Study on the rheological properties and volatile release of cold-set emulsion-filled protein gels

Seven sour substances enhancing characteristics and stability of whey protein isolate emulsion and its heat-induced emulsion gel under the non-acid condition

Protein emulsion gels, as potential novel application ingredients in the food industry, are very unstable in their formation. However, the incorporation of sour substances (phosphoric acid, lactic acid, acetic acid, malic acid, glutamic acid, tartaric acid and citric acid) would potentially contribute to the stable formation of whey protein isolate (WPI) emulsion as well as its gel. Thus, in this work, physical stability of seven acid-treated WPI emulsions, and microstructures, rheological properties, water distribution of its emulsion gels were characterized and compared. Initially, the absolute zeta-potential, interfacial protein adsorption, and emulsifying characteristics of acid-induced WPI emulsions were higher in contrast to acid-untreated WPI emulsions. Moreover, acid-induced WPI emulsions were thermally induced (95 ℃, 30 min) to form its emulsion gel networks via disulfide bonds as the main force (acid-untreated WPI emulsions were unable to form gels). High-resolution microscopic observation revealed that acid-induced WPI in emulsion gel network showed the morphology of aggregates. Dynamic oscillatory rheology results indicated that acid-induced emulsion gel exhibited highly elastic behavior and its viscoelasticity was associated with the generation of protein gel networks and aggregates. In addition, PCA and heatmap results further illustrated that malic acid-induced WPI emulsion gels had the best water holding capacity and gel characteristics. Therefore, this study could provide an effective way for the foodstuffs industry to open up new texture and healthy emulsion gels as fat replaces and loading systems of bioactive substances.

Modulating peppermint oil flavor release properties of emulsion-filled protein gels: Impact of cross-linking method and matrix composition

For some food applications, it is desirable to control the flavor release profiles of volatile flavor compounds. In this study, the effects of crosslinking method and protein composition on the flavor release properties of emulsion-filled protein hydrogels were explored, using peppermint essential oil as a model volatile compound. Emulsion-filled protein gels with different properties were prepared using different crosslinking methods and gelatin concentrations. Flavor release from the emulsion gels was then monitored using an electronic nose, gas chromatography-mass spectrometry (GC-MS), and sensory evaluation. Enzyme-crosslinked gels had greater hardness and storage modulus than heat-crosslinked ones. The hardness and storage modulus of the gels increased with increasing gelatin concentration. For similar gel compositions, flavor release and sensory perception were faster from the heat-crosslinked gels than the enzyme-crosslinked ones. For the same crosslinking method, flavor release and perception decreased with increasing gelatin concentration, which was attributed to retardation of flavor diffusion through the hydrogel matrix. Overall, this study shows that the release of hydrophobic aromatic substances can be modulated by controlling the composition and crosslinking of protein hydrogels, which may be useful for certain food applications.

Effect of soluble dietary fiber on soy protein isolate emulsion gel properties, stability and delivery of vitamin D3

Emulsion gels with denser network microstructure and stronger mechanical properties have attracted increasing attentions for delivering lipophilic compounds. In this study, the effect of three distinct soluble dietary fiber (inulin (IN), resistant dextrin (RD) and stachyose (ST)) on the rheological, mechanical and microstructural properties of soy protein isolate (SPI) emulsion gel were firstly investigated. Compared with RD and IN, ST significantly accelerated water holding capacity and thermal stability, which exhibited more compact microstructure and more uniform emulsified oil droplets. Subsequently, the stability and bioavailability of vitamin D3 (VD3) in different delivery systems (medium chain triglycerides (MCT) embedding, SPI-ST emulsion embedding, SPI emulsion gel embedding and SPI-ST emulsion gel embedding) were continue evaluated. In vitro simulated digestion experiment demonstrated that the bioaccessibility of encapsulated VD3 in SPI-ST emulsion gel (69.95 %) was much higher than that of free embedding (48.99 %). In vivo pharmacokinetic experiment revealed that the bioavailability of VD3 was significantly enhanced in SPI-ST gel (p < 0.05), with the AUC0-24h value of 25-OH VD3 (the main circulating form of VD3) were 1.34-fold, 1.23-fold higher than that of free embedding, MCT embedding, respectively. These findings provide a possible approach for the development of high protein/fiber functional foods containing enhanced hydrophobic bioactives.

Quality characteristics of peanut protein-based patties produced with pre-emulsified olive oil as a fat replacer: Influence of acylglycerol type

The emulsion (O/W) may be used as a fat replacer to develop healthier meat analogs. The purpose of this work was to evaluate the effects of oil incorporation methods (direct oil addition and emulsion addition) and oil types [triacylglycerol (TAG) and diacylglycerol (DAG)] on the quality characteristics of peanut protein-based patties crosslinked by transglutaminase (TGase). The patties formulated with emulsions showed larger texture parameters (springiness, cohesiveness and gumminess), lower cooking loss and higher acceptability compared with directly adding oil. The rheological results confirmed that the presence of emulsions strengthened the gel structure in patties, which allowed the patties containing emulsions to stabilize free water. Whereas, TAG-based emulsion was more effective than DAG-based emulsion in improving quality of products, possibly because the competitive adsorption at oil-water interface of DAG reduced the crosslinking between the interfacial protein and adjacent protein molecules. This study revealed the relationship between the acylglycerol type in emulsion and the patty quality, providing a reference for the development of plant-based patties.

A comparative study of the impacts of preparation techniques on the rheological and textural characteristics of emulsion gels (emulgels)

A subtype of soft solid-like substances are emulsion gels (emulgels; EGs). These composite material's structures either consist of a network of aggregated emulsion droplets or a polymeric gel matrix that contains emulsion droplets. The product's rheological signature can be used to determine how effective it is for a specific application. The interactions between these structured system's separate components and production process, however, have a substantial impact on their rheological imprint. Therefore, rational comprehension of interdependent elements, their structural configurations, and the resulting characteristics of a system are essential for accelerating our progress techniques as well as for fine-tuning the technological and functional characteristics of the finished product. This article presents a comprehensive overview of the mechanisms and procedures of producing EGs (i.e., cold-set and heat-set) in order to determine the ensuing rheological features for various commercial applications, such as food systems. It also describes the influence of these methods on the rheological and textural characteristics of the EGs. Diverse preparation methods are the cause of the rheological-property correlations between different EGs. In many ways, EGs can be produced using various matrix polymers, processing techniques, and purposes. This may lead to various EG matrix structures and interactions between them, which in turn may affect the composition of EGs and ultimately their textural and rheological characteristics.

Effects of Transglutaminase on Myofibrillar Protein Composite Gels with Addition of Non-Meat Protein Emulsion

The emulsions prepared by three non-meat proteins, sodium caseinate (SC), soy protein isolate (SPI) and egg white protein (EPI), were individually added to the continuous phase of myofibrillar protein (MP) sol to form MP composite gels to simulate meat products. The research aimed to investigate the effects of Transglutaminase (TGase) on the physicochemical properties, microstructure and water phase distribution of non-meat protein emulsion MP composite gels. The results of this study revealed that TGase played a crucial role in forming a tight gel network structure in the composite gels. This enhanced their ability to retain water and improved their overall gel strength. Additionally, TGase increased the gel formation temperature of myofibrillar proteins. Electrophoresis analysis showed that when catalyzed by TGase, there was a lighter band compared to those not catalyzed by TGase. This indicated that the addition of TGase facilitated cross-linking interactions between meat proteins and non-meat proteins in the composite gels. Furthermore, microscopy observations demonstrated that composite gels treated with TGase exhibited a more uniform microstructure. This could be attributed to an acceleration in relaxation time T2. The uniform network structure restricted the movement of water molecules in the gel matrix, thereby improving its water-holding capacity. Overall, these findings highlight how incorporating non-meat proteins into myofibrillar systems can be effectively achieved through enzymatic treatment with TGase. Such modifications not only enhanced important functional properties but also contributed towards developing alternative meat products with improved texture and moisture retention abilities.

Transglutaminase, glucono-δ-lactone, and citric acid-induced whey protein isolation-milk fat emulsion gel embedding lutein and its application in processed cheese

In this study, transglutaminase (TG), glucono-δ-lactone (GDL), and citric acid (CA) were used to induce the formation of whey protein isolate (WPI)-milk fat emulsion gels to embed lutein, and the emulsion gels induced in different ways were used for the preparation of processed cheese. The protective effect of emulsion gels induced in different ways on lutein was investigated, and the stability of lutein in emulsion gels and processed cheese was analyzed. The results showed that the acidification rate of CA was higher than that of GDL, which was the key step in acid-induced gels, and that the difference in acidification rate led to differences in gel structure. Compared with the 2 acid inducers (GDL and CA), TG exhibited greater potential for forming gel structures with high strength. The TG-induced emulsion gels showed the best physical stability and the highest embedding efficiency for lutein. After heat treatment (85°C), the GDL-induced emulsion gels had higher retention rate of lutein and showed good thermal stability compared with the CA-induced emulsion gels. The processed cheese added with the TG-induced emulsion gel had higher hardness and springiness compared with the processed cheese added with the other 2 kinds of emulsion gels, whereas the processed cheese added with the CA-induced emulsion gel had a lower density of network structure, showing porosity and a larger aggregated structure, but the highest bioavailability of lutein. These results provide valuable information for the formation of cold-set emulsion gel and provide the possibility for the application of emulsion gel embedding active substances in processed cheese.

Application of guar (Cyamopsis tetragonoloba L.) gum in food technologies: A review of properties and mechanisms of action

With the world continuing to push toward modernization and the consumption of processed foods growing at an exponential rate, the demand for texturizing agents and natural additives has also risen as a result. It has become increasingly common to use thickening agents in food products to modify their rheological and textural properties and enhance their quality characteristics. They can be divided into (1) animal derived (chitosan and isinglass), (2) fermentation produced (xanthan and curdlan), (3) plant fragments (pectin and cellulose), (4) seaweed extracts (agar and alginate), and (5) seed flours (guar gum and locust bean gum). The primary functions of these materials are to improve moisture binding capacity, modify structural properties, and alter flow behavior. In addition, some have another responsibility in the food sector, such as the main ingredient in the delivery systems (encapsulation) and nanocomposites. A galactomannan polysaccharide extracted from guar beans (Cyamopsis tetragonolobus), known as guar gum (GG), is one of them, which has a wide range of utilities and possesses popularity among scientists and consumers. In the world of modernization, GG has found its way into numerous industries for use in food, cosmetics, pharmaceuticals, textiles, and explosives. Due to its ability to form hydrogen bonds with water molecules, it imparts significant thickening, gelling, and binding properties to the solution as well as increases its viscosity. Therefore, this study is aimed to investigate the characteristics, mechanisms, and applications of GG in different food technologies.

Protein-Stabilized Emulsion Gels with Improved Emulsifying and Gelling Properties for the Delivery of Bioactive Ingredients: A Review

In today's food industry, the potential of bioactive compounds in preventing many chronic diseases has garnered significant attention. Many delivery systems have been developed to encapsulate these unstable bioactive compounds. Emulsion gels, as colloidal soft-solid materials, with their unique three-dimensional network structure and strong mechanical properties, are believed to provide excellent protection for bioactive substances. In the context of constructing carriers for bioactive materials, proteins are frequently employed as emulsifiers or gelling agents in emulsions or protein gels. However, in emulsion gels, when protein is used as an emulsifier to stabilize the oil/water interface, the gelling properties of proteins can also have a great influence on the functionality of the emulsion gels. Therefore, this paper aims to focus on the role of proteins' emulsifying and gelling properties in emulsion gels, providing a comprehensive review of the formation and modification of protein-based emulsion gels to build high-quality emulsion gel systems, thereby improving the stability and bioavailability of embedded bioactive substances.

Influence and effect mechanism of disulfide bonds linkages between protein-coated lipid droplets and the protein matrix on the physicochemical properties, microstructure, and protein structure of ovalbumin emulsion gels

In this study, disulfide bonds between the interfacial protein film formed on the lipid particles and the protein in ovalbumin emulsion gels were blocked with 0, 1, 3, 5 and 10 mM of the N-ethylmaleimide (NEM) to explore the influence and effect mechanism of disulfide bonds between the interfacial proteins on the physicochemical properties, microstructure, and protein structure of sunflower oil-ovalbumin emulsion gels. Ovalbumin emulsion gels with NEM-treated ovalbumin emulsion (N-OE) had lower hardness, free sulfhydryl content, water holding capacity (WHC), and surface hydrophobicity, but higher spin-spin relaxation time (T₂) than ovalbumin emulsion gels with NEM-treated ovalbumin substrate solution (N-OSS). In addition, N-OE and N-OSS had lower hardness, free sulfhydryl content, WHC and surface hydrophobicity, as well as a more coarse and disordered microstructure than non-NEM treated ovalbumin emulsion gel (control group). The free sulfhydryl content, hardness, WHC, and surface hydrophobicity of the ovalbumin emulsion gels all decreased as the NEM concentration rose (p < 0.05), whereas the amide A band changed to higher wave numbers. These results collectively indicated that the reduction of disulfide between the interfacial layer and the proteins inhibited the hydrophobic effect, the formation of hydrogen bonds, and prevented the formation of larger aggregates. Thus the disulfide bonds between the interfacial proteins contribute to the hardness enhancement and water stabilization of the ovalbumin gel.

Oral sensation and gastrointestinal digestive profiles of bigels tuned by the mass ratio of konjac glucomannan to gelatin in the binary hydrogel matrix

Bigels with tunable oral sensation and controlled gastrointestinal digestive profiles are highly demanded in the food industry. A binary hydrogel consisting of different mass ratio of konjac glucomannan to gelatin (φ) was designed to fabricate bigels with stearic acid oleogel. The impacts of φ on the structural, rheological, tribological, flavor release, and delivery properties of bigels were investigated. Structural transition of bigels from hydrogel-in-oleogel to bi-continuous, and then to oleogel-in-hydrogel type, as φ increased from 0.6 to 0.8, and then to 1.0-1.2. Enhanced storage modulus and yield stress were achieved along with the increased φ, while the structure-recovery properties of bigel decreased with increased φ. Under all the tested φ, the viscoelastic modulus and viscosity decreased significantly at oral temperatures but maintained the gel state, and the friction coefficient increased along with the increased φ under high chewing degree. Flexible control over the swelling, the lipid digestion and the release of lipophilic cargos were also observed, with the total release of free fatty acids and quercetin significantly reduced with the increased φ. This study presents a novel manipulation strategy to control oral sensation and gastrointestinal digestive profiles of bigels via tuning the fraction of konjac glucomannan in the binary hydrogel.

Recent progress in emulsion gels: from fundamentals to applications

Emulsion gels, also known as gelled emulsions or emulgels, have garnered great attention both in fundamental research and practical applications due to their superior stability, tunable morphology and microstructure, and promising mechanical and functional properties. From an application perspective, attention in this area has been, historically, mainly focused on food industries, e.g., engineering emulsion gels as fat substitutes or delivery systems for bioactive food ingredients. However, a growing body of studies has, in recent years, begun to demonstrate the full potential of emulsion gels as soft templates for designing advanced functional materials widely applied in a variety of fields, spanning chemical engineering, pharmaceutics, and materials science. Herein, a concise and comprehensive overview of emulsion gels is presented, from fundamentals to applications, highlighting significant recent progress and open questions, to scout for and deepen their potential applications in more fields.

Effect of Protein-Glutaminase on Calcium Sulphate-Induced Gels of SPI with Different Thermal Treatments

The effects of protein-glutaminase (PG) on calcium sulphate (CaSO₄)-induced gels of soy protein isolate (SPI) with different heat treatment levels were investigated. The time-dependent degree of deamidation showed that the mild denaturation of the protein favored the deamidation. The particle size distribution showed that the heat treatment increased the SPI particle size, and the particle size distribution of the SPI shifted to the right or increased the proportion of the large particle size component as the degree of deamidation increased for each sample. Rheological analysis showed that the deamidation substantially pushed up the gel temperature and decreased the value of G'. The gel strength and water-holding capacity showed that the higher the amount of enzyme added, the more significant the decrease in gel strength, while the gel water-holding capacity increased. In summary, the deamidation of PG and heat treatment can affect the gel properties of SPI synergistically.

Effect of ultrasonic pretreatment on the rheology and structure of grass pea (Lathyrus sativus L.) protein emulsion gels induced by transglutaminase

In this study, emulsion gels were prepared by sonicated grass pea protein isolates (GPPI) at different ultrasonic amplitudes (25, 50 and 75 %) and times (5, 10 and 20 min). Formation of emulsion gels was induced by transglutaminase. Enzymatic gelation of emulsions stabilized by sonicated GPPI occurred in two stages. A relatively fast stage led to the formation of a weak gel which was followed by a slow stage that strongly reinforced the gel structure. Emulsion gels fabricated by sonicated GPPIs showed a homogeneous and uniform droplet distribution with higher elastic modulus compared to the native protein. A stiffer emulsion gel with a higher G' was formed after the protein was treated at 75 % amplitude for 10 min. After sonication of GPPI, the water holding capacity (WHC) of emulsion gels increased in accordance with the mechanical properties. Higher intermolecular cross-linking within the gel network increased the thermal stability of emulsion gels fabricated by sonicated GPPI. Although sonicated-GPPI emulsion gels clearly displayed homogenous microstructure in comparison to that made with native GPPI, the microstructures of these gels were nearly identical for all sonication amplitudes and times.

Effects of composition and storage time of biopolymers-based emulsion-filled gels on the retention and release of aroma compounds: Thermodynamic and kinetic studies

Studies were performed to determine retention (R) and release kinetics (k_r) of aroma compounds (ACs): ethyl butyrate, linalool, 1-octen-3-ol, 2-heptanone and octanal from emulsion-filled gels (EFGs), stabilized by myofibrillar proteins and waxy rice starch (WRS) or tapioca starch (TS). The R and k_r parameters were affected by non-covalent interactions of ACs with biopolymers and the development of a compact structure induced by starch addition. Higher k_r magnitudes were found in WRS-based samples (88.2-12.8 × 10^-3 day^-1) than in counterparts prepared with TS (87.6-8.96 × 10^-3 day^-1). Thermodynamic tests revealed that vaporization enthalpies of ACs were in ranges: 22.6-41.2 kJ mol^-1 or 21.4-39.8 kJ mol^-1 in samples containing WRS or TS, respectively. This study provides new insight into the factors affecting ACs stability in the EFGs, and the results reported can be used by industry to design relevant systems with extended volatiles retention.

Application of Emulsion Gels as Fat Substitutes in Meat Products

Although traditional meat products are highly popular with consumers, the high levels of unsaturated fatty acids and cholesterol present significant health concerns. However, simply using plant oil rich in unsaturated fatty acids to replace animal fat in meat products causes a decline in product quality, such as lower levels of juiciness and hardness. Therefore, it is necessary to develop a fat substitute that can ensure the sensory quality of the product while reducing its fat content. Consequently, using emulsion gels to produce structured oils or introducing functional ingredients has attracted substantial attention for replacing the fat in meat products. This paper delineated emulsion gels into protein, polysaccharide, and protein–polysaccharide compound according to the matrix. The preparation methods and the application of the three emulsion gels as fat substitutes in meat products were reviewed. Since it displayed a unique separation structure, the double emulsion was highly suitable for encapsulating bioactive substances, such as functional oils, flavor components, and functional factors, while it also exhibited significant potential for developing low-fat or functional healthy meat products. This paper summarized the studies involving the utilization of double emulsion and gelled double emulsion as fat replacement agents to provide a theoretical basis for related research and new insight into the development of low-fat meat products.

Engineering Emulsion Gels as Functional Colloids Emphasizing Food Applications: A Review

Gels are functional materials with well-defined structures (three-dimensional networks) assembled from the dispersed colloids, and capable of containing a large amount of water, oil, or air (by replacing the liquid within the gel pores), known as a hydrogel, oleogel, and aerogel, respectively. An emulsion gel is a gelled matrix filled with emulsion dispersion in which at least one phase, either continuous phase or dispersed phase forms spatial networks leading to the formation of a semisolid texture. Recently, the interest in the application of gels as functional colloids has attracted great attention in the food industry due to their tunable morphology and microstructure, promising physicochemical, mechanical, and functional properties, and superior stability, as well as controlled release, features for the encapsulated bioactive compounds. This article covers recent research progress on functional colloids (emulsion gels), including their fabrication, classification (protein-, polysaccharide-, and mixed emulsion gels), and properties specifically those related to the gel-body interactions (texture perception, digestion, and absorption), and industrial applications. The emerging applications, including encapsulation and controlled release, texture design and modification, fat replacement, and probiotics delivery are summarized. A summary of future perspectives to promote emulsion gels' use as functional colloids and delivery systems for scouting potential new applications in the food industry is also proposed. Emulsion gels are promising colloids being used to tailor breakdown behavior and sensory perception of food, as well as for the processing, transportation, and targeted release of food additives, functional ingredients, and bioactive substances with flexibility in designing structural and functional parameters.

Regulation Effects of Beeswax in the Intermediate Oil Phase on the Stability, Oral Sensation and Flavor Release Properties of Pickering Double Emulsions

Double emulsions (W/O/W) with compartmentalized structures have attracted a lot of research interests due to their diverse applications in the food industry. Herein, oil phase of double emulsions was gelled with beeswax (BW), and the effects of BW mass ratios (0–8.0%) on the stability, oral sensation, and flavor release profile of the emulsions were investigated. Rheological tests revealed that the mechanical properties of double emulsions were dependent on the mass ratio of BW. With the increase in BW content, double emulsions showed a higher resistance against deformation, and lower friction coefficient with a smoother mouthfeel. Turbiscan analysis showed that the addition of BW improved the stability of double emulsions during a 14 days’ storage, under freeze–thawed, and osmotic pressure conditions, but it did not improve the heating stability of double emulsions. The addition of BW contributed to lower air-emulsion partition coefficients of flavor (2,3-diacetyl) compared to those without the addition of BW at 20 °C and 37 °C, respectively. Furthermore, the addition of BW and its mass ratio significantly altered the flavor release behavior during the open-bottle storage of double emulsions. The response value of 0% BW dropped sharply on the first day of opening storage, showing a burst release behavior. While a slow and sustained release behavior was observed in double emulsions with 8.0% BW. In conclusion, gelation of the intermediate oil phase of double emulsions significantly enhanced the stability of double emulsions with tunable oral sensation and flavor release by varying the mass ratio of beeswax.

Plant-Derived Nanoscale-Encapsulated Antioxidants for Oral and Topical Uses: A Brief Review

Several plant-based nanoscale-encapsulated antioxidant compounds (rutin, myricetin, β-carotene, fisetin, lycopene, quercetin, genkwanin, lutein, resveratrol, eucalyptol, kaempferol, glabridin, pinene, and whole-plant bio-active compounds) are briefly introduced in this paper, along with their characteristics. Antioxidants’ bioavailability has become one of the main research topics in bio-nanomedicine. Two low patient compliance drug delivery pathways (namely, the oral and topical delivery routes), are described in detail in this paper, for nanoscale colloidal systems and gel formulations. Both routes and/or formulations seek to improve bioavailability and maximize the drug agents’ efficiency. Some well-known compounds have been robustly studied, but many remain elusive. The objective of this review is to discuss recent studies and advantages of nanoscale formulations of plant-derived antioxidant compounds.

Improved Gel Properties of Whey Protein-Stabilized Emulsions by Ultrasound and Enzymatic Cross-Linking

This study investigated the effects of high-intensity ultrasound (HUS) and transglutaminase pretreatment on the gelation behavior of whey protein soluble aggregate (WPISA) emulsions. HUS pretreatment and TGase-mediated cross-linking delayed the onset of gelation but significantly increased (p < 0.05) the gel firmness (G') both after gel formation at 25 °C and during storage at 4 °C. The frequency sweep test indicated that all gels had a similar frequency dependence at 4 and 25 °C, and the elasticity and viscosity of the WPISA-stabilized emulsion gel were significantly enhanced by HUS pretreatment and TGase-mediated cross-linking (p < 0.05). HUS and TGase-mediated cross-linking greatly improved the textural properties of WPISA-stabilized emulsion gels, as revealed by their increases in gel hardness, cohesiveness, resilience, and chewiness. HUS pretreatment and TGase-mediated cross-linking significantly increased the water-holding capacity but decreased the swelling ratios of the gels (p < 0.05). Interactive force analysis confirmed that noncovalent interactions, disulfide bonds, and TGase-induced covalent cross-links were all involved in the formation of gel networks. In conclusion, the combination of HUS and TGase-mediated cross-linking were beneficial for improving the gelation properties of WPISA-stabilized emulsion as a controlled release vehicle for potential food industrial applications.

Recent progress in the preparation, chemical interactions and applications of biocompatible polysaccharide-protein nanogel carriers

Nanogel carriers are rapidly emerged as a major delivery strategy in the fields of food, biology and medicine for small particle size, excellent solubility, high loading, and controlled release. Natural polysaccharides and proteins are selected for the preparation of biocompatible, biodegradable, low toxic, and less immunogenic nanogels. Different polysaccharides and proteins form complex nanogels through different interaction forces (e.g., electrostatic interaction and hydrophobic interaction). The present review pursues three aims: 1) to introduce several well-known dietary polysaccharides (chitosan, dextran and alginate) and proteins (whey protein and lysozyme); 2) to discuss the types, preparation methods, chemical interactions and properties of various biocompatible complex carriers; 3) to present the application and prospect of polysaccharide-protein complex in bioactive ingredient delivery, nutrient encapsulation and flavor protection. We expect that the integration with nano-intelligent technology will improve the functional ingredient loading, recognition specificity and controlled release capabilities of polysaccharide-protein nanocomposites to generate new intelligent nanogels in the field of food industry in the future.

Enhanced oral oil release and mouthfeel perception of starch emulsion gels

Reducing oil/fat content without compromising the structural and sensory quality of food is a great technical challenge to the food industry. The present work aims to investigate the possibility of a novel emulsion design that gives an enhanced oral release of oil/fat from an emulsion gel and therefore an enhanced mouthfeel of oiliness. Hence, alpha-amylase sensitive emulsifier such as starch was used for this purpose. On the other hand, whey protein isolate (WPI) i.e. α-amylase insensitive emulsifier was used as a reference. The gellan gum was selected as a gelling agent to prepare emulsion gels. The mastication and size reduction of the emulsion gels were examined through in-vitro and in-vivo studies. The amount of oil released as indicated by the β-carotene analysis was monitored and various influencing factors (pH, time, compositions, etc.) were also investigated. Using sensory panelists, oral processing of emulsion gels was examined in terms of both mastication parameters and perceptions of oiliness and thickness. The obtained results showed that the use of a starch emulsifier gives a higher oil release and an enhanced oral sensation of oiliness mouthfeel. Therefore, starch emulsion could provide a novel solution in the design of fat-reduced food products with no effect on the mastication parameter, sensation and perception of fat-related attributes.

Preparation of Pickering emulsion gels based on κ-carrageenan and covalent crosslinking with EDC: Gelation mechanism and bioaccessibility of curcumin

Pickering emulsions stabilized by zein/carboxymethyl dextrin nanoparticles were added to the κ-carrageenan-based gel matrix to prepare emulsion gels via EDC - induced covalent crosslinking. Texture, WHC and freeze-thaw stability of the emulsion gels increased after crosslinking. The Confocal laser scanning microscope and SEM suggested that droplet clusters could be observed in gel with higher concentration of emulsion. The rheological measurements indicated that the viscosity and gel-like structure were relied on crosslinking agent and emulsion concentration. The photothermal stability of curcumin was significantly enhanced after crosslinking. In addition, in vitro digestion study suggested that the bioaccessibility of curcumin in emulsion gel crosslinked was lower compared to emulsion gel without crosslinking agent. These studies might facilitate the preparation of emulsion gels with excellent stability for bioactive compounds delivery in food and pharmaceutical applications.

Comparison of Two Different Natural Oil Body Emulsions: in vitro Gastrointestinal Digestion

The surface compositions and structure of oil bodies (OBs) are dependent on the oil crop, and these factors affect in vitro gastrointestinal digestion behaviors. Herein, a comparative study was conducted to examine the in vitro gastrointestinal digestion characteristics of two natural emulsions prepared with soybean seeds and rapeseed OBs during gastrointestinal digestion process. The average particle size of soybean OBs and rapeseed OBs emulsions was 0.46 and 5.02 µm, respectively. The droplet size of soybean seed and rapeseed OBs emulsions was large with relatively low zeta-potentials at 30 min digestion time in simulated gastric fluid condition. The droplet size of two natural OBs emulsions decreased with increasing digestion time in simulated gastric fluid condition. The average droplet size of both emulsions gradually decreased with increasing digestion time in simulated intestinal fluid conditions. The zeta-potential of the two emulsions increased with increasing digestion time in simulated intestinal fluid conditions. The extent of free fatty acids of soybean OBs emulsions was significantly higher than rapeseed after 20 min digestion time in simulated intestinal fluid conditions. The obtained results suggested that plant OBs could be useful as natural emulsifiers in the development of functional food and achieve controlled release of bioactive compounds from emulsions during gastrointestinal digestion.

Surfactant addition to modify the structures of ethylcellulose oleogels for higher solubility and stability of curcumin

The current study developed ethylcellulose (EC) based oleogels with the addition of a surface active ingredient (sorbitan monopalmitate, SP), in order to increase the active loading of curcumin by reducing lipid oxidation, improving curcumin solubility and chemical stability. With the increase in SP content, EC oleogels had more compact gel networks with evenly distributed smaller pores. Rheological analysis revealed that the gels had shear-thinning behavior, and higher concentration of SP contributed to the systems with higher viscosity. The inclusion of SP also worked to reinforce gel strength as determined by frequency sweep, creep recovery and textural analyses. EC oleogels with higher content of SP were capable to hold more liquid oil during centrifugation, and the T₂ relaxation time was much lower as determined by NMR. Peroxide value of the oleogels was significantly lower in the systems with SP, and a SP content of 4% or 6% was effective in inhibiting lipid oxidation during storage. When curcumin was incorporated within the gel networks, its effective concentration was more retained with the addition of SP, as no curcumin crystals were detected by DSC during a 9-day storage test, and curcumin had much higher retention when exposed to UV light for 8 h.

Protein-based hydrogelled emulsions and their application as fat replacers in meat products: A review

Recent consumers' concerns about diet and its health benefits has triggered a reduction in consumption of foods rich in sugar, fat, salt, and chemical additives. As a result, an expanded market for functional foods has arisen. In particular, high-fat foods normally composed by saturated fatty acids, cholesterol and trans-fatty acids have been reformulated to be healthier. The primary source of saturated fat ingested by humans includes meats and their by-products that have animal fat as lipid source. The reformulation of these products therefore represents an important strategy to make them healthier for human consumption. Substituting solid fat by unsaturated oils usually affects the texture of the products, and therefore, new structuring methods must be developed to provide vegetable oils a similar characteristic to solid fats and improve their functional and health-related properties. Among these structural models, gelled emulsions (GE) show great potential to be used as healthier lipid ingredients in low-calorie and reduced-fat products, including healthier meat products. This review addresses the GE properties to be used as structuring agent, their in vitro bioaccessibility in meat products and effect on technological, sensorial, microstructural and microbiological characteristics.