Oxidative stability of solid fats containing ethylcellulose determined based on the headspace oxygen content

Solid fat was developed by blending fully hydrogenated soybean oil, palm oil, and canola oil, and organogels were prepared using selected solid fats and ethylcellulose. The oxidative stability of organogel was tested at 100 and 180°C using a headspace oxygen assay. Addition of ethylcellulose produced a firmer organogel solid state in selected solid fats ranging from 15.8 to 24.6% saturation at room temperature. Addition of ethylcellulose generally decreased the oxidative stability of organogels prepared using canola oil. The oxidative stability of some organogels made using solid fats changed depending on the concentration of added ethylcellulose (10 or 15%, w/w), and the oxidation temperature. Development of an organogel with a relatively low saturation and a high oxidative stability suitable as a food ingredient is possible.     

Storage stability of cod liver oil organogels formed with beeswax and carnauba wax

In this study, organogels of cod liver oil (CLO) with beeswax (BW) and carnauba wax (CW) were prepared, and compared with a commercial margarine (CM). Oil binding capacities (OBC) of BW organogels were over 99%, while CW had a maximum OBC value of 91.28%. Crystal formation time of BW was shorter. Although the highest solid fat content (SFC) was in the 10% CW containing sample (8.69%), it was 28.99% in the CM sample at 20 °C. The peak melting temperature of CM was 43.70 °C, and BW organogel at 3% addition had the closest values (45.42 °C). Firmness and stickiness values of the organogels were lower than that of CM sample. No significant change in the texture parameters during storage was detected, indicating good stability. There was no hurdle against oxidation by organogelation during storage. This study has shown that CLO organogels can be suitable spreadable products.     

Headspace composition of cod liver oil and its evolution in storage after opening. First evidence of the presence of toxic aldehydes

The headspaces of two samples of cod liver oil, when recently acquired, after five and after fifteen months from opening, were studied by solid phase microextraction, followed by gas chromatography/mass spectrometry. Nearly one hundred compounds were found, some of them identified for the first time as cod liver oil components. In both samples, the presence of the toxic 4-hydroxy-(E)-2-hexenal and of 4-oxo-(E)-2-hexenal was detected, as well as that 4,5-epoxy-2-heptenal in one of the samples; this is the first time that these toxic compounds have been described as being present in cod liver oil. In the early oxidation stages, taking place during storage, the compounds formed are mainly of low molecular weight; some of these could be adopted as oxidation markers of cod liver oil. The possibilities of using the technique to evaluate the oxidation level of cod liver oil are shown. These results suggest the need to monitor the levels of toxic oxygenated α,β-unsaturated aldehydes in cod liver oil in order to ensure its safety.     

Analysis of Early Lipid Oxidation in Salmon Pâté with Cod Liver Oil and Antioxidants

ABSTRACT: Analytical methods that can detect early stages of lipid oxidation in complex food matrixes are highly needed, and the interest in rapid methods is great. In the present study, sensory analysis, dynamic headspace/gas chromatography-mass spectrometry (GC-MS), front-face fluorescence spectroscopy, and an electronic nose were used to detect early lipid oxidation in salmon pâté. The pâté was enriched with cod liver oil to increase the n-3 content, and citric acid (CA) or calcium disodium ethylenediamine tetraacetate (EDTA) were used as metal chelators. The sensory panel, GC-MS, and fluorescence methods detected oxidative changes in the pâté after 4 wk of storage. The fluorescence intensity increased with time. More volatile lipid oxidation products were formed in pâté with cod liver oil than in pâté without oil, but no differences were found between the batches with regard to rancid odor and flavor. CA and EDTA slightly promoted formation of volatile oxidation products. EDTA had a small positive impact on the sensory perception of the samples, whereas CA did not work favorably. With better packaging and antioxidant protection, n-3 enriched salmon pâté could be viable. Front-face fluorescence and dynamic headspace/GC-MS could be well suited to monitor lipid oxidation in such products.     

分子蒸馏单甘酯对谷维素-谷甾醇凝胶油结构和性质的影响

以精炼葵花籽油为基料油,添加分子蒸馏单甘酯与谷维素-谷甾醇制备复合凝胶油,探讨凝胶剂分子间比例对凝胶油结构和性质的影响,以分析单甘酯在复合凝胶油形成过程中的作用。结果表明：在复合凝胶油中单甘酯会与谷甾醇存在着范德华力等弱的非氢键作用力,使得单甘酯和谷甾醇在临界凝胶浓度下,协同形成复合凝胶油。单甘酯的添加对复合凝胶油热力学性质和流变学性质等宏观特性均产生较大影响,添加单甘酯后复合凝胶油微观结构和红外光谱产生了显著变化,随着单甘酯含量的增加,氢键作用逐渐减小直至消失,而微观结构由纤维网状到球状结晶最后为针状结晶;结果还表明添加单甘酯后凝胶油氧化更慢,利于长期贮藏。     

Detection of radical development by ESR spectroscopy techniques for assessment of oxidative susceptibility of fish oils

Detection of radical development by two different Electron Spin Resonance (ESR) spectroscopy techniques has been evaluated for obtaining objective analytical information about oxidative susceptibility of fish oils under mild oxidation conditions. Two oils from different by-products in the fish industry, salmon viscera oil (SVO) and cod liver oil (CLO), were used. In addition, radical formation in the ethyl ester of docosahexaenoic acid (DHA) was studied as representing polyunsaturated fatty acids in fish oils that are very prone to oxidation. The ESR spin trapping technique, using the spin trap α-phenyl-N-tert-butylnitrone, and the ESR spin scavenging technique, using the stable nitroxyl radical 2,2,6,6-tetramethyl-1-piperidinyl-1-oxyl (TEMPO) to be scavenged by radicals generated in the oxidative process, were applied to detect radical development at 40 °C in the dark. For comparative purposes, oxidative susceptibility was evaluated by determination of peroxide value (PV) and the TBARS test under the same oxidation conditions. Results were also compared to the oil stability index (OSI) obtained at 60 °C. Results obtained by ESR spin trapping were consistent with results obtained in the OSI test, as well as those obtained for PV and the TBARS test. Therefore, detection of radical formation by ESR spin trapping provided objective information upon the relative oxidative susceptibility of SVO and CLO. On the other hand, results obtained by ESR spin scavenging were not concluding to establish the different oxidative susceptibility of the two oils found by the other determinations applied. The kinetic curves of TEMPO were similar for both oils, which suggests that mechanisms other than that based on the expected radical-radical interactions might be involved.     

油相结构化对大豆蛋白藻油纳米乳液氧化稳定性的影响

利用蜂蜡结构化藻油结合大豆分离蛋白-甜菊糖（soy protein isolate-stevioside,SPI-STE）复合体系的乳化特性,制备高稳态的藻油纳米乳液体系。藻油凝胶的微观结构观察、热性质测试以及流变学分析表明,当藻油中蜂蜡添加量达到4%(m/m)时,大量晶体组装成稳固的网络结构,从而构筑出稳定的油凝胶。进一步以SPI-STE为稳定剂制备藻油纳米乳液,研究了藻油结构化对纳米乳液形成及稳定性的影响。结果表明,油相中添加蜂蜡对纳米乳液的形成没有显著影响。随着藻油中蜂蜡质量分数的增大（0%～6%）,乳液的物理稳定性逐渐提高;但在高蜂蜡添加量（8%）下,刚性较强的凝胶网络破坏了油滴界面层,乳液稳定性变差。热促氧化及光促氧化结果显示,蜂蜡油相结构化明显提高了纳米乳液的氧化稳定性,其中油相中含有6%蜂蜡的样品延缓氧化的效果最明显。本研究可为食品工业构建高稳态的藻油纳米乳液载体及产品提供一定技术支持。     

微量成分形成的反胶束对亚麻籽油氧化稳定性的影响

以富含α-亚麻酸的亚麻籽油为研究对象,测定多种微量成分（磷脂、油酸、β-谷甾醇、二酰基甘油）在stripped亚麻籽油中的临界胶束浓度,并研究反胶束的形成对亚麻籽油氧化稳定性以及生育酚抗氧化活性的影响。结果表明,磷脂是形成反胶束的重要组分,其临界胶束浓度为125 μmol/kg;与对照组相比,低浓度（低于临界胶束浓度）微量成分对亚麻籽油的热稳定性无显著影响,但形成反胶束后则能显著降低油脂的起始氧化温度（约12%）以及氧化诱导时间（约33%）,增加贮藏过程中氢过氧化物（约36%）、丙醛（约13%）和己醛（约200%）的含量,显示出促氧化活性;与对照组相比,生育酚的添加能抑制油脂氧化进程,但反胶束的形成使油脂中氧化产物浓度高于对照组,降低了生育酚的抗氧化活性。因此控制亚麻籽油中反胶束的形成将有助于油脂氧化稳定性,为富含n-3多不饱和脂肪酸油脂的稳态化控制提供新的策略与途径。     

Fluorescence study of the pro‐oxidant effect of free fatty acids on marine lipids

The free fatty acid (FFA) effect on the oxidative stability of marine lipids was studied by fluorescence assessment. Under different reaction conditions, including time, temperature and FFA content and type (different chain lengths and unsaturation degrees), FFAs were made to interact in model systems with a commercial marine oil (cod liver oil) and two different fish (hake and pout) white muscles. Fluorescence assessment showed a pro‐oxidant effect of all types of FFA, which increased with time, temperature and FFA content in the reaction mixtures. At 30 °C a higher degree of oxidation was obtained in systems including the shorter‐chain‐length fatty acids (lauric and myristic) compared to systems including the longest ones (arachidic and stearic). At the same temperature an increasing pro‐oxidant effect was also observed with increasing degree of fatty acid unsaturation (stearic < oleic < linoleic < linolenic). When a lower temperature (−10 °C) was tested, a differential pro‐oxidant effect among fatty acids (chain length and unsaturation degree) was not observed. © 2001 Society of Chemical Industry     

复合多糖稳定剂在乳白鱼肝油中的应用

采用ＨａａｋｅＲＶ１２粘度仪测定复配胶溶液、７７９６胶溶液以及乳白鱼肝油的流变性质，用光散射仪测定乳白鱼肝油中油滴大小分布，结果表明，复配胶与进口的７７９６胶相比，不仅价格低，而且稳定性能优于７７９６胶。使用ＤＬＶＯ理论探讨了复配胶稳定乳白鱼肝油的稳定机理。     

精制鱼油三甘油酯时与之共存下的胆固醇的氧化分解

使用鳕鱼肝脏抽出的 ,经精制的鱼油三甘油酯、胆固醇和三油酸甘油酯纯品 ,分别组成 4组试样 :胆固醇与精制鱼油三甘油酯 (CFT) ;胆固醇与三油酸甘油酯 (CT) ;三油酸甘油酯 (TO) ;胆固醇 (CHOL) ,放置在 2 5℃干燥空气中贮存 ,定期对各组的氧吸收量进行测定 ,并对其中三甘油酯和胆固醇的氧化分解产物进行定性、定量分析。经 10 4d的贮存 ,只有CFT组的氧吸收量增加 ,并生成游离脂肪酸和胆固醇氧化物。而且胆固醇氧化物的数量 ,随着高度不饱和脂肪酸 (PUFA)和油酸的减少而增加。研究结果表明 ,水产制品中胆固醇的氧化与共存的油脂中的PUFA的氧化分解有关。     

Monoglyceride organogels developed in vegetable oil with and without ethylcellulose

We used two commercial monoglycerides (MGs) with different composition (SKB, ≈ 79% glycerol monostearate and ≈ 12% glycerol monopalmitate; PKB, ≈ 47% glycerol monostearate and 47% glycerol monopalmitate) to develop organogels [2% and 8% (wt/wt) MG content]. The objective was to investigate the effect of shearing (SH) and the presence of 6% ethylcellulose (EC) as factors to limit the sub-α to β polymorphic transition of MG, and the subsequent crystals agglomeration that results in deleterious effect on the organogel's mechanical and oil-binding properties. The results showed that under static conditions (ST) both type of MG developed organogels (OG), but their structure, measured as the complex modulus (G*), was weak particularly in the organogels formulated with PKB at 2%. Nevertheless, the OG-ST had higher strength and lower oil loss than the OG-SH. The X-ray analysis showed that the use of shear during organogelation reduced the time at which the sub-α to β polymorphic transition occurred in both the SKB and the PKB oleogels. Additionally, shearing seemed to hinder the formation of well-organized microplatelet structure, and from there the lack of gelation in the 2% OG-SH and the higher oil loss of the 8% OG-SH compared with their static counterparts. Independent of the concentration of SKB and PKB, the presence of EC resulted in organogels with higher G* than that for OG-ST without EC. This, in spite the EC concentration used was below the critical concentration for vegetable oil gelation. The results showed that EC slowed the rate for the sub-α to β polymorphic transition in the MG organogels. Thus, irrespective of the type of MG and the concentration used, during 14 days of storage at 15 °C the OG-EC systems showed a lower oil loss as a function of time than the corresponding organogels developed without EC. This was particularly evident in the organogels formulated with SKB and those formulated with 8% of MG. We suggest that EC limits the molecular mobility in the MG organogels, and therefore, slows the sub-α to β polymorphic transition and the subsequent β crystals' agglomeration. The results showed that there is a synergistic interaction between MG and EC that result in organogels with higher viscoelastic properties and lower oil loss than those observed in MG-organogels without EC.     

Cheese fortification using saturated monoglyceride self‐assembly structures as carrier of omega‐3 fatty acids

The purpose of this research was to study the capacity of emulsions containing saturated monoglyceride self‐assembly structures to deliver omega‐3 fatty acids in fresh soft cheese. To this aim, fortified emulsions containing different ratios of milk, saturated monoglycerides (MGs) and cod liver oil were added to milk before cheese‐making. These emulsions were characterised by distinct microstructural features observed by polarised light microscopy and apparent viscosity values. The omega‐3 delivery performance of MG emulsions highlighted that this strategy allowed a good retention of the omega‐3‐rich oil in the curd (up to 75%). The fortified cheeses showed yield value and fat content higher than those of control samples. The enriched cheese showed hardness and cohesiveness obtained by texture profile analysis similar to those of the unfortified product. Only a slight decrease in gumminess was detected in fortified cheese.     

Effect of Infrared Heating on the Formation of Sesamol and Quality of Defatted Flours from Sesamum indicum L.

ABSTRACT:  Infrared (IR) heating offers several advantages over conventional heating in terms of heat transfer efficiency, compactness of equipment, and quality of the products. Roasting of sesame seeds degrades the lignan sesamolin to sesamol, which increases the oxidative stability of sesame oil synergistically with tocopherols. IR (near infrared, 1.1 to 1.3 μm, 6 kW power) roasting conditions were optimized for the conversion of sesamolin to sesamol. The resultant oil was evaluated for sesamol and tocopherol content as well as oxidative stability. The defatted flours were evaluated for their nutritional content and functionality. IR roasting of sesame seeds at 200 °C for 30 min increased the efficiency of conversion of sesamolin to sesamol (51% to 82%) compared to conventional heating. The γ-tocopherol content decreased by 17% and 25% in oils treated at 200 and 220 °C for 30 min, respectively. There were no significant differences in the tocopherol content and oxidative stability of the oil. Methionine and cysteine content of the flours remained unchanged due to roasting. The functional properties of defatted flours obtained from either IR roasted or conventionally roasted sesame seeds remained the same.
Practical Applications: Sesame oil is stable to oxidation compared to other vegetable oils. This stability can be attributed to the presence of tocopherols and the formation of sesamol, the thermal degradation product of sesamolin—a lignan present in sesame. Roasting of sesame seeds before oil extraction increases sesamol content which is a more potent antioxidant than the parent molecule. The conversion efficiency of sesamolin to sesamol is increased by 31% by infrared roasting of seeds compared to electric drum roasting. This can be used industrially to obtain roasted oil with greater oxidative stability.     

有机凝胶剂12-羟基硬脂酸及热加工对凝胶化大豆油氧化的影响

制备12-羟基硬脂酸（12-hydroxystearic acid,12-HSA）凝胶化大豆油脂,在探讨12-HSA凝胶剂对大豆油脂氧化指标的影响及比较官能团对油脂氧化作用的基础上,通过室温及热加工时凝胶状态的不同研究12-HSA及热加工对凝胶化大豆油脂氧化的影响机理,并利用核磁共振氢谱法进行热氧化分析。结果表明：12-HSA凝胶剂与碱性滴定液反应使酸价测定值升高,油脂游离脂肪酸所反映的真实酸价应为凝胶化油脂的实测酸价减去因12-HSA消耗KOH所产生的酸价;12-HSA有促氧化作用,相同条件下顶空耗氧量从大到小依次为硬脂酸＞硬脂醇＞12-HSA＞十八烷,提示羟基与羧基单独作用下的促氧化作用要强于同时含有羟基与羧基的12-HSA;流变学结果表明,25 ℃添加2%的12-HSA能使大豆油脂形成稳定的凝胶结构并减少其氧化;当温度高于60 ℃时,凝胶结构逐渐被破坏,12-HSA促氧化性逐渐增加,其顶空耗氧量在90 ℃和120 ℃时与空白组相比分别增加了0.65%和1.78%;核磁共振氢谱法结果表明,脂肪族质子与烯质子峰面积积分比值Rao及脂肪族质子与二烯丙基亚甲基质子峰面积积分比值Rad均随氧化程度的增加而增加,并且与凝胶化油脂的总氧化值具有良好的正相关性。     

谷维素/谷甾醇与单甘酯复合凝胶油形成过程及分子作用特性

以谷维素/谷甾醇和单甘酯为凝胶剂,葵花籽油为原料油制备复合凝胶油,探讨复合凝胶油的形成过程以及单甘酯对凝胶化过程的影响,实验发现凝胶油的形成可分为3?个阶段,在凝胶剂到达过冷、过饱和的平衡阶段,受单甘酯影响较小;在凝胶剂分子聚集成核的对数阶段,单甘酯会增加单位体积焓值,降低总吉布斯自由能,促进成核;而在晶体生长、组装的线性阶段,逐渐形成凝胶油的一级、二级、三级结构,其中三级结构与宏观特性最为紧密,三级结构中永久交联和瞬时交联的比例决定了凝胶油的主要性质。通过核磁分析表明物理截留油是凝胶化植物油的主要机理,在此基础性上通过X-射线衍射和小角X-射线散射分析了凝胶剂的组装结构,结果表明谷维素/谷甾醇凝胶油形成的为六边对称结构,单甘酯凝胶油形成的为层状对称结构,同时含有谷维素/谷甾醇和单甘酯的复合凝胶油为立方对称结构。     

Effects of newly developed waxy rice flour on the quality characteristics and oxidative stability of Korean traditional fried cookie, <Emphasis Type="Italic">Yakgwa</Emphasis>

The effects of waxy rice flour (WRF) in substitution for wheat flour (WF) on the oil absorption, structure, texture and oxidative stability of traditional Korean fried cookies, Yakgwa, were investigated. Fried cookie prepared with WF showed the greatest oil absorption (20.66%), however, the oil absorption reduced as the ratio of WRF substitution increased. The fried cookies prepared with WRF in substitution for WR showed the reduced oil absorption and increased oxidation stability. In addition, the cookies still maintained a layered structure with crispiness and softness. Also, when white WRF was used, the fried cookie showed the increased oxidative stability and reduced oil absorption decreased compared to when brown WRF was used. WRF can be used as a substitute for WF at a percentage of up to 75% and can improve the structure and oxidative stability of Yakgwa during storage. Substitution of WRF for WF significantly improves the structure and oxidative stability of Yakgwa.     

Inhibition of lipid oxidation in anchovy oil (Engraulis encrasicholus) enriched emulsions during refrigerated storage

The aim of this study was to produce a functional emulsion product enriched with anchovy (Engraulis encrasicholus) oil. Tomato and garlic extracts were added to perform oxidative stability. Tomato and garlic extracts were added to avoid oxidative degradation in such a product. The plant extracts delayed the formation of primary and secondary oxidation products. The value of conjugated diens (3.07 ± 0.15) was markedly low in the emulsions containing garlic extract at the end of the storage period. The p–Av values of the emulsions treated with the extracts were significantly (P < 0.01) lower than untreated samples. TBARS formation increased slightly, therewithal statistical difference was not observed in the samples treated with garlic extract during the storage. Strong odour and flavour of the garlic suppressed the odour of fish oil. The panellists preferred the flavour, odour and aroma characteristics of the samples treated with the extracts.     

不同食用油氧化稳定性比较研究

为了比较不同食用油的氧化稳定性,选取紫苏油、亚麻籽油、核桃油、菜籽油和芝麻油5种食用油为原料,以烘箱法为对照,分别采用涂膜法和模拟法以过氧化值和酸值为考察指标对其氧化稳定性进行评价,并对其氧化过程中的脂肪酸组成变化进行探讨。结果表明:5种食用油氧化稳定性从高到低依次为:芝麻油菜籽油核桃油亚麻籽油紫苏油;在氧化初期,多不饱和脂肪酸含量减少,单不饱和脂肪酸含量和饱和脂肪酸含量有不同程度的增加,多不饱和脂肪酸含量对食用油氧化稳定性具有明显的影响,特别是亚麻酸含量;在评价氧化稳定性的方法中,烘箱法操作简便但无法反映氧化实际情况,涂膜法检测过程高效且实时,模拟法可反映食用油在使用中的实际氧化过程。