The hydrogenation of triglycerides using supported alloy catalysts. I. Silica-supported Ni—Ag catalysts

Silica-supported Ni-Ag catalysts with a loading of 2·1·0.6% (w/w) total metal have been prepared using the precursors nickel dimethylglyoxime and silver nitrate by means of a simple impregnation method. The resulting catalysts were activated by calcination at 260°C in air, followed by hydrogen reduction at 450°C. They were then employed for soyabean oil hydrogenation at 1 bar H2 pressure and 160°C in a stirred batch reactor. Characterisation of the catalysts using temperature-programmed reduction and electron microscopy indicated that alloying of nickel and silver had occurred, but metal particle composition, for a given overall composition, varied with metal particle size and smaller metal particles were nickel rich. The hydrogenation activity and selectivity measurements revealed that the catalysts were more active and selective than a commercial nickel catalyst. Furthermore, the specific activities of the alloy catalysts were a maximum for alloys in the range 70–90 at. % Ni. However, the supported alloy catalysts also gave rise to greater trans isomerisation than the commercial catalyst. This is attributed to hydrogen deficiency caused by large triglyceride molecules blocking hydrogen chemisorption on small nickel particles (10–50 Å in diameter), leading to enhanced cis-trans isomerisation.     

Supplementation with Docosahexaenoic Acid and Vitamin E Improves Hepatic Triglyceride Accumulation Induced by High-Fat Diet in Mice

The study aims to investigate the effect of combined supplementation with docosahexaenoic acid (C22:6 n-3, DHA) and vitamin E (VE) on the oxidative stress and liver triglycerides (TG) accumulation induced by high-fat diet (HFD) in mice. C57BL/6J mice are fed either a control diet or an HFD for 8 weeks. Animals are supplemented with DHA, VE, or DHA + VE, respectively. Supplementation with DHA alone shows significant improvement in oxidative stress and hepatic steatosis in mice. Supplementation with DHA significantly reduces the liver TG and total cholesterol contents, and the alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, compared with the HFD. Supplementation with DHA also significantly decreases the mRNA expression level of sterol regulatory element-binding protein 1C. However, supplementation with VE alone does not show improvement in oxidative stress and hepatic steatosis. DHA + VE supply obtains a superior effect in alleviation of hepatic steatosis than DHA supplementation alone in mice fed by HFD. The efficacy of DHA potentiated by VE can be due to that VE enhances the effect of DHA in decrease of ALT and AST levels and increase of antioxidant enzyme activity and glutathione level in mice fed by HFD. Practical Applications: Supplementation with DHA significantly improves the oxidative stress and hepatic steatosis induced by HFD in mice. The efficacy of DHA in the alleviation of hepatic steatosis induced by HFD is potentiated by VE. These findings may provide a rational basis for the use of DHA and VE co-supplementation in patients with liver steatosis.     

Milk fat fractionation today: A review

Although anhydrous milk fat (AMF) has excellent properties, its variable physicochemical properties and its lack of functionality restrict its uses in the food industry. A technology involving dry fractionation of AMF has been developed, and its attributes include selectivity, reliability and general application. Combining two simple and reliable technologies,i.e., multi-step fractionation and blending, it is possible to overcome functionality problems and the seasonal variations of AMF. Lecture presented at the joint meeting of the International Society for Fat Research and the American Oil Chemists’ Society in Toronto, May 10, 1992.     

Polymorphic stability of some shortenings as influenced by the fatty acid and glyceride composition of the solid phase

A number of North American vegetable and animal fat shortenings, which had been analyzed previously for their physical and textural characteristics, were analyzed also for their chemical composition. The fatty acid and triglyceride composition of the solids were calculated by analyzing the composition of the original product and the liquid phase, and by determination of the solid fat content (SFC) of the fat. The solids were also isolated by isopropanol (IP) separation, and the high melting glycerides (HMG) by acetone crystallization at 15°C. There was not much difference in total saturates andtrans content between vegetable and animal fat shortenings. Changing formulations from soy-palm to soy-cottonseed does not change the total saturates plustrans content. The solids of the vegetable shortenings in the β form contained about 20% of 16:0, those in the β′ form 30% or more. The animal fat shortenings were mainly in the β form, their solids contained 30% or more of 16:0. C54 triglyceride content of the solids of β vegetable shortenings (calculated and IP-separated) was >45%, that of all animal fats was <25%. Solids of animal fat shortenings contain high levels of C52. The C54 triglycerides are β-tending and should be kept low in vegetable shortening. In the HMG the C54 should not exceed 30%. This can only be achieved by incorporation of a β′ hard fat, preferably palm hard fat. Animal fat, especially lard, crystallizes in the β form because the palmitic acid in the glyceride molecule is located in the 2-position, whereas those of vegetable fats are in the 1- and 3-position.     

Lipid adsorption on commercial silica hydrogels from hexane and changes in triglyceride complexes with time

The structures of and lipid complexes with two commercial silica hydrogels (Trisyl and Sorbsil 40), which contain about 60% moisture, were examined by diffuse reflectance Fourier transform infrared spectroscopy. The spectra suggested that Trisyl contained less moisture than Sorbsil 40. However, the silanol groups of Sorbsil 40 were more active in adsorbing oleic acid, triglyceride, and phosphatidylcholine (PC) from hexane than those of Trisyl. Both adsorbents strongly bound PC through the PC carbonyl and phosphate groups. Lipid adsorption from hexane solution by Trisyl depended solely on trapped moisture, while Sorbsil 40 used moisture and silanol groups on the silica surface. Spectra of triglyceride-silica hydrogel complexes, obtained 24 and 72 h after obtaining the initial spectra, showed that Sorbsil 40 adsorption was by Van der Waals forces, but the triglyceride reoriented over time with an increase in hydrogen bonding. In contrast, Trisyl initially adosorbed triglyceride by hydrogen bonding which was stable for at least 72 h.     

核桃油对小鼠血脂及胆固醇的影响

采用不同剂量的核桃油对小鼠进行试验，研究其对血脂水平的影响。结果表明，核桃油试验组小鼠的血清甘油三脂（TG）、总胆固醇（TC）和动脉硬化指数（AI）均不同程度低于高脂模型组（P〈0.05或P〈0.01），而高密度脂蛋白（HDL-C）却显著（P〈0．05）高于高脂模型组，表明，核桃油确有显著降低血脂和降低动脉硬化危险性的作用。     

发芽糙米米糠降血脂功效研究

通过研究发芽糙米米糠(GBRB)对高脂膳食大鼠血脂代谢的影响,研究了GBRB的降血脂功效。将50只SD雄性大鼠按体重随机均分为5组,空白对照组饲喂基础饲料,高脂对照组饲喂高脂饲料,高、中、低剂量组分别饲喂添加了30%、20%、10%GBRB的高脂饲料,喂养83 d,结束后,从小鼠股动脉取血,测血清中总胆固醇(TC)、甘油三酯(TG)、高密度脂蛋白胆固醇(HDL-C)和低密度脂蛋白胆固醇(LDL-C)浓度,并计算体脂率。结果表明:食用GBRB对大鼠的体脂率、生长发育没有明显影响;饲喂GBRB的高、中、低剂量组大鼠血清中TC和LDL-C浓度都显著低于高脂对照组(P0.05);高剂量组大鼠的TG浓度显著低于高脂对照组(P0.05),而中、低剂量GBRB没能抑制食用高脂饲料产生的高TG浓度。GBRB的摄入能显著降低食用高脂饲料大鼠的血清TC、TG以及LDL-C水平,显示出GBRB的降血脂功效。     

茶多酚肉碱复方制剂降血脂的实验研究

探讨茶多酚肉碱复方制剂对高脂血症模型大鼠血脂水平的影响。采用高脂饲料喂养SD大鼠建立预防性高脂血症模型,将实验大鼠分成正常对照组、模型对照组、低剂量组、中剂量组和高剂量组。连续灌胃给药45 d,观察茶多酚肉碱复方制剂对高脂血症大鼠血清甘油三酯(TG)、总胆固醇(TC)、高密度脂蛋白胆固醇(HDL-C)的影响。结果表明,与正常对照组比较,高脂饲料连续喂养45 d后,模型对照组大鼠血清TG和TC显著升高(P<0.01);与模型对照组比较,给药45 d后,1)低剂量组大鼠血清TG未见显著性降低(P>0.05),中剂量组和高剂量组血清TG极显著地降低(P<0.01);2)低剂量组大鼠血清TC显著降低(P<0.05),中高剂量组大鼠血清TC极显著降低(P<0.01);3)各剂量组大鼠血清HDL-C无显著性差异。茶多酚肉碱复方制剂具有辅助降血脂的作用。     

中链甘油三酯/玉米醇溶蛋白核壳结构微胶囊载体的构建及表征

以中链甘油三酯（medium-chain triglyceride,MCT）为油相内核,以玉米醇溶蛋白（Zein）为外壳主要成分,低剪切条件下反溶剂法制备大粒径核壳结构的MCT/Zein微胶囊微米载体。通过考察微胶囊载体的宏观形态、微观形态及粒径分布,优化得到微胶囊载体的最佳制备工艺为质量分数0.5%的阿拉伯胶（gum arabic,GA）作为乳化剂、乳化速率800?r/min、Zein沉淀溶液为“30?mL水＋100?mL?GA溶液”、Zein沉淀溶液加入速率6?mL/min,并采用扫描电子显微镜、激光共聚焦显微镜、激光粒度分析仪表征冻干MCT/Zein微胶囊载体的结构特征和粒径特性,结果表明该法制备的微胶囊载体具有典型的核壳结构,粒径均一、稳定性良好。本实验建立MCT/Zein核壳结构微胶囊的反溶剂制备法,该法简单易行,适用于多种油溶性活性组分的包埋和保护研究。