Effect of oil unsaturation and wax composition on stability,properties and food applicability of oleogels

Oleogelation is emerging as one of the most exigent oil structuring technique. The main objective of this study was to formulate and characterize rice bran/sunflower wax-based oleogels using eight refined food grade oils such as sunflower oil, mustard oil, soybean oil, sesame oil, groundnut oil, rice bran oil, palm oil, and coconut oil. Stability and properties of these oleogels with respect to oil unsaturation and wax composition were explored. Sunflower wax exhibited excellent gelation ability even at 1%–1.5% (w/v) concentration compared to rice bran wax (8%–10% w/v). As the oleogelator concentration increased, peak melting temperature also increased with increase in strength of oleogels as per rheological studies. X-ray diffraction and morphological studies revealed that oleogel microstructure has major influence of wax composition only. Sunflower wax oleogels unveiled rapid crystal formation with maximum oil binding capacity of 99.46% in highly unsaturated sunflower oil with maximum polyunsaturated fatty acid content. Further, the applicability of this wax based oleogels as solid fat substitute in marketed butter products was also scrutinized. The lowest value of solid fat content (SFC) in oleogel was 0.20% at 25°C, resembling closely with the marketed butter products. With increase in oil unsaturation, oleogels displayed remarkable reduction in SFC. Depending upon prerequisite, oleogel properties can be modulated by tuning wax type and oil unsaturation. In conclusion, this wax-based oleogel can be used as solid fat substitute in food products with extensive applications in other fields too.     

Stearic Acid Modified Stearyl Alcohol Oleogel: Analysis of the Thermal,Mechanical and Drug Release Properties

The present study delineates the effect of stearic acid on the properties of stearyl alcohol oleogel. Herein, a series of oleogels were prepared by mixing different proportions of fatty alcohol (Stearyl alcohol; gelator) and fatty acid (stearic acid; co‐gelator). The characterization of the oleogels was done by thermal, macro‐scale stress relaxation, drug release, and antimicrobial studies. The oleogels were formed by the self‐assembly of stearyl alcohol/stearic acid. Thermal studies indicated that the stearic acid alters the crystal morphology, polymorphic transition and rate of crystallization of stearyl alcohol. The firmness of the oleogels with higher stearic proportion was better, which was due to the formation of a rigid network structure of stearyl alcohol in the presence of stearic acid. The release of ciprofloxacin hydrochloride, model drug, from the oleogels was better from the oleogels with higher stearic acid content. The release of the drug from the oleogels was Fickian diffusion‐mediated; except the oleogel with the highest stearic acid proportion. The antimicrobial study showed that the drug loaded oleogels were able to resist the growth of Escherichia coli, model microbe.     

Physical Properties of Beeswax,Sunflower Wax,and Candelilla Wax Mixtures and Oleogels

To be able to tailor and optimize the physical properties of oleogels for various food applications, more information is needed to understand how different gelators interact. Therefore, the objectives of this study were to evaluate the interactions between binary mixtures of beeswax (BW), candelilla wax (CLW), and sunflower wax (SFW) in pure form as well as in 5% wax oleogels made with soybean oil, in terms of their crystallization and melting properties, crystal morphology, solid fat content, and gel firmness. CLW:BW mixtures had eutectic melting properties, and oleogels from these mixtures with 40:60 to 90:10 CLW:BW were firmer compared to oleogels made with one wax. The main components in SFW and BW appeared to cocrystallize or crystallize at the same temperature, but nonlinear changes in melting point and solid fat content profile of oleogels prepared with the mixed waxes indicated that SFW dominated oleogel formation. In addition, oleogels prepared with mixtures of SFW and BW had lower firmness compared to oleogels prepared with one wax, indicating an incompatibility between the two waxes. The main wax components in SFW and CLW never cocrystallized, and low levels of CLW appeared to prevent SFW from forming a crystalline platelet network. This resulted in low firmness of oleogels made from mixtures of 90:10 to 60:40 SFW:CLW compared to oleogels prepared with one wax. However, the firmest oleogels of all mixtures were made from 10:90 SFW:CLW. Changes in gel firmness and melting properties with mixed wax oleogels were likely to be due to changes observed in the crystal size and morphology. In addition, the firmest gels were shown to result from mixtures that were predicted to have >40% hydrocarbon content, and a high hydrocarbon to wax ester ratio, but minor components such as free fatty acids and fatty alcohols may have also influenced firmness.     

Rice bran wax structured oleogels and in vitro bioaccessibility of curcumin

Curcumin, the bioactive compound found in turmeric, exhibits a wide range of health-promoting properties. However, its application in food formulations and as nutritional supplements is limited by its poor bioaccessibility. This study investigates the effects of curcumin on the structure formation and physical properties of oleogels made with three different concentrations of rice bran wax (RBW) (2%, 6%, and 10% w/w) compared to an ungelled control oil and examines the bioaccessibility of curcumin contained in those lipid systems. The physical and structural properties were characterized using a penetration test, solid fat content, polarized light microscopy, differential scanning calorimetry, and X-ray diffraction (XRD). Data analysis revealed no significant differences in polymorphic or thermal properties between oleogels with and without curcumin; however, differences in microstructural properties were documented for oleogels with curcumin. Moreover, the percent of lipid crystallinity in 6% and 10% RBW oleogel increased in samples containing curcumin. An in vitro simulated digestion study showed that curcumin bioaccessibility significantly increased with increasing RBW content relative to the ungelled control. Results from this study provide insight into the potential utilization of RBW oleogels for delivering curcumin and other poorly water-soluble compounds in food, dietary supplement, pharmaceutical, and cosmetic products.     

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 Tween 20 on the Properties of Stearate Oleogels: an in-Depth Analysis

This work deals with the investigation of the polymorphic changes associated with stearic acid in the presence of Tween 20 during the formation of oleogels. Tween 20 was utilized as a crystal habit modifier and its effect on the physical and thermal properties of the oleogels have been studied. Tween 20 was found to stabilize the polymorph B of stearic acid, marked by an increase in the leaf‐like structures. Fluorescent recovery after photobleaching studies suggested Tween 20 concentration‐dependent reduction in the mobile fractions. Gelation studies suggested a delay in the induction time of nucleation of stearic acid in the presence of Tween 20 was due to the decrease in the degree of supercooling. Avrami analysis supported the stabilization of the polymorph B of stearic acid in the presence of Tween 20. XRD measurements indicated that Tween 20 promoted the growth of the stearic acid crystals while forming leaf‐like structures. The molecular rearrangement of the gelator network was quicker and ordered in the Tween 20‐containing oleogels. The increase in ordered arrangement of the stearic acid molecules has lowered the crystal imperfections. In other words, it enhanced the crystal gaps (pores) associated with the gelators. When stress (either thermal or mechanical) was introduced, the strength of the oleogels was decreased due to the syneresis of oil through the pores. An increase in the Tween 20 concentration‐dependent relaxation of the oleogels was also observed due to the polymorphic change and arrangement of the gelators.     

Rheological and drug‐release behaviour of a scleroglucan gel matrix at different drug loadings

The aim of this study was to investigate the drug‐loading effects on release and mechanical properties of a scleroglucan gel, with the intention of considering them in delivery systems formulations. The rheological and kinetic properties of a 2 % w/w scleroglucan gel matrix loaded with 0, 0.02, 0.04, 0.06, 0.2 and 0.4 % w/w of theophylline (Th, used as a model drug) were investigated. Rheological measurements were performed in a controlled‐stress rotational‐shear rheometer under isothermal conditions. For theophylline release from the gel a flat Franz cell was used and the kinetic parameters were derived applying a semi‐empirical power law. The influence of scleroglucan molar weight on kinetic and rheological behaviour was also studied. Results suggest two possible effects of drug loading on the gel network: in the 0.04–0.06 % w/w Th range a plasticizing effect and in the 0.2–0.4 % w/w Th range a rigidization effect. In the first range mentioned, the changes in the gel structural properties tested by means of rheological measurements are coincident with changes in drug‐release kinetics. Copyright © 2005 Society of Chemical Industry     

Oxidative stability and characterization of oleogels obtained from safflower oil-based beeswax and rice bran wax and their effect on the quality of cake samples

Safflower oil-based oleogels were produced from beeswax and rice bran wax. Oleogels demonstrated higher oxidative stability than shortening at the cooking temperature. Peroxide values in shortening, rice bran wax oleogels, and beeswax oleogels samples were found in the range of 4.8–27.76, 13.21–20.45 and 4.30–7.72 meqO₂kg⁻¹ oil. Following oleogelation, there was no significant change in fatty acid composition of safflower oil. In addition, after baking process, the changes in the major fatty acids were not determined to be significant. Solid fat content ratios (carried out at 35°C) of rice bran wax oleogels, in beeswax oleogels and in shortening samples were defined in the range of 4.10%–7.70%, 0.80%–5.00%, and 9.61%, respectively. The highest oil binding capacity was revealed in beeswax oleogels with 99.93%–99.98%. The shortest crystallization time was determined as 3 min in oleogel containing 10% rice bran wax. Cakes consisted of oleogel were acceptable in terms of texture and sensory properties compared to cake produced with shortening. Sensory results revealed that some cakes produced with oleogels were found to be more acceptable as compared with control group samples. In this respect, oleogels produced with safflower oil-based beeswax and rice bran wax could be used instead of commercial solid fat widely used in the cake industry.     

Matching the Functionality of Single-Cell Algal Oils with Different Molecular Compositions

The fatty acid composition, triglyceride composition, melting/crystallization profiles, crystallization kinetics, X-ray diffraction patterns, microstructure and mechanical properties of a pair of algal oils were studied to elucidate structural reasons for the similarity in melting and mechanical properties. Oil A is a predominantly saturated fat, rich in capric, myristic and palmitic acids, composed mostly of trisaturated triglycerides while Oil B contains predominantly palmitic and oleic acids in triglycerides such as POP/OPP and OOP/OPO. The DSC thermogram of Oil A shows similar peak melting temperatures to that of Oil B with Oil B exhibiting a few additional peaks. Both oils exhibit identical SFC-temperature profiles. Polarized light microscopy revealed a needle-like morphology for both Oil A and Oil B, with an average length of approximately 3.5–4.0 μm. The similar morphology of the crystals was attributed to a similar polymorphic form (β’) present in both. The fractal dimensions for the distribution of crystalline material within the fat crystal networks of both oils were also similar. The identical melting and mechanical properties of Oil A and Oil B were thus be attributed, respectively, to the presence of different triglycerides (in approximately equal proportions) with similar melting points and the assembly of these triglycerides into crystals of identical shape and size, which are in turn assembled into a network with identical crystal mass distributions. This work suggests that the mechanical and thermal properties of oils with vastly different molecular compositions can be matched by targetting specific TAG combinations which yield similar melting behavior, microstructure and mechanical response.     

Production,health implications and applications of oleogels as fat replacer in food system: A review

Various food formulations widely utilized solid fats to provide specific textural properties and sensory attributes. Partially hydrogenated oil was commonly used as solid fat before being banned by FDA recently because of the existence of trans fats. Oleogels, semi-solid gel typically prepared from liquid vegetable oil and food-grade oleogelators, is developed as an alternative for solid fats that is free of trans fat and low in saturated fats. Oleogels are prepared via indirect or direct oleogelation technology by which the liquid oil is entrapped in a three-dimensional network with the aid of low molecular weight oleogelators (LMOGs) and high molecular weight oleogelators (HMOGs). Oleogels received tremendous attention from food scientists to be used in various food applications, particularly high-fat products such as comminuted meat, chocolates, ice cream, shortening and margarine and even as a deep-frying medium. They satisfy not only the current trends of consumers for healthy food products (free of trans fat and low in saturated fat) but also provide viscoelastic solid- and gel- like properties to structure high fat food products. More importantly, recent studies showed that oleogels tend to be metabolized differently from conventional fats and oils giving them an additional advantage in improving the nutritional value of high-fat foods. Therefore, this review aims to provide an overview that captures the latest studies on oleogels from their production via direct dispersion and indirect dispersion methods, processing conditions that influence the physical properties, metabolism and health attributes as well as recent application in food products.     

Properties of Oleogels Formed With High‐Stearic Soybean Oils and Sunflower Wax

In an effort to develop alternatives for harmful trans fats produced by partial hydrogenation of vegetable oils, oleogels of high‐stearic soybean (A6 and MM106) oils were prepared with sunflower wax (SW) as the oleogelator. Oleogels of high‐stearic oils did not have greater firmness when compared to regular soybean oil (SBO) at room temperature. However, the firmness of high‐stearic oil oleogels at 4 °C sharply increased due to the high content of stearic acid. High‐stearic acid SBO had more polar compounds than the regular SBO. Polar compounds in oil inversely affected the firmness of oleogels. Differential scanning calorimetry showed that wax crystals facilitated nucleation of solid fats of high‐stearic oils during cooling. Polar compounds did not affect the melting and crystallization behavior of wax. Solid fat content (SFC) showed that polar compounds in oil and wax interfered with crystallization of solid fats. Linear viscoelastic properties of 7% SW oleogels of three oils reflected well the SFC values while they did not correlate well with the firmness of oleogels. Phase‐contrast microscopy showed that the wax crystal morphology was slightly influenced by solid fats in the high‐steric SBO, A6.     

Utilization of Beeswax Oleogel-Shortening Mixtures in Gluten-Free Bakery Products

Formulating gluten-free bakery products with acceptable physical properties generally requires a high amount of fat. As the fat used in these products is often high in saturated fatty acids, the objective of this study was to evaluate beeswax (BW) containing oleogels for partial replacement of the shortening in gluten-free aerated products. Oleogels prepared with BW were cocrystallized with a commercial cake shortening in the laboratory scale crystallization unit. Then, the resulting blends were evaluated in the gluten-free cake formulations. When the BW oleogel was used alone, the overrun values of the batter samples decreased, indicating reduced air-holding ability. Product porosity and specific volume of the samples were also diminished with complete replacement of the shortening with BW oleogel. Nevertheless, 45%, 30%, and 15% replacement of the shortening with BW oleogel resulted in batter and baked product properties comparable to those of the control products. Rheological and textural measurements, microscopy, and bubble size distribution suggested that gradual replacement of shortening with oleogels may be an alternative method for a partial reduction of saturated fat without altering the physical properties of gluten-free aerated products.     

The influence of chemical interesterification on the physicochemical properties of complex fat systems. 3. Rheology and fractality of the crystal network

Chemically interesterified and noninteresterified lard-canola oil (LCO) and palm oil-soybean oil blends ranging from 100% hardstock to 50%:50% hardstock/vegetable oil (w/w) were evaluated for hardness index (HI) using cone penetrometry and viscoelastic properties, such as shear storage modulus G′, using controlled-stress rheometry. The HI and G′ of palm oil decreased upon addition of soybean oil, and chemical interesterification did not affect the HI or G′ of palm oil or palm oil-soybean oil blends. The HI and G′ of lard decreased upon addition of canola oil, while chemical interesterification led to increases in both the HI and G′ of lard and LCO blends. All these effects were nonsolid fat content-related, since solid fat content did not change substantially upon chemical interesterification. The microstructure of the fat crystal network in lard and palm oil was quantified rheologically using fractal analysis. Chemical interesterification did not affect the fractal dimension of the fat crystal networks in palm oil or lard (2.82 and 2.88, respectively). The rheological properties of the macroscopic systems were not affected by the spatial distribution of mass within their fat crystal networks. Moreover, our results suggest that the increases in G′ observed in lard upon chemical interesterification are potentially due to changes in the properties of the particles which make up the network (crystal habit).     

Microstructure and fractal analysis of fat crystal networks

This paper reviews the study of the morphology and physical properties of fat crystal networks. Various microscopical and rheological methods can be used to quantify the microstructure of fats, with the ultimate aim of relating structure to mechanical response. Even though a variety of physical models have been proposed to explain the relationship between the mechanical properties of fats and their microstructure, the fractal scaling model most closely describes the experimentally observed behavior. Mass fractal dimensions determined by microscopy and rheology can be used successfully to quantify the microstructure of fats since fractal dimension values are sensitive to the combined effects of crystal size, morphology, and the spatial distribution of mass within the fat crystal network. Methods used to determine the fractal dimension of a fat crystal network such as box counting, particle counting. Fourier transform, light scattering and oil migration are explained in detail here. The relationship between fractal dimensions determined by microscopy and rheology are discussed in light of the fact that different measures of the fractal dimension describe different microstructural features in a fat crystal network.     

Propolis and carnauba wax-based safflower oil oleogels as fat substitutes in cakes: Production,oxidative stability,and characterization

In this study, safflower oil oleogels were made using propolis wax and carnauba wax in three different concentrations each, and their effectiveness as a fat substitute in cake was evaluated afterward. Oleogels' oxidative stability and characterization were looked into. In oleogels, the oil binding capacity, solid fat content, and crystallization time were all assessed. The cakes underwent an examination for moisture content, texture, and sensory evaluation. Additionally, analyses of fatty acid composition, free fatty acidity, oxidative stability (peroxide value, conjugated diene-triene), 3-monochloropropane-1,2-diol (3-MCPD), and glycidyl were carried out both before and after baking in oleogels and shortening. Several of the physical, textural, and sensory qualities of the oleogel-based cakes were acceptable when compared to those of the shortening-based cakes. The general acceptability of cakes made with carnauba wax was very high and almost under control. The acceptability of cakes made with propolis wax oleogels was lower than this. The study of these criteria has shown that safflower oil-based carnauba and propolis wax oleogels can be utilized to produce high-quality, healthful cakes with a high amount of unsaturated fatty acids. Practical Applications : To replace fat phases in cake products high in saturated fatty acids and to enhance the fatty acid profile of the cakes, safflower oil-based oleogels with propolis wax and carnauba wax are a very good option. The results obtained provide useful information for the production of high-quality cakes with higher unsaturated fatty acid content, recommended for a healthier diet, with these oleogels containing different concentrations of oleogelator.     

Physical Properties of Soybean Oleogels and Oil Migration Evaluation in Model Praline System

The present study examined the physical properties of soybean oleogels and commercial confectionery filling fats and evaluated the oil migration properties in model praline systems. Soybean oleogels were prepared using different oleogelators namely monoglyceride (MAG oleogels) and a mixture of sorbitan tri‐stearate (STS) with lecithin (50:50) (Lec‐STS oleogels). Both MAG oleogels and Lec‐STS oleogels demonstrated a flat solid fat content (SFC) profile with zero SFC at 40 °C. At low temperature, MAG oleogels and Lec‐STS oleogels demonstrated a non‐flowing gel‐like property due to the ability of the oleogelator to entrap liquid oil. In addition, oleogels also showed thixotropic behavior indicating the possible capability to prevent migration of filling fats to coatings and also good flow ability during pumping though manufacturing equipment. The textural property of oleogels also did not change significantly upon storage indicating good structural stability. When used as in a model praline system, oleogels demonstrated a migration delaying property.     

Acidolysis Reaction of Sal Fat (Shorea robusta) with Palmitic Acid

Acidolysis reaction of sal fat (Shorea robusta) with palmitic acid has been studied in relation to the operating variables like catalyst system and concentration, reaction temperature and time and molar ratios of reactants with the object of introducing more palmitic acid which is low in sal fat. The results demonstrate that as low as 2.5% and as high as 39% palmitic acid can be introduced in sal fat at the expense of other acids under the influence of various operating conditions. The products obtained differ from original sal fat in respect of chemical composition and slip point. The importance of such study is that there are possibilities of getting plastic fats of diverse properties for edible and industrial uses.     

Physical properties of interesterified fat blends

Fat blends, formulated by mixing fully hydrogenated soybean oil with nine different commonly used vegetable oils in a ratio of 1:1 (w/w), were subjected to interesterification (also commonly referred to as rearrangement or randomization) with sodium methoxide catalyst. Fatty acid composition and triacylglycerol molecular species of each fat blend and the interesterified product were determined and correlated with the following physical properties: melting, crystallization characteristics and solid fat content. The differences in the endothermic and exothermic peak temperatures, total heat of fusion and crystallization (β and β′ crystalline content) and solid fat content among the fat blends clearly showed the effect of the composition of each oil on the physical properties. Oils that contained a considerable amount of palmitic acid had a favorable influence on the crystallization and polymorphic form of interesterified fat blends.     

Cholesterol vehicle in experimental atherosclerosis. 23. Effects of specific synthetic triglycerides

Earlier work has shown that increasing concentration of palmitic acid at the sn-2 position of a fat enhances the atherogenic properties of that fat. This effect has been observed with lard, tallow, cottonseed oil, and palm oil. In the experiment reported here, we have studied the atherogenic effects of four synthetic fats fed to rabbits as 58% (w/w) of the total fat (15%) (w/w) of a semipurified diet containing 0.05% cholesterol. The fats being tested were: 1,3-stearoyl-2-oleoylglycerol (SOS); 1,2-stearoyl-3-oleoylglycerol (SSO); 1,3-palmitoyl-2-oleoylglycerol (POP); and 1,2-palmitoyl-3-oleoylglycerol (PPO). After 20 wk on diet there were no differences among the groups in weight gain, liver weight, serum, or liver lipids. These data are consistent with our previous findings. There were significant differences in atherosclerosis. The most severe atherosclerosis was observed in group PPO and the least in groups SSO and POP. Severity of atherosclerosis was graded visually on a 0–4 scale. The average atherosclerosis [(aortic arch and thoracic aorta)÷2] was: SOS-1.35; SSO-0.97; POP-0.83; and PPO-1.80. Fecal fat excretion (an indicator of fat absorption) was higher in the two groups fed the stearic acid-rich fats and lower in groups fed the palmitic acid-rich fats. There were no differences in low density lipoprotein particle size. The results confirm previous findings concerning the increased atherogenicity of fats bearing palmitic acid at the sn-2 position. The mechanism underlying these observations is moot but may, in part, reflect greater absorption of the atherogenic fat.     

The effects of phospholipids on crystallisation and crystal habit in triglycerides

Many food products contain a network of fat crystals. The sizes and shapes of these triglyceride crystals are extremely important in producing the good physical properties and texture for a high‐quality final product. Control of crystal habit can affect a fat's structure and hence the resultant behaviour. In this work the effects of phospholipids on the crystal habit of triglyceride crystals have been investigated. Optical and scanning electron microscopy, DSC, and X‐ray diffraction have been used. The effects of certain phospholipids on the crystallisation of fats have been shown, and large changes to crystal habit have been demonstrated. These changes are caused by the interactions of the phospholipid molecules with the crystallising triglyceride molecules. Interference with the crystallising molecules causes changes to the shape and size (habit) of the resultant fat crystals. Effects on nucleation and crystal growth are demonstrated. These dramatic changes to the crystal habit can have a significant effect on the properties of the resultant fat system. For example the process of fat fractionation could be significantly enhanced. Alternatively, the network structure of fatty products could be controlled or altered opening up the possibility of the development of new and improved products.