Effect of Span 60 on the Microstructure, Crystallization Kinetics, and Mechanical Properties of Stearic Acid Oleogels: An In-Depth Analysis.
TL;DR: Span 60 can be used to alter the kinetics of the crystallization, crystal habit and crystal structure of stearic acid, and provides a number of clues that could be used further for developing oleogel based formulation.
Abstract: Modulation of crystallization of stearic acid and its derivatives is important for tuning the properties of stearate oleogels. The present study delineates the crystallization of stearic acid in stearate oleogels in the presence of Span 60. Microarchitecture analysis revealed that stearic acid crystals in the oleogels changed its shape from plate-like structure to a branched architecture in the presence of Span 60. Consequently, a significant variation in the mobility of the solute molecules inside the oleogel (Fluorescence recovery after photobleaching studies, FRAP analysis) was observed. Thermal analysis (gelation kinetics and DSC) revealed shortening of nucleation induction time and secondary crystallization with an increase in the Span 60 concentration. Furthermore, isosolid diagram suggested better physical stability of the formulations at higher proportions of Span 60. XRD analysis indicated that there was a decrease in the crystal size and the crystallinity of the stearic acid crystals with an increase in Span 60 concentration in the Span 60 containing oleogels. However, crystal growth orientation was unidirectional and found unaltered with Span 60 concentration (Avarmi analysis using DSC data). The mechanical study indicated a composition-dependent variation in the viscoelastic properties (instantaneous [τ1 ], intermediate [τ2 ], and delayed [τ3 ] relaxation times) of the formulations. In conclusion, Span 60 can be used to alter the kinetics of the crystallization, crystal habit and crystal structure of stearic acid. This study provides a number of clues that could be used further for developing oleogel based formulation.
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TL;DR: The lipid crystal engineering approach followed here offered prospects of obtaining harder self-standing structures at a lower oleogelator concentration, and synergistic interactions provide an opportunity to reduce the wax concentration and, as such, the waxy mouthfeel without compromising the oleOGel properties.
Abstract: In this study, the effect of lecithin (LEC) on the crystallization and gelation of fruit wax (FW) with sunflower oil was researched. A synergistic effect on the gel strength was observed at FW : LEC ratios of 75 : 25 and 50 : 50, compared to the corresponding single component formulations (100 : 0 and 0 : 100). Even below the critical gelling concentration (Cg) of FW, the addition of lecithin enabled gel formation. Lecithin affected the thermal behavior of the structure by delaying both crystallization and gel formation. The phospholipid acted as a crystal habit modifier changing the microstructure of the oleogel, as was observed by polarized light microscopy. Cryo-scanning electron microscopy revealed a similar platelet-like arrangement for both FW as a single oleogelator and FW in combination with LEC. However, a denser structure could be observed in the FW : LEC oleogelator mixture. Both the oil-binding capacity and the thixotropic recovery were enhanced upon lecithin addition. These improvements were attributed to the hydrogen bonding between FW and LEC, as suggested by Raman spectroscopy. We hypothesized that lecithin alters the molecular assembly properties of the FW due to the interactions between the polar moieties of the oleogelators, which consequently impacts the hydrophobic tail (re)arrangement in gelator–gelator and solvent–gelator interactions. The lipid crystal engineering approach followed here offered prospects of obtaining harder self-standing structures at a lower oleogelator concentration. These synergistic interactions provide an opportunity to reduce the wax concentration and, as such, the waxy mouthfeel without compromising the oleogel properties.
46 citations
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TL;DR: The purpose of this opinion paper is to look at oleogelation from a colloidal gel perspective in order to have new insights into the gelling properties of different categories of oleOGelators forming mono and multicomponent gels.
Abstract: The field of oleogelation have shown a tremendous progress in the last decade both in terms of fundamental exploration as well as practical applications. However, one of the main bottleneck that still limits the full-scale commercial exploitation of oleogelation techniques is identification of ideal oleogelator(s) with desired properties. Most, if not all oleogelators that are currently been explored in the field, have been identified serendipitously. A rational understanding of the structuring mechanisms and the consequent gel properties of existing systems could serve as a catalyst to accelerate our efforts in finding the ideal oil gelling agents. The purpose of this opinion paper is to look at oleogelation from a colloidal gel perspective in order to have new insights into the gelling properties of different categories of oleogelators forming mono and multicomponent gels.
37 citations
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TL;DR: The results indicate that the novel hybrid LOG and LOGE formulated with SA can be used as a more stable alternative to SL oleogels particularly when the objective is to achieve semi-solid characteristics.
Abstract: The objective of this study was to characterize a novel soy lecithin (SL) based oleogel (LOG) and oleogel emulsion (LOGE) prepared with different proportions of stearic acid (SA). Oleogels were developed with 1 wt% of water, and two gelator concentrations (20 wt% and 30 wt%) with SL:SA ratios (0:10, 3:7, 5:5, 7:3, 10:0). The same SL:SA proportions were used to prepare LOGE with 10 wt% and 20 wt% of water. Small (SAXD) and wide (WAXD) angle x-ray diffraction studies and polarized light microscopy were conducted to determine the nano- and microstructure of the samples. The hardness of the samples was analyzed using a texture analyzer and the thermal properties with a differential scanning calorimeter. The results indicate that LOG were primarily formed through the entanglement of bundles of reverse worm-like micelles of SL; however, LOGE were structured mainly through SA crystals that interacted in a synergistic fashion with the SL reverse micelles network to stabilize the three dimensional network. The hardness of the LOG and LOGE increased with an increase in SA, however, in samples containing both SL and SA, LOGE were harder than LOG, demonstrating that the oleogelators have a synergistic effect. The novel hybrid LOG and LOGE formulated with SA can be used as a more stable alternative to SL oleogels particularly when the objective is to achieve semi-solid characteristics.
36 citations
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TL;DR: Investigation of the dissolution behavior of levetiracetam from HPMC/Eudragit®NE matrices using magnesium aluminometasilicate (Neusilin® US2) as filler with excellent WAC found that thermal treatment was not revealed as a useful procedure for this system.
Abstract: Burst drug release is often considered a negative phenomenon resulting in unexpected toxicity or tissue irritation. Optimal release of a highly soluble active pharmaceutical ingredient (API) from hypromellose (HPMC) matrices is technologically impossible; therefore, a combination of polymers is required for burst effect reduction. Promising variant could be seen in combination of HPMC and insoluble Eudragits® as water dispersions. These can be applied only on API/insoluble filler mixture as over-wetting prevention. The main hurdle is a limited water absorption capacity (WAC) of filler. Therefore, the object of this study was to investigate the dissolution behavior of levetiracetam from HPMC/Eudragit®NE matrices using magnesium aluminometasilicate (Neusilin® US2) as filler with excellent WAC. Part of this study was also to assess influence of thermal treatment on quality parameters of matrices. The use of Neusilin® allowed the application of Eudragit® dispersion to API/Neusilin® mixture in one step during high-shear wet granulation. HPMC was added extragranularly. Obtained matrices were investigated for qualitative characteristics, NMR solid-state spectroscopy (ssNMR), gel layer dynamic parameters, SEM, and principal component analysis (PCA). Decrease in burst effect (max. of 33.6%) and dissolution rate, increase in fitting to zero-order kinetics, and paradoxical reduction in gel layer thickness were observed with rising Eudragit® NE concentration. The explanation was done by ssNMR, which clearly showed a significant reduction of the API particle size (150–500 nm) in granules as effect of surfactant present in dispersion in dependence on Eudragit®NE amount. This change in API particle size resulted in a significantly larger interface between these two entities. Based on ANOVA and PCA, thermal treatment was not revealed as a useful procedure for this system.
12 citations
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TL;DR: In this paper , the textural and rheological properties of oleogels prepared by low molecular weight Oleogelators (LMWGs) and functional characteristics of foods formulated by these OLEogels are comprehensively discussed against conventional solid fats.
Abstract: There is a growing need for healthier foods with no trans and reduced saturated fat. However, solid fats play critical roles in texture and sensory attributes of food products, making it challenging to eliminate them in foods. Recently, the concept of oleogelation as a novel oil structuring technique has received numerous attentions owing to their great potential to mimic the properties of solid fats. Understanding textural, rheological and sensory properties of oleogels helps predict the techno-functionalities of oleogels to replace solid fats in food products. This research critically reviews the textural and rheological properties of oleogels prepared by low molecular weight oleogelators (LMWGs) and functional characteristics of foods formulated by these oleogels. The mechanical properties of LMWG-containing oleogels are comprehensively discussed against conventional solid fats. The interactions between the oleogel and its surrounding food matrix are explained, and the sensory attributes of oleogel containing reformulated products are highlighted. Scientific insights into the texture and rheological properties of oleogels manufactured with a wide range of low molecular gelators and their related products are provided in order to boost their implication for creating healthier foods with high consumer acceptability. Future research opportunities on low molecular weight gelators are also discussed.
11 citations
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TL;DR: This Account presents recent advances in understanding how and why dilute solutions/sols of low-molecular-mass organic gelators (LMOGs) undergo microscopic phase separation to form self-assembled fibrillar networks in molecular organogels.
Abstract: This Account presents recent advances in understanding how and why dilute solutions/sols of low-molecular-mass organic gelators (LMOGs) undergo microscopic phase separation to form self-assembled fibrillar networks in molecular organogels. Concepts are illustrated structurally at the subnanometer (molecular) to several millimeter (bulk) length scales and dynamically over time scales that follow the assembly of supersaturated solutions/sols into gel phases. Examples include both structurally complicated (ALS molecules with aromatic, linking, and steroidal groups) and simple (n-alkanes or n-alkanes along whose chains a hetero-group has been inserted) LMOGs in a wide range of organic liquids.
775 citations
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TL;DR: In this paper, various mathematical models derived to explain and predict solute diffusion in hydrogels are reviewed and tested against literature data, and it was determined that a scaling hydrodynamic model provided the best explanation for solutes diffusion.
Abstract: Solute diffusion in hydrogels is important in many biotechnology fields. Solute behavior in hydrogels has been explained in terms of reduction in hydrogel free volume, enhanced hydrodynamic drag on the solute, increased path length due to obstruction, and a combination of hydrodynamic drag and obstruction effects. In this article the various mathematical models derived to explain and predict solute diffusion in hydrogels are reviewed and tested against literature data. These models can be divided into those applicable to hydrogels composed of flexible polymer chains (i.e., homogeneous hydrogels) and those composed of rigid polymer chains (i.e., heterogeneous hydrogels). For homogeneous hydrogels it was determined that a scaling hydrodynamic model provided the best explanation for solute diffusion, while for heterogeneous hydrogels obstruction models were more consistent with the experimental data. Both the scaling hydrodynamic model and the most appropriate obstruction model contain undefined parameters w...
756 citations
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TL;DR: In this paper, the authors focus on the field of edible oil structuring and present a review of the general structuring concepts and building blocks which can be found in organic solvents.
Abstract: The structure of many food products is based on networks of crystalline triacylglycerol (TAG) hardstock. These contain high levels of saturated fatty acids, which are among the factors contributing to cardiovascular diseases. Therefore it would be desirable to have alternative routes to structure edible oils. This review starts with general structuring concepts and building blocks which can be found in organic solvents. Subsequently it focuses on the field of edible oil structuring. Among the alternative structuring agents that have received attention in recent years are mono- and diglycerides, fatty acids, fatty alcohols, waxes, wax esters, sorbitan esters, and phytosterols. It is found that the most efficient structuring agents form small, preferably non-spherical particles. Mixing of components often provides superior structuring over use of pure components. Straightforward screening of pure components might be feasible. However, the number of options provided by mixing requires guided screening, for which understanding of the underlying mechanisms is essential. Analytical methods helping to characterise oil structuring and elucidate the structuring mechanisms are discussed.
301 citations
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TL;DR: In this article, a hydrogel for delayed release of an anionic macromolecule was proposed, where the peptide selected from the group consisting of SEQ ID No:1 through SEQ No:33 in an aqueous medium at a pH of 7.4.
Abstract: A hydrogel for delayed release of an anionic macromolecule, wherein the hydrogel comprises the anionic macromolecule, 150 mM NaCl, and a peptide selected from the group consisting of SEQ ID NO:1 through SEQ ID NO:33 in an aqueous medium at a pH of 7.4; wherein the anionic macromolecule has an isoelectric point of at most 6.8; and wherein the hydrogel is capable of retaining at least 25% of the anionic macromolecule after 28-day extraction at 37° C. with a pH=7.4 BTP buffer containing 150 mM NaCl.
200 citations