Effect of storage time on the mechanical and microstructural properties of bigels based on xanthan gum and castor oil

As biphasic systems bigels are formed by hydrogels and organogels. Given their characteristics, they have been studied in food, pharmaceutical and cosmetic applications for bioactives delivery. The rheological characteristics and amount used of the individual structured systems influence the final properties; thus, the objective of this work was to evaluate the effect of the proportion of castor oil organogel, the concentration of organogelator, and the storage time in the mechanical and microstructural properties of bigeles. Bigels were prepared from structured castor oil organogels with monoacylglycerides at concentrations of 6% (MOG) and 6.5% (HOG) wt/wt, and hydrogels with 2% wt/wt xanthan gum (HG) at three organogel/hydrogel ratios 15 of 85, 30 of 70, and 45 of 55. Bigels were characterized by optical microscopy with polarized light filter, centrifugal stability, texture, and rheology for 60 days. The increase in the proportion of organogel favors the mechanical response (k, G₀, and firmness) of bigels. The high viscosity of castor oil slows down the structuring of organogel droplets, showing an improvement in its mechanical properties after 15 days of its preparation. The increase in the organogelator concentration is significant in the bigels with 30% and 45% proportions of organogel in the rheological tests. By using HOG in the formation of bigels, higher values for G₀ and k were obtained, as well as higher centrifugal stability compared with bigels formed from MOG. The rheological and microstructural behavior of bigels can be modified according to their application by varying the proportions of organogel/hydrogel and the concentration of the organogelator.     

Sunflower Oil and Protein-based Novel Bigels as Matrices for Drug Delivery Applications—Characterization and in vitro Antimicrobial Efficiency

The current study deals with the characterization of sunflower oil- and protein-based bigels for drug delivery applications. Span-40 was used as an organogelator for the preparation of bigels. The bigels were characterized by microscopy, XRD, thermal, texture studies and impedance spectroscopy. The microscopic studies revealed that the droplets were apolar in nature (organogels), while the continuum phase was polar in nature (protein hydrogel matrix). Incorporation of the proteins improved the stability of the bigels. The release of the drugs followed diffusion kinetics. The bigels showed good antimicrobial efficiency against E.coli and were cytocompatible in presence of L929 cells.     

Development and characterization of gelatin‐based hydrogels,emulsion hydrogels,and bigels: A comparative study

This study was designed to examine the physicochemical and electrical properties of gelatin‐based hydrogels, emulgels, and bigels. The chemical studies suggested an increase in hydrogen bonding in the emulgel and bigel when sesame oil (SO; representative vegetable oil) and SO organogel (OG; representative OG) were incorporated within the gelatin matrix. The emulgel and bigel showed better mechanical properties and higher electrical impedances compared to the hydrogel. The hydrogel showed similar swelling at pH 1.2 and 7.2. The swelling of the emulgel and bigel was higher at pH 7.2. The formulations were found to be highly hemocompatible; this indicated their biocompatible nature. Ciprofloxacin, a model antimicrobial drug, was incorporated within the formulations. The release of the drug was found to be diffusion‐mediated. The antimicrobial efficiency of all of the drug‐loaded formulations was found to be equivalent. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41502.     

Thermo‐mechanical properties of candelilla wax and dotriacontane organogels in safflower oil

The thermo‐mechanical properties of organogels developed by a complex mixture of n‐alkanes present in candelilla wax (CW) were investigated and compared with the ones of organogels developed by a pure n‐alkane, dotriacontane (C₃₂). In both cases, the liquid phase used was safflower oil high in triolein (SFO) and the variables studied were two levels of gelator concentration (1 and 3%), cooling rates of 1 and 10 °C/min, and two gel setting temperatures, 5 and 25 °C (T_set). Based on comparisons of the organogels made with C₃₂, the presence of minor molecular components in CW had a profound effect on the crystal habit of the n‐alkanes in CW‐based organogels, and therefore on their physical properties. Thus, independent of the cooling rate and T_set, C₃₂ showed a higher solubility and higher self‐assembly capability in the SFO than CW. Nevertheless, for the same gelator concentration and time‐temperature conditions, C₃₂ organogels had lower G' profiles than CW organogels. Additionally, independent of the type of gelator, more stable organogel structures were developed at T_set = 5 °C and using the lower cooling rate. The rheological behavior of the organogels was explained considering the formation of a rotator phase by the n‐alkanes, its solid‐solid transition, and their dependence as a function of the cooling rate and T_set. The results here obtained showed that it is possible to gelate SFO through organogelation with CW and without the use of trans fats.     

The Role of Oil Phase in the Stability and Physicochemical Properties of Oil-in-Water Emulsions in the Presence of Gum Tragacanth

Different emulsions based on six types of vegetable oils (sunflower, canola, sesame, olive, coconut, and palm olein) were studied to investigate the role of the oil phase in the stability and physicochemical characteristics of oil-in-water emulsions prepared with gum tragacanth. The results indicated that the stability, rheological parameters, and size distribution of emulsions were dependent on the oil type. Based on the interfacial tension value, the type of oil did not have a significant effect on the gum tragacanth-emulsifying properties. The formulation based on sunflower and coconut oil led to producing more stable emulsion and a sample containing palm olein resulted in an unstable emulsion. Rheological analysis revealed that the sample based on palm olein showed the lowest consistency coefficient (2.10 ± 0.05 Pas ⁿ), elastic modulus (3.90 ± 0.21 Pa), and energy of cohesion (80.87 ± 1.1 J m⁻³). This study revealed that using oils with lower viscosity and higher density led to the higher stability of the emulsion samples.     

Oxidative stability of sunflower oil bodies

This study investigates the oxidative stability of sunflower oil body suspensions (10 wt‐% lipid). Two washed suspensions of oil bodies were evaluated over 8 days at three temperatures (5, 25 and 45 °C) against three comparable sunflower oil emulsions stabilized with dodecyltrimethylammonium bromide (DTAB), polyoxyethylene‐sorbitan monolaurate (Tween 20) and sodium dodecyl sulfate (SDS) (17 mM). The development of oxidation was monitored by measuring the presence of lipid hydroperoxides and the formation of hexanal. Lipid hydroperoxide concentrations in the DTAB, SDS and Tween 20 emulsions were consistently higher than in the oil body suspensions; furthermore, hexanal formation was not detected in the oil body emulsions, whereas hexanal was present in the headspace of the formulated emulsions. The reasons for the extended resistance to oxidation of the oil body suspensions are hypothesized to be due to the presence of residual seed proteins in the continuous phase and the presence of a strongly stabilized lipid‐water interface.     

Palm oil‐based organogels and microemulsions for delivery of antimicrobial drugs

This study has been designed to develop palm oil (PO) based organogels using span 80/tween 80 mixture (OG) as a gelator system by fluid‐filled structure mechanism. The results suggested formation of organogels, emulsions, and microemulsions as the proportions of PO, OG and water were varied. The emulsions were found to be thermodynamically unstable as compared to the organogels and the microemulsions. Accelerated thermal stability test suggested that all the microemulsions and the organogels of only eight compositions were stable. The organogels showed viscoelastic property while the microemulsions showed viscous flow behavior. Both the organogels and the microemulsions were found to be highly hemocompatible and nonirritant. The antimicrobial efficiency of the ciprofloxacin HCl‐loaded formulations showed equivalent efficiency as compared to marketed formulations. The rates of drug release from the organogels were found to be relatively slower as compared to the microemulsions. The preliminary studies suggested that the developed organogel and microemulsion‐based formulations may be tried for topical delivery of antimicrobials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39979.     

Development of Bigels Based on Stearic Acid–Rice Bran Oil Oleogels and Tamarind Gum Hydrogels for Controlled Delivery Applications

In the last few decades, different types of gels have been widely studied as potential drug delivery carriers. In this paper, we propose the synthesis of an oleogel, a tamarind gum hydrogel, and bigels for applications as drug delivery matrices. The oleogel was prepared by mixing stearic acid and rice bran oil, whereas the hydrogel was prepared by mixing tamarind gum with a hydroethanolic solution. Hydrogel‐in‐oleogel and oleogel‐in‐hydrogel bigels were prepared by mixing the hydrogel and the oleogel. The suitability of the formulations for controlled drug release applications was thoroughly examined using microscopy, Fourier transform infrared (FTIR) spectroscopy, as well as mechanical, electrical, thermal, drug release, and antimicrobial studies. An alteration in the microarchitecture of the bigels is observed when the oleogel and the hydrogel are mixed in varying proportions. The associative interactions within the formulations increase with the increase in the hydrogel content. The bigels exhibit the presence of stearic acid melting endotherm (associated with the oleogel) and water evaporation endotherm (associated with the hydrogel). This study suggests that the hydrogel has lowest bulk resistance compared to the other formulations. The structural breakdown of the bigels is composition‐dependent, and the bulk electrical resistance is mainly governed by the oleogel phase. An increase in the diffusion of the moxifloxacin HCl from the formulations is observed with the increase of the hydrogel proportion, which in turn increases the rate of release of the drug. The proposed formulations also exhibit good antimicrobial efficacy. The analysis of these properties suggests that specific formulations can be tailored by need‐based applications of the drug release rate.     

Effect of lipid type on water‐in‐oil‐emulsions stabilized by phosphatidylcholine‐depleted lecithin and polyglycerol polyricinoleate

Water‐in‐oil (W/O, 30:70) emulsions were prepared with phosphatidylcholine‐depleted lecithin [PC/(PI,PE) = 0.16] or polyglycerol polyricinoleate (PGPR) as emulsifying agents by means of pressure homogenization. The effect of lipid type (medium‐chain triacylglycerols, sunflower, olive, butter oil, or MCT‐oil/vegetable fat blends) was investigated in relation to particle size distribution, coalescence stability and the sedimentation of the water droplets. A significant correlation (p <0.05) was observed between the interfacial pressure caused by the addition of lecithin to the pure lipids and the specific surface area of the emulsion droplets (r_s = 0.700), and between the viscosity of the lipids used as the continuous phase (reflecting the fatty acid composition) and the specific surface area of the emulsion droplets (r_s = 0.8459) on the other hand. Blends of vegetable fat and MCT‐oil led to reduced coalescence stability due to the attachment of fat crystals to the emulsion droplets. Lecithin‐stabilized W/O emulsions showed significantly higher viscosities compared to those stabilized with PGPR. It was possible to adjust the rheological properties of lecithin‐stabilized emulsions by varying the lipid phase.     

Healthier lipid combination oil‐in‐water emulsions prepared with various protein systems: an approach for development of functional meat products

Five protein‐stabilized oil‐in‐water emulsions were prepared using sodium caseinate (O/SC), soy protein isolate (O/SPI), sodium caseinate and microbial transglutaminase (O/SC + MTG), sodium caseinate, microbial transglutaminase and meat slurry (O/SC + MTG + MS) and SPI, sodium caseinate and microbial transglutaminase (O/IPS + SC + MTG); their composition (proximate analysis and fatty acid profile) and physicochemical characteristics were examined. The lipid phase was a combination of healthy fatty acids from olive, linseed and fish oils, containing low proportions (15%) of saturated fatty acids (SFA) and high proportions of monounsaturated fatty acids (MUFA, 47%) and polyunsaturated fatty acids (PUFA, 36%), with a PUFA/SFA ratio >2, and a n‐6/n‐3 PUFA ratio of 0.4. All the oil‐in‐water emulsions showed high thermal and creamy stability. Results of penetration test and dynamic rheological properties showed la existencia de different types of oil‐in‐water emulsion structures according to stabilizing system of emulsion. Those structures ranged from concentrate solution‐like (stabilized only with SC) (gel strength 0.06 mJ) to gel‐like (samples containing MTG) behaviours (gel strength ranged between 3.4 and 6.2 mJ). Morphological differences in the organization of the network structure were observed (by scanning electron microscopy) as functions of the protein system used to stabilize the oil‐in‐water emulsions.     

Design of Roll-In Margarine Analogous by Partial Drying of Monoglyceride-Structured Emulsions

A novel process is proposed to turn soft gelled emulsions containing saturated monoglyceride (MG), sunflower oil, and water into a fat material with the typical water content (20 g/100 g) and rheological properties of roll-in margarine. A gentle drying procedure at 30 °C is proposed to allow partial water removal from the emulsions, without causing phase separation. Upon water removal, the soft emulsion, initially stabilized by a highly hydrated liquid crystalline lamellar phase of MG, converts into a high internal phase oil–water emulsion (HIPE) stabilized thanks to the presence of MG crystals around gelled oil particles, which are interconnected via polar groups of MG. HIPE at the highest MG content (13.7 g/100 g) shows rheological properties (Gʹ = 4.6 × 10⁵ Pa, critical stress = 634 Pa) comparable to those of commercial roll-in margarine and is successfully used in baking trials of puff pastry. Practical Applications: The last years have seen an increasing demand for strategies for the nutritional improvement of lipid-containing foods, due to the emerging health concern related to the consumption of unbalanced saturate/unsaturated fats. Moreover, sustainability issues have arisen due to the abundant use of tropical fats in foods. However, the unique technological and sensory properties of fats make this task very challenging, especially considering the production of laminated products requiring the use of plastic fat materials with peculiar rheological properties. The results obtained in this study are very promising, as they show that the novel fat can be used as an alternative to traditional laminating margarine.     

Functional Food Ingredients Based on Sunflower Protein Concentrates Naturally Enriched with Antioxidant Phenolic Compounds

The functional properties of three sunflower protein concentrates having different content of phenolic compounds (mainly chlorogenic and caffeic acids) obtained from sunflower oil cake, a by-product of the oil industry, were evaluated. Sunflower protein concentrates exhibited high water solubility and moderate water-imbibing and water-holding capacities. It was possible to obtain foams and emulsions of different stability at different pH and ionic strength from these protein concentrates, as well as self-supporting gels produced by thermal induction. The presence of phenolic compounds not only conferred antioxidant activity and changed the color of protein products, but also reduced the water imbibing capacity of sunflower protein concentrates, the stability of the emulsions obtained, and the hardness of protein gels. In contrast, phenolic compounds did not modify the water holding capacity, their water solubility or their foaming properties. These results suggest that these protein products may be used as functional ingredients in the food industry.     

Comparison of the pomegranate seed oil organogels of carnauba wax and monoglyceride

The aims of this study were to prepare organogels from pomegranate seed oil (PO) with carnauba wax (CW) and monoglyceride (MG), compare the organogels with a commercial margarine (CM) and evaluate 3 months storage stability. At 3% organogelator addition, no gels were formed, while at 7 and 10% additions, the oil binding capacities increased and were always higher in CW organogels, with crystal formation times of 8.0 to 14.0 min. Solid fat content (SFC) of the CW organogels varied between 2.96 and 8.71% at 20°C, while MG gels had 2.89–9.43%, and CM had 29.73% SFC. The peak melting temperatures of the CW organogels ranged from 74.73 to 75.74°C and MG organogels ranged from 11.09 to 50.63°C, whereas CM product exhibited 45.92°C peak melting temperature. The hardness of CW organogels was higher than that of MG organogels. The organogels showed potential as spreadable products. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41343.     

A Novel Cinnamic Acid‐Based Organogel: Effect of Oil Type on Physical Characteristics and Crystallization Kinetics

Oil sources (canola, sunflower, and flax‐seed oil) characterized by unsaturated fatty acids are gelled by using cinnamic acid. The physical characteristics and crystallization kinetics of cinnamic acid‐based organogels are investigated. A phase diagram with cinnamic acid concentrations ranging from 1% to 7% (w/w) shows that both canola and sunflower oil organogels are formed at 3.0% (w/w) cinnamic acid at 5 °C. The flax‐seed oil organogels are formed at 4.0% (w/w) at 5 °C. Firmness is shown to be dependent on the fatty acid composition and viscosity of the oil. Flax‐seed oil with a higher degree of unsaturation and lower viscosity tends to produce harder organogels. This result is consistent with the observations of polarized light microscopy. The organogels have low solid fat content at 35 °C which is close to the human body temperature, and no effect of oil type is found. The X‐ray diffraction measurements show β'‐form crystal exists in three types of organogels. The thermal properties vary in different types of organogels. The crystallization kinetics results suggest that three types of organogels crystallize by 1D and 2D mixed growth and instantaneous nucleation. Practical Applications: These findings provide in‐depth characteristics of cinnamic acid‐based organogels, which are a substitute for solid fats.     

Rheological Properties of Candelilla Wax and Dotriacontane Organogels Measured with a True-Gap System

The rheology of organogels developed by candelilla wax (CW) and a pure n-alkane (dotriacontane, C32) was evaluated with a rheometer equipped with a true-gap system and compared with the rheograms obtained with a fixed-gap system. The two systems used a cone and plate geometry. In contrast to the fixed-gap system, the true-gap system makes the corrections in the gap size associated with the expansion/shrinkage of the sample and/or the rheometer geometry when changing temperature conditions are used during measurements. The CW and C32 organogels were prepared using safflower oil high in triolein (SFO) as the liquid phase, and the treatments studied resulted from the factorial combinations of two levels of gelator concentration (1 and 3%) and two gel setting temperatures (T _set; 5 and 25 °C) achieved using a cooling rate of 1 or 10 °C/min. The use of the true-gap system provided rheological parameters (i.e., G′ profiles) that agreed with the micro structure and the calorimetric (i.e., heat of melting, ΔH _M) behavior of both the CW and the C32 organogels. The use of a fixed-gap system in the rheological characterization of organogels must be treated with caution, specially with time dependent G′ determinations involving the use of fast temperature ramps (i.e., 10 °C/min).     

Novel agar–stearyl alcohol oleogel-based bigels as structured delivery vehicles

The present study describes the synthesis of novel bigels as delivery matrices for controlled delivery applications. The bigels were prepared by mixing agar hydrogel and stearyl alcohol oleogel in different proportions. The microscopic analysis of the bigels suggested the formation of biphasic bigels at lower proportions of oleogel and bicontinuous bigel at higher proportions. Stress relaxation study was used to analyze the mechanical properties. The viscoelastic property of the bigels was estimated by modeling the relaxation profile using Weichert model of viscoelasticity. The analysis of the electrical property of the bigels showed an increase in the impedance values as the oleogel content was increased. Further, a corresponding decrease in the electrical stability of the bigels was observed with an increase in the oleogel proportion. The analysis was prepared using (RQ)Q equivalent electrical circuit model. The ciprofloxacin hydrochloride release from the bigels was predominantly diffusion-mediated as analyzed by Korsmeyer–Pappas and Peppas–Sahlin models.     

Self-Organizing Structures of Phosphatidylcholine in Nonaqueous Solvents: Tailoring Gel-like Systems

In this paper, we investigated the role played by solvent type and additives (water [W] and citric acid [CA]) on the self-assembly of phosphatidylcholine (PtdCho) into gels. Soybean lecithin (L) served as the PtdCho source used in this study. Lecithin was combined with different oils: hexadecane (HEX), sunflower oil, and medium-chain triacylglycerol to explore its ability to form organogels. Among the solvents, only HEX was able to form a translucent self-sustainable gel with lecithin. It was found that the lower water solubility and viscosity of HEX favored gel formation. Small-angle X-ray scattering revealed different structures arisen from lecithin organization depending on the organic medium type. In addition, the gel properties of the L-HEX binary system were also tailored through inclusion of the “primers” W or CA. Oscillatory rheological behavior of organogels was effectively described by a single relaxation-time Maxwell model, with good fitting at low and intermediate frequencies and with deviations at higher frequencies, indicating the presence of reverse wormlike micelles. Organogels were thermoreversible and, upon CA addition, a substantial increase in zero-shear viscosity was observed. Incorporation of W led to a similar microstructure to that obtained only with L, whereas CA promoted a different ordering of PtdCho assemblies. Formation and properties of PtdCho-based organogels were dictated by using different oil types or by changing the polarity of the medium with the incorporation of primers. A better understanding of phospholipid-based nonlamellar mesophases in organic solvent offers the prospect of adapting the gel properties to the desired application and functionality.     

Nanocomposites based on ionene–bentonite used to treat oily water

A large number of processes are used to treat the oily water (oil emulsions in water) produced in the petroleum industry. The treatment strategy depends not only on the strictness of the environmental requirements in the jurisdiction where the water is discharged, but also on the relative treatment cost. The present study reports tests to assess the effectiveness of removing oil from oily water by adsorption in polymer nanocomposites. These composites were prepared from ionenes (cationic polyelectrolytes) and sodium bentonite or organophilic bentonite. They were characterized by infrared spectrometry, thermogravimetry, X‐ray fluorescence, and X‐ray diffraction. The oil‐removal effectiveness was evaluated by mixing nanocomposites and oily water in a shaker bath (batch test). In the tests conducted only with treated sodium bentonite and organophilic bentonite, the oil removal was ～ 70%, whereas the use of polymer nanocomposites raised the adsorption of oil to ～ 90%. These values depended on the mass of material, concentration of oil in the contaminated water, and the contact time. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Micromorphology and adhesive properties of sulfonated polyurethane/polyacrylate emulsions prepared by surfactant-free polymerization

Novel eco-friendly sulfonated polyurethane/polyacrylate (SPUA) emulsions were synthesized by surfactant-free emulsion polymerization method using PU as seeds. The sodium sulfonate modified polyester polyol (SDNP) was used as internal emulsifier to make the PU emulsion disperse in deionized water. Effects of the SDNP content on the properties of the emulsions and membranes were studied. Dynamic light scattering (DLS) result showed that the average particle sizes of SPUA emulsions decreased first from 124.1 nm to 102 nm when the SDNP content was lower than 40 wt% and then increased to 138 nm. Transmission electron microscopy (TEM) morphology showed that the particle sizes were all spherical and an apparent core-shell structure was observed. Fourier transform infrared spectroscopy (FT-IR) result ascertains that SPUA was successfully prepared. X-ray photoelectron spectroscopy (XPS) analysis demonstrates that the carbon, oxygen, nitrogen, sulfur, and sodium peaks were all revealed and the polyurethane component was rich in the upper surface. Thermo gravimetric analysis (TGA) of the membranes showed that the thermal stability of the SPUA membranes was enhanced by increasing the SDNP content. Scanning electron micrograph (SEM) results demonstrates that the coexistence of a dual phase. The SPUA could be used as adhesives in footwear industry, and the T-peel strength of the SPUA membranes increased from 5.98 N/mm to 12.06 N/mm when the SDNP content was up to 40 wt%. The wettability of SPUA emulsions on the rubber surface results showed that the emulsions could wet the rubber surface well.     

Preparation and characterization of waterborne polyurethane/polyacrylate emulsions containing sulfonate groups

Polyurethane/polyacrylate emulsions (SDPUA) with high solid content were obtained by using carboxyl groups and sulfonate groups as hydrophilic chain-extenders and internal emulsifiers through surfactant-free emulsion polymerization. Polyurethane/polyacrylate emulsions with ethylene diamine (EDA) as chain-extender (EDPUA) were also prepared. The influence of the different 2,4-diamino-benzenesulfonic acid sodium salt (DABS) content on the properties of the SDPUA products was investigated. The main properties of EDPUA were also discussed compared with the SDPUA samples. Dynamic light scattering results showed that when DABS/DMPA molar ratios increased from 1/4.7 to 1/2.28, the particle size increased from 72.2 to 99.7 nm. The particle size of EDPUA emulsion was larger. The steady rheological measurements illustrated that the viscosity decreased with the shear rate increase and the emulsions were displayed as pseudoplastic behavior. Attenuated total reflection Fourier transform infrared results demonstrated the SDPUA products were successfully prepared. As the function of DABS groups, the thermal stability was enhanced. With the increment in DABS/DMPA molar ratio, the contact angles on SDPUA membranes decreased, and the surface free energies increased. The T-peel strength increased to 88.2 N/mm and DABS/DMPA molar ratio increased to 1/2.28, and it was larger than the EDPUA samples. The compatibility of the dual phases was enhanced.