中链甘油三酯在动物体内的代谢及应用研究

中链甘油三酯(MCT)是由6～12个碳原子的脂肪酸组成的甘油三酯,它们在体内具有消化、吸收、转运、代谢快的特点.MCT能迅速提供能量,但同时也产生大量的酮体,进入血液,使血液中酮体水平升高.MCT用于仔猪的饲养效果不一致,但用于母猪和鸡的饲养中有明显的正效果.如何消除MCT在肝细胞内氧化产生的大量酮体带来的不利影响,以及寻找一种简便的饲喂方法,都有待今后进一步的研究.     

MCT重构脂质及其在临床营养中的应用

MCT重构脂质是一种改性的甘油三酯,其甘油结构骨架特定位置上包含中碳链脂肪酸、长碳链脂肪酸和特殊脂肪酸,有独特的生理功能和营养价值.MCT重构脂质可以通过生物技术、化学工程和酶工程进行生产.MCT重构脂质在临床营养品中有广泛的应用前景.     

Effects of methionine addition in soya bean or casein diets supplemented with carrageenan on weight gain and blood lipids in rats

Seven groups of 12 Wistar rats were fed during two experimental periods. During the first period of 4 weeks, rats were fed diets containing 100 g kg^?1 of casein or soya-protein. In the case of casein, diets contained casein, casein + 3.5 g kg^?1 of sodium carrageenan and casein + 3.5 g kg^?1 of sodium carrageenan + 1 g kg^?1 of DL-methionine. In the case of soya protein, diets contained soya protein, soya protein + 6.2 g kg^?1 of sodium carrageenan, soya protein + 6.2 g kg^?1 of sodium carrageenan + 1 g kg^?1 of DL-methionine and soya protein + 1 g kg^?1 of DL-methionine. During the second period of 8 weeks, all rats were fed laboratory pellets containing 170 g kg^?1 of standard protein mixture. Methionine supplementation of heated soya bean meal containing carrageenan prevented the decrease of growth observed with unsupplemented diet. Methionine supplementation of casein improved protein efficiency ratio and had no effect on long-term growth of rats because carrageenan did not cause growth retardation. At the end of second period, carrageenan ingested during the first period had no effect on plasma cholesterol. When carrageenans added to casein were ingested during the first period, plasma triglycerides were significantly lower after the second period. It would seem that carrageenans induce protein malnutrition by a lack of methionine when they are present in low protein diets with low methionine content, and that a sufficient content of methionine in diets prevents the carrageenan effect.     

Sterolic composition and triacylglycerols of Oueslati virgin olive oil: comparison among different geographic areas

The main triglycerides (TG) identified in the Oueslati virgin olive oil were 1,2,3‐trioleylglycerol (OOO), 2,3‐dioleyl‐1‐palmitoylglycerol (POO) and 2,3‐dioleyl‐1‐linoleylglycerol (LOO) representing more than 80% of the total area of peaks in the chromatogram. Other minor triacylglycerols were 2,3‐dioleyl‐1‐stearoylglycerol (SOO), 2‐oleyl‐3‐palmitoyl‐1‐stearoylglycerol (SOP), 1‐linolenoyl‐2‐oleyl‐3‐palmitoylglycerol (LnOP), 1, 2‐dilinoleyl‐3‐palmitoylglycerol (LLP), 1, 3‐dioleyl‐2‐linolenoylglycerol (OLnO), 1‐linolenoyl‐2‐linoleyl‐3‐oleylglycerol (LnLO) and 1,2,3‐trilinoleylglycerol (LLL). The sterol profile of Tunisian virgin olive oils produced from Oueslati cultivar was established by gas chromatography using a flame ionisation detector (GC‐MS). More than 10 compounds were identified and characterised. As expected for virgin olive oil, the main sterols found in all Oueslati olive oils were β‐sitosterol, Δ5‐avenasterol, campesterol and stigmasterol. Cholesterol, 24‐methylenecholesterol, clerosterol, campestanol, sitostanol, Δ7‐stigmastenol, Δ5, 24‐stigmastadienol and Δ7‐avenasterol were also found in all samples, but in lower amounts. Most of these compounds are significantly affected by the geographical origin of the oil. Besides the sterol components, two triterpene dialcohols, erythrodiol and uvaol, were also detected.     

Effects of feedingCuphea oil to three generations of CBA/2 and C57B1/6 mice

Three generations of CBA/2 and C57B1/6 mice were reared on semipurified diets containing either 17.2% beef tallow and 3.5% corn oil or 8.6% beef tallow, 8.6% crudeCuphea oil and 3.5% corn oil. TheCuphea oil contained 76% decanoic acid; therefore, health effects of long-term feeding of moderate amounts of medium-chain triacylglycerols were evaluated. The reproductive performance of both strains of mice varied little with diet but, compared with the F1 generation, survival of F2 and F3 pups was diminished. At several time points during 13 wk,Cuphea feeding suppressed body weights and food intakes of males of three generations of both strains. But during long-term feeding of males (5–12 mon),Cuphea did not suppress body weight or food intake. Mice of both strains developed fatty livers. Mice of the CBA/2 strain had hepatic nodular hyperplasia.Cuphea oil feeding caused no specific pathological changes. Although medium-chain triacylglycerols have been reported to be hypocholesterolemic, the substitution ofCuphea for half of the dietary beef tallow did not suppress serum cholesterol concentrations in males aged 4–13 mon. The effects of long-term substitution of medium-chain triacylglycerols for beef tallow do not differ from feeding the beef tallow diet. Long-term and multigenerational feeding of crudeCuphea oil does not cause any specific toxic effect in mice.     

W/O型中链脂肪酸微乳的制备及其性质的测定

以中链脂肪酸(MCFA)为原料,用HLB值法制备的W/O型中链脂肪酸(MCFA)微乳,可提高油溶性药物或营养物的溶解性和生物利用率.考察了滴定方法,确定用蒸馏水滴定MCFA、表面活性剂和助表面活性剂三组分的混合物为最佳;通过乳化效率、伪三元相图和反应过程中的现象,得到制备W/O型MCFA微乳的最适HLB值为4.7,最佳表面活性剂为单独使用司盘60,最佳助表面活性剂为异丙醇,最优配方为m司盘60:m异丙醇:mMCFA:m蒸馏水=1:2:3:0.5.考察优化配方的理化性质,初步稳定性良好,表面张力可达到25.50 mN/cm,粘度50.06 cP,电导率3.31 μs/cm,粒径20.1±3.3 nm,zeta电位-6.23 mV.     

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.     

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.     

The influence of food emulsifiers on fat and sugar dispersions in oils. I. Adsorption,sedimentation

The adsorption isotherms of several emulsifiers to fat and sugar crystals dispersed in oils have been determined. Further, the influence of the emulsifiers on the interactions between the crystals has been estimated in sedimentation experiments, where an increased sediment volume due to adsorption corresponds to an increased adhesion between the crystals andvice versa. Most of the emulsifiers examined adsorb weakly to fat crystals and form tight monolayers, resulting in increased adhesion between the crystals at high concentrations. On the other hand, loosely packed layers are formed at low concentrations, and a decreased adhesion is observed. Unsaturated monoglycerides and phospholipids cause a decrease in adhesion for all concentrations examined. The emulsifiers adsorb more strongly to sugar crystals than to fat crystals and form tightly packed monolayers with hydrocarbon chains directed to the oil. The crystals are then stabilized sterically—the adhesion between them is weaker and the sediments are more compact. At low concentrations, the opposite behavior often occurs. Monoglycerides interact in a specific way with sugar and cause increased adhesion between the crystals for all concentrations examined. Phospholipids reduce the adhesion between sugar crystals, resulting in much denser sediments. Saturated monoglycerides in amounts over the solubility limit tend to precipitate as a network between fat or sugar crystals, which causes bulky sediments and results in better stability against oiling out.     

Determination of milk fat in chocolates by gas-liquid chromatography of triglycerides and fatty acids

The combination of two routine methods is proposed to determine the content of milk fat (MF) in chocolates, which is applicable even in the presence of lauric fats or others. The content of MF is obtained from the sum of C₄₀, C₄₂, and C₄₄ medium-chain triglycerides, determined by capillary gas-liquid chromatography (GLC). A new method, based on methyl esters of lauric acid and on minor acids situated between myristic and palmitic, is proposed. It enables detection and estimation of potential lauric fats, as well as the determination of the actual content of MF. The influence of other vegetable and animal fats is discussed. We analyzed 45 MF samples extracted from industrial milk powders and from pure or fractionated MF for chocolate manufacturing or pastry by GLC of triglycerides. We also analyzed by capillary GLC the methyl esters from 22 of those fats. Mixtures of these 22 MF samples with a cocoa butter also were used for chromatographic analyses of methyl esters and triglyceride. Results from the various analytical methods have been presented.