Dietary Energy Value of Medium-chain Triglycerides

As a fat source in our diet, medium-chain triglycerides (MCTs) result in lower fat deposition when compared by 2 methods to long-chain triglycerides. Using data from 10 animal studies, the calculated energy loss during utilization of MCTs was 16%, resulting in a net energy value (NEV) of 6.97 kcal/g. The NEV calculated from the molecular composition of 9 MCTs with widely varying caprylic:capric fatty acid ratios was 6.72 ± 0.16 kcal/g. For 5 MCTs with completely defined fatty acid compositions, the NEV was 6.80 ± 0.15 kcal/g. Establishing the NEV for dietary MCTs at 6.8 kcal/g is proposed.     

Modeling,analysis and optimization of calibration uncertainty in clinical laboratories

Uncertainty in the calibration of a clinical laboratory measurement process has a significant effect on the uncertainty of the measurement result. We develop a mathematical model of the analytical stage of the measurement of serum triglyceride concentration in the clinical laboratory, and use the Monte Carlo method to estimate the net uncertainty associated with this model. We then use the model to study the effect of instrument calibration on the uncertainty of the laboratory measurement result. The effect of the correlation between the parameters of the linear calibration function on the measurement result is quantified using the model. In addition, the effect of the choice of calibrator concentration levels on the measurement result distribution is studied using the model, by studying the effect of the value or the position of the calibrator concentration, and the difference or the distance between calibrator concentrations, on the uncertainty of the measurement result.     

A reverse-phase high-performance liquid chromatographic method for analyzing complex mixtures of triglycerides. Application to the fat fraction of an aged cheese

Analysis of complex mixtures of triglycerides that span a broad range of partition numbers can entail a number of difficulties. The present study was therefore intended to develop a method of reverse-phase high-performance liquid chromatography using a light scattering detector for analyzing such mixtures. Stationary phase type, mobile phase gradient, column temperature, and injection solvent were the factors used to develop the method. The method improved the selectivity of critical pairs of milk fat triglycerides, providing good resolution for 115 peaks with partition numbers of between 22 and 53. The use of tristearin as internal standard and the relative response factors for different partition number ranges made it possible to more accurately estimate the weight of the sample triglycerides.     

Performance of palm olein in repeated deep frying and controlled heating processes

The stability of refined, bleached and deodorised (RBD) palm olein was studied under both repeated frying and controlled heating conditions. Two different frying foods i.e. chicken nuggets and French fries were used to evaluate the oil performance under various frying conditions. Thermo-oxidative alterations were measured through various physical and chemical parameters. Total polar compounds (TPC), polymeric triglycerides (PTG), blueness (b^∗ value), chroma (C^∗ value), refractive index and viscosity increased linearly with the number of frying/heating cycles. Palmitic acid content increased and linoleic acid content decreased linearly with the number of frying cycles. No significant changes in oleic acid were detected. Thermo-oxidative reactions induced under the heating conditions were found to be faster as compared to those under the frying conditions. The PTG formed at the end of heating cycles (16.42%) were substantially higher as compared to those formed at the end of frying French fries (9.72%) and chicken nuggets (5.34%).     

中链甘油三酯抗疲劳作用及其机制研究

研究中链甘油三酯(MCT)的抗疲劳作用及其相关的机制。将KM雄性小鼠100只随机分为5组,每组20只,每组再随机分成2个小组,每小组10只,分别为安静对照组(CC_1和CC_2)、游泳对照组(SC_1和SC_2)、低剂量组(SL_1和SL_2)、中剂量组(SM_1和SM_2)、高剂量组(SH_1和SH_2)。1小组SC_1、SL_1、SM_1和SH_1在灌胃给药30 d后用于无负重游泳60 min实验,测定各生化指标;2小组SC_2、SL_2、SM_2和SH_2小鼠在灌胃给药30 d后用于负重游泳力竭实验,测定负重游泳力竭时间。结果表明:与游泳对照组相比,MCT可以显著延长小鼠负重游泳力竭时间,降低运动后血清尿素氮含量和血清乳酸含量,减少血糖和肝糖原消耗,提高肝脏超氧化物歧化酶活性、谷胱甘肽含量和游离脂肪酸含量,降低肝脏丙二醛含量,提高血清乳酸脱氢酶活性。因此,MCT具有抗疲劳的作用,且以低剂量组效果最明显。     

人乳脂肪球的研究进展

人乳是婴儿最理想的食物,人乳脂肪是人乳中的重要组成,不仅是婴儿生长发育所需能量的主要来源,也提供了各种脂溶性营养物质。人乳脂肪在乳清相中并非呈完全均匀地分散,而是以人乳脂肪球的形态稳定存在。人乳脂肪球是由一个三层的膜结构包裹住中心层状排列的甘油三酯组成,这种结构不仅维持了乳液本身的稳定性,还为婴儿的生长发育提供了特有的营养学功能。近年来,这种天然而特殊的物理形态引起了学者们的广泛关注。对国内外人乳脂肪球的相关文献进行综述,主要包括人乳脂肪球的形成、组成、营养学意义以及其在加工过程中的变化,并对今后研究的方向和重点进行了展望。     

Determination of MG and TG phase composition by time-domain NMR

The feasibility of time-domain NMR curve-fitting methodology for the quantitative determination of TG blend phase compositions was investigated. By studying a range of TG in their different crystal forms, it was shown that the transverse NMR relaxation characteristics of TG differ for the respective crystal polymorphs {α,β,β′}. This enables the TG polymorphism in fat blends to be quantitatively determined by curve fitting. If a liquid phase is present in the blend, curve fitting is able to determine the solid fat content, and the results compare well with those of the accepted NMR methods. The curve-fit method is less hindered by some of the disadvantages of these accepted methods, such as the use of a calibration factor.     

Transesterification kinetics of triglycerides for a modified lipase inn-hexane

A simple kinetic model for the transesterification of triglycerides catalyzed by a modified lipase inn-hexane has been proposed. The model assumes that the enzyme has 1,3-positional specificity and does not distinguish among the different fatty acid residues considered in this study. The model is based on material balances of consecutive second-order reversible reactions and requires only one parameter that can easily be determined experimentally. The differential rate equations have been solved analytically to give explicit equations that link the concentrations of all possible triglycerides to the initial conditions and the reaction time. The model was in good agreement with experimental data for different biocatalyst concentrations with the same value of the specific rate constant. The same value of specific rate constant also gave a good fit with experimental data for an acidolysis reaction between a triglyceride and a fatty acid, implying that the modified lipase did not distinguish between free fatty acids and fatty acid residues attached to the 1 and 3 positions of glycerol backbone.