Polysaccharide-stabilized aqueous foams to fabricate highly oil-absorbing cryogels: Application and formation process for preparation of edible oleogels

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.

Acid-induced hydrogels of edible Chlorella pyrenoidosa protein with composite biopolymers network

This study aimed to prepare Glucono-δ-lactone (GDL)-induced Chlorella pyrenoidosa protein (CPP) hydrogel and further investigate the effect of polysaccharides on the mechanical properties and stability enhancement of the composite hydrogels. Polysaccharides composed of different ratios of low acyl gellan gum (GE) and guar gum (GU) imparted dense honeycomb-like networks and adjustable textural properties to the composite hydrogels induced by CaCl2. In particular, the hardness of hydrogels increased significantly from 14 to 833 g. Scanning electron microscopy results revealed that CPP-GE/GU composite hydrogels had better stable spatial porous structures. Moreover, fourier transform infrared spectroscopy (FTIR) indicated hydrogen bonding interaction between CPP and GE/GU. The composite network showed improved viscoelasticity, increased thermal stability, and self-healing ability of hydrogels. The composite hydrogels also showed high water holding (89-98%) and swelling (747-862%) properties compared to the pure CPP hydrogel. These findings further expand CPP hydrogel products and broaden application in plant protein-based food.

Novel organic-inorganic composite pea protein silica food-grade aerogel materials: Fabrication, mechanisms, high oil-holding property and curcumin delivery capacity

The fragility of the skeleton and poor bioaccessibility limit Silica aerogel's application in the food industry. In this study, composite gels were obtained by cross-linking pea proteins isolate (PPI) with Tetraethoxysilane (TEOS)to improve the bioavailability of silica-derived aerogels. It indicated that TEOS first condensed with H+ to form secondary particles and then complexed with PPI via hydroxyl groups to form a composite aerogel. Meanwhile, the PPI-Si composite aerogel formed a dense mesoporous structure with a specific surface area of 312.5 g/cm3. This resulted in a higher oil holding percentage of 89.67 % for the PPI (10 %)-Si aerogel, which was 34.1 % higher than other studies, leading to a more stable oleogel. Finally, as a delivery system, the composite oleogel not only could significantly increase the bioaccessibility rate by 27.4 % compared with silica aerogel, but also could efficiently inhibit the premature release of curcumin in the simulated gastric fluids, while allowed sustainably release in the simulated intestinal fluids. These results provided a theoretical basis for the application of silica-derived aerogels in food and non-food applications.

O1/W/O2 double emulsion gels based on nanoemulsions and Pickering particles for co-encapsulating quercetin and cyanidin: A functional fat substitute

An O1/W/O2 double emulsion gel, as a functional fat substitute and based on nanoemulsions and hydrophobic Pickering particles, is prepared by two-step emulsification to co-encapsulate hydrophilic cyanidin and hydrophobic quercetin. Nanoemulsions loading quercetin are fabricated by Tween-80 and combining high-speed and high-pressure emulsification. Phytosterol nanoparticles stabilize the W-O2 interface of the secondary emulsion to load cyanidin in the W phase. The concentration of Tween-80 is optimized as 0.3% by the droplet size and viscosity of nanoemulsions. The structural stability of double emulsion gels will be weakened along with the increase of nanoemulsions, showing lower modulus and encapsulation efficiency (EE) and bigger droplets. In double emulsion gels, the EE of quercetin and cyanidin reaches 93% and 85.6%, respectively. Analysis of molecular interaction indicates that Tween-80 would decrease the in-situ hydrophobicity of phytosterol nanoparticles by hydrogen bonding adsorption, thereby weakening the emulsification. The pH-chromic 3D printing of double emulsion gels is designed according to the pH sensitivity of cyanidin. Texture profile analysis is performed to test the textural properties of 3D-printed objects. The simulated digestion is conducted on double emulsion gels. The double emulsion gel with fewer nanoemulsions is beneficial for protecting quercetin and improving the delivery due to the higher structural stability, while that with more nanoemulsions is conducive to the digestion of cyanidin and camellia oil due to weakened semi-solid properties. This double emulsion gel further simulates fat tissues by co-encapsulating hydrophilic and hydrophobic substances, promoting the application of fat substitutes in the food industry.

An overview of edible foams in food and modern cuisine: Destabilization and stabilization mechanisms and applications

Foam, as a structured multi-scale colloidal system, is becoming increasingly popular in food because it gives a series of unique textures, structures, and appearances to foods while maintaining clean labels. Recently, developing green and healthy food-grade foaming agents, improving the stability of edible foams, and exploring the application of foam structures and new foaming agents have been the focus of foam systems. This review comprehensively introduces the destabilization mechanisms of foam and summarizes the main mechanisms controlling the foam stability and progress of different food-grade materials (small-molecular surfactants, biopolymers, and edible Pickering particles). Furthermore, the classic foam systems in food and modern cuisine, their applications, developments, and challenges are also underlined. Natural small-molecular surfactants, novel plant/microalgae proteins, and edible colloidal particles are the research hotspots of high-efficiency food-grade foam stabilizers. They have apparent differences in foam stability mechanisms, and each exerts its advantages. However, the development of foam stabilizers remains to be enriched compared with emulsions. Food foams are diverse and widely used, bringing unique enjoyment and benefit to consumers regarding sense, innovation, and health attributes. In addition to industrial inflatable foods, the foam foods in molecular gastronomy are also worthy of exploration. Moreover, edible foams may have greater potential in structured food design, 3D/4D printing, and controlled flavor release in the future. This review will provide a reference for the efficient development of functional inflatable foods and the advancement of foam technologies in modern cuisine.

Foam-templated oleogels constructed by whey protein isolate and xanthan gum: Multiple-effect delivery vehicle for Antarctic krill oil

To address the limitations of Antarctic krill oil (AKO) such as easy oxidation, unacceptable fishy flavor and low bioaccessibility of astaxanthin in it, a multiple-effect delivery vehicle for AKO is needed. In this study, whey protein isolate (WPI) and xanthan gum (XG) were utilized to construct AKO into oleogels by generating foam-templates. The effects of the concentration of XG on the properties of foam, cryogel and the corresponding oleogels were investigated, and the formation mechanism of oleogel was discussed from the perspective of the correlation between foam-cryogel-oleogel. The results demonstrated that with the increase of the concentration of XG, the foam stability was improved, the cryogel after freeze drying had a more uniform network structure and superior oil absorption ability, and the corresponding oleogel had excellent oil holding ability after oil absorption. The AKO oleogels showed superior oxidative stability compared with AKO. The in vitro digestion experiments demonstrated that the bioaccessibility of the astaxanthin in this oleogel was also considerably higher than that in AKO. In addition, this oleogel had masking effect on the odor-presenting substances in AKO, while retaining other flavors of AKO. The foam-templated oleogel can be considered as a multiple-effect vehicle for AKO to facilitate its application in food products. This study provides theoretical basis and data support for the development and utilization of novel vehicle for AKO, broadening the application of AKO in the field of food science.

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.

Shortening replacement by emulsion and foam template hydroxypropyl methylcellulose (HPMC)-based oleogels in puff pastry dough. Rheological and texture properties

Shortening plays an essential function in the formulation of sweet laminated bakery products, but has a potential health risk due to their high percentage of saturated fatty acids. In this paper, the feasibility of hydroxypropyl methylcellulose (HPMC) oleogels prepared with emulsion template (ET) and foam template (FT) approaches as fat sources in a puff pastry dough was investigated. Spreadability and thermal properties of control shortening, 100% ET and FT oleogels and shortening/oleogel (50/50) blends were measured. The different systems were applied as the fat source in a puff pastry dough, and their effect on rheological and texture properties was investigated. Results showed that partial replacement of shortening with oleogels could significantly decrease the firmness values (from 115 to 26 N) (P < 0.05) and increased the spreadability of shortening. The methodology to prepare the oleogel (FT or ET) also significantly affected the texture parameters. FT blends had the highest spreadability with significantly lower firmness values and area under the curve. Thermal values showed that both oleogels could slightly increase the melting point of shortening from 47 to 50 °C. The replacement of shortening with oleogel decreases the viscoelasticity of puff pastry dough and increases its thermal stability but does not significantly change dough viscoelasticity in the shortening/oleogel mixture. These results indicated that both oleogels have promising potential to replace shortening in puff pastry dough formulations, but the ET oleogel showed a more similar behavior to the control shortening than the FT oleogel.

Development and characterization of antioxidant-fortified oleogels by encapsulating hydrophilic tea polyphenols

The application of hydrophilic compounds in lipid systems was limited due to their poor solubility. In this study, antioxidant-fortified oleogels containing hydrophilic antioxidants tea polyphenols (TP) were developed. The hydrophilic TP was encapsulated in glyceryl monostearate (GMS) to form TP gelling agents, which successfully made TP uniformly dispersed in oleogels. The lipophilic curcumin was directly dissolved in soybean oil to distribute in oleogels. Oxidative stability experiments showed that the addition of TP greatly improve the oxidative stability of oleogels. Compared to curcumin, TP played a particularly stronger antioxidant effect, indicating that hydrophilic antioxidants had promising applications in oleogels. In addition, the synergistic value was calculated to confirm that there was a certain synergistic effect between these two antioxidants. This study initiated a method to uniformly disperse hydrophilic antioxidants in oleogels, providing an effective solution for the construction of lipid products loaded with hydrophilic bioactive ingredients.

Effects of polysaccharide thickening agent on the preparation of walnut oil oleogels based on methylcellulose: Characterization and delivery of curcumin

Walnut oil-based oleogels were prepared by the emulsion-templated method using methylcellulose at different concentrations and viscosities as the oleogelators and polysaccharides (sodium alginate, xanthan gum and κ-carrageenan) as the thickening agents. The microscopic properties, rheological properties and oil binding capacity (OBC) of the oleogels were evaluated. The intermolecular and intramolecular hydrogen bonding of polysaccharide stabilized the network structure of the oleogel. The increasing methylcellulose concentration contributed to forming a more stable interfacial layer and providing oleogel with a compact structure. κ-Carrageenan resulted in a better OBC (97.37 %) and rheological properties of the methylcellulose-based oleogel. When served as a delivery system of curcumin, the highest encapsulation rate of curcumin (38.06 %) was achieved by the κ-carrageenan oleogel. The structure of oleogels slowed down the release rate of free fatty acids and curcumin during the early stage of in vitro digestion and the κ-carrageenan oleogel exhibited the highest inhibiting effect. This finding suggests that the polysaccharide-based walnut oil oleogels had a firmer structure and could be a promising approach to deliver curcumin.

Effects of Polysaccharide Concentrations on the Formation and Physical Properties of Emulsion-Templated Oleogels

An emulsion template method was an effective way to prepare oleogels. However, there were few reports on how hydroxypropyl methylcellulose-pectin (HPMC-PC) mixtures affected the physicochemical properties of the obtained oleogels. In this study, the oleogels were prepared by an emulsion template method. The influences of HPMC and PC concentrations on the formation and physical properties of the emulsions and oleogels were investigated, by analyzing particle size distribution, microstructure, rheological test, oil loss, and crystallinity. The results of particle sizes and microstructure showed that a high concentration of HPMC and PC exhibited a better emulsification performance. The rheological tests indicated that a high concentration of HPMC and PC contributed to an increase in the mechanical strength of emulsions and oleogels. Moreover, an increase in an HPMC and PC concentration was beneficial to reduce the oil loss of oleogels. However, the change of HPMC and PC concentrations had no significant effect on the X-ray diffraction pattern of oleogels. This study could provide a theoretical basis for the construction of polysaccharide-based oleogels.

The role of nanostructured lipid carriers and type of biopolymers on the lipid digestion and release rate of curcumin from curcumin-loaded oleogels

Curcumin-nanostructured lipid carrier-loaded oleogels (Cur-NLC-OGs) have been developed with biopolymer cryogels as an efficient delivery system to overcome the extremely low water solubility and instability of curcumin. The effect of NLC and biopolymer types on the encapsulation and release of curcumin from Cur-OGs was investigated. Alginate, carboxymethyl cellulose (CMC), and pectin solutions were firstly freeze dried to make biopolymer cryogels and they were mixed with Cur and Cur-NLC to obtain stable and self-standing Cur-OGs and Cur-NLC-OGs, respectively. As compared to Cur-OGs, Cur-NLC-OGs had higher encapsulation efficiency and showed slower release of curcumin under acidic condition. Although Cur-NLC affected the rapid release of free fatty acids, the Cur-NLC-OGs prepared with CMC cryogel was most efficient in delaying lipid digestion. Overall, NLC and CMC-based OGs could be effectively used to improve encapsulation efficiency and control lipolysis of lipid droplets. These results will be advantageous for the development of oleogels with desirable functionality.

Double network oleogels co-stabilized by hydroxypropyl methylcellulose and monoglyceride crystals: Baking applications

Edible double network oleogels were prepared by hydroxypropyl methylcellulose (HPMC) and glyceryl monostearate (GMS) by the cryogel-templated method. Hot GMS soybean oil solutions were absorbed by HPMC cryogels, which were further homogenized and cooled to form oleogels containing both the HPMC network and GMS network. The crystal network constructed by GMS crystal clusters significantly enhanced the mechanical and rheological attributes of oleogels. Both the HPMC network and the GMS network were built up due to hydrogen bonds. According to the normalization analysis of FTIR and the deepening of the shift of the absorption peak, hydrogen bonds could also be formed between HPMC and GMS to connect the two independent networks. Double network oleogels were further used to fabricate cookies and cakes, assessed by the texture profile analysis. The combination of the HPMC network and GMS network in preparing oleogels will promote the application of oleogels as the fat replacer.

Synergetic effects of water-soluble polysaccharides for intensifying performances of oleogels fabricated by oil-absorbing cryogels

Oleogels were prepared by the cryogel-templated method from porous cryogels, which were co-structured using hydroxypropyl-methylcellulose and structural enhancers (such as flaxseed gum, κ-carrageenan, carboxymethyl-cellulose, arabic gum, and guar gum). The hardness, network density, pore size, pore volume, and SEM micrographs of cryogels showed that κ-carrageenan and flaxseed gum could keep the integrity of aqueous foams during freeze-drying and endow cryogels with the high hardness and content to hold oils (>98%). Oil absorption curves indicated that flaxseed gum and guar gum-enhanced cryogels provided the fastest oil absorption rate due to bigger pores. The absorption model was fitted well with all experimental data. Physical and mechanical properties of cryogels were positively related to the rheological property and oil bonding capacity of oleogels. κ-carrageenan and flaxseed gum were more suitable as structural enhancers to improve hydroxypropyl-methylcellulose-based cryogels for preparing oleogels to replace plastic fats in foods.

Fabrication and characterization of superior stable Pickering emulsions stabilized by propylene glycol alginate gliadin nanoparticles

Gliadin, a kind of amphiphilic protein from wheat, has been widely used for stabilizing Pickering emulsions, which is easy to form colloidal particles. Herein, gliadin/propylene glycol alginate (PGA) colloidal particles (GPPs) with different gliadin/PGA ratios were developed and used as emulsifiers to prepare Pickering emulsions with an internal phase of 80% (v/v). The addition of PGA made the GPPs a tree-fruit-like morphology, increasing the particle size and changing the zeta-potential. Hydrogen bond and electrostatic interaction are the major forces between gliadin and PGA. The wettability of GPPs was improved significantly in the presence of PGA. The oil-water contact angle reached 89.5° when the gliadin/PGA ratio was 1 : 1. The emulsion could be maintained at room temperature for 6 months when the oil phase ratio (Φ) was 70%. The high stability of the Pickering emulsion could be attributed to the thin film formed by GPPs on the surface of oil droplets. The improved resistance of algal oil in emulsions against oxidation was proved as the induction time increased six times. In addition, the porous material prepared using GPPs-stabilized emulsion as the template displayed an oil absorption ability of 106.41 g g^-1 and heavy metal adsorption ability of 202.71 mg g^-1. Such performance implies that GPPs are highly efficient food-grade Pickering emulsifiers that may be applied in various fields.