Diglycerol Esters Research Articles

Sustainable production of biodiesel and transformation of glycerol to glycerol laurate esters over inner diameter-controlled sulfonic acid functionalized ethyl-bridged-organosilica nanotubes

Solid acid-catalyzed biodiesel production from inedible oils offers a promising mean to reduce the cost of feedstocks and avoid the competition with edible oil market. Here we demonstrate a series of inner diameter-controlled sulfonic acid functionalized ethyl-bridged-organosilica nanotubes (Ar/PrSO3H–Si(Et)Si) by a toluene swollen mixed Pluronic surfactant micelle-templating co-condensation route for transesterification of tripalmitin or plant oils with methanol to produce fatty acid methyl esters and esterification of glycerol with lauric acid to produce mono- and di-glycerol esters. By combination of superstrong Brønsted acidity, unique hollow tubular nanostructure, excellent porosity properties and hydrophobic surface, the Ar/PrSO3H–Si(Et)Si nanotubes display higher catalytic activity as compared with acidic resin and zeolite. Additionally, the inner diameters and lengths of Ar/PrSO3H–Si(Et)Si nanotubes influence the activity obviously. The Ar/PrSO3H–Si(Et)Si nanotubes also show excellent catalytic reusability, attributing to covalent bonding of Ar/PrSO3H groups within silica/carbon framework and surface hydrophobicity of the catalysts.

Effect of Addition of Purified Diglycerol Linoleic Acid Esters on the Crystallization Behavior of Diacylglycerol Oils

AbstractLiquid oils containing high‐melting diacylglycerols (DAGs) are more likely to cause precipitation than triacylglycerol‐based oils during long‐term storage, which is not desired for consumer products. Therefore, we attempted to retard the crystallization of high‐melting DAGs by adding emulsifiers, diglycerol esters of fatty acids (DGEs), which were synthesized by esterification of diglycerol and linoleic acid using Novozym 435. The reaction product was isolated by silica gel column chromatography to obtain pure mono‐, di‐, and triesters of diglycerol, and the composition was analyzed by HPLC and ESI‐MS. Further structural analysis of the purified products was performed by 1H‐ and 13C‐NMR. The retardation effect of DGEs with a different esterification degree on the crystallization of DAGs was investigated using solid fat content, differential scanning calorimetry, polarized light microscopy, and X‐ray diffraction. The results reveal that addition of 0.5 % (w/w) DGEs could effectively retard the crystallization of high‐melting DAGs by inhibiting the nucleation process and delaying the crystal growth, but their addition did not alter the crystal forms of DAGs. Moreover, the retardation effect was enhanced as the esterification degree of DGE decreased.

Structural Analysis of Partial and Total Esters of Glycerol Undecenoate and Diglycerol Undecenoate

AbstractThe direct esterification reaction between glycerol and undecylenic acid or between diglycerol and undecylenic acid generates all the possible types of glycerol or diglycerol esters. Purification by silica gel chromatography resulted in the isolation of each of these types of ester in a pure form. The molecular structures of the compounds isolated were characterized and identified by mass spectrometry, 1H NMR, 13C NMR and DEPT‐135. We then studied the composition of esters of undecylenic acid formed with glycerol or diglycerol as a function of their reaction conditions, which constitute a highly complex system. We purified undecylenic acid esters from each polyol family to allow the structural identification of each ester of glycerol and each ester of diglycerol with undecylenic acid. We found that the polarity of these non‐ionic amphiphilic esters directly affected their affinity for organic and inorganic solvents and that these esters behaved very differently from anionic amphiphilic molecules, such as undecylenic acid.

Diglycerol esters of fatty acids promote severe coalescence between protein-stabilized oil droplets by emulsifier–protein competitive interactions

Diglycerol ester of mono-oleic acid (DO), a bacteriostatic emulsifier causes severe coalescence of oil droplets stabilized by milk proteins and phase separation between oil and aqueous phase under agitating conditions. In order to clarify the destabilizing mechanism of the emulsifier, physicochemical and colloidal properties of the emulsifier were compared to similar emulsifiers without destabilizing effects. DO, that is dispersible both in oil and water, adsorbed to the oil–water interface to reduce the interfacial tension, and migrated from oil phase to aqueous phase and vice versa in a plane interface system. Experiments performed in an emulsion system revealed that DO had little ability to emulsify food-grade oil, but displaced milk proteins from the oil droplet surface. These data indicate that DO with little emulsifying ability predominantly occupies the oil droplet surfaces via emulsifier–protein competitive interactions to promote severe coalescence of emulsion oil droplets probably because DO actively migrates between oil and aqueous phase and it favors to form the planar oil–water interface.

Destabilization of protein-based emulsions by diglycerol esters of fatty acids – The importance of chain length similarity between dispersed oil molecules and fatty acid residues of the emulsifier

Destabilizing effects of diglycerol mono-esters of different saturated or one mono-unsaturated fatty acids (DF) on protein-based emulsions prepared with various types of oil were examined by visual observations and particle size analyses. By diglycerol esters of oleic acid (DO), a hexadecane-in-water emulsion was more obviously destabilized than an octadecane-in-water emulsion or food oil-in-water emulsions. Interfacial tension measurements indicated that the adsorbed protein on oil droplet surfaces of hydrocarbon emulsions can be more easily displaced by DO compared to the case of food oil emulsions. The degree of hydrocarbon emulsion destabilization by DO varied with the chain length of hydrocarbon molecules. From the results of combination tests of five hydrocarbons varying in chain length in oil phase and five DF having different mono-fatty acid residue, we described a possibility that DF could effectively destabilize the hydrocarbon emulsion when the chain length of fatty acid residue of DF was similar to that of hydrocarbon molecules.

Role of static and dynamic characteristics of diglycerol esters and β-lactoglobulin mixed films on foaming, 2: Adsorption and foaming

Foam formation and foam stability are criteria of primary importance for many aerated food formulations because consumer perception of quality is influenced by appearance. In this work, we have studied the effect of emulsifier concentration and protein/lipid ratio on the adsorption and foaming characteristics of mixed β-lactoglobulin and diglycerol ester (diglycerol-monolaurate and diglycerol-monostearate) aqueous solutions. The temperature, pH, and ionic strength were maintained constant at 20 °C, 7, and 0.05 M, respectively. The surface pressure isotherm of the mixed systems depended on the emulsifier concentration in solution and the protein/lipid ratio in the mixture. The saturation of the interface by the protein or lipid has a significant effect on the foaming capacity of mixed protein and lipid aqueous solutions. We have observed that there exist close relationships between foaming and the rate of diffusion of mixed β-lactoglobulin and diglycerol esters to the air–water interface. For a particular system the overall foam destabilization (the half-life time of the foam) and the individual destabilization processes (drainage, disproportionation, and coalescence) depend on the lipid, the protein and lipid concentrations, and the protein/lipid ratio in the mixture. The results for β-lactoglobulin+diglycerol ester aqueous solutions also confirm that there exists a relationship between the half-life time of volume of liquid drained from the foam ( θ 1/2) and the long-term surface pressure. However, a general correlation between foam stability and surface dilatational properties was not clearly reflected in this study.

The role of static and dynamic characteristics of diglycerol esters and β-lactoglobulin mixed films foaming. 1. Dynamic phenomena at the air–water interface

In this work, we have studied dynamic surface pressure and surface dilatational characteristics of diglycerol esters (diglycerol monolaurate and diglycerol monostearate) and β-lactoglobulin mixed films adsorbed at the air–water interface. The concentrations of protein and lipid and the protein/lipid ratio in the aqueous bulk phase were studied as variables, while pH (7), ionic strength (0.05 M) and temperature (20 °C) were maintained constant. We have observed competitive adsorption from aqueous solutions of mixed emulsifiers ( β-lactoglobulin and diglycerol esters) and/or the displacement between emulsifiers at the air–water interface depending on the chemistry of the lipid and on the protein/lipid ratio. For the mixed systems a lag period was not observed, even for low concentrations of emulsifiers in solution. During the initial period the kinetics of adsorption of mixed emulsifiers at the air–water interface are controlled by a diffusion mechanism. At long-term adsorption the rate of penetration controls the adsorption of mixed emulsifiers at the interface, which increases with the lipid concentration in solution and is faster for diglycerol monostearate than for diglycerol monolaurate. From a rheological point of view, mixed films behave as viscoelastic (practically elastic) with a loss angle tangent higher than zero. The evolution of surface dilatational modulus ( E) with surface pressure ( π) for β-lactoglobulin–diglycerol ester mixed films reflects the amount of emulsifier adsorbed at the interface (giving high values of E at the higher π) and confirms the idea that the protein–lipid interactions at the air–water interface are somewhat weak, there even being the possibility of phase separation.

Formulation Engineering of Food Model Foams Containing Diglycerol Esters and β-Lactoglobulin

The foaming characteristics of low-molecular-weight emulsifiers (LMWEs) and proteins are important attributes during the production, storage, transport, and consumer perception of quality (appearance) of food dispersions (emulsions and foams). In this article, we consider the analysis of interfacial (adsorption isotherm and rate of adsorption) and foaming (foaming power and foam stability) properties of a typical milk protein (β-lactoglobulin) and diglycerol esters (diglycerol monostearate and diglycerol monolaurate) as LMWEs, as a function of the foaming agent concentration in aqueous solution. We observed that the adsorption and foaming power (foam capacity, gas and liquid retention in the foam, and foam density) increase with the foaming agent concentration in the aqueous phase. The adsorption kinetics at short adsorption times is diffusion-controlled. However, the mechanism that controls the long-term adsorption is the penetration of the foaming agent at the interface. At surface pressures lower than ...

Enhancement of antilisterial activity of essential oil constituents by nisin and diglycerol fatty acid ester

Plant-derived essential oil components in combination with nisin and diglycerol fatty acid esters were investigated for their antibacterial activity against Listeria monocytogenes. Carvacrol and thymol were found to have the strongest antilisterial properties, followed by eugenol, cinnamaldehyde and isoeugenol. The antilisterial activity of the other essential oils (limonene, pinene, ally lisothiocyanate and linalool) was found to be low, even at the highest concentration used (0.1%). Among the diglycerol esters of fatty acids with different carbon chain lengths, diglycerol monolaurate was the most active against L. monocytogenes. A combined antilisterial effect was observed between nisin and the essential oils (carvacrol, thymol and eugenol); moreover, the addition of diglycerol monolaurate as a third preservative factor led to further combined antilisterial activities between the essential oil constituents (carvacrol, thymol and eugenol) and nisin even at lower, sub-lethal concentrations. These results indicate that nisin and diglycerol monolaurate can be used to enhance the antilisterial activity of essential oils, allowing for a reduction in the dosage used in food preservation and thereby resulting in the reduction of undesirable flavors.

Novel sustained-release dosage forms of proteins using polyglycerol esters of fatty acids

In order to develop a novel delivery system for proteins based on polyglycerol esters of fatty acids (PGEFs), we studied a model system using interferon-α (IFN-α) as the test protein. A cylindrical matrix was prepared by a heat extrusion technique using a lyophilized powder of the protein and 11 different types of synthetic PGEFs, which varied in degree of glycerol polymerization (di- and tetra-), chain length of fatty acids (myristate, palmitate and stearate) and degree of fatty acid esterification (mono-, di- and tri-). In an in-vitro release study using an enzyme-linked immunosorbent assay (ELISA) as a detection method, the matrices prepared from a monoglyceride (used for comparison) and from diglycerol esters exhibited a biphasic release pattern with a large initial burst followed by slow release. In contrast, the matrices prepared from tetraglycerol esters showed a steady rate of release without a large initial burst. In an in vivo release study, initial bursts of IFN-α release were, also, dramatically reduced when the matrices were prepared from the tetraglycerol esters of palmitate and stearate, and the mean residence time (MRT) of IFN-α was prolonged, whereas the matrices prepared from monoglyceride and from diglycerol esters showed large initial bursts of IFN-α release. Since the release rates from the matrices prepared from the tetraglycerol esters of palmitate and stearate were governed by Jander’s equation modified for a cylindrical matrix, the release from those matrices was concluded to be a diffusion-controlled process. The bioavailability of IFN-α after implantation of the matrix formulation prepared using all types of PGEFs, except for tetraglycerol triesters, was almost equivalent to that after injection of IFN-α solution; consequently, IFN-α in these matrices appears to remain stable during the release period.

Physical properties of diglycerol esters in relation to rheology and stability of protein-stabilised emulsions

The surface activity and lyotropic phase behaviour of concentrated diglycerol-esters of fatty acids with chain length of C14, C16, C18 and C18:1 (cis-oleic acid) are investigated. Diglycerol-esters show a much stronger reduction in the interfacial tension at a low concentration (0.01–0.1%) than corresponding monoglycerides. The diglycerol-esters form lamellar mesophases above their Krafft point, and no other types of mesophases are found in the temperature region examined (0–80°C). The lamellar phases show a limited swelling capacity, corresponding to a water layer thickness of ≈24 Å, which is found when the ratio of diglycerol-ester to water is 60:40, or lower. At high water concentrations (>90%) multi-lamellar liposomes are formed. The diglycerol-monooleate form lamellar phases in water in the temperature region from zero to 80°C. This is in strong contrast to the corresponding glycerol-monooleate, which forms cubic and reversed hexagonal mesophases in water. Oil in water emulsions are stabilised by diglycerol-esters by formation of liquid crystalline interfacial films around the oil droplets, which can be seen in polarised light microscopy. In presence of milk proteins in the aqueous phase the emulsion stability is depending on the protein to emulsifier ratio. At 40°C a mixed interfacial film of diglycerol-monooleate (DIGMO) and protein is present at the oil–water interface, but when cooled to 5°C, the proteins are displaced by DIGMO. This behaviour affects the stability and rheological properties of emulsions stored at low temperatures.

Preparation and surfactant properties of diglycerol esters of fatty acids

AbstractFatty acid mono‐ and diesters of diglycerol constitute the major portion of commercial polyglycerol esters; hence, their composition influences the performance of the latter as emulsifiers. The correlation of structure of the fatty acids in the mono‐ and diesters with surfactant properties is of interest. Linear diglycerol was isolated from polymerized glycerol by acetonation, fractional distillation and regeneration. Diglycerol mono‐ and diesters of undecenoic, lauric, stearic, oleic and ricinoleic acids were prepared by reacting diglycerol and fatty acids in a refluxing mixture of acetonitrile‐tetrahydrofuran (75:25) in the presence of p‐toluenesulfonic acid and molecular sieves. Mono‐ and diesters were separated by silica gel column chromatography, and their purities were ascertained by thin layer chromatography and determination of saponification value. The structures were confirmed by periodic acid oxidation, chemical‐ionization mass spectrometry and 13 C‐NMR spectroscopy. Surfactant properties of the esters were determined. Monoesters showed higher ability in surface tension reduction, emulsification and foaming than the diesters. Short‐chain fatty acid esters showed better surfactant properties than the long‐chain fatty acid esters. The presence of a central double bond in the lipophilic part of the monoesters reduced emulsion stability. The presence of a hydroxy group in acyl chain retarded foaming and surface tension reducing power.