烹饪方法对兔排油脂氧化和挥发性呈味物的作用研究

本文对比研究了煎、炸、微波和烤4种中式烹饪方式处理的兔排脂质氧化程度和挥发性呈味物的异同与联系。烹饪导致兔排油脂氧化,以微波和烤制样品的TBARs值升高最为显著(P0.05),分别达到1.31 mg MDA/kg样品和1.23 mg MDA/kg样品。烹制兔排样品中共检测出56种挥发性化合物,不同烹制方式导致兔排中各挥发性化合物含量存在一定差异;烤兔排的总挥发性化合物含量最高。新鲜兔排挥发性化合物的主成分是酯类,而醛类是烹饪样品中挥发性化合物的主成分,在煎制、油炸、微波和烤制兔排样品中醛类化合物分别占据总挥发性化合物的54.31%、53.21%、59.99%和65.19%。兔排油脂氧化指数TBARs值与挥发性化合物中总酯类含量呈线性负向相关,与总醛类、总呋喃类及总挥发性化合物含量呈正相关,其中与己醛的相关系数高达0.793,说明油脂氧化产物是烹制兔排挥发性化合物的主成分物来源。     

快速测定煎炸油中极性组分的方法

油脂在煎炸过程中,由于高温及水分、氧气等的存在,会发生一系列物理化学变化.测定油样中极性组分含量是监控煎炸油质量的一种方法.极性组分含量的标准测定方法(柱层析法)存在费时、需大量溶剂等缺点.采用Testo 265食用油脂品质检测仪对煎炸油中的总极性成分进行测定,并与柱层析法进行了对比,结果表明食用油脂品质检测仪法具有操作简单快速,非破坏性,不使用溶剂等优点.     

鱼油氧化稳定性研究—感官及理化参数评价

目的:研究鱼油样品在储藏过程中氧化指标(游离脂肪酸含量、过氧化值、挥发性二级氧化产物含量)和感官属性之间的关系,以更好地监控鱼油的质量。方法:通过加速储藏实验,将2种鱼油样品(花生四烯酸、二十二碳六烯酸)于40℃避光储藏30d,每天监控检测其感官属性(香气)、游离脂肪酸含量、过氧化值及挥发性二级氧化产物(己醛及丙醛)的含量。以感官评价结果为判定依据,研究各理化指标与鱼油氧化程度的关系。结果:2种油脂样品中的游离脂肪酸含量在储藏过程中无明显变化,不是一个可以评价油脂货架期内氧化程度的有效指标。过氧化值的测定结果显示,此指标可以反映油脂初期氧化的趋势,但不能很好地反映油脂感官属性的变化。挥发性二级氧化产物的测定结果与油脂感官属性的变化显示了高度的一致性,能够很好地反映油脂氧化状态。结论:在不具备感官评价条件的情况下,建议同时监测鱼油中挥发性二级氧化产物(ω-6脂肪酸监测己醛;ω-3脂肪酸监测丙醛)及过氧化值的含量,以更全面有效地评价鱼油的氧化状态,更好地控制鱼油的质量。     

油炸豆制品中极性组分含量的检测研究

豆制品含有丰富的蛋白质,经高温油炸后,香气宜人,色泽金黄,但在煎炸过程中会产生极性物质。选取上海市三家企业的不同油炸豆制品,研究油炸豆制品中油脂极性组分含量。采用制备型快速柱层析法进行极性组分的检测,并对油炸豆制品中水分含量、油脂含量、油脂极性组分含量以及对应的煎炸油中极性组分含量进行同步测定。结果表明:油炸豆制品中水分含量、油脂含量及油脂极性组分含量与油炸豆制品的生产工艺有关;油炸豆制品中油脂极性组分含量与其煎炸油中极性组分含量相对应;三家企业的三种油炸豆制品中油脂极性组分含量均低于国家限定标准27%,但仍应及时对煎炸油进行净化和更新。     

金银花种子中脂溶性成分分析

以金银花种子为原料,在索氏提取仪中用乙醚提取脂溶性成分, 测定其含量,并将其分成极性和非极性两类,用GC-MS 进行分析。结果表明,忍冬种子中油脂含量为25%,极性成分有21 种化合物,非极性成分有45 种化合物。     

煎炸食物中油脂极性组分的提取及分析

以油炸花生、油条、麻花3种中式煎炸食物为研究对象,选取10种溶剂配方提取其内含油脂,基于制备型快速柱层析和高效体积排阻色谱,深入分析煎炸食物内油脂极性组分的构成比例。结果表明:在提取煎炸食物中油脂极性组分时,石油醚对油炸花生和麻花的提取结果最高,正己烷-异丙醇(体积比4∶1)对油条的提取结果最高,与石油醚的无显著性差异。在测定煎炸食物中油脂极性组分时,可选用石油醚作为提取溶剂。石油醚提取所得油炸花生油脂中极性组分含量为4.5%,主要为氧化甘油三酯单体类和甘油二酯类,油条油脂中极性组分含量为28.8%,主要为甘油三酯聚合物类,麻花油脂中极性组分含量为8.0%,主要为甘油三酯聚合物类、氧化甘油三酯单体类和甘油二酯类。     

浓香花生油中挥发性风味物质的鉴别分析

本试验对花生油中挥发性风味物质进行顶空固相微萃取,并采用强极性和弱极性色谱柱对浓香花生油中的挥发性风味物质进行测定。结合谱库检索及匹配度分析,研究了挥发性风味物质的化学成分,测定了各化合物的含量。结果表明：通过采用两种不同极性的色谱柱对花生油中挥发性气味物质的检测,能够更加全面的了解花生油中的挥发性气味物质,鉴别出不同花生油中的相同挥发性成分,使得分析的结果与真实成分更加接近,为浓香型花生油的真实性及掺伪鉴别提供技术参考。     

煎炸油脂中极性成分的色谱分析

利用LC/MS法分析油脂在180℃高温下重复使用后油脂的降解情况,及物质降解的解析过程。结果表明:随着油炸时间的增加,油中的极性成分的种类和含量有所增加,主要为羟基、羧基等化合物,尤其以羧基为主;极性组分中以分子质量较小的脂肪酸为主,其中所形成的聚合物的聚合度不高。利用硅胶柱色谱和高效体系排斥色谱对极性成分和聚合物含量的测量表明,随着油炸时间的延长,极性成分、聚合物含量均与油炸时间呈线性关系,且二者间也呈线性关系。     

油脂煎炸持续性起泡与极性化合物及聚合物的关系

油脂煎炸持续性起泡与极性化合物及聚合物的关系四川省粮科所廖泳贤校译安徽省粮科所吴正达编译持续性起泡是因羰基和羟基等氧化油脂的生成而引起的。无类井等着眼于对氧化油脂成份用标准油脂分析试验法所规定的极性化合物及聚合油脂（聚合物）进行表示，对它们在持续性起...     

油炸过程中茶多酚对油脂品质的影响

研究茶多酚在油炸过程中对油脂品质的影响。通过测定油脂的理化指标、脂肪酸组成以及挥发性风味成分,评价茶多酚对油脂品质的影响,并进一步测定油脂的总酚含量和油脂热力学性质,分析茶多酚的作用机理。结果表明,与空白对照相比,茶多酚对煎炸油理化品质的下降有显著抑制作用。同时,茶多酚能够抑制煎炸油中不饱和脂肪酸的降解以及反式脂肪酸的生成。此外,茶多酚显著抑制了油脂中挥发性醛类物质的生成。茶多酚的添加增加了油脂中酚类物质的含量,并且增加了油脂的氧化稳定性,进而对油脂在油炸过程中的品质起到保护作用。研究结果表明茶多酚在食品、化工等行业具有应用于保护煎炸油品质的潜在价值。     

Rapid determination of polar compounds in frying fats and oils using image analysis

Fats and oils were exposed to high temperature at 145°C for 80 h with frying steamed noodles, and the polar compounds were determined using a standard column chromatography and a novel image analysis method. The image was separated into polar and nonpolar component on TLC plate, and recorded with a camera. When the original image was transformed into 3 monochrome components of red, green and blue, respectively, pseudo-mass (the intensity-weighted area) ratio of image processed with a red-frame was highly correlated with real mass determined by column chromatography. The content of polar compounds for respective frying oils was calculated with the standard curves of first order regression that showed the determination coefficients of R²>0.8 (P<0.001). Consequently, it seemed that image analysis on polar compound could replace the extremely time and chemical consuming standard method for estimating the quality of frying fats and oils.     

Qualitative and quantitative characterisation of the lipid fraction of bouillon cubes

An experimental investigation was performed to characterise the fat fraction of bouillon cubes. Besides the routine analyses, the analytical methods used were: silica-gel column chromatography to separate polar compounds, high performance size-exclusion chromatography (HPSEC) for the qualitative and quantitative determination of the single classes of substances constituting the polar compounds, and gas chromatography to determine the acid composition and the trans isomers of unsaturated fatty acids. The fats blended into the bouillon preparations were highly variable and were mainly made up of refined vegetable oils that had undergone hardening, by hydrogenation in most cases. Determination of the free fatty acids and of the peroxide values yielded figures that in some cases exceeded the limits set for the commercialisation of refined vegetable oils. Compared to the routine analyses, the HPSEC analysis of the polar compounds provided a better evaluation of the level of degradation of the fat extracted from the bouillon formulations. The levels of oxidative and hydrolytic degradation were rather high, and similar to those reported for poor quality oils. Analyses of the trans isomers of oleic acid yielded particularly high values (even over 20%) and differentiated the cubes on the basis of the type of fat added.     

Quality assessment of edible vegetable oils used as liquid medium in canned tuna

An experimental investigation was conducted to assess the quality of vegetable oils used as liquid medium in preserved fish. Sixteen tuna preserves were tested, including two in extra virgin olive oil, nine in olive oil (refined olive oil plus virgin olive oil) and five in refined seed oil. Next to the traditional routine analyses prescribed by the EEC Regulation N° 2568/91 (useful for a preliminary characterisation of oils used as liquid medium), the content of trans isomers of unsaturated fatty acids was determined and the analysis of polar compounds was performed by HPSEC (high performance size-exclusion chromatography). The acid composition showed the presence of highly unsaturated fatty acids, typical of fish lipids. Trans isomers were always absent in extra virgin olive oils, whereas they were always present in olive oils and in refined seed oils. Triglyceride oligopolymers, oxidised triglycerides and diglycerides, measured by means of the HPSEC analysis of polar compounds, ranged within 0.13-1.07%, 0.51-2.36% and 0.96-4.02%, respectively. The HPSEC analysis of polar compounds and the determination of trans isomers enabled better assessment of the quality of different types of oils used as liquid medium for canned tuna.     

AUTOMATED REPORTING ON THE QUALITY OF HOPS AND HOP PRODUCTS

The quality of a hop variety or a hop product can readily be assessed by a fully automated sequence of selective extraction, fractionation and quantitative analysis. To illustrate the elegance of the method, nine hop varieties and three hop extracts were compared with respect to the content of important marker compounds in the hop oils and of the hop acids. Supercritical fluid extraction at different densities of carbon dioxide was applied to extract selectively, the hop oils and the hop acids, respectively. The hop oils were further fractionated into an apolar and a polar fraction by solid phase extraction and consecutive elution with n-hexane and ethyl acetate. Separation and identification were achieved by capillary gas chromatography coupled to mass spectrometry. Myrcene, β;-caryophyllene, α;-humulene and β;-farnesene in the apolar fraction, linalool, undecan-2-one, tridecan-2-one and humuladienone in the polar fraction were selected for quantitative evaluation of the respective hop oils. Sulphur-containing compounds were revealed by capillary gas chromatography using sulphur-selective atomic emission detection. Complete separation and quantification of all hop α;-acids and β;-acids was effected by microemulsion electrokinetic chromatography coupled to diode array detection .     

Short-Chain Fatty Acid Formation during Thermoxidation and Frying

Formation and evolution of the short-chain fatty acids originated by oxidation and remaining bound to the parent triglyceride, specifically heptanoate and octanoate, were studied during thermoxidation of palm olein, conventional sunflower oil and high-oleic sunflower oil at 180°C, as well as in real used frying oils of unknown history collected by Food Inspection Services. Fatty acids were quantified by gas–liquid chromatography following transesterification of samples and using methyl nonanoate and methyl heptadecanoate as internal standards. Alteration level was determined through analyses of polar compounds and polar fatty acids. Results showed high correlation coefficients between short-chain fatty acids and polar compounds or polar fatty acids, thus suggesting that quantification of short-chain fatty acids is a good indication of the total alteration level in used frying oils.     

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.     

Pro-oxidant action of polar triglyceride oligopolymers in edible vegetable oils

The aim of the research was to evaluate the pro-oxidant action of oxidized triglyceride oliogopolymers, a class of oxidation compounds present in refined vegetable oils. Silica gel column chromatography was used to obtain the polar compounds from a thermally oxidized oil and preparative gel permeation chromatography to separate and collect the oxidized triglyceride oligopolymers. A purified oil that was practically free of oxidation and hydrolytic degradation products, pigments and anti-oxidants was prepared in the laboratory to evaluate pro-oxidant activity without interferences. Addition of percent amounts of oxidized triglyceride oligopolymers of 0.25 to 1.0% to both the purified and unpurified oils clearly evidenced the pro-oxidant activity of this class of compounds.     

A very simple,fast, and non-destructive approach to predict the time at which edible oils submitted to high temperature reach the established limits of safety

Relationships between the time at which edible oils reach 25% in weight of polar compounds and their original composition, expressed as molar percentage of their acyl groups, were tested; the aim was to analyze the influence of oil composition on its performance at high temperature. Likewise, relationships between the composition of the oils and their original percentage in polar compounds were explored. It has been shown for the first time that a very close relationship between the percentage in weight of polar compounds of the original oils, and the time at which they reach 25% of polar compounds exits. This relationship permits the prediction, in a very simple, fast and non-destructive way, of the performance of edible oils at frying temperature from their original percentage in polar compounds, in other words from their original dielectric constant. This approach is very useful for food safety, with important technological and economic repercussions.     

拉曼光谱技术快速检测专用煎炸油极性组分

为能够快速、无损检测专用煎炸油的极性组分含量,采集不同煎炸时间下煎炸油样本的拉曼光谱图。为建立稳定性高、误差小、精度高的模型,研究不同预处理方法对模型效果的影响,建立相应的偏最小二乘回归模型以选择最优的光谱预处理方法。结果表明：标准正态变换处理后的偏最小二乘模型最优,预测均方根误差（root mean square error of prediction,RMSEP）为1.18,决定系数R2为0.940?4。其次,将标准正态变换处理后的光谱数据分别建立误差反向传播（error back propagation,BP）算法和径向基函数算法神经网络模型,通过比较稳定性以及误差大小,得出采集到的拉曼光谱经过标准正态变换处理后采用BP神经网络建立的模型效果最好,RMSEP为0.032?6,R2为0.972。该方法可以用作专用煎炸油极性组分的快速分析。     

Development of a method predicting the oxidative stability of edible oils using 2,2-diphenyl-1-picrylhydrazyl (DPPH)

The 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was used to predict the oxidative stability of edible oils. The principle of DPPH method is to measure the free radicals generated from oxidized oils directly. The absorbance of DPPH from oils before thermal oxidation decreased proportionally to the concentration of free radical scavenging compounds such as butylated hydroxytoluene (BHT). Oxidized oils with high polyunsaturated fatty acid (PUFA) contents showed high changes in DPPH absorbance or free radical formation rates than those with low PUFA. Oxidized oils with high BHT content were more stable and showed slower pattern change of DPPH absorbance from positive to negative slopes than those with low BHT content. Oxidative stability of oils could be predicted considering the initial values of DPPH absorbance, the free radical formation rates, and the oxidation period for pattern changes. The results from DPPH method on the oxidative stability of vegetable oils agreed with conventional methods such as p-anisidine value (p-AV), conjugated dienoic acids (CDA), or total polar matter (TPM).