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The influence of curcumin (model hydrophobic compound) and riboflavin (model hydrophilic compound) on the structure and physicochemical properties of bigels produced with cold-set whey protein isolates (WPI) was assessed. The hydrogel phase was produced with WPI (11% w/v) while for the oleogel phase, sunflower oil and glycerol monostearate (GM) (10% w/v) were used. Curcumin (0.03 mg/mL) was added to the oil phase and riboflavin (0.5 mg/mL) to the water phase. Bigels were produced by hot emulsification (18.000 min−1, 2 min, 55 °C) of different hydrogel:oleogel ratios (90:10, 50:50 and 10:90). NaCl (200 mM) was added to the aqueous phase prior the emulsification. Bigels were evaluated through microscopy, XRD, FTIR, viscoelastic, texture, release kinetics and in vitro digestion analyses. XRD and FTIR showed that the addition of compounds led to some possible structural differences. Microscopy images showed an increase of the oil droplets size proportionally to the amount of oil present, and a conversion of the structure from oil in water (O/W) to water in oil (W/O). The structural differences led to different mechanical behavior. For the bigels with the isolated compounds an improvement in the gel network was observed, making it more structured, according to the phase that is being added. Regarding controlled release, higher values for the 90:10 formulation were observed for both compounds due to the matrix erosion. For bioaccessibility, curcumin presented similar values for 90:10 and 10:90 bigels, and riboflavin showed a growing bioaccessibility, with lower values for bigel 90:10. [Display omitted] • Incorporation of the model compounds exerted influence on the gels' properties. • Riboflavin can react with protein, increasing the strength of the aqueous phase. • The compounds' release was dependent on the structure organization. • The matrix erosion of 90:10 gels led to higher release of compounds. • Bioaccessibility of curcumin presented similar values for 90:10 and 10:90 bigels. [ABSTRACT FROM AUTHOR]

This study investigates the development of diacylglycerol (DAG)-based bigels as a healthier substitute for baking oil by combining hydroxypropyl methyl cellulose (HPMC)-based hydrogel with beeswax (BW)-based oleogel. Results indicated that increasing the concentration of BW enhances the interpenetration ability between the oleogel and hydrogel, leading to the formation of a stable bi-continuous bigel, as well as improved gel properties and thermal stability. The lipid profiles revealed that DAG's fatty acid composition could result in higher viscosity (0.07 ± 0.00 Pa.s) and lower interfacial equilibrium ability (14.02 ± 0.23 mN/m) compared to triglycerides (TAG). These characteristics contributed to enhanced mechanical properties and the maintenance of oil-water interface stability in the bigel. Spectroscopy and molecular dynamics simulations demonstrated that the DAG-based bigel could exhibit stronger van der Waals forces and hydrogen bonding between molecules compared to the TAG-based bigel. Consequently, DAG-based bigels showed superior gel properties and stability. Furthermore, textural analyses and sensory evaluations indicated that replacing 50% of butter with the DAG-based bigel in bread does not significantly alter the product compared to using 100% butter. This study underscores the potential of DAG in the preparation of bigels, promoting their application as the fat substitutes. [Display omitted] • Bigels containing a HPMC hydrogel and a TAG- or DAG-based oleogel were prepared. • The microstructure of the bigel took a bicontinuous type under the influence of BW. • The DAG-based bigel exhibits superior mechanical properties and stability. • Strong van der Waals and hydrogen bonding are observed among DAG, HPMC, and BW. • 8 wt% BW-DAG-based bigel can be successfully used as a butter substitute for bread. [ABSTRACT FROM AUTHOR]

Low-fat mayonnaise has gained widespread popularity as a condiment, driven in part by the global rise in obesity rates, which is partially linked to excessive fat consumption. In this study, the bigel systems were designed by preparing fish oil oleogels and gelatin hydrogels to produce low-fat mayonnaise. As the oleogel content increased in bigels, a phase inversion shifted from oil-in-water (O/W) systems to water-in-oil (W/O) systems. Rheology and mechanical property analysis revealed that the hardness and gel strength of bigels improved as the oleogel content increased. The freeze-thaw stability of bigels was impacted by the ratio of oil and water phases, with O/W systems enduring one additional freeze-thaw cycle compared to W/O systems. The bigel containing 40% oleogel (BG 40) and lemon essential oil significantly enhanced antioxidant properties, as measured by the levels of primary and secondary oxidation products. The antioxidative capacity of the gel, as indicated by the reduced development of primary and secondary oxidation products, was 301.4% and 196.7% greater, respectively, compared to that of the pure oleogel. Based on magnetic resonance imaging and sensory rating analysis, sample BG 40 demonstrated the most homogeneous structure and the best sensory properties. The sample BG 40, used as the fat substitute in preparing low-fat mayonnaise, reduced total oil content compared to full-fat mayonnaise. Our findings contributed to the development of low-fat mayonnaise using fish oil-based bigels, which exhibit exceptional sensory and antioxidant properties. [Display omitted] • Bigel systems with fish oil oleogels and gelatin hydrogels were prepared. • The bigels exhibited outstanding mechanical and rheological properties. • The O/W bigel with LEO had outstanding sensory and antioxidant properties. • The low-fat mayonnaise was employed as a substitute for less healthy fats. [ABSTRACT FROM AUTHOR]

Oral delivery systems for nutrients and nutraceuticals are required for personalized nutrition applications. In some applications, these delivery systems need to encapsulate both hydrophilic and hydrophobic bioactive agents. In this study, bigel beads (2 mm) were prepared using pea protein (PP) and sodium alginate (SA) to form the hydrogel phase, and glyceryl monostearate and soybean oil to form the oleogel phase. The hydrogel phase was crosslinked by using Ca2+ ions to form electrostatic bridges between the alginate molecules. The bigel beads had an oil-in-water type structure consisting of an oleogel dispersed phase within a hydrogel continuous phase. These beads were used to encapsulate and control the release of model hydrophobic (curcumin) and hydrophilic (epigallocatechin gallate) nutraceuticals. The textural and microstructural characteristics of the bigel beads were evaluated by dynamic shear rheology, textural profile analysis, cryo-electron microscopy, and fluorescence confocal microscopy. As the concentration of SA increasing from 0.2 to 1.0%, the hardness of bigel beads increased from 306.75 g to 792.40 g. In vitro digestion experiments showed that most of the nutraceuticals were released in the small intestine, rather than the stomach. Nutraceutical release could be controlled by manipulating bead composition, with the extent of nutraceutical release decreasing with increasing alginate concentration. The bigel beads developed in this study could be used as easy-to-swallow carriers for the controlled release of hydrophilic and hydrophobic bioactive ingredients. These kinds of products may be especially useful for people with dysphagia. [Display omitted] • Core-shell bigel beads (2 mm) were prepared from food grade biopolymers. • The hydrogel part consisted of Ca2+-crosslinked pea protein and alginate. • The oleogel part consisted of glyceryl monostearate and soybean oil. • Bigel beads could encapsulate hydrophilic and hydrophobic active ingredients. • The release characteristics could be manipulated by altering alginate level. [ABSTRACT FROM AUTHOR]

Bigel inks were developed for high-precision 3D food printing using soy protein isolate (SPI) hydrogel and beeswax oleogel. The ratio of hydrogel to oleogel played a crucial role in determining the rheology and moisture state of the inks. When the ratio of hydrogel to oleogel reached 7:3, the ink was softer and showed stronger shear-thinning properties, which resulted in better recoverability and stronger self-supportability. These were demonstrated by the lowest flow index (n value) of 0.135, the largest recovery viscosity of 10.920 × 105 mPa s, and the biggest yield stress (1034.200 Pa), complex modulus (G* of 6608.066 Pa), and gel strength (A value of 488.34 × 103 Pa s1/ z ). Additionally, the ink contained more semi-solid water (T 22) and had a higher proportion of moisture freedom (A 23). Consequently, the ink had a smooth extrusion while exhibiting strong mechanical properties and better structure stability. As a result, a hollow-rotating structure was achieved with a height of 20.05 mm, a gap diameter of 10.11 mm, and an inclination angle of 46.13° with precision beyond 99%. This was attributed to the presence of more β′ and β crystals with high oleogel content, which might protect the completeness of the SPI hydrogel network structure and prevent the aggregation of oleogel particles. In this turn, it improved the microstructure of the SPI-based bigel inks and made them more resistant to shearing during extrusion. This work provides a new insight into the application of SPI in personalized diets. [Display omitted] • Soy protein isolate-based bigel ink with 30% oleogel had highest printing precision. • Oleogel significantly enhanced the rheological properties and moisture distribution. • Hydrogel or oleogel network would be damaged during extrusion with lower 25% oleogel. • Bigel ink remained O/W type and crystal structure was unchanged after printing. [ABSTRACT FROM AUTHOR]

In this paper, bigels systems were prepared by using 20 wt% palm stearin (POs) structured soybean oil oleogels and 80 wt% xanthan gum hydrogels in different ratios of polyglycerol polyricinoleate (PGPR). The proportion of PGPR in bigels was changed to explore the phase inversion and stabilization mechanism of bigels by multiple microscopy techniques, and the mechanical properties have been evaluated by the rheology analysis and 3D printability. When the PGPR content was less than 0.4 wt%, bigels presented as the O/W type. As the PGPR content was 1.0 wt% and 1.2 wt%, the bigel presented as the W/O type with a high internal phase, and a high level of droplets dispersed closely within an oil phase. The increase in PGPR content slowed down the nonlinear viscoelastic behavior under large strains. In terms of 3D printing capability, bigels (oleogels containing 20 wt% POs) showed an unsatisfactory 3D printing capability. However, with the increase of POs and PGPR content, more plastic and printable W/O high internal phase bigels were obtained due to the formation of a more stable, homogeneous, and strong ink. In addition, the bigels systems were investigated for the preparation of 3D biscuit printing, and it was found that the K′ value of W/O bigels batter (1511.39) was larger than that of O/W bigels batter (1394.82), showing greater hardness and better 3D printing performance. These findings could facilitate the broadening of bigels systems that could be applied for 3D biscuit printing. [Display omitted] • Phase inversion from O/W to W/O high internal phase bigel by adjusting PGPR content. • Two types of bigels showed significant differences in LAOS experiments. • The increase of PGPR decreased the fluidization of W/O bigels in LAOS. • The increase of POs and PGPR content improved the printing formability of W/O bigels. • There was some potential for using bigels in 3D food printing as a solid fat substitute. [ABSTRACT FROM AUTHOR]

This study introduces an innovative approach for the encapsulation and heat-triggered release of natural pigment, paprika oleoresin (PO) as a model pigment, by formulating oleogel-in-hydrogel bigels incorporating candelilla wax (CW). By varying the CW concentrations, the impact on the critical physicochemical properties of bigels was investigated. Increasing CW concentration from 2 to 8% elevated the sol-gel transition temperature (Tg) of the oleogels significantly, ranging from 45.83 ± 0.83 to 61.38 ± 0.51 °C (p < 0.05). Across all CW concentrations, high encapsulation efficiency over 95% was consistently observed. Conversely, reducing CW concentration increased droplet size within the bigels, varying from 13.19 ± 2.97 to 2.97 ± 0.60 μm (p < 0.05). Notably, these bigels exhibited distinct heat-triggered pigment release characteristics. In specific, the amount of released PO decreased with increased CW concentration, resulting in a lower ΔE* value. Correlation analysis highlighted CW's positive correlation with the Tg of the oleogel and bigel lightness, and its negative correlation with droplet size, cumulative pigment release content, release rate constant, redness, yellowness, and ΔE* of the bigel. These results indicate that controlling pigment release through CW-based bigels with thermoresponsive properties can enhance color stability and preserve the integrity of pigment during heat processing. This novel bigel system with heat-triggered release properties holds promise for wider application in the food industry. Overall, it addresses the critical need to stabilize and precisely regulate natural pigment release, which is important for both product quality and consumer satisfaction in the food industry. [Display omitted] • Tg of candelilla wax (CW) oleogel affected the thermal properties of the bigels. • CW oleogel-based bigels demonstrate a heat-triggered pigment release pattern. • The color of the bigels has changed due to the pigment released by the heating. • CW concentration can control the physicochemical properties of the bigels. [ABSTRACT FROM AUTHOR]

The current study developed novel gel beads with bigel structures based on alginate hydrogel and glycerol monostearate oleogel. Bigel beads with different structures were prepared by varying oleogel content, and the beads were also used to co-encapsulate lipophilic and hydrophilic biaoctives. All the beads had high sphericity (>0.94), and the bead size was increased with the increase in oleogel content. Beads with higher content of oleogel had lower shrinking rates and higher level of oil filling the gel pores. The oil droplets were generally acting as inactive fillers in the gel beads, as the mechanical strength (Young's modulus and hardness) was declining with the increase in oleogel content, and no interaction between the oleogel and hydrogel was detected by FTIR. Swelling studies revealed that beads in salt solution at higher temperature had higher swelling ratio, and the increase in oleogel content could inhibit the swelling. The bigel beads were able to encapsulate EGCG and curcumin simultaneously, and beads with higher oleogel content generally had lower encapsulation efficiency of EGCG but higher efficiency of curcumin. The gel structures provided good protection for curcumin, and about 70% of the original curcumin was retained after a 40-day storage test. The study provided novel information regarding the structure-function relationship of the bigel beads, which could be useful for the development of functional food materials. [Display omitted] • Gel beads with bigel structures were developed with alginate hydrogel and GMS oleogel. • Bigel beads with higher oleogel content had lower shrinking rate and swelling rate. • Oil droplets were acting as inactive fillers. • Bigel beads could encapsulate EGCG and curcumin simultaneously. • 70% of the original curcumin in the beads was retained after 40 days. [ABSTRACT FROM AUTHOR]

The focus of the present research was to produce new bigels as a semi-solid base matrix (gel or cream) with great potential in the food industry. Bigels were fabricated by the mixture of oleogels based on whey protein isolate (WPI)-aggregates and WPI-hydrogels in different ratios. Our results from the confocal microscopic observations showed that oleogel was dispersed throughout the entire network with the protein backbone and side chains in any of these structures; also a strongly punctuated fluorescence (pseudo-colored red) in the system revealed that the created bigels were categorized as oleogel-in-hydrogel type. Obviously, the hardness and viscoelastic moduli of bigels increased with a higher proportion of oleogels. Based on the 3D structure integrity of bigels, solid-like characteristics were observed (indicating the storage modulus was higher than the loss modulus). Moreover, temperature ramp analysis revealed that the thermal stability of the bigels directly was dependent on oleogel fraction. [Display omitted] • A new double network bigel was prepared based on WPI-aggregate oleogels and WPI hydrogel. • A bigel with a greater oleogel fraction could produce stronger mechanical properties. • Bigel properties was depended on both the protein level and oleogel fractions. • The gel strength increased at higher protein concentrations. [ABSTRACT FROM AUTHOR]

In this study, a novel ultra-stable bigel-based foamed emulsion was constructed. The bigels were prepared by mixing xanthan gum (XG) hydrogel and oleogel structured by fatty acid mixtures (stearic acid and myristic acid) in different proportions. The foamed emulsion was prepared by whipping the bigel. The influence of oleogel/hydrogel ratio on the microstructure, rheological properties and thermal properties of bigel and bigel-based foamed emulsion were investigated. It was observed that with the increase of oil phase, the system changed from oleogel/hydrogel to bicontinuous, and to hydrogel/oleogel state, which was a typical characteristic of bigel system. The system was observed with higher G′, crystallinity and melting enthalpy when oleogel was the continuous phase. During the whipping process, oleogel changed from the dispersed phase to the continuous phase, even at low oil proportion. The aqueous phase and air bubbles were incorporated into the oleogel matrix as the dispersed phase. When the oil content reached 50%, a uniform bigel-based foamed emulsion with enhanced stability was obtained, where fatty acid crystals serve as the primary stabilizers. Some crystals in the oil phase adsorbed to the air-oil interface, and others formed a continuous 3-dimensional network structure in the bulk phase to stabilize the whole system. The resultant bigel-based foamed emulsion was temperature sensitive. It exhibited ultra-high stability at low temperature, while rapidly collapsed at high temperature (T > T m). These results highlighted the importance of oleogel/hydrogel proportion and fat crystals in formation and properties of the bigel-based foamed emulsions, which assisted in rational design of lipid formulations with distinct texture. [Display omitted] • A novel ultra-stable bigel-based foamed emulsion was constructed. • Oleogel/hydrogel ratio significantly affected the micro- and macro-properties of foamed emulsions. • Fat crystals in oleogel stabilized the dispersed water droplets and air bubbles. [ABSTRACT FROM AUTHOR]

Anthocyanins-based colorimetric volatile amines sensors have recently received great attention for monitoring meat and fish freshness. However, most of the sensors suffered from anthocyanins leaching problems in humid packaging environments, severely limiting their indication ability. The present study developed a hydrogel-in-oleogel bigel to protect anthocyanins from leaching. The internal hydrogel was composed of water, agar and purple sweet potato anthocyanins (PSPA), and the external oleogel was made up of sunflower oil, beeswax and glyceride monooleate (GMO). The agar concentration and water-to-oil-phase volume ratio (W/O) were optimized to be 1.0% and 2:8, respectively. The optimal pH value of hydrogel was determined to be 6.50, taking into consideration of the gas sensitivity and color stability of the bigel. The bigel was extruded onto polyvinylidene fluoride (PVDF) film through a 3D printing method to form the composite film. The results of the study revealed that PVDF-bigel composite film showed good stability in water, indicative of strong anti-leaching properties. Meanwhile, the PVDF-bigel film was sensitive to trimethylamine (TMA) with a limit of detection of 2.52 μM. The PVDF-bigel film was subjected to in-situ and real-time monitor beef and salmon freshness. The film exhibited a red-to-purple color change upon reacting with volatile amines generated from beef and salmon. Henceforth, this study presented a new method to develop anthocyanins-based colorimetric gas sensors for intelligent food packaging. [Display omitted] • A hydrogel-in-oleogel bigel containing anthocyanins was developed. • The bigel with a W/O ratio of 2:8 showed good rheological properties for 3D printing. • The bigel showed good color stability in water, indicating its anti-leaching ability. • The bigel was sensitive to TMA with LOD of 2.52 μM. • The bigel used to monitor beef and salmon freshness showed visible color changes. [ABSTRACT FROM AUTHOR]

The preparation of a novel in-situ bigel system, using hot emulsification, based on a glycerol monostearate (GMS) oleogel and a gelatin hydrogel, with the addition of lecithin and glycerol as surfactant and co-surfactant, respectively, was established. This combination led to the formation of a bi-continuous system of a hydrogel polymeric network and an oleogel crystalline network. The effect of bigel composition, water:oil ratio, and homogenization time on bigel structure, hardness, and stability was examined. A positive relationship was found between the structuring agent concentration and gel hardness and stability, with maximum enhancement at 2 %wt. gelatin and 25 %wt. GMS. Lecithin showed maximum strength enhancement and stabilization at 5 %wt. of the oil phase, above which a significant decrease was observed. Increasing oil content up to 50 %wt. led to an increase in hardness, but further increasing of oil content above 50 %wt. failed to produce stable bigels. Superior mechanical and stability properties were observed when the samples were homogenized for 3 min. Optimized bigel systems maintained their mechanical integrity for 90 days with a moderate decrease in OBC. Moreover, low PV, below 10 meqkg−1, were maintained for 30 days at 4 °C, 25 °C, and 40 °C, compared with the oil sample. An opposite trend was, however, observed in the TBA values, suggesting different transition kinetics between the primary and secondary oxidation products. These results provide a comprehensive overview of the composition-structure-function relationship of the bigel system, which should be considered in future development of textured food products. Image 1 • Bigel system was prepared using one-step hot emulsification procedure. • Gelatin hydrogel and GMS oleogel produces bi-continuous biphasic system. • Optimized bigel formulation was obtained. • Bigel formulation exhibit low PV while stored at 4–40 °C over 30 days. [ABSTRACT FROM AUTHOR]

Bigels based on κ-carrageenan hydrogel and monoglyceride oleogels were developed as carriers for lipophilic bioactives. Bigels were prepared by mixing the hydrogel and oleogels under temperature control, and the roles of oleogel fraction in the structures of the bigels and the delivery of β-carotene were investigated. Microstructural observation indicated that the structures of bigels changed from oleogel-in-hydrogel type (25, 40, 50%) to bi-continuous type (60%) and to hydrogel-in-oleogel type (75%). Mechanical properties (storage modulus, stiffness, fracture stress) of the bigels were enhanced with higher content of oleogel, and the biggest enhancement was observed when the bigel was transformed into bi-continuous or hydrogel-in-oleogel structures. XRD analysis revealed the crystalline structures of monoglyceride and liquid state of the corn oil, and the highest crystallinity was found in the bigel with 50% oleogel. Thermal stability of the bigels was improved with the increase in oleogel fraction, as monoglyceride tended to melt at higher temperature with higher oleogel content. All the bigels had low swelling ratio except for the sample with 50% oleogel. When bigels were used to encapsulate β-carotene, oleogel fraction also influenced stability and in vitro gastrointestinal release of the bioactive. Both light stability and thermal stability of β-carotene were improved with the increase in oleogel fraction, and about 70% of the original β-carotene could be retained after 8 h of UV-light exposure in the bigel with 75% oleogel. All the bigels had minor release in simulated gastric juice, and the release ratios were greatly increased in the simulated intestinal juice, and higher content of oleogel could promote the release. Image 1 • Bigels based on monoglyceride oleogels and κ-carrageenan hydrogel were developed. • The types of bigels were varied by changing oleogel fraction. • Higher oleogel fraction enhanced the mechanical properties of the bigels. • β-Carotene incorporated in bigels had improved stability with the increase in oleogel content. • β-Carotene had higher release in bigels with higher oleogel fraction. [ABSTRACT FROM AUTHOR]

Bigels are a new technology with great potential in the food industry. Their success with drug delivery suggests they may be able to deliver sensitive compounds in foods, such as probiotics and bioactives. The purpose of this study was to develop and characterize a novel, edible bigel system. The bigel was prepared by homogenizing, at high shear, an oleogel emulsion composed of soy lecithin, stearic acid, soybean oil, and water, and a hydrogel composed of whey protein concentrate and water. Characterization was conducted through small angle x-ray scattering, rheology, and fluorescence microscopy. With addition of the hydrogel component, the oleogel emulsion retained its basic structural characteristics, but lost higher order structuring. The bigels were found to have temperature-dependent G′ values. Despite temperature sensitivity, the bigels showed G'>G″ at all temperatures from 8 to 98 °C. Fluorescence microscopy revealed that a bi-continuous bigel was formed at equal proportions of oleogel emulsion and hydrogel; nevertheless, when either of those phases increased one of them became the dominant continuous phase. Some interaction between the phases may have occurred at 10 wt% water and 15 wt% protein usage in the oleogel emulsion and hydrogel, respectively, and this synergy improved the bigel's mechanical properties. On the contrary, at protein and water contents outside those listed above, the relationship between phases became antagonistic towards the bigel's mechanical properties. Image 1 • Oleogel's key structural features are retained upon hydrogel addition. • Gelators synergistically and antagonistically affect bigel characteristics. • Oil and fat phases can be visualized at various oleogel and hydrogel ratios. [ABSTRACT FROM AUTHOR]