92 pmol of PhIP/μmol of creatinine produced by the control phenylalanine/creatinine reaction mixture. 4-Oxo-2-nonenal reactivity was similar to that of most carbohydrates; although ribose and arabinose produced more PhIP (44–46 pmol of PhIP/μmol of creatinine). In addition to single LOP, the addition of oxidised soybean oil for 24–144 h at 60 °C also increased PhIP formation. All these results pointed out to a potential contribution of LOP to the formation of PhIP in food products. This contribution will depend on the lipid content of the food product and its easiness to be oxidised.     

化学计量学与三酰甘油酯在食用油保真中的研究进展

食用植物油保真检测技术是食用植物油打假和保证人民身体健康的重要手段。三酰甘油酯是占食用植物油90%以上的主要成分,但是我国目前的检测技术仅能检测三酰甘油酯酰基链结构,即通过甲酯化方式检测脂肪酸含量,该方法不能真实反映三酰甘油酯的结构和含量。本文综述国内外最新的三酰甘油酯分析技术和化学计量学分析三酰甘油酯指纹谱的食用植物油保真检测技术研究进展,为保障我国食用植物油安全消费提供重要的技术支撑。     

不同热损程度大豆油脂品质及组成分析

目的 探究不同热损程度大豆油脂品质与组成的差异性。方法 以同一批次含有热损现象的美湾大豆为研究对象,通过测定不同热损程度大豆油脂的酸价、过氧化值、茴香胺值、全氧化值、氧化诱导期、甘油酯及脂肪酸的组成以及微量成分(磷脂、生育酚、色素)含量的差异,分析大豆热损对油脂品质和组成的影响。结果 热损会导致油脂的品质显著下降,酸价、过氧化值、茴香胺值、全氧化值均随热损程度的增加显著上升,氧化稳定诱导时间显著降低;重度热损过程中油脂发生氧化和Sn-1,3位为主的水解反应,氧化反应主要导致多不饱和脂肪酸含量降低,水解反应导致甘三酯含量由95.71%下降至91.79%,甘二酯和游离脂肪酸含量显著上升;大豆热损导致油脂中的总磷脂含量下降,磷脂酸的相对含量显著上升,生育酚在热损过程中易发生氧化损失,总生育酚损失率高达11%。结合大豆外观、磷脂组成和色素含量分析,未成熟大豆易发生热损,导致油脂中叶绿素含量显著上升。结论 大豆热损会导致油脂的品质和组成差异显著,热损程度越深,油脂品质越差。     

Oxidation of free and esterified linoleic and linolenic acids in bread doughs by wheat and soya lipoxygenases

Lipids containing ¹⁴C-labelled linoleic and linolenic acids were added to flour which was then made into bread doughs with or without 2% enzyme-active soya flour. The ¹⁴C-labelled lipids and their oxidation products were analysed as intact lipids or as ¹⁴C fatty acid methyl esters by thin-layer chromatography. In the control doughs wheat lipoxygenase oxidised free fatty acids and monoglycerides. In doughs containing soya flour, steryl esters, triglycerides, diglycerides, mono-galactosyl diglycerides, digalactosyl diglycerides and phosphatidyl choline were also oxidised, and the oxidation of these lipids is attributed to soya lipoxygenase.     

Oil Bodies Extracted from High‐Fat and Low‐Fat Soybeans: Stability and Composition During Storage

Soybeans contain oil bodies (OBs) that encapsulate triacylglycerols (TAGs) with a phospholipid monolayer carrying scattered proteins. In nature, soybean OBs can form natural emulsions in aqueous media and may serve as natural, minimally processed, stable, and pre‐emulsified oil for addition into appropriate food systems. In this study, OBs were obtained by aqueous extraction from the mature seeds of 2 soybean crop cultivars, high‐fat soybean and low‐fat soybeans. The compositions of the extracted OBs were analyzed during storage at room temperature up to 14 d (pH = 7). The oxidative stability of these OBs, stored at 60 °C, was evaluated by measuring the presence of primary (lipid hydroperoxides) and secondary lipid oxidation products (malondialdehyde) by determining the standard peroxide value (PV) and thiobarbituric acid‐reactive substances (TBARS) value. During storage, the contents of unsaturated fatty acids, phospholipids, and tocopherols declined in both OBs, while their mean particle diameters (d₃₂) and ζ‐potentials increased. The changes in PV and TBARS values exhibited a similar trend for both OBs, but the OBs from low‐fat soybeans had significantly lower PV and higher TBARS values than the OBs from high‐fat soybean cultivars (P < 0.05). Overall, the OBs from both soybean cultivars had good stability during storage.     

不同制油工艺对酸木瓜籽油成分及氧化稳定性的影响

目的 研究低温压榨、高温压榨和超声波辅助溶剂提取3种不同制油工艺对酸木瓜籽油提取率、成分及氧化稳定性的影响。方法 利用气相色谱-质谱法(gas chromatography-mass spectrometry, GC-MS)对木瓜籽油脂肪酸组成和挥发性成分进行分析;采用schaal烘箱法加速氧化,以酸价和过氧化值为指标对木瓜籽油氧化稳定性进行评估。结果 超声波辅助溶剂提取法出油率最高,其中不同溶剂提取以二氯甲烷最佳,出油率达44.21%;不同制油工艺对酸木瓜籽油脂肪酸组成影响很小,共鉴定出7种脂肪酸,相对含量最高的是油酸,其次是亚油酸、棕榈酸、硬脂酸,其中不饱和脂肪酸占比可达80.35%;在酸木瓜籽油中鉴定出47种挥发物,以烷烃类为主,溶剂法与压榨法制取的木瓜籽油挥发物组成差异较大,其中以2,4-二叔丁基苯酚和反式角鲨烯为首,溶剂法制得的油中2,4-二叔丁基苯酚占比为23.94%,反式角鲨烯占比为4.14%,而由低/高温榨取法制得的油中2,4-二叔丁基苯酚占比分别为3.20%和2.77%,反式角鲨烯占比分别为29.15%和23.38%;低温压榨制油清除1,1-二苯基-2-三硝基苯肼(1...     

高粱复配米脂肪体外消化产物及其氧化稳定性

为探究高粱复配米脂肪体外消化产物及其氧化稳定性,将熟化高粱与大米按质量比1:4和1:1复配进行模拟体外消化,采用气相色谱-质谱联用法分析复配米饭的脂肪消化产物,并以脂质过氧化物值和丙二醛浓度为指标探究其氧化稳定性。结果表明,1:1和1:4复配米经胃肠液消化后含有25种脂肪酸,主要为棕榈酸、硬脂酸和亚油酸。不饱和脂肪酸占到34.34%和28.50%,人体必需脂肪酸亚油酸和α-亚麻酸含量分别为91.41、3.05和59.36、1.83μg/g,均显著高于大米组（P<0.05）。此外,1:1和1:4复配米消化后肠液过氧化值为33.83和43.16 nmol/g、丙二醛含量为28.17和27.72 nmol/g,总氧化程度均低于高粱组。综上,食用高粱复配米比单纯食用大米改善了摄入的饮食脂肪酸组成,又比单纯食用高粱减少了人体对脂质氧化产物的吸收积累。     

Influence of the oxidative quality of dietary oil on broiler meat storage stability

Broilers were fed a high fat diet containing 11% oil (9% rapeseed oil, 2% soya bean oil) and the oil was given either as fresh (peroxide value of 1 meqv. O₂kg⁻¹ oil) or as highly oxidised (peroxide value of 156 meqv. O₂kg⁻¹ oil). Diets were supplemented with 46 mg all-rac--tocopheryl acetate kg⁻¹ diet, resulting in a tocopherol content of 80.8 mg -tocopherol and 58.6 mg γ-tocopherol per kg diet in the fresh oil diet and of 44.0 mg -tocopherol and 18.3 mg γ-tocopherol per kg diet in the oxidised oil diet, respectively, reflecting the degradation of the natural occurring tocopherols in the oxidised diet. Only minor differences were seen with respect to fatty acid composition in muscles from birds fed the two diets. The oxidation of the dietary oil lowered lipid stability significantly (p < 0.01) in both raw and precooked meats during chill storage, whereas only minor effects on the stability of frozen meat were seen. Tocopherol levels were significantly lower (p < 0.01) in muscles from birds fed the oxidised oil diet, explaining the decreased lipid stability of meat from these birds. Thigh meat was more susceptible to lipid oxidation during storage than breast meat, regardless of dietary treatment, although thigh meat had markedly higher tocopherol levels than breast meat. The molar ratio of PUFA > 18:2 (polyunsaturated fatty acids with three or more double bonds) to -tocopherol was significantly (p < 0.01) higher in thigh meat compared with breast meat, explaining the lower stability of the former during storage.     

Oxidative stability of olive oil after food processing and comparison with other vegetable oils

The use of olive oil showed an important protection of meat and potatoes when compared with other vegetable oils, with sunflower oil samples being oxidised after 60 min of processing at 180 °C. Olive oil samples were not oxidised, independently of the olive oil quality used. Shelf life was longer for extra-virgin olive oil containing samples and this fact was positively correlated with their higher phenolic content. The radical-scavenging activity of extra-virgin olive oil was higher than for other olive oil samples and was also positively correlated with the phenolic content of the oil. Seed oil antioxidants showed little capacity in delaying the oxidative degradation of seed oils and meat processed with them. However, tocopherol content and the identity of tocopherols present in the oil were shown to have a more important role in the oxidative stability of seed oils than the fatty acid composition.