Molecular interaction of triglycerides on a modified silica (Kieselguhr G): a thermodynamical approach by surface tension calculation and DSC measurements

Peanut and linseed oils were drained vertically on thin layers, made of either native, hydrophilic or hydrophobic Kieselguhr G (silica), in order to get information on the interactions that may occur between triglycerides (TGs) and the filtering material. Except for hydrophobic silica, a partition of the TGs as function of the distance run was observed. Highly‐unsaturated TGs were concentrated at the starting point of the running distance and distances between fractions grew larger with the hydrophobicity of the silica. Surface tension components of silica were calculated: whereas Van Oss' method could not discriminate between hydrophilic and hydrophobic Kieselguhr G, Chibowski's method differentiated both compounds by a higher electron donor component (γ) in hydrophilic silica. Calorimetric studies of pure TGs interacting with Kieselguhr G discriminated between saturated TGs exhibiting a lower melting temperature as they interacted with the support, and unsaturated TG having a higher melting temperature. It is concluded that electron densities are involved in interactions occurring between TGs and silica, i.e. high unsaturation number and high γ component.     

复合型海藻膳食纤维功能食品的降血脂作用

研究以海藻膳食纤维为主,传统降脂中药山楂、绞股蓝、泽泻为辅的功能食品的降血脂作用。参考卫生部保健食品辅助降血脂功能评价方法,以高脂饲料建立高脂血症小鼠模型,灌胃给予含不同成分的复合物（海藻膳食纤维高、中、低剂量组,复合物Ⅰ、Ⅱ、Ⅲ组,辛伐他汀组,正常对照组和模型组灌胃生理盐水）。4 周后,测定血清总胆固醇（total cholesterol,TC）、甘油三酯（triglyceride,TG）、高密度脂蛋白胆固醇（high densitylipoprotein cholesterol,HDL-C）以及低密度脂蛋白胆固醇（low density lipoprotein cholesterin,LDL-C）水平,计算肝脏系数,苏木精-伊红染色观察肝脏脂肪变性程度。结果表明：海藻膳食纤维能显著降低高脂血症小鼠血清TC、TG及LDL-C水平,升高HDL-C水平;且加入少量药食同源的中药（绞股蓝提取物和泽泻提取物）后的复合型海藻膳食纤维能使高脂小鼠血脂水平更接近正常值。说明复合型海藻膳食纤维功能食品有较好的降血脂作用。     

分子蒸馏分离提纯甘二酯中试工艺研究

研究了中试分子蒸馏分离提纯甘二酯的工艺方法。棕榈油在一定的条件下经过中试分子蒸馏设备蒸馏,得到重相与轻相。轻相主要是甘二酯,重相主要是甘三酯。通过进料量、温度及刮膜转速的控制可以得到纯度70%以上的甘二酯。研究结果表明,在温度220℃、压力0.01 Pa、进料量10 L/h、蒸发器转速200 r/min的条件下,通过脱气,薄膜蒸发与短程蒸馏可以得到纯度较高的甘二酯。用棒状薄层色谱―氢火焰离子化检测器法(TLC–FID)与反相高效液相色谱–蒸发光散射检测法(RP–HPLC–ELSD)分别分析测定了棕榈油以及轻相、重相中甘油酯的含量,并进行了对比;用气相色谱分析了棕榈油以及轻相、重相脂肪酸组成。     

芝麻油掺棕榈油鉴别方法的研究

以4种不同熔点棕榈油与4种芝麻油所配制的128个掺伪芝麻油样品为原料,分别采用全样脂肪酸组成分析法、Sn-2位脂肪酸组成分析法和甘三酯结构分析法对芝麻油中掺棕榈油的鉴别方法进行了研究。结果表明:在全样脂肪酸组成分析法中,当以棕榈酸为标准与芝麻油纯样和国标数据比较时,检出限分别为5%和15%。在Sn-2位脂肪酸组成分析法和甘三酯结构分析法中,当与芝麻油纯样数据比较,分别以亚油酸与棕榈酸含量比值(18:2/16:0)和β-POO(Sn-1-棕榈酸-2,3-二油酸甘油酯)含量为判断标准时,检出限分别为20%和12%。综合这3种方法的检出限高低及分析操作难易程度,初步得出结论:在芝麻油掺棕榈油的鉴别方法中,全样脂肪酸组成分析法是最好的鉴别方法,其余2种方法一般不优先采用,但可作为对上述方法的验证与补充。     

Computer modeling of packing arrangements and transitions in saturated-cis-unsaturated mixed triglycerides

Conformational analysis of modeledcis-unsaturated chains in triunsaturated and symmetrical monounsaturated triglycerides has identified pseudo-linear chain orientations that allow lower molecular mechanical energies than are possible with conventionalcis-chains. Energy plots recorded during bond rotations near the double bond show that energy barriers between linear and normalcis-configurations are often less than 5 Kcal/mol. Pseudo-linear orientations, which allow compatible side-by-side packing of saturated and unsaturated chains in double-chainlength mixed triglycerides, also provide a route for efficient transformation between double-chainlength and triple-chainlength configurations in solid polymorphic triglycerides.     

Behavior of diglycerides and conjugated fatty acid triglycerides in reverse-phase chromatography

The behavior of conjugated fatty acid triglycerides and diglycerides on reverse-phase chromatography was studied. Trieleostearin is a geometric isomer of trilinolenin. The conjugated double bond arrangement in trieleostearin enhances its hydrophobic interaction with the stationary phase and causes it to be eluted later than trilinolenin. In separation of “critical pairs” of tri- and diglycerides, diglycerides elute later than triglycerides due to the longer fatty acid constituent. Position isomers of 1,2- and 1,3-diglycerides can be separated by reverse-phase high-performance liquid chromatography.     

Triacylglycerols responsible for the onset of nucleation during clouding of palm olein

This paper discusses the results of an investigation to identify triacylglycerols that induce clouding of refined bleached deodorized (RBD) palm olein, which occurred within 24 h after fractionation. The experiments were conducted in a jacketed glass vessel in which the liquid sample was cooled from 70 to 23°C at a predetermined rate. Clouding began at around 28.5°C. The presence of three different types of saturated triglycerides, namely tripalmitin, dipalmitoyl-myristoylglycerol and dipalmitoyl-stearoyl-rac-glycerol, is critical in the formation of nuclei and thus clouding of the RBD palm olein. This conclusion is based on the significant increase in the relative concentration of these components in the nuclei as compared to the mother oil.     

Regressional models that describe oil absolute viscosity

Equations that describe the temperature dependence (298–338°K) of absolute viscosity (μ) of 21 oils and oil-liquid fat mixtures were obtained based on two different approaches. Fitting each particular viscosity profile to a quadratic extension of the Andrade equation provided the best predictive models (R²>0.96). However, the coefficients associated with temperature effect did not have a physical-chemical meaning. In contrast, the multiple variable regressional approach fitted, in just one equation, the μ of all 21 oil systems (R²≈0.93). This equation included terms associated with structural parameters of acylglycerides, namely the degree of unsaturation (i.e., iodine value) and chainlength (i.e., saponification value) of the fatty acids. The models described effects of thecis double bonds and fatty acid chainlength on the acylglycerides’ interactions that determine both the μ of the system and its capability to crystallize. Therefore, multiple variable regressional analysis might be an excellent tool to better understand the quantitative structure-functional property relationships in lipids systems.     

Characterization of oils of hazelnuts from Asturias,Spain

Nine varieties of virgin hazelnut oil from different autochthonous cultivars from distinct locations in Asturias (Spain) were obtained by extraction under a pressure of 280 kg/cm² at a temperature of 45 °C. The extracted oils were separated and filtered. The overall composition (percentages of husk, oil and moisture) of unhusked seeds was determined as well as moisture, ash, total sulfur and heat power of the husks for their possible use as biomass. Recovery of the oil extraction procedure for its application to the production of extra virgin edible hazelnut oil was studied. Fatty acid, tocopherol and sterol compositions as determined by capillary column gas chromatography and triglyceride compositions as determined by high performance liquid chromatography are reported in this study. All values were compared with a Turkish and a French hazelnut oil, with solvent‐extracted hazelnut oil and with a 75/25 blend. A cluster analysis was performed as a criterion to differentiate the different hazelnut oils as groups.     

Formation of short‐chain glycerol‐bound oxidation products and oxidised monomeric triacylglycerols during deep‐frying and occurrence in used frying fats

Heating fats and oils at high temperature in the presence of air, a common procedure in culinary practices such as frying, results in a complex mixture of oxidation products. These compounds may impair the nutritional value of the food. Among them, there is a growing interest in the group of oxidised triacylglycerol monomers because of their high absorbability. The main structures in this group include triacylglycerols (TG) containing short‐chain acyl groups formed by homolytic β‐scission of the alkoxy radicals coming from allylic hydroperoxides. In addition there are TG containing oxidised fatty acyl groups of molecular weight similar to that of their parent TG, i.e., epoxy, keto and hydroxy fatty acyl groups. In this review, the main routes of formation of oxidised TG monomers are detailed. Also, the most relevant advances in the analysis of intact TG molecules by high‐performance liquid chromatography coupled with mass spectrometry are discussed. Special attention is paid to the present analytical possibilities for accurate quantification of the most important oxidised compounds formed at high temperature. Both the need to convert fats and oils into simpler derivatives, thus concentrating the compounds bearing the oxidised structure, and the methylation procedure selected to avoid artefact formation are justified. Typical concentrations of short‐chain fatty acids, short‐chain aldehydic acids, short‐chain diacids, and monoepoxy fatty acids, ketoacids and hydroxyacids in frying oils from restaurants and fried‐food outlets, with polar lipids levels at the limit of rejection for human consumption, are given.