The role of hydrogen bonds in TAG derivative-based oleogel structure and properties

Development and Characterization of Ethylcellulose Oleogels Based on Pumpkin Seed Oil and Rapeseed Oil

In contrast to rapeseed oil, pumpkin seed oil has yet to be well investigated in terms of oleogelation, and, to the best of our knowledge, no study related to the use of ethylcellulose (EC) in the structuring of this oil has been identified in the current scientific literature. Therefore, the present study evaluated several oleogels formulated with EC as the oleogelator in different concentrations of 7% (OG7) and 9% (OG9), based on cold-pressed pumpkin seed oil (PO) and refined rapeseed oil (RO), as well as on mixtures of the two oils in different combinations: PO:RO (3:1) (PRO) and PO:RO (1:1) (RPO). Physicochemical properties such as visual appearance, gel formation time (GFT), oil-binding capacity (OBC), oxidative and thermal stability, and textural characteristics were analyzed. Analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD) were used in the statistical analysis of the data, with a significance level of p < 0.05. EC proved to be an effective structuring agent of the mentioned edible oils; the type of oils and the concentration of oleogelator significantly influenced the characteristics of the obtained oleogels. The 9% EC oleogels exhibited a more rigid structure, with a higher OBC and a reduced GFT. Pumpkin seed oil led to more stable oleogels, while the mixture of pumpkin seed oil with rapeseed oil caused a significant reduction in their mechanical properties and decreased the OBC. After 14 days of storage, all oleogels demonstrated proper oxidative stability within the bounds set by international regulations for edible fats, regardless of the kind of oil and EC concentration. All of the oleogels showed a higher oxidative stability than the oils utilized in their formulation; however, those prepared with cold-pressed pumpkin seed oil indicated a lower level of lipid oxidation among all oleogels. The P-OG9 and PR-OG9 oleogels, which mainly included PO and contained 9% EC, demonstrated the optimum levels of quality in texture, GFT, OBC, and oxidative stability.

Microstructure, Physical Properties, and Oxidative Stability of Olive Oil Oleogels Composed of Sunflower Wax and Monoglycerides

The utilization of natural waxes to form oleogels has emerged as a new and efficient technique for structuring liquid edible oil into solid-like structures for diverse food applications. The objective of this study was to investigate the interaction between sunflower wax (SW) and monoglycerides (MGs) in olive oil oleogels and assess their physical characteristics and storage stability. To achieve this, pure SW and a combination of SW with MGs in a 1:1 ratio were examined within a total concentration range of 6-12% w/w. The formed oleogels were characterized based on their microstructure, melting and crystallization properties, textural characteristics, and oxidative stability during storage. All the oleogels were self-standing, and, as the concentration increased, the hardness of the oleogels also increased. The crystals of SW oleogels were long needle-like, while the combination of SW and MGs led to the formation of crystal aggregates and rosette-like crystals. Differential scanning calorimetry and FTIR showed that the addition of MGs led to different crystal structures. The oxidation results revealed that oleogels had low peroxide and TBARS values throughout the 28-day storage period. These results provide useful insights about the utilization of SW and MGs oleogels for potential applications in the food industry.

Self-Healing Oxalamide Organogelators of Vegetable Oil

The aim of this study was to assess the gelling potential of chiral oxalamide derivatives in vegetable oils. Special emphasis was given to the potential applications of the examined oil gels as sustained delivery systems and as fat substitutes in food products. The applicability of oil gelators is envisaged in food, cosmetics, and the pharmaceutical industry. The regulations requiring the elimination of saturated fats and rising concerns among consumers health motivated us to investigate small organic molecules capable of efficiently transforming from liquid oil to a gel state. The oxalamide organogelators showed remarkable gelation efficiency in vegetable oils, thermal and mechanical stability, self-healing properties, and a long period of stability. The physical properties of the gels were analysed by TEM microscopy, DSC calorimetry, and oscillatory rheology. The controlled release properties of acetylsalicylic acid, ibuprofen, and hydrocortisone were analysed by the LC-MS method. The influence of the oil type (sunflower, soybean, and olive oil) on gelation efficiency of diverse oxalamide derivatives was examined by oscillatory rheology. The oxalamide gelators showed thermoreversible and thixotropic properties in vegetable oils with a minimum gelation concentration of just 0.025 wt%. The substitution of palm fats with gelled sunflower oil applied in cocoa and milk spreads at gelator concentrations lower than 0.2 wt% have shown promising viscoelastic properties compared to that of the original food products.

Interfacial behavior, gelation and foaming properties of diacylglycerols with different acyl chain lengths and isomer ratios

Diacylglycerols (DAG) of varying chain lengths were synthesized and the acyl migrated samples with different 1,3-DAG/1,2-DAG ratios were obtained. The crystallization profile and surface adsorption differed depending on DAG structure. C12 and C14 DAGs formed small platelet- and needle-like crystals at the oil-air interface which can better reduce surface tension and pack in an ordered lamellar structure in oil. The acyl migrated DAGs with higher ratios of 1,2-DAG showed reduced crystal size and lower oil-air interfacial activity. C14 and C12 DAG oleogels exhibited higher elasticity and whipping ability with crystal shells surrounding bubbles, whereas C16 and C18 DAG oleogels had low elasticity and limited whipping ability due to the formation of aggregated needle-like crystals and loose gel network. Thus, acyl chain length dramatically influences the gelation and foaming behaviors of DAGs whereas the isomers exert little influence. This study provides basis for applying DAG of different structures in food products.

Rheological and thermal properties of reinforced monoglyceride-carnauba wax oleogels

BACKGROUND

Oleogels can be used in the food industry to reduce the consumption of solid fat in the human diet and diminish some of the industrial-technological issues of using oil instead of fat. Regarding the structural weakness of neat monoglyceride oleogel and the waxy mouthfeel of pure carnauba wax oleogel, as a result of the high melting and crystallization points, the present study aimed to diminish these defects.

RESULTS

Carnauba wax (CBW) was used as a co-gelator with distilled monoglyceride (DMG) at different weight ratios (100:0, 85:15, 70:30, 55:45, 40:60, and 0:100) (DMG: CBW) and two total gelator concentrations (50 and 100 g kg^-1 ) to improve the DMG oleogel characteristics. The addition of CBW strengthened the DMG network and decreased the polymorphic transition. Thermal analysis showed just co-crystallization at the 85:15 ratio, whereas, in the other combinations, high melting components of CBW crystalized at first. As a result of the crystal homogeneity and long-time development, the oleogel properties improved at the 85:15 ratio. The low concentration of CBW and the formation of the eutectic system were efficient in the waxy mouthfeel reduction of oleogel at the 85:15 ratio in food applications.

CONCLUSION

The DMG/CBW oleogel at the 85:15 ratio, with better structural and sensorial properties than DMG and CBW oleogels, respectively, has the potential for use instead of fat in food formulations. © 2023 Society of Chemical Industry.

Sucrose Esters as Oleogelators in Mono or Binary Structured Oleogels Using Different Oleogelation Routes

Sucrose esters (SE) have been investigated as structuring agents in oleogels. Due to the low structuration power of SE as single agent, this component has recently been explored in combination with other oleogelators to form multicomponent systems. This study aimed to evaluate binary blends of SEs with different hydrophilic-lipophilic balances (HLBs) with lecithin (LE), monoglycerides (MGs) and hard-fat (HF), according to their physical properties. The following SEs, SP10-HLB2, SP30-HLB6, SP50-HLB11, and SP70-HLB15, were structured using three different routes: "traditional", "ethanol" and "foam-template". All binary blends were made using a 10% oleogelator in 1:1 proportion for binary mixtures; they were then evaluated for their microstructure, melting behavior, mechanical properties, polymorphism and oil-binding capacity. SP10 and SP30 did not form well-structure and self-standing oleogels in any combination. Although SP50 showed some potential blends with HF and MG, their combination with SP70 led to even more well-structured oleogels, with a higher hardness (~0.8 N) and viscoelasticity (160 kPa), and 100% oil-binding capacity. This positive result might be attributed to the reinforcement of the H-bond between the foam and the oil by MG and HF.

Food-Grade Oleogels: Trends in Analysis, Characterization, and Applicability

Currently, a large number of scientific articles can be found in the research literature in the field focusing on the use of oleogels for food formulation to improve their nutritional properties. The present review focuses on the most representative food-grade oleogels, highlighting current trends in terms of the most suitable methods of analysis and characterization, as well as trends in their application as substitutes for saturated and trans fats in foods. For this purpose, the physicochemical properties, structure, and composition of some oleogelators are primarily discussed, along with the adequacy of oleogel incorporation for use in edible products. Analysis and characterization of oleogels by different methods are important in the formulation of innovative foods, and therefore, this review discusses the most recent published results regarding their microstructure, rheological and textural properties, and oxidative stability. Last but not least, issues related to the sensory properties of oleogel-based foods are discussed, highlighting also the consumer acceptability of some of them.

In situ formation of injectable organogels for punctal occlusion and sustained release of therapeutics: design, preparation, in vitro and in vivo evaluation

The treatment of dry eye mainly includes instillation of cyclosporine A (CsA) nanoemulsion or the use of punctal plugs. Therefore, in this study, a novel injectable in situ organogel plug was developed using CsA as a model drug, stearic acid, injectable soybean oil, and N-methyl-2-pyrrolidinone (NMP) (1.25:10:0.6, w/v/v) as gel materials, to provide a dual mechanism for dry eye treatment. The formulated CsA injectable in situ organogel (CsA-OG) was evaluated in terms of stability, in vitro release, rheology, ocular irritation, punctal occlusion tests, and ocular distribution assessment. In vivo ocular distribution investigations showed that CsA-OG achieved considerably higher C_max (1.94, 1.92 and 1.97-fold respectively) and AUC_0-72h in the cornea, conjunctiva, and sclera (2.49, 2.27 and 2.15-fold respectively) than ciclosporin eye drops (p < 0.05). In vitro model evaluation demonstrated significant decrease in flow flux to 52.78% at 2 min after CsA-OG injection. According to evaluation of the in vivo model, the organogel plug can completely block the lacrimal passages and greatly decrease the lacrimal drainage rate (p < 0.05). The above results suggest that these intracanalicular CsA-OG plugs can offer more extensive clinical applications than existing lacrimal drainage plugs and may act as a drug delivery system.

Physicochemical Properties and Cookie-Making Performance as Fat Replacer of Wax-Based Rice Bran Oil Oleogels

Reducing the intake of trans and saturated fatty acids is a trend in healthy eating. In this study, the oleogels were prepared from rice bran oil (RBO), candle wax (CDW), beeswax (BW), rice bran wax (RBW), and carnauba wax (CRW), respectively, and the results based on their physicochemical properties and crystal structures at critical concentrations, 6 wt.%, 8 wt.%, and 10 wt.%, were determined to further investigate the oleogels as a shortening substitute in cookie recipes. Oleogel has a smooth, spreadable β' crystal shape which creates excellent sensory properties and improves the texture, but also has some economic benefits. A comparison between the oleogels formed at critical concentrations and those with improved mass fractions was performed in several analyses such as PLM and texture, and the oleogels with higher mass fractions had a greater hardness and stickiness and denser crystal structures. This study was used to optimize the cookie recipe by partially replacing shortening with oleogel and preparing the cookies according to the 0:1, 3:7, 1:1, 7:3, 1:0 oleogel shortening mixture, respectively. Based on the results of the textural analysis, a colorimetric and sensory evaluation of the optimized formulation of oleogels in cookies, it was evident that BW and RBW oleogels have more potential to replace shortening in cookies than CDW and CRW oleogels. In particular, oleogels with a concentration of 6 wt.% RBW (RBW-6) and at a 7:3 (oleogel:shortening) shortening replacement exhibited a hardness and crispness of 15.75 N and 97.73 g, respectively, with an L* value of 66.66 and a sensory score of 22.32 ± 0.09. The value for the color perception difference (dE) between the cookies and the control group was -3.73, which allowed us to obtain a good product with a quality and characteristics similar to shortening. This supports the feasibility of new solid fats to replace traditional plastic fats in baked goods.

Stabilisation of oleofoams by lauric acid and its glycerol esters

Four types of pure lipid, namely lauric acid (LA), glycerol monolaurate (MAG), diglycerol laurate (DAG) and triglyceride laurate (TAG) were used to prepare oleofoams. The relationship between crystal profiles and their performance in oleofoams was established. DAG formed small needle-like crystals while MAG formed large flake-like crystals in oleogels, and crystal shells around air bubbles were observed in LA-, MAG- and DAG-based oleofoams. LA and DAG displayed higher over-run whereas DAG-stabilised foam possessed smaller bubbles and higher physical stability due to the presence of small β and β' crystals. Upon heating, DAG and TAG-based foams showed varying extents of oil drainage indicating the crystals were distributed in a different manner. Therefore, DAG was shown to be an excellent gelator in the fabrication of ultra-stable oleofoams. This work extends the lipid varieties with nutritional features and allows a better understanding on the stabilization mechanisms of lauric acid lipids in oleofoams.

Preparation and Characterization of Novel Oleogels Using Jasmine Floral Wax and Wheat Germ Oil for Oral Delivery of Curcumin

Oleogels (OGs) have gained a lot of interest as a delivery system for a variety of pharmaceuticals. The current study explains the development of jasmine floral wax (JFW) and wheat germ oil (WGO)-based OGs for oral drug (curcumin) delivery application. The OGs were made by dissolving JFW in WGO at 70 °C and cooling it to room temperature (25 °C). The critical gelation concentration of JFW that induces the gelation of WGO was found to be 10% (w/w). The OGs were characterized using various techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), microscopic analysis, and mechanical test. XRD data indicated that JFW influences the crystallinity of the OGs. Among the prepared OGs, OG 17.5 showed higher crystallization in the series. Optical microscopic studies demonstrated the formation of fiber structures due to the entanglement of crystals whereas, polarized light micrographs suggested the formation of spherulites or clustered crystallite structures. The mechanical properties of the OGs increased linearly with the increase in the JFW concentration. Curcumin-loaded OGs were examined for their controlled release applications. In summary, the developed OGs were found to have the necessary features for modulating the oral delivery of curcumin.

Gel Properties and Formation Mechanism of Camellia Oil Body-Based Oleogel Improved by Camellia Saponin

This study aimed to investigate the effect of camellia saponin (CS) on the structural characteristics, texture properties, rheological properties, and thermal stability of camellia oil body-based oleogel (COBO). In addition, the formation mechanism of COBO was further studied in terms of the microstructure and texture of freeze-dried products, the mobility of hydrogen protons, and the conformation and structure changes of oleosin. The texture and rheological properties of the oleogels were found to be gradually improved with the incorporation of CS. This was attributed to the CS-induced enhancement of oil body interfacial film. CS was likely to bind to oleosin via hydrogen bonding and hydrophobic interactions, thereby forming a thick CS-oleosin complex interface, which was revealed by the oleosin fluorescence quenching and an increase in the ordered structure (α-helix). The composite interface could resist the crystallization damage and air disturbance caused by solidification and sublimation of water during freeze-drying, resulting in a denser and more uniform three-dimensional gel structure to trap the liquid oil, which could be explained by the decreased mobility of hydrogen protons in oleogel. The work offers a new proposal and theoretical basis for the development of saponin-enhanced oleogels using non-thermal processing.

DMA Study of the Molecular Structure of Porcine Fat in-Water Emulsions Stabilised by Potato Starch

The aim of the study was to determine how the molecular structure of porcine fat-in-water type emulsions stabilised with potato starch affected their rheomechanical properties. Dynamic mechanical analysis (DMA) and instrumental analysis of the texture were the method used in experiments. Starch gels with concentrations corresponding to the water starch concentration of the examined emulsions were used as control systems. The analysis of the starch and starch-fat systems showed that the values characterising their rheomechanical and textural properties reflected the spatial reaction of the amylose matrix to dynamic mechanical interactions. Changes in their values resulted from conformational changes in the structure of segments and nodes of the lattice, conditioned by the concentration of starch and the presence of fat. As a result of these changes, starch-fat emulsions are distinguished by greater densities of network segments and nearly two times greater functionalities of nodes than starch gels. The instrumental analysis of the texture showed that the values of the texture parameters in the starch gels were greater than in the starch-fat emulsions. The high values of the correlation coefficients (R~0.9) between the texture determinants and the rheological parameters proved that there was a strong correlation between the textural properties of the tested systems and their rheomechanical properties.