Crossflow filtration of oils on metal oxides. Influence of chemical composition of the layer

A new technique of fat fractionation was described in which butter oil and a formulated oil (olive, grapestone, coconut, and linseed) have been submitted to crossflow percolation at 45°C on different metal oxides layers (Al₂O₃, TiO₂, ZrO₂) of various thickness. The metal oxides layers were used in order to highlight the interaction between triglycerides (TG) and filtering materials. Experiments have been checked by high-performance liquid chromatography and by differential scanning calorimetry. Partition number was used to take the double bonds into account, and nonpolarity index was used to estimate the relative hydrophobicity of TG molecules. Results point out a two-step complex partition phenomenon: The filtering layer that is initially hydrophilic is coated by less hydrophobic TG acting as a second interface with hydrophobic characteristics. The three tested metal oxides did not provide comparable patterns. The specific property of aluminum oxide is related to a better polarizability of the Al−O bond.     

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.     

Differential scanning calorimetry of confectionery fats: Part II—Effects of blends and minor components

Differential scanning calorimetry (DSC) measurements of the crystallization and melting phenomena of typical confectionery fats are presented. The results show the sensitivity and reproducibility with which DSC data can be used to classify the types of confectionery fat. Calculations of the reproducibility of crystallization and melting parameters obtained from DSC are presented. In addition, the effects are shown on the thermograms of progressive changes in formulation to a typical cocoa butter equivalent. Further, the effects brought on by the presence of minor components, such as trisaturated triglycerides and other polar materials, which are common in confectionery fats, are described and quantified. On behalf of Loders-Croklaan, Wormerveer, Netherlands.     

Butter texture: The prevalent triglycerides

The effect of composition on butter texture usually has been treatedvia the iodine value or the fatty acid content. The development of a new analytical technique allowed accurate determination of triglyceride composition of five different types of butters collected in winter and summer periods. The firmness of these samples has been measured in parallel, by using an Instron® universal testing machine and a cone penetrometer. As expected, a regional and seasonal variation of butter firmness was found. The correlation between firmness at 15°C and triglyceride composition allows the selection of four triglyceride fractions (TG1, TG2, TG3 and TG4) mainly represented by: TG1, POO; TG2, MyOO; TG3, CLaO + CyMyO + CoPO + BuSO and TG4, BuPO + CoMyO + CoPL (P, palmitic acid; O, oleic acid; My, myristic acid; C, capric acid; La, lauric acid; Cy, caprylic acid; Co, caproic acid; Bu, butryic acid; S, stearic acid; L, linoleic acid). The proportions of TG1 and TG2 are negatively correlated with firmness (r=0.89 and r=0.95, respectively). The level of the two other groups runs parallel to firmness (r=0.95 and r=0.91, respectively). The high correlation coefficients of these prevalent triglyceride fractions could be a better representative indication than iodine value or fatty acid content on the variation of this physical property of butter.     

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.     

HPLC analysis of phenolic antioxidants,tocopherols and triglycerides

Triglycerides, together with nine synthetic phenolic antioxidants most commonly used to prevent oxidation of edible oils and fats, as well as the natural antioxidants tocopherols andα-tocopherol acetate, were separated by high performance liquid chromatography by means of a reversed phase C₁₈-column and gradient elution with water/acetonitrile/methanol/isopropanol. Besides dilution of the oil with isopropanol/hexane, no further example preparation was required. UV detection was applied. The synthetic antioxidants propyldodecylgallate, octyldodecylgallate, dodecylgallate, 3-tert-butyl-4-hydroxyanisol,tert-butylhydroquinone, 3,5-di-terf-butyl-4-hydroxytoluene, 2,6-di-tert-butyl-4-hydroxymethyl-phenol, 2,4,5-trihydroxybutyrophenone and nordihydro-quaiaretic acid, as well asα- andδ-tocopherol andα-tocopherol acetate were base-line separated;β- andγ-tocopherol, however, eluted together. The triglycerides, detected at λ = 215 nm, were separated according to then-partition number. The absorption at λ = 215 nm revealed saturated and unsaturated triglycerides. The absorption at λ = 280 nm indicated triglycerides with conjugated unsaturation, relating information about refining and heat treatment of the oil. Oxidized unsaturated triglycerides showed absorption at γ = 230 nm. Triglycerides of ricinoleic acid, a hydroxymonoun-saturated acid, gave identical UV spectra. The simultaneous detection of antioxidants and triglycerides may be used to study inhibition effects by antioxidants in oils. To whom correspondence should be addressed.     

Crystallization kinetics of emulsified triglycerides

Nucleation and crystal growth process of triglycerides in water emulsions composed of trimyristin (c l4:0) admixed with 0, 40, and 80 ml litre^?1 trilaurin (c 12:0) (expressed v per total v emulsion) were followed with NMR (nuclear magnetic resonance) and DSC (differential scanning calorimetry). Mathematical analysis of the time dependence of the phase changes and thermal data distinguished two distinct ‘apparent’ kinetic phases. These phases were tentatively referred to as nucleation and crystal growth. With 40 and 80 ml litre^?1 trilaurin (NMR data at 293 K) nucleation and crystal growth phases of trimyristin were simulated with zero order and second order rate expressions, respectively. Relative to these mixtures, pure trimyristin nucleation was delayed in the initial phase, but crystal growth occurred with fast homogeneous nucleation and slower growth in the second phase. Statistical analyses indicated that homogeneous nucleation similarly occurred when 40 or 80 ml litre^?1 trilaurin was admixed with trimyristin. NMR resolution made it possible to follow the crystallization phenomena in different locations of the crystallization vessel effectively in situ and undisturbed. Statistical analyses in this case revealed a significant trilaurin-location interaction confirming that the rate of nucleation processes was affected both by the concentration of trilaurin and the heat transfer properties of the sample and vessel. The time-location interactions were not significant, confirming the hypothesis that in the absence of tilaurin, zero order nucleation did not occur in the first phase.