结构脂质的合成及应用

结构脂质(SLs)是一类具有营养性和功能性的甘油三酯。对结构脂质的合成方法(酯交换法、酸解法和二步法)和几种常见结构脂质(中碳链甘油三酯、中长碳链甘油三酯、类可可脂、人造母乳、磷酸甘油酯、酚酸甘油酯)的应用进行了综述。     

Dietary Structured Lipids and Phytosteryl Esters: Blood Lipids and Cardiovascular Status in Spontaneously Hypertensive Rats

This study examined the dietary effects of enzymatically modified sesame oil with caprylic acid (structured lipids, SL) and phytosteryl esters (PE) on blood lipid profiles and cardiovascular parameters of spontaneously hypertensive rats (SHR) fed high-fat and high-cholesterol (HFHC) diets. The dietary groups were: normal diet (control), sesame oil (SO), SL, SO fortified with PE (SOP), and SL fortified with PE (SLP). After 9 weeks of feeding, the body weights, liver weights, and liver weight/body weight ratios in all HFHC-fed groups were higher than controls. Plasma total and LDL cholesterol levels in all HFHC-fed groups were similar to one another but higher than those in controls. Plasma HDL cholesterol levels in rats fed SOP and SLP were higher than those in controls or rats fed SO and SL. Plasma HDL/total cholesterol ratios in rats fed SOP and SLP were similar to those in controls and were higher than those in rats fed SO and SL. There was no difference in plasma lipid profiles between rats fed SO and SL. Arterial blood pressures (BP) in conscious HFHC-fed rats were similar to those in controls whereas heart rates (HR) in all HFHC-fed groups were similar to one another but were higher than that in controls. These findings demonstrate that (1) the dietary effects of SL on plasma lipid profiles and resting BP and HR are similar to those of SO, (2) PE had positive effects on plasma lipid profiles, and (3) 9-week intake of SL and PE did not have pronounced effects on resting BP but induced tachycardia in SHR.     

Biotechnological and Novel Approaches for Designing Structured Lipids Intended for Infant Nutrition

Human milk fat (HMF) is a perfect nutritional source that includes all the required ingredients which are necessary for the growth of infants up to 6 months. Although its composition may differ among mothers or during lactation stage, its unique triacylglycerol (TAG) structure remains constant which is characterized by the presence of palmitic acid (PA) at the sn‐2 position. Previous reports provided convincing information of higher PA and calcium absorption and efficient use of dietary energy when at this specific position in the TAG moiety than when PA is at the sn‐1,3 positions. During the design of structured lipids (SLs) intended for infant nutrition, this unique property is taken into consideration. Human milk fat substitutes (HMFS) enriched with important fatty acids such as omega‐3 and omega‐6 fatty acids are intended to better mimic the functions of HMF as well as provide associated health benefits. The use of microencapsulation technology and novel technologies such as ultrasound technology in conjunction with SL production and enzyme‐catalyzed reactions are evolving and ongoing issues in infant formula production. Therefore, further studies should be directed towards new process improvements in order to increase the functional properties and oxidative stabilities of HMFS. Novel technologies in lipid biotechnology related to HMFS preparation should also be explored.     

相平衡理论在样品分析中的应用

油气处理的过程,即是改变流体的压力或温度,使流体中的各种组分在气液两相之间发生物质转换,从而达到气液分离或组分精馏的目的。所以流体组分的准确性对工艺流程设计至关重要。本文利用相平衡理论对油气田现场取样的油品进行分析判断,并对取样过程提出一些建议。     

Characterization and Oxidative Stability of Structured Lipids: Infant Milk Fat Analog

Structured lipids (SLs) for infant milk formulation were produced by enzymatic interesterification of tripalmitin with vegetable oil blends and fish oil. The SLs were characterized by fatty acid content and structure, melting profiles, oxidative stability index, free fatty acid (FFA) concentration, and tocopherol content. Oxidative stability was studied using accelerated methods by quantifying FFA, peroxides (peroxide value) and aldehydes (p-anisidine value) production. Total oxidation (TOTOX value) was calculated as 2 × (peroxide value) + (p-anisidine value). The structured lipids after purification by distillation and addition of antioxidants had melting profiles, oxidative stability index, and initial FFA concentration that were similar to that of the starting oil blends, while the fatty acid composition and structure of the SLs were similar to that of human milk fat. Oxidative stability of the SLs was improved with tocopherol addition as antioxidants and was comparable to that of the vegetable oils and oil blends.     

基于混合粒子群算法的复杂相平衡计算方法

对于含有两个部分互溶液相的相平衡问题,采用经典方法收敛困难或易陷于平凡解。为此根据最小Gibbs自由能原理,提出采用混合粒子群算法搜索全局最优解,计算得到系统的最小Gibbs自由能状态,实现复杂相平衡计算。通过改建目标函数,减少计算量,并引入组分相分率,将物料平衡约束转换为规范型立方空间的优化问题,适于粒子群算法搜索。在常规粒子群算法中引入Nelder-Mead单纯形操作,可显著提高搜优的速率和精度。将其应用于甲苯-水-苯胺液液平衡和苯-乙腈-水汽液液平衡计算,取得了良好的效果。     

状态方程在气固相平衡计算中的应用

状态方程法是研究气固平衡的一种常用方法,但是目前仅有SRK和PR方程运用于元素硫沉积机理的研究。采用RK、SRK、PR、PT和LHSS状态方程对含硫天然气气固相平衡进行了计算,并且比较了不同状态方程对计算结果的影响。通过算例分析可知,对含硫天然气气固相平衡进行计算时每种状态方程都会存在误差,而误差主要来源于实验过程中的误差、状态方程参数设置的误差、数值计算方法的误差等。计算结果表明,采用RK和SRK方程计算误差较大,PR和PT方程两者计算误差差别不大,LHSS方程更适合描述含硫天然气的气固相平衡。     

Equilibrium and Rate Data for the Extraction of Lipids Using Compressed Carbon Dioxide

Abstract

Equilibrium data are given for the solubilities in compressed C0₂ of the lipid components in freshly ground rape seed and of glycerol trioleate (a typical constituent of rape oil) at pressures up to 200 bar and temperatures 25 to 75C. Continuous flow tests in which a bed of ground rape seed was contacted with a stream of liquid CO₂ at 25C and varied flow conditions are also reported. The results are collated in terms of an empirical mass transfer coefficient. A sharp change took place in the lipid concentration in the extractant stream leaving the bed when about 65% of the available oil had been extracted. This, and changes in the composition of the extract, are discussed, together with the use of this type of data for design purposes.     

Microstructure and Thermal Profile of Structured Lipids Produced by Continuous Enzymatic Interesterification

Enzymatic interesterification has been shown to be an alternative for the production of structured lipids resembling human milk fat. The knowledge of the physical properties of fat is an important tool for the implementation of this fat in a food matrix. The enzymatic interesterification reaction modifies the composition of triacylglycerols changing the crystallization properties and polymorphic form of fats. Blends containing different proportions of lard and soybean oil (80:20, 70:30, 40:60, 30:70 and 20:80) were enzymatically interesterified in a continuous flow tubular reactor and analyzed for crystalline structure by polarized light microscopy, the polymorphic form using X-ray diffraction and thermal properties by differential scanning calorimetry. The structural modifications resulting from continuous enzymatic interesterification changed the crystallization behavior and thermal profile of the samples, reducing enthalpy values. Structural changes were also evident on polarized light microscopy images, disclosing an increase in the crystallization rate among the samples after the continuous enzymatic reaction.     

Gravitational Search,Monkey, and Krill Herd Swarm Algorithms for Phase Stability,Phase Equilibrium,and Chemical Equilibrium Problems

Phase equilibrium calculations (PECs) and phase stability (PS) analysis of reactive and nonreactive systems problems are important for the simulation and design of chemical engineering processes. These problems, which are challenging, multi-variable, and non-convex, require optimization techniques that are both efficient and effective in finding the solution. Stochastic global optimization algorithms, especially swarm algorithms, are promising tools for such problems. In this study, monkey algorithm (MA), gravitational search algorithm (GSA), and Krill Herd algorithm (KHA) were used to solve PS, phase equilibrium, and chemical equilibrium problems. We have also studied the effect of adding a local optimizer at the end of the stochastic optimizer run. The results were compared to determine the strengths and weaknesses of each algorithm. When a local optimizer was used, MA was found to be a reliable algorithm in solving the problems. GSA had relatively the least numerical effort for all problems among the three algorithms but with low reliability. KHA was more reliable than other two algorithms without the use of a local optimizer. The performance of GSA, MA, and KHA was compared with firefly algorithm and cuckoo search (CS). In summary, this study found that CS algorithm was more reliable than the newly tested algorithms. Nevertheless, MA and GSA algorithms, when combined with a local optimizer, solve the thermodynamic problems as reliably and efficiently as CS.     

Modifications of Quenching Techniques for Phase Equilibrium Studies

A variation of technique and thermal-gradient apparatus from that previously used has been devised for quenching samples. This consists of a modified furnace and a roller and crimping machine. These modifications provide a higher maximum temperature of operation, a more satisfactory method of loading sample tubes, and a more efficient method of measuring temperature than previously used.     

低温甲醇洗相平衡模型和气液平衡计算(1)——相平衡模型

以实验和文献数据为基础建立了能描述低温甲醇洗工艺中Ｈ２、Ｎ２、ＣＯ２、Ｈ２Ｓ和ＣＨ３ＯＨ气液相平衡的模型；用修改的ＲＫ方程，并考虑量子气体Ｈ２存在的影响，处理气相的非理想性；用Ｗｉｌｓｏｎ方程处理液相的非理想性，获得满意结果。     

辛烷—水二元部分互溶体系的相平衡

采用改进的Ｐａｒｔ釜测定了在０．１０１３ＭＰａ下,辛烷－水二元部分互溶体系的汽液相平衡数据,经热力学一致性检验表明,所测的数据是可靠的。采用等温法制定了５～７５℃范围内的液液相平衡数据。实验结果表明,辛烷在水中的溶解度仅为７．３×１０－５～７．５×１０－４,水在辛烷中的溶解度为３．８×１０－３～１．０×１０－１,该体系是互溶度极小的体系。     

电动工具外壳注塑模拟与成型方案优化

利用Moldflow/MPI技术对电动工具外壳进行注塑模拟分析,预测了成型过程中的填充情况,并对型腔压力分布、温度分布、锁模力大小和体积收缩率等进行计算分析,掌握了翘曲变形产生的原因。根据注塑模拟分析结果优化了浇口、冷却系统设计方案和成型工艺参数,使模具设计更趋合理。优化后的成型方案用于实际生产,缩短了试模周期。     

Lipase-Catalyzed Synthesis of Medium-Long-Medium Type Structured Lipids Using Tricaprylin and Trilinolenin as Substrate Models

The synthesis of medium-long-medium type structured lipids (SL) by the interesterification of tricaprylin (TC) and trilinolenin (TLN), using selected commercial lipases from Rhizomucor miehei (Lipozyme RM IM) and Candida antarctica (Novozym 435) was investigated. Although the bioconversion yield (BY) for Lipozyme RM IM (24.7 %) was close to that for Novozym 435 (24.0 %), the initial enzyme activity was 6.3 μmol CLnC/g enzyme/min and 1.6 μmol CLnC/g enzyme/min, respectively. Lipozyme RM IM was subsequently selected for further investigation. The structural analyses of SL indicated that the major products were 1,3-dicapryl-2-linolenyl glycerol (CLnC) and 1(3)-capryl-2,3(1)-dilinolenyl glycerol (CLnLn). In order to optimize the BY, selected parameters were investigated. The experimental results showed that using hexane as the reaction medium, at an initial water activity (a _w ) of 0.06, 10 mg solid enzyme/mL, substrate molar ratio of TC to TLN of 6:1 and a reaction time of 9 h, resulted in the highest BY (73.2 %). Using the optimized conditions, the effects of TLN concentration and other selective parameters, including the denaturation of the enzyme, controlling the a _w and the addition of silica gel, on the mass productivity (P _M), enzymatic productivity (P _E) and volumetric productivity (P _V ) of the interesterification reaction, were also investigated.     

氰化氢在煤气和冷凝液中的相平衡

用气液平衡装置测定了不同温度下氰化氢在煤气和冷凝液中的气液平衡数据,并得出了氰化氢在煤气和冷凝液中的气液平衡关系式。     

Phase Equilibrium and Martensitic Transformation in Lanthana-Doped Zirconia

The system ZrO₂-La₂O₃ has been studied in the 0 to 15 mol% La₂O₃ range using X-ray diffraction and thermal analysis. Two kinds of diagrams were elaborated: First is a phase equilibrium diagram where the eutectoid decomposition of ZrO_{2, ss} (T) → ZrO_{2, ss} (M) + Py _ss occurs at 1100°C and 0.75 mol% La₂O₃ (Py is the pyrochlore compound Zr₂La₂O₇). The maximum solubility of La₂O₃ in ZrO_{2, ss} (M) is 0.5 mol% at room temperature. Second, a nonequilibrium diagram is determined showing the correlations between grain size, La₂O₃ content, and the martensitic transformation temperature start ( Ms ).     

二元溶液气液相平衡实验物系选择的探索

本文讨论了二元溶液气液相平衡实验中物系的选择问题.经过实验研究及分析讨论,结果表明采用正丙醇-水二元溶液物系,利用折光法测定气液相摩尔组成进行二元溶液相平衡实验是合适的.由该物系的实验数据关联得到的模型方程参数与Van Laar方程的文献值吻合较好.另外,正丙醇-水二元体系毒性小,价格便宜,适合高校化工热力学与化工原理教学实验使用.     

间二甲苯-磷酸-水三元体系的液-液相平衡

实验测定了不同温度下,间二甲苯-水二元体系和间二甲苯-磷酸-水三元体系的液-液相平衡数据。研究了磷酸中的杂质Fe~(3+)、Al~(3+)和Mg~(2+)对间二甲苯-磷酸-水三元体系相平衡的影响,以及杂质在两相中的分配情况。研究结果对共沸精馏浓缩磷酸提供了必要的理论依据和基础数据。