Effect of fish gelatin and gum arabic interactions on concentrated emulsion large amplitude oscillatory shear behavior and tribological properties

Structure, characterization, and application of a novel thermoreversible emulsion gel fabricated by citrate agar

A novel thermoreversible emulsion gel was successfully prepared with citrate agar (CA) as the sole emulsifier. Compared with native agar gel emulsion, CA gel emulsion (CAGE) formed a stable emulsion gel when the CA concentration was increased to 1.25 % (w/w). Results of time-temperature scanning experiments showed that the emulsion gel rapidly transformed into liquid emulsion when heated to 40-50 °C and then solidified into emulsion gel after cooling to the critical temperature of solidification. The emulsion gel had stable sol-gel transformation ability after seven cycles repeated heating-cooling treatment (HCT) at 85 °C and 4 °C. However, the stability of emulsion gels gradually decreased because of the large-droplet formation during heating, which affected the CA molecular-reconfiguration network structure in cooling. The conjunction analysis of microstructure and properties of the emulsion gel indicated that its stability depended primarily on the spatial repulsion and electrostatic repulsion provided by CA gel, and the main factor driving thermal reversibility was the temperature-responsive gelation performance of CA. The retention of quercetin was >90.23 % after seven HCTs because CAGEG enhanced the homogeneity and stability of the droplets.

Freeze-thaw stability of high-internal-phase emulsion stabilized by chickpea protein microgel particles and its application in surimi

BACKGROUND

Future applications of high-internal-phase emulsions (HIPEs) are highly regarded, but poor freeze-thaw stability limits their utilization in frozen products. This study aimed to characterize the structure of chickpea protein microgel particles (HCPI) induced by NaCl and to assess its impact on the freeze-thaw stability of HIPEs.

RESULTS

The results showed that NaCl induction (0-400 mmol L-1) increased the surface hydrophobicity (175.9-278.9) and interfacial adsorbed protein content (84.9%-91.3%) of HCPI. HIPEs prepared with HCPI induced by high concentration of NaCl exhibited superior flocculation index and centrifugal stability, and their freeze-thaw stability was better than that of natural chickpea protein. The increase in NaCl concentration reduced the droplet aggregation and coalescence index of the freeze-thaw emulsions, diminishing the precipitation of oil from the emulsion. Linear and nonlinear rheology showed that the strengthened gel structure (higher G' values) restricted water flow and counteracted the damage to the interfacial film by ice crystals at 100-400 mmol L-1 NaCl, thus improving the viscoelasticity of the freeze-thaw emulsions. Finally, the thawing loss of surimi gel with HCPI-200 HIPE was reduced by 2.04% compared to directly adding oil.

CONCLUSION

This study provided a promising strategy to improve the freeze-thaw stability of HIPEs and reduce the thawing loss of frozen products. © 2024 Society of Chemical Industry.

Pickering emulsion with high freeze-thaw stability stabilized by xanthan gum/lysozyme nanoparticles and konjac glucomannan

In this study, freeze-thaw cycle experiments were conducted on food-grade Pickering emulsions co-stabilized with konjac glucomannan (KGM) and xanthan gum/lysozyme nanoparticles (XG/Ly NPs). The rheological properties, particle size, flocculation degree (FD), coalescence degree (CD), centrifugal stability, Differential scanning calorimetry (DSC), X-ray diffraction (XRD) and microstructure of Pickering emulsion stabilized by KGM before and after freeze-thaw were characterized. It was found that as the concentration of KGM increased, the flocculation degree (FD) and coalescence degree (CD) of the emulsion decreased after the freeze-thaw cycle compared to the control sample, and the microscopic images showed that the droplets became smaller and less affected by the freeze-thaw cycles. The rheological and water-holding properties also confirmed that the KGM-added emulsions still had a strong gel network structure and prevented the separation of the continuous and dispersed phases of the droplets after freezing and thawing. Freeze-thaw treatments had a negative effect on the stable emulsion of XG/Ly NPs, while the addition of KGM improved the freeze-thaw stability of the emulsion, which provided a theoretical basis for the development of emulsion products with high freeze-thaw stability.

Salmon protein gel enhancement for dysphagia diets: Konjac glucomannan and composite emulsions as texture modifiers

The growing prevalence of dysphagia among the aging population presents a significant challenge. Many highly nutritious foods, like salmon, are often unsuitable for the elderly due to their firm texture when heated. To address this concern, a combination of salmon myofibrillar protein (SMP), Konjac glucomannan (KGM), and different emulsion fillers-such as oil droplets, octenyl succinic anhydride (OSA)-modified potato starch emulsion, and high methoxylated pectin (HMP) emulsions-was selected to enhance the network of salmon protein gels with the aims to create potential applications as dysphagia-friendly foods. The International Dysphagia Dietary Standardization Initiative (IDDSI) test indicated that all gel samples were classified as level 5. The OSA-SMP-KGM gel exhibited notably higher cohesiveness (P < 0.05), reduced adhesion, and enhanced mouthfeel. The OSA-SMP-KGM gel exhibited a smooth surface and excellent water retention (92.4 %), rendering it suitable for individuals with swallowing difficulties, particularly those prone to experiencing dry mouth. The yield stress of OSA-SMP-KGM gel was 594.14 Pa and stable structure was maintained during chewing and swallowing (γe/γv = 62.5). This study serves as a valuable reference for developing salmon-based products that are not only highly nutritious but also fulfill the criteria for a desirable swallowing texture.

Effect of simulated saliva on rheological and tribological properties of oleogel-in-water HIPEs during oral processing

HYPOTHESIS

High internal phase emulsions (HIPEs) have great potentials in the food industry to control fat consumption. Textural perception of HIPEs during oral processing is strongly influenced by saliva, which has not been systematically investigated. Therefore, we investigated the roles of saliva in the rheological and tribological properties of HIPEs during oral processing.

EXPERIMENTS

HIPEs (O/W) stabilized by oleogel and a protein were fabricated. Small (SAOS) and large (LAOS) amplitude oscillatory shearing measurements and tribological tests were performed, in combination with structural characterization of the emulsions.

FINDINGS

Particle size and CLSM observation indicated that saliva induced coalescence of droplets by weakening the interface and more EC resulted in faster clustering. SAOS tests revealed that emulsions mixed with saliva had weaker structural strength and lower resistance to deformation. Particularly in large deformation, the HIPEs mixed with saliva presented an acceleration in the droplet-droplet structure breakdown, which led to the pronounced strain-thinning behavior and energy dissipation. Tribological curves further revealed that the corporation of saliva contributed to the release of oil to reduce friction coefficient.

Stabilization of oil-in-water high internal phase emulsions with octenyl succinic acid starch and beeswax oleogel

High internal phase emulsions (HIPEs) based on beeswax (BW) oleogels and octenyl succinic acid starch (OSA starch) were prepared by a facile one-step method. Effects of the oleogelation of internal phase on the formation, stability and functionality of the HIPEs were investigated. OSA starch absorbed at the interface allowed high surface charge (|ζ| > 25 mV) of the droplets, and small droplet size (d ≈ 5 m). Microstructural observation suggested that the HIPEs were of O/W type with droplets packed tightly. With the increase in BW content (0-4 %), the particle size (4-7 μm) and ζ-potential (-25 ~ -30 mV) of the HIPEs were first decreased and then increased. Stability analysis revealed that the addition of BW effectively improved emulsion stability against centrifugation, freeze-thawing, changes in pH and ionic strength, and the HIPE with 2 % BW presented the best stability. Rheological tests indicated that the HIPEs with higher content of BW exhibited higher storage modulus, solid-like properties, and shear thinning behaviors. Creep-recovery results implied that the oleogelation enhanced the structure of HIPEs and improved the deformation resistance of the systems. When subjected to light and heat, oleogel-in-water HIPEs showed advantages in protecting β-carotene from degradation, and β-carotene in the HIPEs with 2 % BW had the lowest degradation rate. These findings suggested that gelation of oil phase could improve the stability of HIPEs and the encapsulation capability, which would be meaningful for the development of novel healthy food.

A critical study of the nonlinear rheological properties in major classes of foods using the Sequence of Physical Processes (SPP) method and the Fourier Transform Coupled with Chebyshev Decomposition (FTC) method

The nonlinear rheological behaviors of three different classes of foods (emulsion, suspension, and elastic network) were studied and analyzed using the Rogers Sequence of Physical Processes (SPP) method and the Ewoldt-McKinley method of coupling Fourier Transform with Chebyshev Decomposition (FTC). SPP analysis led to instantaneous rheological parameters G't and G″t at any point in time, providing a more accurate picture of the linear viscoelastic region and crossover points by the 3D amplitude sweep. When G't is plotted against G″t, the resulting graph is a deltoid which offers a detailed and distinctive intracycle behavior of each class of food. Analyzing the revolution of deltoids with increasing strain allows for the determination of a critical strain, beyond which irreversible network breakdown occurs. The strain range between the linear viscoelastic limit and the critical strain found in SPP is comparable to the MAOS region as determined with FTC. Under increasing amplitude, predominantly elastic networks showed a gradual structural rearrangement, while more erratic and abrupt changes were observed in the suspension and emulsion we studied. Under increasing frequency, elastic responses dominate viscous responses in all samples due to the shorter experimental time, allowing less relaxation.

Synergistic effect and mechanism of cellulose nanocrystals and calcium ion on the film-forming properties of pea protein isolate

The current serious environmental problems have greatly encouraged the design and development of food packaging materials with environmental protection, green, and safety. This study aims to explore the synergistic effect and corresponding mechanism of cellulose nanocrystals (CNC) and CaCl2 to enhance the film-forming properties of pea protein isolate (PPI). The combination of 0.5 % CNC and 4.5 mM CaCl2 resulted in a 76.6 % increase in tensile strength when compared with pure PPI-based film. Meanwhile, this combination effectively improved the barrier performance, surface hydrophobicity, water resistance, and biodegradability of PPI-based film. The greater crystallinity, viscoelasticity, lower water mobility, and improved protein spatial conformation were also observed in CNC/CaCl2 composite film. Compared with the control, the main degradation temperature of composite film was increased from 326.23 °C to 335.43 °C. The CNC chains bonded with amino acid residue of pea protein at specific sites via non-covalent forces (e.g., hydrogen bonds, Van der Waals forces). Meanwhile, Ca2+ promoted the ordered protein aggregation at suitable rate and degree, accompanied by the formation of more disulfide bonds. Furthermore, proper Ca2+ could strengthen the cross-linking and interaction between CNC and protein, thereby establishing a stable network structure. The prepared composite films are expected to be used for strawberry preservation.

Sucrose Esters and Beeswax Synergize to Improve the Stability and Viscoelasticity of Water-in-Oil Emulsions

W/O emulsions are commonly used to prepare stable low-fat products, but their poor stability limits widespread applications. In this study, sucrose ester (SE) and beeswax were utilized to prepare an oil dispersion system in rapeseed oil, which was used as the external oil phase to further synergistically construct the W/O emulsion systems. The results show that spherical and fine crystals are formed under the synergistic effect of SE and BW (1.5 SE:0.5 BW). In this state, a dense interfacial crystal layer was easily formed, preventing droplet aggregation, leading to droplet size reduction (1-2 μm) and tight packing, improving viscoelasticity and resistance to deformation, and increasing the recovery rate (52.26%). The long-term stability of W/O emulsions containing up to 60 wt% water was found to be more than 30 days. The increase in the aqueous phase led to droplet aggregation, which increased the viscosity (from 400 Pa·s to 2500 Pa·s), improved the structural strength of the emulsion, and increased the width of the linear viscoelastic region (from 1% strain to 5% strain). These findings provide some technical support for the further development of stable low-fat products.

Glassy and compressed nanoemulsions stabilized with sodium dodecyl sulfate in the presence of poly(ethylene glycol)-diacrylate

The rheology of concentrated nanoemulsions is critical for their formulation in various applications, such as pharmaceuticals, foods, cosmetics, and templating advanced materials. The rheological properties of nanoemulsions depend on interdroplet interactions, Laplace pressure, dispersed phase volume fraction, and continuous phase properties. The interdroplet forces can be tuned by background electrolytes (i.e., charge screening), surfactant type, the excess surfactant micelle concentration, and depletant molecules such as polymer chains. In the current research, we study the effect of varying the content of poly(ethylene glycol)-diacrylate (PEGDA) on the interfacial tension of the water-oil phase and rheological properties of concentrated nanoemulsions with 50% and 60% volume fractions. Sodium dodecyl sulfate (SDS) is used as the ionic surfactant. The final concentrated nanoemulsions are repulsive according to overall interaction potentials and are in the glass and compressed states based on the effective volume fraction estimation. They contain nearly same SDS concentration on the droplet surface and also in the bulk, but a different amount of PEGDA. The scaled rheological properties of the glassy nanoemulsions show a higher dependency on the PEGDA content and the possible effect of polymer-surfactant complexations compared to those of the compressed ones. This dependency is more pronounced in small strain amplitudes but not in large strains in the non-linear regime. These results provide insights into formulating concentrated nanoemulsions with controlled rheology for expanded application areas.

Characteristics of reduced-fat mayonnaise prepared by oleaster as a fat replacer and natural antioxidant

Due to the disadvantages of consuming fat and synthetic preservatives, the demand to reduce them in lipid-based products like mayonnaise is increasing. In the current research, there were two goals, the first one was studying the effect of using oleaster flour in different concentrations (4%, 6%, and 8%) as a natural preservative, whereas the second one was studying the effect of oleaster as different fat replacement (FR) levels (10%, 20%, 30%, and 40%) on the physicochemical, antioxidant, and the rheological properties and stability of reduced-fat mayonnaise samples. Given results showed that with increasing the oleaster concentration, the antioxidant property increased significantly. The peroxide value after 60 days of storage for the 30% FR 8 was 2.01%, compared to the control sample without antioxidant and with TBHQ, which were 10% and 2.68%, respectively. The highest stability index (100%) was observed in the 30% FR and 40% FR samples. In terms of rheological characteristics, the 30% FR 8 oleaster showed the highest viscosity and the lowest frequency dependency. It can be concluded that oleaster has a high potential to be used in the formulation of low-fat mayonnaise as a fat replacer.

Effect of Cold Atmospheric Pressure Argon Plasma Jet Treatment on the Freeze-Dried Mucilage of Chia Seeds (Salvia hispanica L.)

In the present study, the effects of the treatment of chia seeds with a cold atmospheric pressure plasma jet (CP) using argon as a working gas for different times (30, 60, and 120 s) on the rheological, structural, and microstructural properties of the freeze-dried mucilages at -54 °C were investigated. All mucilage gels showed pseudoplastic flow behavior, and CP treatment of chia seeds increased the viscosity of mucilages, probably due to the cross-linking between polymer molecules. The dynamic rheological analysis revealed that all mucilages were elastic gels and that CP treatment improved the elastic properties in a treatment time-dependent manner. Large amplitude oscillatory shear (LAOS) results showed that freeze-dried mucilages showed Type I strain-thinning behavior. Similar to small amplitude oscillatory shear (SAOS) results, CP treatment has affected and improved the large deformation behavior of mucilages depending on treatment time. Meanwhile, Fourier transform infrared spectroscopy (FTIR) revealed the incorporation of hydroxyl groups onto the surface and the formation of C-O-C glycosidic bonds during plasma treatment. Scanning electron microscope (SEM) micrographs showed the formation of denser structures with CP treatment time. Regarding color properties, CP treatment decreased the lightness values of mucilages. Overall, this study showed that CP is an effective way to modify both the SAOS and LAOS properties of freeze-dried chia mucilage and improve viscosity.

Reversibility of freeze-thaw/re-emulsification on Pickering emulsion stabilized with gliadin/sodium caseinate nanoparticles and konjac glucomannan

The reversibility of freeze-thaw/re-emulsification of Pickering emulsion stabilized by gliadin/sodium caseinate nanoparticles (Gli/CAS NPs) was improved by adding konjac glucomannan (KGM). With the increase in the KGM concentration, the delamination of emulsions after freeze-thaw treatment was significantly improved. The microstructure showed that the presence of KGM helped to maintain the network structure of continuous phases. In particular, the particle size of the emulsion did not increase significantly after three freeze-thaw cycles when the KGM concentration was 0.6 % and the oil phase fraction was 60 %. The results of flocculation degree and coalescence degree also indicated that KGM promoted the cross-linking between particles on the surface of the droplet and increased the thickness of the interfacial film of the droplet. Rheological analysis also proved the same result: the elastic modulus of the emulsion was still larger than the viscous modulus, which showed the ideal freeze thaw reversibility. After adding KGM, the emulsion formed a strong network structure with good stability for long-term storage and reversibility for freeze-thaw cycling/re-emulsification. Thus, the emulsion has broad application prospects in food, cosmetics, and pharmaceutical fields.

Pickering emulsions synergistic stabilized with konjac glucomannan and xanthan gum/lysozyme nanoparticles: Structure, protection and gastrointestinal digestion

The effect of konjac glucomannan (KGM) on the stability and digestion characteristics of xanthan gum/lysozyme nanoparticles (XG/Ly NPs) stabilized Pickering emulsions was investigated. Results indicated that the high viscosity of KGM prompted the particles to be adsorbed toward the interface, which decreased the particle size and increased the stability of emulsions. As the concentration of KGM increased, the G' and G″ of emulsions became larger and approached a "solid-like" state. When the KGM concentration was ≥0.2 %, the large amplitude sweeps of the emulsion exhibited a "weak strain overshoot". The network structure formed by KGM molecular chain and particles was intertwined around the droplets to form a polysaccharide layer and fibrous network structure. Emulsions containing KGM showed a "spider web" epidermal network pattern. It was found by illumination for 4 h that samples with 0.2 % KGM concentration increased the retention of β-carotene by 18.74 %. KGM decreased the release rate of fatty acids and bioaccessibility by hindering bile salt and lipase adsorption.

Comparative Large Amplitude Oscillatory Shear (LAOS) Study of Ionically and Physically Crosslinked Hydrogels

Hydrogels are highly versatile and widely applicable materials within various scientific, technological, and food sectors. Alginate and gelatin hydrogels, along with their crafted variations, are possibly the most common ones. However, the ionic crosslinking of alginate-Ca⁺⁺ is a different gelation mechanism than the physical crosslinking of gelatin. In this work, we prepare alginate-Ca⁺⁺ hydrogels using individual layer gelation and experimentally evaluate LAOS rheological behavior. We apply shear-stress decomposition using the MITlaos software and obtain the elastic and viscous contributions within the nonlinear response of the individual alginate-Ca⁺⁺ layer. We compare these results with the nonlinear responses of the gelatin-alginate ex situ individual layer. The strain-sweep patterns are similar, with loss modulus overshoot. The applied shear can destroy the larger-scale structural units (agglomerate/aggregates), resulting in analogous patterns. However, the critical strain points are different. Based on the shear-thickening ratio T of the LAOS analysis, it can be assumed that the common feature of ex situ preparation, i.e., gelation as individual layers, provides a matching bulk microstructure, as the hydrogels differ significantly at a molecular-binding level.

Development of edible films by incorporating nanocrystalline cellulose and anthocyanins into modified myofibrillar proteins

In this study, a myofibrillar protein (MP) system was used to investigate the film properties changes by adjusting the intensity of the interaction of proteins with other food components. The structure and rheological properties of several film-forming solutions were then determined. Furthermore, the structure of these composite films was examined using Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The smooth and uniform surface acquired by scanning electron microscopy (SEM) substantiated the increased compatibility and continuity observed for films with greater food component interaction. In addition, the MP-based edible films with stronger food component interactions (the MP-Myr/ANT/NCC group) displayed superior mechanical (tensile strength: 6.68 MPa, elongation at break: 94.43%), water vapor barrier (10.01 × 10^-9 g m^-1 s^-1 Pa^-1), and ammonia sensitivity (total color difference: 17.00) capabilities compared to those of the other groups (the MP/ANT/NCC, MP-Lut/ANT/NCC, and MP-Que/ANT/NCC groups).

Development and characterization of ultrastable emulsion gels based on synergistic interactions of xanthan and sodium stearoyl lactylate

Emulsion gels with the mixtures of low-molecular-weight emulsifier (LME) and polymer have attracted much attention in food; however, the LME-polymer interactions in emulsion system are complex and unclear. Here, the interactions between SSL and xanthan in emulsions and the mechanisms of stabilizing emulsions were investigated by using tensiometry, zeta potential, Fourier transform infrared spectroscopy (FTIR), confocal laser scanning microscopy (CLSM), cryo-scanning electron microscopy (cryo-SEM) and rheology. SSL was more efficiently adsorbed on the oil-water interface than xanthan. Interestingly, the honeycomb structure was formed in emulsion gels, which firmly immobilized oil droplets. Furthermore, electrostatic repulsion and hydrophobic interactions between xanthan and SSL facilitated the efficient bonding at interface and in bulk. Both linear and nonlinear rheology strongly supported the fact that the interactions between xanthan and SSL enhanced gel-like viscoelastic structure of emulsion gels. This structure endows excellent stability of emulsion gels under high temperature storage, sealed conditions and pH change.

Evaluating the Mechanical Response of Agarose-Xanthan Mixture Gels Using Tensile Testing, Numerical Simulation, and a Large Amplitude Oscillatory Shear (LAOS) Approach

Large deformation stress response characteristics of hydrocolloid mixture gel systems were investigated based on texture and rheological measurements. Agarose and xanthan mixtures at different ratios (1:0, 0.75:0.25, and 0.5:0.5) were chosen as the model systems. A decrease in failure stress from 2.65 to 1.82 MPa and an increase in failure strain from 0.08 to 0.13 with higher xanthan ratios were obtained based on the ring tensile test, indicating that xanthan molecules could improve the flexibility of the agarose network. The gels showed severe water loss by compression, particularly for the pure agarose gel (6.74%). Compared to the compression test, the gels presented low water loss after the ring tensile test (<1.3%) indicating that the ring tensile test could calculate the correct stress−strain relationship. Digital image correlation (DIC) and numerical simulation revealed that agarose-xanthan gel systems possess a deformation behavior with homogeneous strain distribution before failure. Elastic and viscous Lissajous−Bowditch curves from the large amplitude oscillatory shear (LAOS) measurement at different strains and frequencies elucidated that the agarose-xanthan gel was dominated by the agarose structure with a similar magnitude of elasticity at a low frequency. The large deformation approach from this study has great potential for elucidating and understanding the structure of food and biopolymer gels.

Twin-Screw Extrusion of Oat: Evolutions of Rheological Behavior, Thermal Properties and Structures of Extruded Oat in Different Extrusion Zones

Further investigation of material properties during the extrusion process is essential to achieve precise control of the quality of the extrudate. Whole oat flour was used to produce low moisture puffed samples by a twin-screw extruder. X-ray diffraction (XRD), Scanning electron microscopy (SEM), infrared spectroscopy (FTIR), thermal analysis, and rheological experiments were used to deeply characterize changes in the structure and cross-linking of oats in different extrusion zones. Results indicated that the melting region was the main region that changed oat starch, including the major transformation of oat starch crystal morphology and the significant decrease of enthalpy representing the starch pasting peak in the differential scanning calorimeter (DSC) pattern (p < 0.05). Moreover, the unstable structure of the protein increased in the barrel and then decreased significantly (p < 0.05) after being extruded through the die head. The viscosity of oats increased in the cooking zone but decreased after the melting zone. A transformation occurred from elastic-dominant behavior to viscoelastic-dominant behavior for oats in the melting zone and after being extruded. This study provides further theoretical support for the research of the change of materials during extrusion and the development of oat-based food.

Fabrication and characterization of oleogels and temperature-responsive water-in-oil emulsions based on candelilla (Euphorbia cerifera) wax

Developing novel fats with zero trans and low saturated fatty acids represents a research hotspot in the colloid field today. Herein, natural candelilla (Euphorbia cerifera) wax was used as an oleogelator to construct oleogel systems, and can make strong oleogels at low concentrations (3 wt%). These oleogels were further employed as continuous phases to fabricate surfactant-free W/O emulsions with excellent stability (at least 30 days). Microstructural observation confirmed that the stability of emulsions was attributed to the interface and bulk phase crystallization of wax. All oleogels and emulsions were pseudoplastic fluids whose gel properties could be tuned via regulating oleogelator concentration. Water content also influenced the emulsion rigidity, denoting the droplets acted as "active fillers". Additionally, the emulsions displayed a temperature-responsive property, beneficial in mimicking the "fat-like" melt-in-the-mouth effect. These findings greatly enrich the formulation of surfactant-free W/O emulsions, providing technical support for the development of novel fats.

Intermolecular Interactions in the Formation of Polysaccharide-Gelatin Complexes: A Spectroscopic Study

Gelatin, due to its gelling and stabilizing properties, is one of the widely used biopolymers in biotechnology, medicine, pharmaceuticals, and the food industry. One way to modify the characteristics of gelatin is molecular modification by forming non-covalent polyelectrolyte complexes with polysaccharides based on the self-organization of supramolecular structures. This review summarizes recent advances in the study of various types and the role of intermolecular interactions in the formation of polysaccharide-gelatin complexes, and conformational changes in gelatin, with the main focus on data obtained by spectroscopic methods: UV, FT-IR, and 1H NMR spectroscopy. In the discussion, the main focus is on the complexing polysaccharides of marine origin-sodium alginate, κ-carrageenan, and chitosan. The prospects for creating polysaccharide-gelatin complexes with desired physicochemical properties are outlined.

Linear and non-linear rheological properties of water–ethanol hybrid pectin gels for aroma enhancement

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Linear to non-linear rheological responses of WEPGs were characterized.

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Gel rheological properties can be tuned by changing ethanol concentration.

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Non-linear viscoelasticity should be considered for aroma enhancement of WEPGs.

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The most relevant indicator to aroma release is e₃/e₁ under critical strain.

Whereas water–ethanol hybrid gels present an opportunity to realize aroma enhancement, translating hypothesis into practice is limited by poorly defined viscoelastic characteristics of those gels. In this work, the linear and non-linear rheological properties of water–ethanol hybrid pectin gels (WEPGs) were studied. Those WEPGs are physical gels in nature and the WEPG of 28.6% v/v ethanol differs basically from those of higher ethanol concentrations in the gel strength, resistance to deformation and non-linear properties. The retention of isopentyl acetate of WEPGs is dramatically improved by increasing the ethanol concentration to 33.3% v/v in the co-solvent system, but it is not further improved at 37.5% v/v. The cluster analysis reveals strong positive correlations between the isopentyl acetate release concentration and v₃/v₁ and absolute value of S/T ratio under 100% strain, suggesting the non-linear rheological responses of WEPGs have to be taken into account for which the enhancement of aroma is desired.

Rheological and tribological nature of flaxseed gum influenced by concentration and temperature and its application as a coating agent for potato chips

Influence of different concentrations (0.5, 1.0, 2.0, and 3.0% w/v) and temperatures (4, 25, 50, and 75°C) on particle size distribution (PSD) and rheological and tribological characteristics of flaxseed gum (FSG) solutions was investigated. Besides, FSG dispersions (0.5, 1.0, and 2.0% w/v) were used as edible coating and their influence on the quality parameters (oil uptake, moisture loss, texture, and sensory properties) of fried potato chips was studied. All FSG dispersions revealed shear-thinning nature and viscous properties (as G″ > G') that were more dominant at higher concentrations and lower temperatures. The power-law model presented a good fit in demonstrating the flow behavior of FSG dispersions. Concentration was the variable that affected the tribology of FSG dispersions, while temperature had little effect on the tribology. Particle size distribution was increased with the increasing concentration of FSG. FSG dispersions as an edible coating effectively reduced the moisture loss, oil uptake, and hardness properties of potato chips. Practical Application Profiling the influence of concentration and temperature on the rheology and tribology of flaxseed gum is particularly valuable during food processing. The results predict the physical properties of coated potato chips that can support the potential application of flaxseed gum as a coating agent. Today's consumers prefer healthier food products with low caloric, higher fiber content, functional properties, and sensory qualities. Food industries can use FSG as a low-cost natural coating material in terms of economic benefits, consumer acceptance, and providing an inordinate potential both for its protective effect and carrying functional compounds such as antioxidants in their coating matrix.

Effect and Mechanism of Acid-Induced Soy Protein Isolate Gels as Influenced by Cellulose Nanocrystals and Microcrystalline Cellulose

The effects of cellulose nanocrystals (CNC) and microcrystalline cellulose (MCC) on the gel properties and microstructure of glucono-δ-lactone-induced soy protein isolate (SPI) gels were investigated. The water-holding capacity, gel strength, and viscoelastic modulus of CNC–SPI gels were positively associated with CNC concentration from 0 to 0.75% (w/v). In contrast, MCC–SPI gels exhibited decreased water-holding capacity, gel strength, and viscoelastic modulus. All composite gels displayed high frequency dependence and the typical type I (strain thinning) network behavior. Changes in viscoelasticity under large strain were correlated with differences in the microstructure of SPI composite gels. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) showed that CNC were more evenly and steadily distributed in the protein matrix and formed a compact network structure. In contrast, MCC–SPI gels exhibited a discontinued and rough gel network with some large aggregates and pores, in which MCC was randomly entrapped. Fourier transform infrared spectroscopy (FTIR) and molecular forces results revealed that no new chemical bonds were formed in the gelation process and that the disulfide bond was of crucial importance in the gel system. With the addition of CNC, electrostatic interactions, hydrophobic interactions, and hydrogen bonds in the SPI gel network were significantly strengthened. However, the incorporation of MCC might obstruct the connection of the protein network. It is concluded that both cellulose type and concentration affect gelling properties.

Oral behavior of emulsified systems with different particle size and thickening agents under simulated conditions

Food behavior during oral processing plays an essential role in the perception of texture. It depends on different factors, including food structure and composition, as well as its behavior when interacting with saliva. This study aimed to investigate the effect of particle size and thickener type of emulsified systems on physical, rheological, tribological, and oral oily coating properties under oral conditions. Six matrices based on oil-in-water emulsions with different particle sizes (NE-nanoemulsion and CE-conventional emulsions) were prepared using a mixture of emulsifiers (10% w/w) and sunflower oil (10% w/w). Thickened agents were added to the matrices (NE and CE) at different concentrations (3-4.5% w/w of starch-ST or 0.4-0.8% w/w xanthan gum-XG) to obtain equi-viscous samples (NE-EV) with their CE-based counterpart. Results showed a decrease in apparent viscosity values under oral conditions (saliva and shearing at 10 s^-1) during the shear time, but this behavior was more evident in starch-based matrices. The lubrication properties of the different matrices depended mainly on the thickener concentration since equi-viscous samples (NE-ST-EV and NE-XG-EV) showed higher coefficient of friction (CoF) values. Finally, oral oily coating was more related to the oil droplets size than to the type of thickener since all NE-based matrices showed a higher amount of coating retained compared to the CE-based ones. Therefore, NE-based matrices could be used as an alternative to increase mouthfeel sensations in food emulsions.

Production, characterization and bio-emulsifying application of exopolysaccharides from Rhodotorula mucilaginosa YMM19

Microbial exopolysaccharides (EPS) are high molecular weight polymers having different sugar residues. EPS have potential applications in different fields, such as medicine, food and environment. Therefore, there is a growing interest in production, characterization and application of EPS from different microorganisms. The present study designed to investigate the production and characterization of EPS from Rhodotorula mucilaginosa YMM19 isolated from Morus nigra L. fruits as well as to examine their potential emulsifying properties. Effect of NaCl concentration, incubation period and pH on the production of EPS was studied. The maximum EPS production by yeast was achieved at 10% NaCl (9741.84 mg/l). The best incubation time for production of EPS was 5 days. Production of EPS decreased under neutral condition and increased at acidic and alkaline condition. The structural feature of EPS was examined by FT-IR and NMR spectral analysis and confirmed the presence of glucose, glucopyranose and galactose. The isolated EPS showed higher emulsification capacity with emulsification activity of 71% and emulsifying index of 60%. The EPS gave strong emulsification for farnesol and was more effective than sodium dodecyl sulphate, a reference emulsifier, in enhancing the herbicidal activity of farnesol against Melilotus indicus under greenhouse condition. The results suggest that the EPS produced by YMM19 strain has a potential to be used as emulsifying agent in pesticide formulations.

Nonlinear (Large-Amplitude Oscillatory Shear) Rheological Properties and Their Impact on Food Processing and Quality

Large-amplitude oscillatory shear (LAOS) testing has been increasingly used over the past several decades to provide a fuller picture of food rheological behavior. Although LAOS is relatively easy to perform on a wide variety of foods, interpretation of the resulting data can be difficult, as it may not be possible to link the results to food components, microstructural features or changes, or physicochemical properties. Several analysis methods have been developed to address this issue, but there is currently no standard method for foods. In food research, LAOS has mainly been used to investigate connections between food microstructures and rheological behaviors, although there have been some studies on connections between food LAOS behaviors and processing or sensory behaviors. LAOS has the potential to be a valuable tool for investigating food structure-function-texture relationships, but much work remains to develop these relationships, particularly in the area of connecting LAOS to sensory attributes.