Formation Of Gel Network Research Articles

Effect of limited hydrolysis on the structure and gel properties of soybean isolate proteins: A comparative study of papain or/and trypsin

Plant protein's gelation is crucial in various food applications, and hydrolysis may enhance their gelation properties. In this study, we prepared soybean protein isolate hydrolysates (SPIH) using trypsin and/or papain, and found significant improvement in the solubility and gelling properties. These proteases broken down the peptide bonds and caused the exposure of hydrophobic groups as well as the unfolding of protein. Low molecular weight (<35 kDa) SPIHs were generated by the two-step enzymatic hydrolysis, showing significant improvements in storage modulus (G′), loss modulus (G″), viscosity, strength, and water-holding capacity (WHC). Among, PT-10 exhibited the highest WHC (61.72 ± 0.36 %), gel strength (4.67 ± 0.12 g), and network cross-linking density (0.33 ± 0.01 mol/m3), while its solubility was also significantly increased up to 254 %. According to the results of gel molecular force interactions, disulfide bonds, hydrophobic interactions and hydrogen bonds involved in the gel network formation. These findings reveal that the appropriate hydrolysis modification may improve SPI gel's properties and expand its application in gel foods.

Hydrogel network formation triggers atypical hygroscopic behavior in atmospheric aerosols

The phase state of atmospheric aerosol particles, dictated by composition, intermolecular interaction, size, and pH, profoundly impacts climate, human health, and air quality. Herein, the phase behavior of internally mixed sodium bitartrate (SBT) and ammonium sulfate (AS) aerosols with equal molar ratio was studied using microscopic imaging, confocal Raman and infrared spectroscopy. We observed atypical phase transition during hygrosopic cycles. On dehydration, micro-solids formed at relative humidity (RH) of 80.1 % without further efflorescence, namely limited efflorescence (LE). On hydration, droplets effloresced at 39.8 % RH and deliquesced at 68.8 % RH, referred as efflorescence on hydration (EH). Raman spectra show that Na2SO4 solids form during LE, while both Na2SO4 and (NH4)2SO4 solids form during EH. The phase transition of the SBT/AS (1:1) droplets is size-dependent, where smaller droplets are prone to “EH” while larger droplets are prone to typical efflorescence. Combining AIOMFAC-VISC viscosity predictions with scanning electron microscopy (SEM) images, we attribute the “LE” and “EH” phenomena to the formation of an ion-organic hydrogel network structure within droplets. pH and organic/inorganic mixing ratios can collaboratively affect the stability of hydrogel network by changing the organic/inorganic mixing ratios. Our study shows that gel network formation can cause atypical phase transition in atmospheric aerosols.

Improving the Gelation Properties of Pea Protein Isolates Using Psyllium Husk Powder: Insight into the Underlying Mechanism.

The industrial application of pea protein is limited due to its poor gelation properties. This study aimed to evaluate the effects of psyllium husk powder (PHP) on improving the rheological, textural, and structural properties of heat-induced pea protein isolate (PPI) gel. Scanning electron microscopy (SEM), intermolecular forces analysis, the quantification of the surface hydrophobicity and free amino groups, and Fourier transform infrared spectroscopy (FTIR) were conducted to reveal the inner structures of PPI-PHP composite gels, conformational changes, and molecular interactions during gelation, thereby clarifying the underlying mechanism. The results showed that moderate levels of PHP (0.5-2.0%) improved the textural properties, water holding capacity (WHC), whiteness, and viscoelasticity of PPI gel in a dose-dependent manner, with the WHC (92.60 ± 1.01%) and hardness (1.19 ± 0.02 N) peaking at 2.0%. PHP significantly increased surface hydrophobicity and enhanced hydrophobic interactions, hydrogen bonding, and electrostatic interactions in PPI-PHP composite gels. Moreover, the electrostatic repulsion between anionic PHP and negatively charged PPI in a neutral environment prevented the rapid and random aggregation of proteins, thereby promoting the formation of a well-organized gel network with more β-sheet structures. However, the self-aggregation of excessive PHP (3.0%) weakened molecular interactions and disrupted the continuity of protein networks, slightly reducing the gel strength. Overall, PHP emerged as an effective natural gel enhancer for the production of pea protein gel products. This study provides technical support for the development of innovative plant protein-based foods with strong gel properties and enriched dietary fiber content.

Shear and cooling effects on lamellar gel network structure: Insights from Rheo-SANS

We investigate the formation of lamellar gel networks (LGNs) composed of long-chain fatty alcohols (C16, C18) and their mixture, combined with the surfactant cetyltrimethylammonium chloride (CTAC). The study aims to understand how fatty alcohol chain length and preparation processes affect the structural and mechanical properties of LGNs. Using small-angle neutron scattering (SANS) and in-situ rheology, we track the effects of mixing and cooling rates on formulations in aqueous solution. Additional insights into the nanostructure are provided by small- and wide-angle X-ray scattering (SAXS/WAXS), while microscopy and rheology shed light on macroscopic behavior. Results show that all formulations form lamellar structures, with C16/C18 mixtures exhibiting properties intermediate to those of pure C16 and C18 systems. While C16 and C16/C18 exhibit hexagonal lateral packing, C18 leads to an orthorhombic structure. Faster cooling rates favor the formation of multilamellar vesicles and promote system homogeneity. A patchy organization of the surfactant within the fatty alcohol bilayers is also observed. These findings enhance our understanding of the role of long-chain fatty alcohols in LGN formation and their behavior during mixing and cooling.

Effects of fermentation with Lactobacillus plantarum on rice flour: The role of granular characteristics

This study examined the effects of lactic acid bacteria fermentation on the physicochemical and functional properties of the flours from two rice varieties, Shindongjin (SF) and Hitomebore (HF), both with similar amylose content. Fermentation with Lactobacillus plantarum over 48 h resulted in significant changes. Protein content decreased substantially in both varieties, especially in SF, and amylose content increased. Swelling power and solubility also increased more in SF. The gel hardness of fermented SF increased by approximately 22 %, whereas HF showed minimal change. These differences are due to variations in granule rigidity and starch molecule leaching. SF granules maintained rigidity and a robust external network due to higher amylose leaching. In contrast, the lower initial rigidity and higher amylopectin leaching in HF hindered strong gel network formation. These findings offer insights into the structural and molecular mechanisms of rice fermentation with lactic acid bacteria.

Effect of gelled phases on the relevance of double emulsion gels for probiotics encapsulation, rheological properties, and stability

This study aimed to develop a stable double emulsion gel (DEG) based on whey protein cold-set gelation of the external water phase and carnauba wax-based solidification of the oil phase as a potential delivery system for probiotics in high-protein food products. The effect of the gelation of different phases on the microstructure, gel properties, and stability of DEGs under storage and freezing–thawing conditions and the viability of L. plantarum loaded in the inner water phase of DEGs were evaluated. The oil phase crystallization allowed the formation of stable DEGs during storage, showing negligible changes in consistency index, G′, and particle size after 56 d of storage and under four freeze–thaw cycles. The gelation of both the oil and external water phases allowed a stronger gel network formation, with a six times lower creaming index than non-gelled double emulsions. All samples demonstrated that the encapsulation of L. plantarum into the inner water phase of the DEG is beneficial for the storage stability of probiotics.

Amelioration of tiger nut insoluble dietary fiber as a partial substitute for fat in meat emulsions: Techno-functional properties and in vitro protein digestibility

The effects of tiger nut insoluble dietary fiber (TNF) (1%-3% w/w) on techno-functional properties and in vitro protein digestibility of low-fat meat emulsions were examined. The results showed that TNF (especially 2% and 3%) could improve techno-functional performances of low-fat meat emulsions in terms of water binding capacity and textural attributes, which were even preferable to the high-fat control. The improvements were associated with the attenuated fluidity of inner water within the gels, the increased storage modulus (G′), the formation of a well-joined gel network with uniformly-dispersed fat particles and the uncoiling of α-helix and the formation of β-sheet. The weakened water mobility, the heat-triggered conformational shift from α-helix to β-sheet, as well as less and evenly distributed fat particles ulteriorly led to elevated protein digestibility in meat emulsions. Therefore, TNF shows promise as a fat substitute to develop fat-reduced emulsified pork meat products with desirable quality and digestion behaviors.

Effect of polysaccharide on structures and gel properties of microgel particle reconstructed soybean protein isolate/polysaccharide complex emulsion gels as solid fat mimetic

In this work, a soybean protein isolate (SPI)/polysaccharide microgel particle reconstructed emulsion gels (MPEG) were fabricated through heat-induced gel (HG)–microgel particle–transglutaminase (TG) induced gel process in the presence of four polysaccharides (κ-carrageenan, κC; konjac glucomannan, KGM; high-acyl gellan, HA and xanthan gum, XG). HG exhibited a higher springiness than that of pig back fat (PBF) regardless of polysaccharide type and concentration. After forming MPEG, the springiness was significantly lowered at ≥0.6 % κC, which made MPEG exhibit similar springiness of PBF; while SPI/KGM, SPI/XG and SPI/HA systems failed to regulate the springiness property. Rheological behavior revealed the loss in elasticity, the increase in the plastic deformation of SPI/κC MPEG, while KGM, XG and HA systems still exhibited elasticity dominated rheological properties. Compared with KGM, XG, the presence of excess κC and HA disturbed the continuous protein network structure, resulting to the aggregation of microgel particles and oil droplets. Disulfide bonds and hydrophobic interactions mainly contributed to the formation of MPEG, while the addition of κC weakened the contribution of them, which was not conducive to the formation of gel network. This study provides a guidance on the development of solid fat mimetic based on the microgel particle emulsion gels.

Reduced fat content of fried batter-breaded fish nuggets by adding dietary fibers: Insight into wheat starch and gluten conformations, fiber properties and anti-fat absorption capacities

Dietary fibers with excellent processing characteristics and water-holding capacity garnered significant attention in low-fat fried products manufacturing, but further research is lacking to elucidate fat reduction mechanisms. Three dietary fibers were added to the batter of fried batter-breaded fish nuggets, the increased maximum wavelength, fluorescence intensity, surface hydrophobicity value, and S-S/free-SH ratio revealed the enhanced exposure and interaction of hydrophobic groups within gluten. Conversion from both -SH into S-S bonds, and α-helix into β-turn confirmed the establishment of the gluten gel network and a substantially increased gel strength. X-ray diffraction demonstrated the inhibition of amylose-lipid complex formation due to the competitive amylose binding to dietary fiber. Finally, reduced oil effects were evident in surface and penetrated oil contents and oil distribution fluorescence diagram. The work clarified the interactions among dietary fiber, wheat starch and gluten, indicating the composite gel network formation and the crust characteristics alterations, ultimately inhibiting oil penetration.

Influence of 7-day subfreezing storage on physicochemical, nutritional, and microstructural attributes of porcine longissimus thoracis et lumborum muscle.

The effect of 7-day subfreezing storage on the physicochemical properties, nutritional composition, and microstructure of pork was investigated. After 7 days of chilling at 4°C, the meat exhibited color deterioration and the development of off-flavors. In contrast, the -12°C treatment significantly reduced the deterioration in water-holding capacity and color of samples (p<0.05) and prevented changes in pH value. Similarly, the treatments at -12 and -18°C effectively preserved the meat's tenderness, thiobarbituric acid-reactive substances, protein solubility, and textural properties, maintaining these qualities close to those of fresh meat (p>0.05). The nutrient content of samples stored at -12°C was comparable to those stored at -18°C (p>0.05). Furthermore, subfreezing at -12°C was found to protect muscle integrity, promoting the formation of an elastic gel network and a homogenous muscle fiber structure. Therefore, the study concludes that 7-day subfreezing storage at -12°C can reduce protein denaturation and maintain thequality of pork, a result that is typically achieved under more extreme freezing conditions at -18°C.

Tailoring pea proteins gelling properties by high-pressure homogenization for the formulation of a model spreadable plant-based product

This study investigated the impact of high-pressure homogenization (HPH) at varying intensities on the gelling properties of a commercial pea protein concentrate for the formulation of emulsion-filled gels as a model spreadable plant-based product. As a preliminary characterization, pea protein dispersions (10%-15%–20% w/w) underwent HPH treatments, 60 and 150 MPa for 5 cycles. Mechanical characteristics of heat-set gels were evaluated through rheological measurements. Emulsion-filled gels were then produced, starting from a common primary emulsion, incorporating either native or treated pea protein suspensions, and characterized with frequency and amplitude sweep tests, back extrusion, texture profile analysis (TPA) and confocal laser scanning microscopy (CLSM). Results revealed that HPH treatments had a significant influence on the aggregation state of protein suspensions reducing residue size, but inducing the formation of new, albeit smaller, agglomerates, with a direct impact on gel network formation. Treatment at 150 MPa consistently produced a stiffer, compact, and elastic gel structure, as confirmed by frequency sweep, back extrusion and TPA tests. Additionally, when this structure was disrupted, it exhibited creamy-viscous characteristics, as verified by amplitude sweep analyses. CLSM micrographs showed the formation of a more structured and compact gel matrix with the increase of the pressure applied.

Effect of non-covalent binding of tannins to sodium caseinate on the stability of high-internal-phase fish oil emulsions

In this study, we designed the noncovalent binding of sodium caseinate (SC) to tannic acid (TA) to stabilize high internal phase emulsions (HIPEs) used as fish oil delivery systems. Hydrogen bonding was the dominant binding force, followed by weak hydrophobic interaction and weak van der Waals forces, as demonstrated by FTIR, fluorescence spectroscopy, and molecular docking experiments, with a binding constant of 3.25 × 106, a binding site of 1.2, and a static quenching of the binding. Increasing SC:TA from SC to 2:1 decreased the particle size from 107.37 ± 10.66 to 76.07 ± 2.77 nm and the zeta potential from −6.99 ± 2.71 to −22 ± 2.42 mV. TA increased the interfacial tension of SC, decreased the surface hydrophobicity from 1.3 × 104 to 1.6 × 103 and improved the oxidation resistance of SC. The particle size of high internal phase emulsions stabilized by complexes with different mass ratios (SC:TA from 1:0 to 2:1) increased from 4.9 ± 0.02 to 12.9 μm, the potential increased from −32.37 ± 2.7 to −35.07 ± 2.58 mV, and the instability index decreased from 0.75 to 0.02. Thicker interfacial layers could be observed by laser confocal microscopy, and an increase in the storage modulus indicated a formation of a stronger gel network. SC:TA of 1:0 showed emulsion breakage after 14 d of storage at room temperature. SC:TA of 2:1 showed the lowest degree of oil-water separation after freeze-thaw treatment. Especially, the most stable high endo-phase emulsion (at SC:TA of 2:1) prepared at each mass ratio was selected for further stability exploration. The emulsion particle size increased only from 15.63 ± 0.06 to 22.27 ± 0.35 μm at salt ion concentrations of 50–200 mM and to 249.33 ± 31.79 μm at 300 mM. The instability index and storage modulus of the high endo-phase emulsions increased gradually with increasing salt ion concentrations. At different heating temperatures (55–85 °C), the instability index of the high internal phase emulsion gradually decreased and the storage modulus gradually increased. Meanwhile, at 50 °C for 15 d of accelerated oxidation, the content of hydroperoxide decreased from 53.32 ± 0.18 to 37.48 ± 0.77 nmol/g, about 29.7 %, and the thiobarbituric acid value decreased from 1.06 × 103 to 0.8 × 103, about 24.5 %, in the high endo-phase emulsions prepared by 2:1 SC:TA compared to the fish oils, and the SC-stabilized high endo-phase only emulsion broke at the sixth day of oxidation. From the above findings, it was concluded that the high internal phase emulsion prepared with SC:TA of 2:1 can be used as a good delivery system for fish oil.

Insight into gelation quality of low‐grade surimi as affected by fava bean protein isolate

SummaryThe effect of fava bean protein isolate (FPI) at varied concentrations (1%–4%, w/w) on gelation of sardine surimi was evaluated. Breaking force, gel strength, textural profile, and water holding capacity were improved with the addition of FPI (P &lt; 0.05). However, deformation and whiteness of gel samples decreased slightly when higher levels (3%–4%) of FPI were used (P &lt; 0.05). The improved gel properties were supported by enhanced rheological properties (G′ and G″) of gels containing FPI. Microstructure also revealed the formation of gel network with higher connectivity in samples containing 3%–4% FPI. No major changes in the myofibrillar proteins in surimi gel were observed as determined by FTIR spectra and protein patterns. Higher scores for texture and overall likeness were obtained for surimi gel containing 3%–4% FPI. Therefore, FPI is a promising plant‐based ingredient that can effectively improve the gel properties of low‐grade sardine surimi without causing beany flavour.

Gelatinous quality and quantitative proteomic analyses of snakehead (Channa argus) surimi treated by atmospheric cold plasma

In this study, the comprehensive quality characteristics and proteome changes of snakehead (Channa argus) surimi gel under different atmospheric cold plasma (ACP) treatment times were systematically analyzed and compared. The results showed that the ubiquitin-associated proteins and heat shock proteins were activated after ACP treatment for 90 s (ACP90), thus inducing rearrangement of surimi structural proteins. Meanwhile, the increased hydrophobic interactions and disulfide bonds might strengthen the interactions among the myofibrillar protein, keratin, and type-I collagen, which led to the formation of a dense gel network. Moreover, the high nodality between actin and myosin promoted the regulation of muscle contraction by changing the spatial obstruction of their binding sites. These beneficial effects obviously contributed to the superior water-holding capacity (76.13%), gel strength (285.6 g·cm) and viscoelasticity of snakehead surimi in the ACP90 group. These results would provide some useful information for the in-depth and efficient processing of surimi products.

Probing into the mechanism of adding tussah pupa powder to improve the deterioration of a pork batter emulsified gel

SummaryThe purpose of this experiment was to explore the improvement of tussah pupa powder on the deterioration of pork batter emulsion gel by using proteomics, distribution of moisture, rheological properties and surface hydrophobicity. The results showed that the myosin decomposed as the heating temperature increased; as the increase of the addition proportion of tussah pupa powder at each sterilisation temperature point, compared to the control group, the pH of a pork batter emulsified gel showed a significant increased trend (P &lt; 0.05); the low molecular weight proteins or formed oligomers of tussah pupa powder could be used as fillers to participate in the formation process of gel network; the vitellogenin of tussah pupa powder could form a ‘skeleton’ in the pork batter system; as the sterilisation temperature at 100 °C (30 min) and 110 °C (30 min), the surface hydrophobicity was the largest as the addition amount 2%. In short, the tussah pupae powder could improve the deterioration characteristics of the pork batter emulsified gel by influencing the pH, surface hydrophobicity and the formation of gel network of pork batter system. This research provided theoretical support for improving the process property of the meat products.

Structural characteristics and gelling properties of citrus pectins after chemical and enzymatic modifications: Conformation plays a vital role in Ca2+-induced gelation

Due to the excellent health benefits of rhamnogalacturonan I (RG-I)-enriched pectin, there has been increasing research interest in its gelling properties. To elucidate its structure–gelation relationship, chemical modifications were used to obtain RG-I-enriched pectin (P11). Then, enzymatic modification was performed to obtain debranched pectins GP11 and AP11, respectively. The effects of RG-I side chains on structural characteristics (especially spatial conformation) and gelling properties were investigated. Among the low-methoxylated pectins (LMPs), AP11, with a loose conformation (Dmax 52 nm) showed the poorest gelling, followed by GP11. In addition to primary structure, spatial conformation (Dmax and Rg) also showed strong correlations (r2 > 0.8) with gelation. We speculate that compact conformation may shorten distance between pectin chains and reduces steric hindrance, contributing to formation of strong gel network. This is particularly important in LMPs with abundant side chains. The results provide novel insights into relationship between spatial conformation and gelling properties of RG-I-enriched pectin.

Formation dynamics of branching structure in the slippery DLCA model.

We numerically investigated the aggregation dynamics and resulting network structures of colloidal gels using the slippery diffusion-limited cluster aggregation (DLCA) model. In this model, bonds are irreversibly formed upon the particle contacts, but the angles among them are not fixed, unlike the conventional DLCA. This allows clusters to be deformed in the process of aggregation. By characterizing the aggregation dynamics and using a reduced network scheme, our simulation revealed two distinct branching structure formation routes depending on the particle volume fraction ϕ. In lower volume fraction systems (ϕ ≤ 8%), the deformations of small-size clusters proceed prior to the percolation. When the Maxwell criterion is satisfied and the clusters become mechanically stable, the formation of the branching structure is nearly completed. After forming the branching structures, they aggregate and form a larger percolating network. Then, the aggregation proceeds through the elongation and straightening of the chain parts of the network. In higher volume fraction systems (ϕ > 8%), on the other hand, the clusters percolate, and a fine and homogeneous branching structure is formed at the early stage of the aggregation. In the aging stage, it collapses into a denser and more heterogeneous structure and becomes more stable. Our quantitative analyses of the branching structure will shed light on a new strategy for describing the network formation and elasticity of colloidal gels.

Effects and improvement mechanisms of ultrasonic pretreatment on the quality of fermented skim milk

Fermented skim milk is an ideal food for consumers such as diabetic and obese patients, but its low-fat content affects its texture and viscosity. In this study, we developed an effective pretreatment method for fermented skim milk using low-frequency ultrasound (US), and investigated the molecular mechanism of the corresponding quality improvement. The skim milk samples were treated by optimal ultrasonication conditions (336 W power for 7 min at 3 °C), which improved the viscosity, water-holding capacity, sensory attributes, texture, and microstructure of fermented skim milk (P < 0.05). Further mechanistic analyses revealed that the US treatment enhanced the exposure of fluorescent amino acids within proteins, facilitating the cross-linking between casein and whey. The increased surface hydrophobicity of fermented milk indicates that the US treatment led to the exposure of hydrophobic amino acid residues inside proteins, contributing to the formation of a denser gel network; the average particle size of milk protein was reduced from 24.85 to 18.06 µm, which also contributed to the development of a softer curd texture. This work is the first attempt to explain the effect of a low-frequency ultrasound treatment on the quality of fermented skim milk and discuss the molecular mechanism of its improvement.

Heat-induced lupin-whey protein emulsion-filled gels: Microstructural and rheological insights

This work investigates the rheological properties of lupin-whey emulsion-filled gels (EFGs) formed using a pilot scale plate heat exchanger. Samples were prepared with either lupin, whey, or a lupin-whey stabilized emulsion, mixed in a whey protein continuous phase. While whey protein in the continuous phase was mainly responsible for the formation of a primary gel network, differences were observed depending on the droplet-whey protein matrix interactions. Full or partial replacement of interfacial proteins with lupin proteins resulted in softer, more ductile gels. Amplitude sweeps showed that the structure was not only affected by the interactions between the droplets and the continuous network, but also by the droplet distribution within the matrix. This work demonstrates the importance of fine tuning the interactions and the distribution of oil droplets within the gel, as these properties will lead to structural heterogeneity at the micro-scale, causing profound differences in the rheological properties. Finally, continuous heating led to stiffer, more particulate gels compared to quiescent conditions, but similar mechanisms underpinned gel formation. Thus, it is demonstrated that the design of the interactions can be screened using an in situ rheometer, although the rheological properties are affected by the shear effect of the plate heat exchanger.

The effect of concentration on rheological properties of sago (Metroxylon sagu) starch

The concentration of starch is one of the main factors influencing the rheological characteristics of starch-based foods. The rheological behavior of sago starch at varied concentrations of 3, 5, 10, 20 and 30% (w/w) were investigated using small oscillatory temperature and frequency sweep measurements. All concentrations of sago starch expressed less solid-like behavior, with tan δ values of approximately 0.2. A flowable viscous paste of sago starch was generated at low concentrations (3 and 5% (w/w)). The gel network formation of sago starch initially occurred at a critical concentration of 10% (w/w). Further increases in the concentration to 20 and 30% (w/w), stronger gel network formation was occurred. In addition, the tan δ values for concentrations of 20 and 30% (w/ w) were approximately 0.2 with elastic and soft gel characteristics. A positive power law correlation between G' and sago starch concentration was found, with a coefficient of determination (R2 ) value of 0.99. The gelatinized sago starch was unstable as a frequency sweep was applied, indicating that it may be less stable during storage or processing.