Partition coefficient of diglycerides in crystallization of palm oil

Crystallization of palm oil with and without solvent was carried out over a temperature range of 10–25°C. The yields of olein, the diglyceride contents, and compositions of the stearin and olein phases were determined by thin-layer and gas-liquid chromatography. The three major diglycerides, analyzed as C₃₂, C₃₄, and C₃₆, are mainly dipalmitoyl glycerol, palmitoyloleoyl glycerol, and dioleoyl glycerol. In crystallization without solvent, C₃₂ (PP) had a strong affinity for the stearin fraction and C₃₆ diglycerides concentrated in the olein phase. The partition coefficient of diglycerides between the olein and stearin phases was temperature-dependent and was influenced by the type of solvent used. Although solvent enhances the diglyceride partition into the olein phase, partitioning is more effective at low temperatures and with acetone as the solvent for fractionation.     

Product sampling during transient continuous countercurrent hydrolysis of canola oil and development of a kinetic model

A chemical kinetic model has been developed for the transient stage of the continuous countercurrent hydrolysis of triglycerides to free fatty acids and glycerol. Departure functions and group contribution methods were applied to determine the equilibrium constants of the four reversible reactions in the kinetic model. Continuous countercurrent hydrolysis of canola oil in subcritical water was conducted experimentally in a lab-scale reactor over a range of temperatures and the concentrations of all neutral components were quantified. Several of the rate constants in the model were obtained by modeling this experimental data, with the remaining determined from calculated equilibrium constants. Some reactions not included in the present, or previous, hydrolysis modeling efforts were identified from glycerolysis kinetic studies and may explain the slight discrepancy between model and experiment. The rate constants determined in this paper indicate that diglycerides in the feedstock accelerate the transition from “emulsive hydrolysis” to “rapid hydrolysis”.     

Glycerolysis of Fatty Acid Methyl Esters: 1. Investigations in a Batch Reactor

The present work focused on the glycerolysis of fatty acid methyl esters. The aim was to develop and test a kinetic model that could be used to reliably simulate different process alternatives for this reaction. A prerequisite was the identification and characterization of the factors that affect the reaction kinetics. Experiments were carried out in a batch reactor with and without forced removal of methanol, which is one of the reaction products. Concentrations of all components in the two-phase system were measured. It was found that the methanol concentration has a strong effect on the reaction rate and equilibrium conversion. Near-complete conversions were obtained by stripping methanol with an inert gas. The glycerol concentration in the ester phase was found to increase as the reaction proceeds, which also accelerates the reaction. Effects of mass transfer on the reaction rate were not found to control the reaction rate under well-agitated conditions. A semi-empirical model was used to simulate the reaction. The results from the semi-empirical model show good agreement with experimental results.     

Kinetics of Soybean Oil Hydrolysis on Niobium Catalysts

The catalytic hydrolysis of soybean oil was used as an alternative for the production of monoglycerides (MG) and diglycerides (DG). The reactions were conducted in a stainless-steel tubular reactor in the temperature range of 240–290 °C, on niobium phosphate (NBP) and niobium oxide (NBO) as catalysts. In the hydrolysis reactions at 270 °C, the maximum selectivities of the products of interest were obtained at 22 % MG and 48 % DG for the reaction with NBP, and 7 % MG and 33 % DG with NBO, for 59 % and 36 % of triglyceride conversion in 10 min, respectively. The proposed kinetic model presented a good fit of the theoretical model with the experimental data, showing that the previous hypotheses considered for the mechanism development are suitable for describing the kinetics of soybean oil hydrolysis.     

Preferential degradation of noncholine phosphatides in soybean lecithin by thermalization

Purified soybean lecithin and the gum derived from soybean oil processing were heated separately in bulk at 125 to 200°C for 60 min, or at 175°C for 30, 60, 90 and 120 min, and the products were analyzed by thin-layer chromatography and high-performance liquid chromatography. It was found that the noncholine phosphatides are preferentially degraded relative to phosphatidylcholine, and that these phosphatides are broken down in the order phosphatidyl-ethanolamine (PE)>phosphatidylinositol (PI)>phosphatidic acid (PA) with increasing temperature. At 175°C, the heating time required to degrade the noncholine phosphatides was between 30 and 60 min. Diglycerides were the principal products of thermalization at 77% of the total material, indicating that the 3-phosphoester linkage is the most heat-labile portion of the noncholine phosphatide molecules. Cleavage of the fatty acids from positions 1 and 2 of the phosphatides was minimal, as indicated by the relatively low amount of free fatty acids (8% of the total) when the lecithin was heated at 180°C for 90 min. The appearance of brown discoloration, characteristic of heated lecithin, coincided mainly with the decomposition of PE.     

Characterisation of the lipidic components of margarines by H Nuclear Magnetic Resonance

In this work, ¹H Nuclear Magnetic Resonance (¹H NMR) has been used to study the lipidic fraction of margarines of different compositions, determining simultaneously both major components, which is to say triglycerides, and other minor ones, such as 1- and 2-monoglycerides, 1,2-diglycerides, vegetable stanols and sterols, and sorbic acid. The results show a wide variety of acyl group compositions, with polyunsaturated groups ranging from 22% to 50%, monounsaturated from 23% to 50%, and saturated from 21% to 55%. 1,2-Diglycerides and vegetable stanols and/or sterols have been detected in all the studied margarines, in concentrations varying between 2.73 and 26.06 mmol/kg, and between 3.40 and 240.01 mmol/kg, respectively. A good agreement has been found between the results obtained by ¹H NMR and some composition data of these margarines, showing the usefulness of this technique to analyse the lipidic composition of margarine in a quick and easy way.     

Kilogram-scale ester synthesis of acyl donor and use in lipase-catalyzed interesterifications

Scaling up of Lipozyme-catalyzed ester synthesis with >99% conversion and a reflux trap to remove product water from the reaction mixture is reported. Ethyl stearate was synthesized in 2000-g batch reactions from technical stearic acid. The ethyl stearate was purified to 97% by crystallization and interesterified with sunflower seed oil by means of a lipase catalyst to investigate reaction parameters of temperature, substrate ratio, enzyme content and catalyst water activity. The endpoint of the reaction was defined as the incorporation of stearate into sunflower seed oil corresponding to the amount of stearate necessary to be incorporated into palm oil mid-fraction to produce a cocoa butter substitute. No tristearate was formed at the reaction endpoint in any of the reactions conducted. Reaction times decreased and levels of free fatty acids and diglycerides increased with increasing temperature and with increasing ratio of acyl donor to triglyceride. Increasing the enzyme content of the reaction mixture reduced reaction times but caused higher levels of free fatty acids and diglycerides. In reactions catalyzed by Lipozyme of defined water activity, the shortest reaction times were obtained at intermediate water activity, while free fatty acid and diglyceride levels increased with water activity. When the interesterification reaction was carried out in refluxing pentane with the condensed solvent dried by passage through a reflux trap, the free fatty acid and diglyceride levels were reduced to 6 and 3.3%, respectively.     

Continuous transesterification of biodiesel in a helicoidal reactor using recycled oil

The main problem with biodiesel is the high cost of oils made from oleaginous crops. For this reason, various raw materials have been analysed with a view to reducing production costs and obtaining a product that can compete with the price of petrodiesel. Recycled oil is one of the most promising alternatives in the production of biodiesel because not only is the cheapest raw material but it also avoids the expense of treating the oil as a residue.Another way to reduce costs is to make the process more economical. Conventional technology uses sodium hydroxide as the basic catalyst and large-scale batch reactors, whose mechanical agitation requires high energy consumption due to residence times of at least 60 min and temperatures of 60 °C.In this paper we use a recycled pretreated oil to compare conventional transesterification with continuous transesterification in a tubular reactor. In this reactor the reactants (oil, methanol and sodium hydroxide) flow through a helicoidal tube submerged in a heating bath at 60 °C. The reactor has five outlets distributed non-uniformly to enable samples to be taken at different reaction times. This is to reduce the reaction time and avoid the need for mechanical agitation. With the aim of improving the quality of the biodiesel obtained, we varied the helicoidal system by incorporating a static micromixer and supplying energy in the form of ultrasound from the heating bath. This reactor produced biodiesel and glycerine at compositions roughly equal to those obtained in the batch process (89% FAME content at 75 min) but did so continuously (2.5 mL/min) and just 13 min after the reactants were integrated in a single line using a T device. Both the oil and the biodiesel were characterized and analysed in accordance with European standard UNE EN14214 for biodiesel.     

Use of Glycerol Carbonate in an Efficient, One-Pot and Solvent Free Synthesis of 1,3-sn-Diglycerides

An efficient solvent-free synthesis of a variety of highly pure 1,3-sn-diglycerides (1,3-sn-diacylglycerols) in a two-step one pot process is described. Heating glycerol carbonate (4-hydroxymethyl-1,3-dioxolan-2-one) with fatty acid anhydrides 2a–d affords 1:1 mixtures of glycerol carbonate fatty esters 3a–3d and the corresponding fatty acids. Further heating the reaction mixtures in the presence of catalytic amounts of 1,4-diazabicyclo[2.2.2]octane (DABCO) at 195–200 °C yields highly pure 1,3-sn-diglycerides 4a–4d.     

Behavior of diglycerides and conjugated fatty acid triglycerides in reverse-phase chromatography

The behavior of conjugated fatty acid triglycerides and diglycerides on reverse-phase chromatography was studied. Trieleostearin is a geometric isomer of trilinolenin. The conjugated double bond arrangement in trieleostearin enhances its hydrophobic interaction with the stationary phase and causes it to be eluted later than trilinolenin. In separation of “critical pairs” of tri- and diglycerides, diglycerides elute later than triglycerides due to the longer fatty acid constituent. Position isomers of 1,2- and 1,3-diglycerides can be separated by reverse-phase high-performance liquid chromatography.