Key characteristics and modelling of bigels systems: A review

Structural and rheological properties of bigels formed with xanthan gum hydrogel and lecithin/glycerol monostearate oleogel

This study aimed to investigate the structural and rheological properties of bigels formed with xanthan gum hydrogel and lecithin/glycerol monostearate oleogel. Different ratios (7:3, 6:4, 5:5, 4:6, and 3:7, respectively) of xanthan gum hydrogel and lecithin/glycerol monostearate oleogel were used for producing bigels (BG-7:3, BG-6:4, BG-5:5, BG-4:6, and BG-3:7). Through visual appearance, inversion test, and storage stability test, all bigels showed a white creamy appearance with self-standing properties and storage stability for three weeks. According to CLSM analysis, BG-7:3, BG-6:4, and BG-5:5 formed an oleogel-in-hydrogel system, whereas BG-4:6 and BG-3:7 showed a bicontinuous system. Solvent holding capacity was >95 % for all bigels. Steady shear rheological analysis and three interval thixotropic test revealed that all bigels exhibited shear-thinning behavior and thixotropic recovery. Frequency sweep test revealed that storage modulus (G'), loss modulus (G″), and complex viscosity (η*) of bigels were remarkably increased as the ratio of oleogel fraction increased in bigels. These results suggest that bigels formed with xanthan gum hydrogel and lecithin/glycerol monostearate oleogel can be unique candidates for replacing fat in the food industry.

Physicochemical Properties of Freeze-Dried Bigel-Based Materials Composed of Sodium Alginate/Whey Protein Isolate Hydrogel and Ethylcellulose/Sunflower Oil Oleogel

Freeze-drying bigels is a novel technique for developing functional materials for dermatological and cosmetic use, leveraging the benefits of two structured phases. This study optimized freeze-dried bigels composed of whey protein isolate (WPI)/sodium alginate/glycerin hydrogel and ethylcellulose (EC)/Span 80/sunflower oil oleogel at varying hydrogel/oleogel ratios. The materials showed swelling ratios from 50% to 255%, with higher values for a lower oleogel content and higher polymer concentration. The higher oleogel content extended the degradation from a few hours to 7 days. The polymer concentrations and hydrogel/oleogel ratios influenced Young's modulus (1.25-3.7 MPa). Porosity varied from 35% to 58%, and density varied from 100 to 200 mg/mL. The residual moisture content (5% to 20%) increased with EC content and decreased with WPI and oleogel content. These findings underscore the role of polymer concentrations and phase ratios in tuning the physicochemical properties of freeze-dried gels, positioning them as promising biomaterials for skincare and cosmetic applications.

Roles of different polysaccharides on the structures of alginate-based Bigel beads and co-delivery of bioactives

Bigels are novel soft-solid materials, which attract increasing attentions in the food industry. In this study, bigel beads based on alginate hydrogel and monoglyceride oleogel were developed, and their structures were modified by adding various polysaccharides (pectin, carrageenan, chitosan, xanthan gum and konjac gum). The inclusion of polysaccharides generally increased bead size and decreased hardness, with chitosan reducing the shrinking rate and swelling ratio during simulated gastric-intestinal digestion. FTIR analysis confirmed no interactions between alginate hydrogel and monoglyceride oleogel, nor covalent bonds formation between alginate and the polysaccharides. The bigels were tested for simultaneously delivery of epigallocatechin gallate and curcumin, and the results showed that bead structures significantly influenced their release. Among all tested bigels, pectin and carrageenan beads exhibited the highest cumulative release in simulated intestinal fluid. The results suggested that polysaccharides effectively modified the physicochemical properties of alginate-based bigel beads, leading to adjustable release of the incorporated bioactives.

Rice starch, millet flour supplemented with algal biomass for 3D food printing

3D printing has facilitated food production customization, yet there is a lack of exploration into gluten-free cereal materials within this domain. This study investigates the utilization of millet-based 3D printing to produce fortified products incorporating Azolla filliculoides (AF) microalgae. AF contains essential nutrients like carbohydrates, lipids, dietary fiber, and amino acids emphasizing its nutritional significance. Experimental assessments were conducted on dough formulations containing pearl millet flour fortified with AF to standardise rheological and textural characteristics, ensuring precision in 3D printing. Optimal results were observed in formulations with 15 % microalgae incorporation (AF-15 %). Regarding rheology, AF-25 % and AF-15 % formulations exhibited shear-thinning behaviour, with enhanced pseudoplasticity. The texture of 3D printing formulations reflected increased firmness with higher algal biomass, attributed to increased protein and carbohydrate content. Moreover, printing efficiency for gluten-free blends exhibited variability, with occasional errors and increased viscosity in AF-15 % formulations, while AF-25 % formulations proved impractical for printing due to reduced cohesiveness. Color assessments indicated increased pigment saturation with increased algal biomass. Further, mineral analysis demonstrated a significant elevation in the mineral content of the 3D printed products. This affirms the positive impact of Azolla biomass on nutritional and rheological properties in gluten-free 3D printed products.

Advantages and therapeutic applications of different semisolids as vehicles for nano-based systems

The aim of this review is to highlight the role of semisolid systems as vehicles for nanovesicles and nanoparticles. In general, nanotechnology plays a critical role in facilitating the delivery of therapeutic agents to their active sites, and several nanocarrier systems have been explored for the topical administration of active components. The major disadvantage of the prepared nanosystems is their low viscosity, which reduces the time needed for enough absorption and negatively affects their stability and bioavailability. The role of semisolid systems is to overcome this limitation. In conclusion, this review presents an updated summary of recent advances in the use of semisolids as vehicles for various nanosystems through comprehensive scrutiny of the types of semisolids and their advantages and their role in enhancing the absorption of nanoparticles and nanovesicles.

Advances in the preparation, applications, challenges, and future trends of polysaccharide-based gels as food-grade delivery systems for probiotics: A review

Probiotics are highly regarded for their multiple functions, such as regulating gut health, enhancing the immune system, and preventing chronic diseases. However, their stability in harsh environments and targeted release remain significant challenges. Therefore, exploring effective protection and delivery strategies to ensure targeted release of probiotics is critically important. Polysaccharides, known for their non-toxicity, excellent biocompatibility, and superior biodegradability, show broad prospects in probiotic delivery by forming physical barriers to protect the probiotics. Particularly, polysaccharide-based gels (PBGs), with their unique "spider-web" like structure, capture and ensure the targeted release of probiotics, significantly enhancing their efficacy. This review discusses common polysaccharides used in PBG preparation, their classification and synthesis in food applications, and the advantages of PBGs as probiotic delivery systems. Despite their potential, challenges such as inconsistent gel properties and the need for improved stability remain. Future research should focus on developing novel PBG materials with higher biodegradability and mechanical strength, optimizing the physicochemical properties and cross-linking methods, as well as designing multilayered structures for more precise release control. Additionally, exploring the co-delivery of probiotics with prebiotics, active ingredients, or multi-strain systems could further enhance the efficacy of probiotic delivery.

Hybrid Systems of Oleogels and Probiotic-Loaded Alginate Carriers for Potential Application in Cosmetics

Oleogels (organogels) are systems resembling a solid substance based on the gelation of organic solvents (oil or non-polar liquid) through components of low molecular weight or oil-soluble polymers. Such compounds are organogelators that produce a thermoreversible three-dimensional gel network that captures liquid organic solvents. Oleogels based on natural oils are attracting more attention due to their numerous advantages, such as their unsaturated fatty acid contents, ease of preparation, and safety of use. As a result of the research, two oleogels were developed, into which freeze-dried alginate carriers with a probiotic, L. casei, were incorporated. Two techniques were used to produce probiotic-loaded capsules-extrusion and emulsification. Alginate beads obtained by the extrusion process have a size of approximately 1.2 mm, while much smaller microspheres were obtained using the emulsification technique, ranging in size from 8 to 17 µm. The trehalose was added as a cryoprotectant to improve the survival rate of probiotics in freeze-dried alginate carriers. The encapsulation efficiency for both of the methods applied, the emulsification and the extrusion technique, was high, with levels of 90% and 87%, respectively. The obtained results showed that the production method of probiotic-loaded microspheres influence the bacterial viability. The better strain survival in the developed systems was achieved in the case of microspheres produced by the emulsification (reduction in bacterial cell viability in the range of 1.98-3.97 log in silica oleogel and 2.15-3.81 log in sucragel oleogel after 7 and 30 days of storage) than by the extrusion technique (after a week and a month of oleogel storage, the decrease in cell viability was 2.52-4.52 log in silica oleogel and 2.48-4.44 log in sucragel oleogel).

Novel approaches in food grade bigels properties and applications: A review

Food-grade bigels represent a highly innovative and versatile gel system within the food industry, characterized by their unique ability to combine the advantages of both oleogels and hydrogels. This dual-phase system can effectively address the limitations of each gel type and offers enhanced functionality. This review classifies food-grade bigels and their properties, highlighting examples of novel methods in bigel preparation. Additionally, the study delves into the use of bigels as fat replacers, bioactive and probiotic capsulation systems, and active packaging materials, as well as their significant potential in emerging 3D/4D food printing and nanotechnologies. Choosing the optimal combination of hydrogels and oleogels along with appropriate preparation technology, helps achieve the desired techno-functional and sensory properties in bigel. Advances in 3D printing and nanotechnology have further enabled precise control over the bigel properties, facilitating customized formulations tailored to specific needs. Therefore, the food industry can significantly benefit from using bigels in various food sectors. The integration of sustainable ingredients such as plant-based and insect proteins in bigel production presents a promising avenue for reducing the ecological footprint of food production and disposal. Ongoing research and development in this area will be essential to optimize these systems for sustainability.

Relieving postherpetic neuralgia pain via gabapentin-loaded bigels as an auspicious topical drug delivery system

BACKGROUND

Over the past decades, a substantial portion of the population worldwide has been infected with varicella zoster and most cases developed shingles. Unfortunately, shingles is usually accompanied by postherpetic neuralgia, which may persist for months to years after the resolution of the viral infection.

OBJECTIVES

Gabapentin is an orally gamma-aminobutyric acid analogue approved by the Food and Drug Administration to manage shingles postherpetic neuralgia. However, gabapentin shows nonlinear pharmacokinetics, with variable absorption and bioavailability along with its short half-life and long side effects that may include dizziness and somnolence, which calls for an appropriate topical dosage form. Bigels are unique semisolid dosage forms with boosted penetrability and satisfactory hydrophilic texture.

METHODS

The current work pointed to formulating gabapentin-loaded bigels for the treatment of postherpetic neuralgia, where the analysis and optimization of design were performed via Design-Expert®.

RESULTS AND CONCLUSIONS

The selected bigel (F5), incorporating 400 mg Span 60, 1000 mg Tween 80, and 1000 mg Transcutol, displayed spherical nanosized particles with acceptable viscosity and spreadability. Subsequent topical application of the selected bigel on the skin of Wistar rats, F5, demonstrated a boosted accumulation of gabapentin in the skin similar to PLO gel but superior to the drug solution. Furthermore, a histopathological study demonstrated the biosafety of the selected bigel when applied topically. Accordingly, gabapentin-loaded bigel would be considered a potentially topical dosage form for the delivery of gabapentin for the management of postherpetic neuralgia.

Development and characterisation of a novel bigel based on pea protein hydrogel and rice bran wax oleogel: Enhancement of rheological properties and freeze-thaw stability

In this study, a novel pea protein (PP)-based bigel was developed, featuring a high internal phase emulsion. The impact of gelling agent concentration on the gel properties and freeze-thaw stability of the bigel was investigated. The bigel was comprised of two distinct gel phases: an aqueous-phase gel with a covalent network formed by PP and transglutaminase (TGase), and an oil-phase gel with a crystal network structure of rice bran wax (RBW). Microstructural analysis revealed a bi-continuous network structure in the bigel, with network density increasing as TGase and RBW concentrations rose. Rheological analysis showed that storage modulus (G'), apparent viscosity, and structural recovery of the bigel increased with higher TGase and RBW concentrations. Temperature scanning experiments confirmed that the bigel maintained its elastic solid behavior even at elevated temperatures. Optimal sensory properties and low coefficient of friction were achieved at 0.4 % TGase and 7 % RBW concentrations. Additionally, the bigel exhibited notable freeze-thaw stability at TGase and RBW concentrations exceeding 0.2 % and 5 %, respectively. These findings highlight the excellent gelation properties and stability of the PP-RBW-based bigel, suggesting its potential as a fat substitute in the food industry.

Novel bigel based on nanocellulose hydrogel and monoglyceride oleogel: Preparation, characteristics and application as fat substitute

In the present study, bigels containing nanocellulose hydrogel and monoglyceride oleogel were prepared as a novel fat substitute. The nanocellulose was derived from chestnut shells via TEMPO oxidation, resulting a yield of 59.6 %. The impact of varying the oleogel/hydrogel ratio on the macroscopic and microscopic structures, chemical interactions, and the textural, thermal and rheological properties of the bigels was explored. As the hydrogel content increased from 20 % to 50 %, the average droplet diameter in the bigels increased. The bigels transitioned from a water-in-oil structure to a bi-continuous structure, and the textural hardness, cohesiveness, and rheological properties improved significantly. Shortbread cookies were prepared by incorporating different proportions of the bigels to replace animal butter as shortening, and the color, spreadability, hardness and baking loss rate of cookies were analyzed. The result showed that replacing butter with bigels in cookie preparation could reduce fat content without significantly altering the appearance or properties of the cookies. These prepared bigel have the potential to serve as a healthy and sustainable solid fat substitute in the food industry.

Food-Grade Bigel Systems: Formulation, Characterization, and Applications for Novel Food Product Development

Bigels are characterized as biphasic systems consisting of two structured phases of different polarity, namely the oleogel and hydrogel phases. These systems have been widely used in pharmaceuticals and cosmetics, owing to their enhanced physicochemical stability compared to other structured systems and their ability to simultaneously deliver both hydrophilic and lipophilic compounds. Considering the above advantages, bigels could have considerable potential for the food industry. This review aims to provide a detailed description of the edible components used for structuring the oleogel and hydrogel phases and the preparation methods applied for the formation of food-grade bigels with application-specific tailored properties. The impact of the processing parameters, such as the oleogel-to-hydrogel ratio, methodology used for component mixing, and cooling rates, is presented. Moreover, the most applicable bigel characterization techniques, such as rheology, DSC, texture analysis, etc., are critically discussed. Finally, different bigel applications in foods as animal fat substitutes or as complex delivery systems for both polar and non-polar bioactive compounds are examined.

Design of Aerated Oleogel-Hydrogel Mixtures for 3D Printing of Personalized Cannabis Edibles

Cannabis seed oil oleogel structured with Glycerol Monostearate (20% w/w) was mixed with xanthan gum hydrogel (2% w/w) at different ratios ranging from 0% w/w hydrogel to 75% w/w hydrogel, using a syringe-to-syringe apparatus, for the preparation of 3D-printable food inks. This process enabled the simultaneous blend of oleogel and hydrogel phases and the incorporation of air in a reproducible and accurate manner. The printability of bigel inks with different mass ratios was evaluated by using a conventional benchtop food 3D printer. The printability of the inks was found to be negatively affected by the presence of higher portions of the hydrogel phase, while the printing performance of pure cannabis seed oil oleogel was superior compared to the printing performance of the bigel inks. The physicochemical properties of hybrid gels were investigated with rheological studies, thermophysical studies (Differential Scanning Calorimetry), Polarized Light Microscopy, and Confocal Laser Scanning Microscopy. The microstructure of the aerated inks was affected by the presence of a higher oleogel fraction, in terms of air bubble shape and distribution. The addition of hydrogel at concentrations higher than 50% w/w had a strong negative effect on the mechanical properties of the inks leading to a partial collapse of the printed structures and subsequently to poor printing performance.

Phase inversion regulable bigels co-stabilized by Chlorella pyrenoidosa protein and beeswax: In-vitro digestion and food 3D printing

Algal proteins are an emerging source of functional foods. Herein, Chlorella pyrenoidosa protein (CPP)/xanthan gum-based hydrogels (HG) and beeswax-gelled oleogels (OG) are adopted to fabricate bigels. The phase inversion of bigels can be regulated by the ratio of OG and HG: As the OG increased, bigels turn from OG-in-HG (OG/HG) to a semicontinuous state and then HG-in-OG (HG/OG). In OG/HG bigels (OG ≤ 50 %), hydrophilic CPP acts as the emulsifier at the interface of OG and HG, while beeswax emulsifies the system in HG/OG bigels (OG = 80 %). A semicontinuous bigel appears during the transition between HG/OG and OG/HG. The increase of OG can enhance the viscoelasticity, hardness, adhesiveness, chewiness, and thermal stability. OG/HG bigels exhibit stronger thixotropic recovery and oil-holding capacity than HG/OG bigels. In the in-vitro digestion and food 3D printing, the high specific surface area and the highest thixotropic recovery caused by the emulsion structure of the OG/HG bigel (OG = 50 %) are conducive to the release of free fatty acids and molding of 3D-printed objects, respectively. This study provides a new approach to structure the gelled water-oil system with CPP and helps to develop edible algal proteins-based multiphase systems in food engineering or pharmacy.

Lipid-Based Gels for Delivery of 3-O-Ethyl L-Ascorbic acid in Topical Applications

This study explores the incorporation of 10% 3-O-ethyl L-ascorbic acid (ETVC), a derivative of vitamin C, into two lipid gel systems: a hydrogel (HG) consisting exclusively of lipids and water and a bigel (BG) combining the hydrogel with an oleogel made from olive oil and beeswax. We investigated the ETVC release profiles from both materials using synthetic membranes and measured their permeation through porcine skin in vitro. Additionally, the interaction of these lipid gel systems with the stratum corneum (SC) was determined. Results from the release study indicate that the BG exhibited slower ETVC release compared to the HG. The permeation experiments showed that the presence of lipids in the formulations enhanced ETVC retention in the skin. The HG delivered a higher amount to the SC, while the BG achieved greater retention in the epidermis. This difference is attributed to the different lipophilic nature of each material. The structural analysis of SC lipids revealed that the organization of surface lipids remained unaltered by the application of the gels. Finally, an in vitro efficacy test in porcine skin using methylene blue indicated that our ETVC gels exhibited antioxidant activity. These findings provide valuable insights into the potential of lipid-based gels for topical applications.

One-bite-sized 3D printed finger foods, oriented to malnutrition, sarcopenia and frailty prevention in the older people

BACKGROUND

In this study, innovative chocolate, citrus and mixture flavoured tofu-based nutritionally customised, dysphagia-oriented, comfortably consumed, appetising, one-bite-sized finger foods, oriented to malnutrition, sarcopenia and frailty prevention in older people were created by using 3D printing technology. Developed products were characterised by evaluating chemical composition and physical properties and performing sensory evaluation among geriatric clinic residents (≥60 years).

RESULTS

The dietary composition of the developed foods was: 19-21 g (100 g)-1 protein, 6-8 g (100 g)-1 fibre, 8-9 g (100 g)-1 fat, 11 mg (100 g)-1 iron, 14 mg (100 g)-1 zinc, 70 μg (100 g)-1 selenium. Foods were also enriched with branched-chain amino acids, such as leucine, isoleucine and valine. All formulated foods were classified as level 6 by International Dysphagia Diet Standardisation Initiative classification. Chocolate-flavoured food was much harder (4914 g) with lower adhesiveness value (-33.6 g s), compared to the citrus- or mixture-flavoured foods. Older people evaluated all finger foods as very easy handled by hand, soft, easy to swallow, having a moderate flavour intensity and a weak afterfeel. Despite the fact that the chocolate food was evaluated as having the highest hardness and gumminess values by the instrumental method, this difference was not noticeable to the evaluators. However 7% of the participants said that 3D printed foods were sticky to dentures.

CONCLUSION

The results suggest that it is possible to create nutrient-dense comfortably consumed 3D printed foods, oriented to malnutrition, sarcopenia and frailty prevention in older people. © 2024 Society of Chemical Industry.

Hydrogel delivery systems of functional substances for precision nutrition

Hydrogel delivery systems based on polysaccharides and proteins have the ability to protect functional substances from chemical degradation, control/target release, and increase bioavailability. This chapter summarizes the recent progress in the utilization of hydrogel delivery systems for nutritional interventions. Various hydrogel delivery systems as well as their preparation, structure, and properties are given. The applications for the encapsulation, protection, and controlled delivery of functional substances are described. We also discuss their potential and challenges in managing chronic diseases such as inflammatory bowel disease, obesity, liver disease, and cancer, aiming at providing theoretical references for exploring novel hydrogel delivery systems and their practical prospects in precise nutritional interventions.

Different interfaces for stabilizing liquid-liquid, liquid-gel and gel-gel emulsions: Design, comparison, and challenges

Interfaces play essential roles in the stability and functions of emulsion systems. The quick development of novel emulsion systems (e.g., water-water emulsions, water-oleogel emulsions, hydrogel-oleogel emulsions) has brought great progress in interfacial engineering. These new interfaces, which are different from the traditional water-oil interfaces, and are also different from each other, have widened the applications of food emulsions, and also brought in challenges to stabilize the emulsions. We presented a comprehensive summary of various structured interfaces (stabilized by mixed-layers, multilayers, particles, nanodroplets, microgels etc.), and their characteristics, and designing strategies. We also discussed the applicability of these interfaces in stabilizing liquid-liquid (water-oil, water-water, oil-oil, alcohol-oil, etc.), liquid-gel, and gel-gel emulsion systems. Challenges and future research aspects were also proposed regarding interfacial engineering for different emulsions. Emulsions are interface-dominated materials, and the interfaces have dynamic natures, as the compositions and structures are not constant. Biopolymers, particles, nanodroplets, and microgels differed in their capacity to get absorbed onto the interface, to adjust their structures at the interface, to lower interfacial tension, and to stabilize different emulsions. The interactions between the interface and the bulk phases not only affected the properties of the interface, but also the two phases, leading to different functions of the emulsions. These structured interfaces have been used individually or cooperatively to achieve effective stabilization or better applications of different emulsion systems. However, dynamic changes of the interface during digestion are only poorly understood, and it is still challenging to fully characterize the interfaces.

Modeling, the Optimization of the Composition of Emulgels with Ciclopirox Olamine, and Quality Assessment

The design and development of pharmaceutical products require specific knowledge, time, and investment. Response surface methodology (RSM) is a widely used technique in the design of experiments (DoE) to optimize various processes and products. The aim of this study was to model and produce experimental emulgels containing 1% ciclopirox olamine and to evaluate their physical, rheological, and mechanical properties and their ability to release ciclopirox olamine. The objective was to optimize the composition of the experimental emulgel containing 1% ciclopirox olamine by applying a central composite design based on selected criteria. The surfactant (polysorbate 80) had the greatest influence on the physical, rheological, and mechanical properties of the emulgels, as well as on the release of ciclopirox olamine from these systems. During the optimization process, an emulgel of optimal composition was generated containing 38.27% mineral oil, 6.56% polysorbate 80, and 55.17% hydrogel containing 1% ciclopirox olamine, meeting specified criteria (dependent variables) including the maximum flux of ciclopirox olamine, the minimum sol-gel transition temperature (Tsol/gel), and the minimum particle size of the oil phase. The oil phase particle size (D50) of this emulgel was determined to be 0.337 µm, the system Tsol/gel was 9.1 °C, and the flux of ciclopirox olamine from this gel matrix was calculated to be 1.44 mg/cm2. This emulgel of optimal composition could be used to treat fungal skin diseases.

Advancements in lipid-based delivery systems for functional foods: a comprehensive review of literature and patent trends

Lipid-based delivery systems (LDS) have emerged as cornerstone techniques for bolstering the bioavailability of lipophilic bioactive compounds, addressing challenges related to solubility, stability, and absorption. This critical review examined a substantial dataset of 6,907 scientific articles and 3,021 patents from 2001-2023, elucidating the multifaceted evolution of LDS, with a particular focus on its industrial and patent-driven perspective. Notably, there were pronounced surges in functional food patent applications in 2004, 2011, and 2019. The trajectory revealed a shift from foundational nanoemulsions to more complex structures, such as double/multiple emulsions, solid lipid nanoparticles, Pickering emulsions, and bigels. The review further identified the top 10 leading institutions shaping this domain. Technologies like spray-drying, microfluidics, and phase gelation had revolutionized the landscape, resulting in refined sensory experiences, innovative reduced-fat formulations, enriched beverages, tailor-made infant nutrition, and nuanced release mechanisms for flavors. The review also spotlighted current research frontiers, notably Pickering emulsions, bigels, and multiple emulsions. These emerging technologies not only exemplified the ongoing innovation in the field but also underscored their potential in reshaping the future landscape of value-added functional foods.

Novel bigels based on walnut oil oleogel and chitosan hydrogel: Preparation, characterization, and application as food spread

This study developed new biphasic gel systems containing a walnut oil-based oleogel and a chitosan hydrogel and evaluated the application on food spread. The effects of different oleogelators [γ-oryzanol/β-sitosterol (γ-ORY/β-SIT), candelilla wax/span 65 (CW/SA), and mono- and diglycerides of fatty acids] were explored. Rheological analysis showed that γ-ORY/β-SIT-based bigel had the strongest gel strength, but XRD confirmed that β' crystal form (d = 3.72 Å, 4.12 Å) was predominantly in the CW/SA-based bigel, which was more appropriate for application as spread. The characteristics of CW/SA-based bigel with different oleogel fractions (40-80 wt%) were investigated. The microscopic images indicated that the hydrogels were dispersed as small droplets in the oleogels after oleogel fraction reaching 60 %. The highest crystallinity was achieved when the oleogel fraction was 60 %, and its oil binding capacity was 96.49 %. Textural analysis showed that the CW/SA-based bigel (OG-60 %) had similar properties with commercial spread B, and can be used as a partial replacement for spread B. Replacing 75 % of the commercial spread B with the bigel was found to be optimal and displayed acceptable sensory features. This study developed a healthy bigel based on walnut oil and provided the in-depth information for bigels as an alternative to plastic fats.

Production of Novel Bigels from Cold Pressed Chia Seed Oil By-Product: Application in Low-Fat Mayonnaise

The objective of this study was to produce an innovative bigel formulation by combining glycerol monostearate (GMS) oleogel with hydrogels stabilized by various agents, including cold pressed chia seed oil by-product gum (CSG), gelatin (G), and whey protein concentrate (WPC). The findings indicated that the choice of hydrogel influenced the rheological, textural, and microstructural properties of the bigels. The G' value of the bigel samples was higher than G″, indicating that all the bigels exhibited solid-like characteristics. In order to numerically compare the dynamic rheological properties of the samples, K' and K″ values were calculated using the power law model. K' values of the samples were found to be higher than K″ values. The K' value of bigel samples was significantly affected by the hydrogel (HG)/oleogel ratio (OG) and the type of stabilizing agent used in the hydrogel formulation. As the OG ratio of bigel samples increased, the K' value increased significantly (p < 0.05). The texture values of the samples were significantly affected by the HG/OG ratio (p < 0.05). The study's findings demonstrated that utilizing CSG, G, and WPC at an OG ratio more than 50% can result in bigels with the appropriate hardness and solid character. The low-fat mayonnaise was produced by using these bigels. The low-fat mayonnaise showed shear-thinning and solid-like behavior with G' values greater than the G″ values. Low-fat mayonnaise produced with CSG bigels (CSGBs) showed similar rheological properties to the full-fat mayonnaise. The results showed that CSG could be used in a bigel formulation as a plant-based gum and CSGB could be used as a fat replacer in low-fat mayonnaise formulation.

Effect of the gelling mechanism on the physical properties of bigels based on whey protein isolate

The effect of the cold-set and heat-set gelling mechanism of whey protein isolate on bigel production was assessed. For this purpose, hydrogel phase was produced with whey protein isolated (10 % w/v) and for oleogel sunflower oil and glycerol monostearate (7.5 % w/v) were used. Bigels were produced by hot emulsification of different hydrogel:oleogel ratios (from 90:10 up to 10:90). For cold-set bigels (CSB) NaCl (200 mM) was added to the aqueous phase prior to the emulsification and the emulsion was cooled to promote the 3D network formation. On the other hand, heat-set bigels (HSB) were produced by heating the emulsion (80 °C, 60 min). Bigels were evaluated through microscopy, FTIR, thermal and texture analyzes. Results showed that depending on the hydrogel:oleogel ratio and gelling mechanism different structures organization were obtained. CSB were more organized, showing that the rate of gelation was the mechanism responsible for the structure. However, for HSB the heat treatment destabilized the emulsion and disorganized structures were observed for high oleogel content. FTIR corroborates the visual observation and showed that the arrangement was purely physical. In addition, the structural arrangement led to different mechanical properties. In general, HSB produced gels with rubber-like behavior, higher elasticity modulus and the presence of a breaking point. In contrast, CSB behaves as squeezing gel, with no breaking point and lower values of elasticity modulus. Moreover, for O/W bigels the dispersed oleogel particles disrupted the WPI network decreasing the gel strength in comparison to pure hydrogels. However, for systems where oleogel was the continuous phase, the gel strength was recovered due to the metastable and dynamic character of these systems. Thus, results showed that the gelling mechanism of the protein exerted an effect on the physical properties of bigels. In addition, the mechanical properties also can be modulated according to the bigel composition, allowing its application in products with different sensorial characteristics.

Edible polysaccharide-based oleogels and novel emulsion gels as fat analogues: A review

Polysaccharide-based oleogels and emulsion gels have become novel strategies to replace solid fats due to safe and plentiful raw material, healthier fatty acid composition, controllable viscoelasticity, and more varied nutrition/flavor embedding. Recently, various oleogelation techniques and novel emulsion gels have been reported further to enrich the potential of polysaccharides in oil structuring, in which a crucial step is to promote the formation of polysaccharide networks determining gel properties through different media. Meanwhile, polysaccharide-based oleogels and emulsion gels have good oil holding, nutrient/flavor embedding, and 3D food printability, and their applications as fat substitutes have been explored in foods. This paper comprehensively reviews the types, preparation methods, and mechanisms of various polysaccharide-based oleogels and emulsion gels; meanwhile, the food applications and new trends of polysaccharide-based gels are discussed. Moreover, some viewpoints about potential developments and application challenges of polysaccharide-based gels are mentioned. In the future, polysaccharide-based gels may be flexible materials for customized nutritional foods and molecular gastronomy. However, it is still a challenge to select the appropriate oleogels or emulsion gels to meet the requirements of the products. Once this issue is addressed, oleogels and emulsion gels are anticipated to be used widely.

Food gel-based systems for efficient delivery of bioactive ingredients: design to application

Food gels derived from natural biopolymers are valuable materials with significant scientific merit in the food industry because of their biocompatibility, safety, and environmental friendliness compared to synthetic gels. These gels serve as crucial delivery systems for bioactive ingredients. This review focuses on the selection, formulation, characterization, and behavior in gastrointestinal of hydrogels, oleogels, and bigels as delivery systems for bioactive ingredients. These three gel delivery systems exhibit certain differences in composition and can achieve the delivery of different bioactive ingredients. Hydrogels are suitable for delivering hydrophilic ingredients. Oleogels are an excellent choice for delivering lipophilic ingredients. Bigels contain both aqueous and oil phases, whose gelation makes their structure more stable, demonstrating the advantages of the above two types of gels. Besides, the formation and properties of the gel system are confirmed using different characterization methods. Furthermore, the changing behavior (e.g., swelling, disintegration, collapse, erosion) of the gel structure in the gastrointestinal is also analyzed, providing an opportunity to formulate soft substances that offer better protection or controlled release of bioactive components. This can further improve the transmissibility and utilization of bioactive substances, which is of great significance.

A biocompatible lipid-based bigel for topical applications

The development of biocompatible delivery systems is a necessity for medical and topical applications. Herein, the development of a new bigel for topical application is described. It is composed of 40% colloidal lipid hydrogel and 60% olive oil and beeswax oleogel. Its characterization and the potential of the bigel as a drug carrier through the skin was evaluated in vitro using fluorescence microscopy and two phases of the bigel were labeled with two fluorescent probes: sodium fluorescein (hydrophilic phase) and Nile red (lipophilic phase). The structure of the bigel showed two phases with fluorescence microscopy in which the hydrogel phase was incorporated into a continuous oleogel matrix. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) presented a combination of vibrations characteristic of the different molecules forming the bigel, and Differential Scanning Calorimetry (DSC) showed different transitions attributed to beeswax lipids. Small-angle and wide-angle X-ray scattering (SAXS and WAXS) indicated a predominant lamellar structure with orthorhombic lateral packing that could be related to the arrangement of beeswax crystals. Bigel enables deeper penetration of hydrophilic and lipophilic probes into deeper layers, making it a promising candidate for effective topical carriers in medical and dermatological applications.

Characteristics of a Lipid Hydrogel and Bigel as Matrices for Ascorbic Acid Stabilization

Ascorbic acid (AA) has many health benefits, including immune and cardiovascular deficiency protection, prenatal problems, and skin diseases. Unfortunately, AA is easily oxidized and has limited bioavailability. Thus, the development of formulations that stabilize and enhance the efficacy of AA is a challenge. In this study, 4% AA was encapsulated in two recently developed gels, a hydrogel and a bigel. The hydrogel was formed exclusively with lipids and water, and the bigel was a combination of the hydrogel with an oleogel formed with olive oil and beeswax. The effect of AA in gel microstructures was determined using X-ray scattering, rheology, and texture analysis. Additionally, the capacity of these materials to protect AA from degradation upon temperature and sunlight was studied. Results showed that the incorporation of AA into both materials did not affect their microstructure. Moreover, hydrogel-protected AA showed only 2% degradation after three months at 8 °C, while in aqueous solution, it degraded by 12%. Regarding sunlight, bigel showed a good shielding effect, exhibiting only 2% AA degradation after 22 h of exposure, whereas in aqueous solution, AA degraded by 10%. These results suggest that both proposed gels could be used in biomedical applications and the field of food.

Bigels as Delivery Systems: Potential Uses and Applicability in Food

Bigels have been mainly applied in the pharmaceutical sector for the controlled release of drugs or therapeutics. However, these systems, with their intricate structures, hold great promise for wider application in food products. Besides their classical role as carrier and target delivery vehicles for molecules of interest, bigels may also be valuable tools for building complex food structures. In the context of reducing or even eliminating undesirable (but often highly functional) food components, current strategies often critically affect food structure and palatability. The production of solid fat systems that are trans-fat-free and have high levels of unsaturated fatty acids is one of the challenges the food industry currently faces. According to recent studies, bigels can be successfully used as ingredients for total or partial solid fat replacement in complex food matrices. This review aims to critically assess current research on bigels in food and pharmaceutical applications, discuss the role of bigel composition and production parameters on the characteristics of bigels and further expand the use of bigels as solid fat replacers and functional food ingredients. The hydrogel:oleogel ratio, selected gelators, inclusion of surfactants and encapsulation of molecules of interest, and process parameters (e.g., temperature, shear rate) during bigel production play a crucial role in the bigel's rheological and textural properties, microstructure, release characteristics, biocompatibility, and stability. Besides exploring the role of these parameters in bigel production, future research directions for bigels in a food context are explored.

Rheological and physicochemical properties of Spirulina platensis residues-based inks for extrusion 3D food printing

Novel food matrices (such as microalgae, plants, fungi, and microbial proteins) with high protein content and biological value, good amino acid profile, and functionality have been explored. Phycocyanin and active polysaccharides extracted from Spirulina platensis are used as food additives, treatment of colitis, as well as obesity prevention. However, most of the remaining Spirulina platensis residues are mainly used as fish feed at present. 3D food printing is one of the promising development techniques used in the food industry. The aim of this study was to develop a novel 3D printing material of Spirulina platensis residues with shear thinning characteristics, high viscosity and rapid recovery. The effects of moisture content and pretreatment method on the rheological properties of Spirulina platensis residues were clarified. Scanning electron microscopy was used to observe the microstructure and texture profile analysis was used to determine the texture characteristics of Spirulina platensis residues, rheology was used to determine the key 3D printing factors such as viscosity and modulus of Spirulina platensis residues. More importantly, the printing process could be realized under ambient conditions. The development of microalgae residue ink promoted the high-value and comprehensive utilization of microalgae, and also broadened the application of microalgae in the food field.

Fabrication and Characterization of Novel Food-Grade Bigels Based on Interfacial and Bulk Stabilization

Novel food-grade bigels were fabricated using zein nanoparticles for interfacial stabilization and non-surfactant gelators (beeswax and tapioca) for bulk stabilization. The present study demonstrated the importance of interfacial stability for biphasic gels and sheds light on the roles of the gelation mechanism and the oil/water ratio of a bigel on its microstructure, physical properties, and digestion behaviors. The results indicated that it is not an easy task to realize homogenization and subsequent gelation in beeswax-tapioca biphasic systems, as no amphiphilic components existed. However, applying the binding of zein nanoparticles at the oil-water interface allowed us to produce a homogeneous and stable bigel (oil fraction reach 40%), which exhibited enhanced structural and functional properties. Oleogel structures play a crucial role in determining the deformation response of bigel systems. As the oil content increased, the mechanical strength and elastic properties of bigels were enhanced. In the meantime, clear bigel-type transitions were observed. In addition, the fabricated bigels were shown to be beneficial for delayed digestion, and the lowest degree of lipolysis could be found in bigel with 50% oleogel.

Recent Advances in Cellulose-Based Hydrogels: Food Applications

In the past couple of years, cellulose has attracted a significant amount of attention and research interest due to the fact that it is the most abundant and renewable source of hydrogels. With increasing environmental issues and an emerging demand, researchers around the world are focusing on naturally produced hydrogels in particular due to their biocompatibility, biodegradability, and abundance. Hydrogels are three-dimensional (3D) networks created by chemically or physically crosslinking linear (or branching) hydrophilic polymer molecules. Hydrogels have a high capacity to absorb water and biological fluids. Although hydrogels have been widely used in food applications, the majority of them are not biodegradable. Because of their functional characteristics, cellulose-based hydrogels (CBHs) are currently utilized as an important factor for different aspects in the food industry. Cellulose-based hydrogels have been extensively studied in the fields of food packaging, functional food, food safety, and drug delivery due to their structural interchangeability and stimuli-responsive properties. This article addresses the sources of CBHs, types of cellulose, and preparation methods of the hydrogel as well as the most recent developments and uses of cellulose-based hydrogels in the food processing sector. In addition, information regarding the improvement of edible and functional CBHs was discussed, along with potential research opportunities and possibilities. Finally, CBHs could be effectively used in the industry of food processing for the aforementioned reasons.

Novel biphasic gels can mimic and replace animal fat in fully-cooked coarse-ground sausage

Four biphasic gels (BPG) were developed and tested as pork fat replacers in coarse-ground fully-cooked sausages. An oleogel (OG) phase (92.5% high-oleic soybean oil, 7.5% rice bran wax) and one of two hydrogel (HG) phases (water and 7% or 8% gelatin) were combined in 7:3 or 6:4 OG:HG ratios, for a total of four test formulations. Control sausages were formulated to 27.5% fat and stored at 0-2 °C for 98 d. BPGs allowed for fat reductions of up to 26%. Visually, all BPGs resembled pork fat. There were no differences in external L* and a* but, internally, controls were darker and redder. Except for one control, there were no differences in Texture Profile Analysis (TPA) hardness, cohesiveness, springiness, and chewiness. Warner-Bratzler Shear (WBS) force was highest in 6:4 samples, which were also highest in Sensory First Bite Firmness and lowest in Smoked Sausage Aroma and Smoked Sausage Flavor. TBARS values remained steady, with no rancid flavors detected by the sensory panel.

Hydrogels, Oleogels and Bigels as Edible Coatings of Sardine Fillets and Delivery Systems of Rosemary Extract

Edible coatings provide an alternative way to reduce packaging requirements and extend the shelf life of foods by delaying oxidation and microbial spoilage. Hydrogels, oleogels and bigels were applied as coatings on fresh sardine fillets. The effectiveness of these coatings as delivery systems of rosemary extract (RE) was also evaluated. Three groups of sardine fillet treatments were prepared: (i) the control (C), which comprised sardine fillets without coating, (ii) sardine fillets with plain hydrogel (H), oleogel (O) or bigel (BG) coatings, and (iii) sardine fillets with RE incorporated into the H, O and BG coatings. The different treatments were evaluated for lipid oxidation (TBA test), total volatile basic nitrogen (TVB-N) and microbiological growth during cold storage at 4 °C. Results showed that hydrogel, oleogel and bigel coatings delayed oxidation. The incorporation of RE into coatings significantly retarded lipid oxidation but did not affect the proliferation of microorganisms during storage. When RE was incorporated in the oleogel phase of the bigel coating, it produced significantly lower TVB-N values compared to the control and BG treatments. The incorporation of RE into the oleogel phase of the bigel coating may be a promising method of maintaining the storage quality of the sardine fillets stored at refrigerated temperatures.

Fabrication of chitosan-cinnamaldehyde-glycerol monolaurate bigels with dual gelling effects and application as cream analogs

In this study, chitosan-based bigels were fabricated, where glycerol monolaurate was added in MCT oil to produce a gelled lipid phase and cinnamaldehyde was included in the lipid phase in order to act as a crosslinking agent. The synergistic effect of pH on chemical crosslinking effects was investigated. The potential of using these bigels as an alternative to cream was also investigated. The pH of the aqueous phase played an important role in controlling the extent of the Schiff-base reaction promoted by cinnamaldehyde. At pH 3.8, the bigels formed were homogenous but at pH 5.0 and 5.5 they exhibited phase separation, which highlighted the importance of chemical crosslinking. To better mimic the properties of real cream, span 80 was added to create a more homogeneous and smoother structure of the bigels. These bigels might provide a healthy and more sustainable alterative to food products that contain plastic fats, like cream.

Assessment of Physical, Mechanical, Biopharmaceutical Properties of Emulgels and Bigel Containing Ciclopirox Olamine

Emulsions are thermodynamically unstable systems and it is difficult to produce biphasic formulations with large amounts of oil. The aim of our study was to prepare biphasic formulations containing 1% ciclopirox olamine and to determine the influence of the method of oil incorporation (without and with emulsifier and gelifier) on the physical (pH, particle size, rheological properties), mechanical, and biopharmaceutical properties of the formulations. It was found that the use of a poloxamer 407 gel as the hydrophase could result in a stable formulation when an oil with (EPG) or without an emulsifier (APG) or oleogel (OPG) was used as the oily phase. The results of the studies showed that the addition of an emulsifier (polysorbate 80) led to a decrease in the sol-gel temperature, a slower release of ciclopirox olamine, and a higher stability in the freeze–thaw test. However, regardless of the way the oil is incorporated, the particles are distributed in the same range and the antifungal activity against T. rubrum is the same. It is possible to create a biphasic formulation with a large amount of oil and poloxamer gel, but for greater stability, it is recommended to include an emulsifier in the composition.

An Experimental Investigation on the Thermo-Rheological Behaviors of Lactic Acid-Based Natural Deep Eutectic Solvents

The rheological studies of Lactic Acid (LA)-based Natural Deep Eutectic Solvents (NADES) are provided in the present investigation. Those mechanisms were also studied in which three distinct Hydrogen Bond Acceptors (HBAs) of Choline Chloride (ChCl), Betaine (Be), and β-Alanine (β-Al), after being added to a specific Hydrogen Bond Donor (HBD) at a predefined mole-to-mole ratio of 1:1, affected the rheological properties of the prepared NADES. The alterations in the rheology-related characteristics in association with the mechanical and physical properties indicate the tolerance of the material under various operational conditions in the field and show their potential utilization as environmentally suitable and feasible solvents for industrial applications. In the present research, the viscoelastic properties of the three samples of NADES were assessed along with their shear flow properties. The backward and forward temperature change in the Apparent Viscosity (AV) pattern related to the NADES system was described by a rheogram. Furthermore, the density was determined and compared with the AV while considering the temperature-related factor. On a further note, the viscoelastic characteristics were utilized in describing and investigating the network disturbance on the level of the microstructure of NADES upon frequency sweep. A series of experiments were carried out using Thermogravimetry Analysis (TGA) to investigate the thermo-physical properties to optimize them. The rheological properties of shear flow measurements were analyzed using the Bingham model that is best suited for the AV developed with the shear rate with the dynamic yield stress of three systems. The Bingham model was used to determine the lowest stress necessary to disturb the network structure and commence the flow of LA-based NADES. Overall, the viscoelastic behavior of the LA-based NADES revealed the dissimilarity between their strength and viscosity. In addition, shear flow investigations demonstrated that LA-based NADES systems exhibit non-Newtonian properties and substantial shear-thinning effects equivalent to those of alternative IL sorbents. Assessing the rheological properties of LA-based NADES is crucial for a better understanding the key challenges associated with high viscosity. Defining the transport yield stress requirements for NADES systems under different conditions benefits their future development and potentially opens the door to more challenging applications.

Bigels as drug delivery systems: From their components to their applications

Bigels are systems that usually result from mixing a hydrogel and an organogel: the aqueous phase is commonly formed by a hydrophilic biopolymer, whereas the organic phase comprises a gelled vegetable oil because of the presence of an organogelator. The proportion of the corresponding gelling agent in each phase, the organogel/hydrogel ratio, and the mixing temperature and speed all need to be taken into consideration for bigel manufacturing. Bigels, which are particularly useful drug delivery systems, have already been formulated for transdermal, buccal, and vaginal routes. Mechanical assessments and microscopy are the most reported characterization techniques. As we review here, their composition and unique structure confer promising drug delivery attributes, such as mucoadhesion, the ability to control drug release, and the possibility of including both hydrophilic and lipophilic drugs in the same system.