Stability of Essential Fatty Acids and Formation of Nutritionally Undesirable Compounds in Baking and Shallow Frying

During cooking oils and fats are exposed to high temperatures that may affect the nutritional quality of foods that are prepared in this way. Concerns have been raised about the degradation of polyunsaturated fatty acids and the formation of potentially harmful compounds during deep frying, but relatively little is known about these changes in other cooking processes. In the present study sponge cakes and fried potatoes were prepared via standardised baking and shallow frying procedures by using different oils and fats (sunflower oil, rapeseed oil, various margarines or butter). The effect of cooking on the retention of two essential fatty acids (linoleic acid and α-linolenic acid) and the formation of trans fatty acids (TFA) and polymerised triacylglycerols (PTG) was evaluated by analyzing fat extracted from the cooked food. It was found that over 95 % of essential fatty acids were retained upon completion of both cooking techniques. The formation of TFA was not significant. Polymerisation was noticeable only in shallow frying, although the final levels of PTG were negligible (<1.3 %). Overall, in contrast to deep frying, oil-based media high in polyunsaturated fatty acids seem to be a good alternative for domestic cooking techniques as they increase the nutritional value of the prepared food.     

Molecular Mechanisms for the Modulation of Selected Inflammatory Markers by Dietary Rice Bran Oil in Rats Fed Partially Hydrogenated Vegetable Fat

Industrially produced partially hydrogenated vegetable fat (PHVF) contains trans fatty acids (TFA) mostly comprising elaidic acid (EA, 18:1?9t). Though, the harmful effects of TFA on health have been repeatedly publicized, the fat containing TFA have been continued to be used as a cooking medium in many regions of the world. The adverse effects of PHVF on oxidative stress and inflammatory markers and the possible ameliorative action of rice bran oil (RBO) on these markers were evaluated. Weaning rats were fed a AIN‐93 purified diet supplemented with the following lipids: groundnut oil (GNO, 10 wt%), PHVF (10 wt%), RBO (10 wt%), PHVF blended with RBO at 2.5, 5.0 and 7.5 wt% levels. The final concentration of the lipids in the diet was maintained at 10 wt%. Rats were fed these diets for 60 days. They were sacrificed and analyzed for oxidative stress and inflammatory markers. The rats fed PHVF showed lower levels of lipid peroxidation and hepatic antioxidant enzymes. The rats fed PHVF‐containing diets showed enhanced levels of interleukin‐1β, C‐reactive proteins and also showed enhanced levels of paw inflammation when injected with carrageenan as compared to rats given GNO, RBO or PHVF blended with incremental amounts of RBO. The macrophages from rats fed diet containing PHVF showed up‐regulation in the expressions of cytosolic phospholipase A₂ (cPLA₂), nuclear factor‐κB p65, toll like receptor (TLR)‐2, TLR‐4 and down‐regulation in the expressions of peroxisome proliferator activated receptor gamma (PPAR)γ, adiponectin receptor (AdipoR)‐1 and AdipoR‐2 when compared to rats fed diet containing GNO, RBO and PHVF blended with RBO. It was concluded that dietary PHVF enhance pro‐inflammatory markers which can be reduced by judiciously blending PHVF with RBO.     

负载型钛催化剂催化异戊二烯溶液聚合动力学

研究了TiCI4/MgCI2-AI(i-Bu)3催化体系在加氢汽油中催化异戊二烯聚合的动力学行为。考察了影响聚合速率的各种因素,测定了催化剂利用率、活性中心浓度、链增长速率常数及增长链平均寿期等动力学参数。在铝－钛摩尔比为20－50的范围内,聚合速率对单体浓度和主催化剂浓度均呈一级关系,而对烷基铝浓度呈零级关系。     

跨大气层飞行器爬升段飞行仿真研究

跨大气层飞行器在爬升过程中飞行参数及质量特性变化剧烈,因而飞行器的操纵稳定特性也相应迅速变化。各种干扰因素的影响对飞行控制系统设计起着不可忽视的作用。对此进行了分析研究,仿真结果表明分离时刻载机与飞行器之间的干扰气流影响飞行安全;点火时机合理地选择、缓和拉起爬升动作对爬升初始阶段飞行参数稳定合理地变化也很重要;无动力爬升段结束后姿态控制对稳定飞行器横侧特性起着关键的作用。爬升过程中出现发动机停车状况,只要控制合理,也可以将飞行器安全着陆。     

结型场效应晶体管的主要参数的探讨

本文讨论了结型场效应晶体管的几个主要参数 ,找出影响它们的主要因素     

Elaidic acid in rat liver identified by gas chromatography and nuclear magnetic resonance spectroscopy

Fatty acid composition has been commonly determined by gas chromatography (GC). In the most commonly used methods, the lipids must be converted into methyl esters or other derivatives of the fatty acids before being analyzed by GC. Nuclear magnetic resonance (NMR) spectroscopy has become one of the most promising methods to determine organic structures, providing useful data for analyzing the fatty acid composition of edible vegetable oils. The major advantage of NMR is that identification of each fatty acid is carried out by evaluation of particular signals. We report in this work the fatty acid profile of rat liver after consumption of diets containing different concentrations of partially hydrogenated vegetable fat. The fatty acid composition was identified by GC, and trans fatty acids were also identified by ¹³C NMR spectroscopy. The results obtained by the ¹³C NMR method were close enough to those obtained by conventional GC.     

轿车用地毯刀具激光热处理工艺研究

研究用CO2激光器对切割地毯刀的刃口进行激光相变硬化处理,选择最佳工艺参数,达到刃口最佳的金相组织,硬度及淬火深度等技术条件.     

Three Hen Strains Fed Photoisomerized <Emphasis Type="Italic">trans,trans</Emphasis> CLA-Rich Soy Oil Exhibit Different Yolk Accumulation Rates and Source-Specific Isomer Deposition

Most CLA chicken feeding trials used cis,trans (c,t) and trans,cis (t,c) CLA isomers to produce CLA‐rich eggs, while reports of trans,trans (t,t) CLA enrichment in egg yolks are limited. The CLA yolk fatty acid profile changes and the 10–12 days of feeding needed for maximum CLA are well documented, but there is no information describing CLA accumulation during initial feed administration. In addition, no information on CLA accumulation rates in different hen strains is available. The aim of this study was to determine a mathematical model that described yolk CLA accumulation and depletion in three hen strains by using t,t CLA‐rich soybean oil produced by photoisomerization. Diets of 30‐week Leghorns, broilers, and jungle fowl were supplemented with 15 % CLA‐rich soy oil for 16 days, and eggs were collected for 32 days. Yolk fatty acid profiles were measured by GC‐FID. CLA accumulation and depletion was modeled by both quadratic and piecewise regression analysis. A strong quadratic model was proposed, but it was not as effective as piecewise regression in describing CLA accumulation and depletion. Broiler hen eggs contained the greatest concentration of CLA at 3.2 mol/100 g egg yolk, then jungle fowl at 2.9 mol CLA, and Leghorns at 2.3 mol CLA. The t,t CLA isomer levels remained at 55 % of total yolk CLA during CLA feeding. However, t‐10,c‐12 (t,c) CLA concentration increased slightly during CLA accumulation and was significantly greater than c‐9,t‐11 CLA. Jungle fowl had the smallest increase in yolk saturated fat with CLA yolk accumulation.