Gel Texture Research Articles

The Addition of Pumpkin Flour Impacts the Functional and Bioactive Properties of Soft Wheat Composite Flour Blends

Growing interest in functional food ingredients has led to the exploration of pumpkin flour as a nutritional enhancer in wheat-based products. This study investigated the impact of pumpkin flour incorporation (0–20%) on soft wheat flour blends’ technological and bioactive properties. The comprehensive analysis included granulometric distribution, techno-functional properties (WHC, WAC, WAI, WSI, SP, OAC), pasting characteristics (RVA), gel texture (TPA), rheological behaviour (frequency sweeps), colour parameters, and bioactive compounds (TPC, DPPH, ABTS) in both water and ethanol extracts. Pumpkin flour addition systematically modified blend properties, with higher fine particle content (13.26% < 80 μm), enhancing water interaction capabilities (WHC increased from 2.52 to 3.56). Pasting behaviour showed reduced peak viscosity (2444.0 mPa·s to 1859.5 mPa·s) but enhanced gel structure stability, evidenced by increased storage modulus (112.7 Pa to 1151.0 Pa) and reduced frequency dependence. Colour parameters showed progressive darkening (L* 91.00 to 84.28) and increased yellow-orange intensity (b* 10.13 to 27.13). Bioactive properties improved significantly, with TPC increasing up to 0.57 mg/1 g DM and 0.34 GAE mg/1 g DM in water and ethanol extracts, respectively, accompanied by enhanced antioxidant activity. Pumpkin flour incorporation successfully enhanced both functional and bioactive properties of wheat flour blends, with particle size distribution and water interactions serving as fundamental determinants of technological functionality, while contributing to improved nutritional value through increased bioactive compounds.

Effects of transglutaminase on the gelation properties and digestibility of pea protein isolate with resonance acoustic mixing pretreatment.

Our previous research confirmed that resonance acoustic mixing (RAM) pretreatment effectively improved the emulsification and water retention of commercial pea protein isolate (PPI), but significantly reduced its gel performance. This study aimed to investigate the effect of transglutaminase (TGase, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%) on the gel properties and digestibility of PPI with RAM pretreatment (RAM-PPI). Results showed that moderate TGase (0.1-0.3%) significantly increased the α-helix/β-sheet ratio, surface hydrophobicity and covalent crosslinking of protein molecules, enhancing the texture and digestibility of RAM-PPI gels. The SEM imaging demonstrated a fine, uniform and dense network structure with many pores in these RAM-PPI gels. However, excessive TGase (0.5%) reduced the water holding capacity and intestinal digestibility of the RAM-PPI gels, mainly due to the excessive protein cross-linking and re-aggregation. These findings suggest that the combined treatment of moderate TGase with RAM can be a promising approach for the modification of plant-based proteins.

Influence of starch on freeze-thaw stability of Hypophthalmichthys molitrix surimi gel observed via ice crystal distribution and gel properties

Starch has been recognized as a vital ingredient in surimi products due to its ability to absorb water, which reduces the deterioration of gels and water loss during freezing and thawing. However, it is essential to ascertain the role of starch in the formation of ice crystals and the texture of surimi gels. The impact of freeze-thaw cycles on the morphology and distribution of ice crystals, as well as the textural characteristics of gelatinized and ungelatinized starch-surimi gels was investigated. The results of light microscopy revealed that the presence of starch, irrespective of whether it was gelatinized, resulted in a reduction in the size of ice crystals within the surimi gel network during the freeze-thaw process. In addition, starch in surimi gels was subjected to freeze-thaw cycles, resulting in the emergence of two distinct states of bound water (0.1–1 ms and 1–10 ms). The higher relative content of immobile water indicated that the gelatinized starch had improved water holding properties. Furthermore, the incorporation of gelatinized starch into surimi enhanced its freeze-thaw stability and retarded the loss of gel strength, hardness, and whiteness. The addition of starch had a synergistic impact, enhancing the gel properties by affecting the formation of ice crystals and water absorption.

Rice bran oil-in-water emulsion stabilized by Amur catfish myofibrillar protein: Characteristics and its application in surimi gels

The objective of this investigation was to isolate amur catfish myofibrillar protein (AMP), emulsify it with rice bran oil, and assess its application in the silver carp surimi gel. The proportion and addition of AMP/rice bran oil emulsion on the gel properties were compared. The emulsion stabilized by 3 % AMP was stable when an oil/water ratio of 0.70 and 0.75 was employed, as evidenced by its appearance, microstructure, and rheological characteristics. The L*, a* and whiteness values of gels observably elevated when the emulsion blended (p < 0.05). The mechanical capacities (texture and rheology indicators) of surimi gels were dramatically improved with 5 % emulsion added (p < 0.05). However, the addition of excessive emulsion (up to 15 %) impeded the formation of surimi protein network and lowered water retention ability of surimi gels. Moreover, 5 % emulsion was distributed uniformly throughout the gel matrix, giving rise to the development of a dense and uniform network with high water binding capacity. Furthermore, the study on protein solubility expressed that the addition of the emulsion facilitated protein-protein interactions in surimi gels. In summary, the addition of 5 % AMP stabilized rice bran oil emulsion could yield a stronger surimi gel with increased whiteness. The resulting gels could serve as healthy fat-rich surimi-based products.

Impact of process conditions and type of plant protein on aggregate formation with whey protein and resulting ricotta-like gel texture

Aim of the study was to investigate the effect of process conditions and type of plant protein on protein aggregation and texture of hybrid ricotta alternatives. Four different plant proteins (soy, pea, lupin, potato) were used and first underwent a pre-treatment to increase solubility, followed by thermally-induced pre-aggregation of the hybrid systems with β-lactoglobulin-rich whey protein at varying pH and temperature. Aggregates were analysed via particle size distribution and SDS-PAGE. For production of the ricotta alternative, acidification and subsequent thermal coagulation formed the protein gel network. Texture analysis and visual evaluation of macroscopic structure was carried out.Results showed that aggregate size significantly affects gel strength. For soy-whey mixtures pH during pre-aggregation was the main factor affecting aggregate size, with a favourable diameter of 5 μm and a corresponding gel strength to whey-based ricotta of 0.9 N. Pea protein generally behaved similar to soy protein due to the similarity in protein composition and structure. In contrast, use of lupin resulted in a weaker gel, due lupin’s dense molecular structure and high denaturation temperature. Potato-whey hybrid systems formed large insoluble aggregates, which as a consequence did not contribute to gel formation. In summary, the results of the present study show that a variation of the protein type in hybrid ricotta alternatives requires process adaptations, but at the same time allows the creation of new gel structures for hybrid cheese alternatives.

Insights into transglutaminase on structural and rheological properties of gels from adzuki bean protein pretreated by electric fields

The demand for protein is increasing as the global population continues to grow. The plant protein has been favored and plant-based food has become a research hotspot for healthy diet, environmental protection, animal ethics and other issues. Adzuki bean protein (ABP) is a quality source with complete amino acids, abundant essential amino acids and beanless flavour. ABP is rich in glutamine and lysine which are good substrates for transaminase (TGase) induced gelation. The pulsed electric field (PEF), alternating current EF (ACEF), direct current EF (DCEF) were applied to pretreat ABP aiming at improving the efficacy of TGase induced crosslinking. The results showed that the TGase decreased the free amino amount significantly and increased the molecular weight of ABP. The EF pretreatments significantly influenced the secondary and tertiary structures of ABP with a decrease in β-sheets, increase in random coils, β-turns, and α-helices, also decrease in fluorescence intensity with blueshift. The content of disulfide bond increased with the decrease of free sulfhydryl groups. The ionic bonds decreased and hydrophobic actions surpassed significantly hydrogen bonds. The hydrophobicity increased. The electric field intensity corresponded to variation of microstructure, texture and rheological behaviour of the ABP gel according to the type of the EF.

Electric fields and transglutaminase in preparing adzuki bean protein emulsion gel for plant-based steamed egg custard

Alternating current (ACEF), direct current (DCEF) and pulsed (PEF) electric field (EF) were applied for adzuki bean protein (ABP) pretreatment to prepare substitutes of steamed egg custard. Emulsion gels of EF pretreated ABP dispersions with flaxseed oil were mediated by transglutaminase (TGase). The emulsion particle size and the oil droplet size increased with the oil portion. PEF and ACEF pretreatment significantly reduced the number of large droplets. With the increase of oil portion, the infrared spectra at 2854 and 1747 cm−1 changed significantly and a new peak emerged in amide A zone. Three EF pretreatments all increased the β-sheets of ABP, ACEF pretreatment led to the random coils slightly higher than DCEF and PEF. DCEF pretreatment increased the α-helices significantly higher than ACEF and PEF. The EF pretreatments improved the emulsion gel texture in gel strength, hardness, and chewiness, and water holding capacity (WHC). The largest apparent viscosity and energy storage modulus were obtained in DCEF pretreatment and larger than PEF and ACEF pretreatments. The 0.15 % curcumin and 0.10 % β-carotene pigmentation of ABP-flaxseed oil emulsion gel gave the smallest difference in colour, and higher WHC, close springiness, slightly lower chewiness, and gel strength, compared with the real steamed chicken egg custard control.

A method for improving the gelation properties and 3D printing performance of reduced-sodium chicken breast paste: The addition of tiger nut protein, transglutaminase, and calcium chloride

This study investigated the effects of tiger nut protein (TNP) (4%), transglutaminase (TG) (0.5%), and calcium chloride (CaCl2) (1.5%) on the gelling properties and 3D printability of reduced-sodium chicken breast paste, which contained 0.3% sodium chloride (NaCl). Compared with the control group, the addition of TNP-TG-CaCl2 increased the gel's hardness from 833.5 g to 1544.7 g, improved the water-holding capacity (WHC) by 2.4%, reduced the cooking loss (CL) by 2.3%, and enhanced the printing accuracy by 10.3%. Structural and rheological analysis indicated that the physical filling effect of TNP, the enhancement of protein interactions by TG, which includes increased hydrophobic interactions and disulfide bonds, along with the alteration of protein structure from α-helix to β-sheet, and the aggregation effect of Ca2⁺ during gel formation process, are the key factors that contribute to the formation of a dense network structure during gel formation, and help to improve the gel performance and 3D printing suitability of reduced-sodium chicken mince. Results of correlation analysis between the structure, gel performance and 3D printing performance indicate that the hydrophobic interactions are mostly responsible for the gel performance and 3D printing performance, and there exists a strong correlation between gel hardness, WHC and the 3D printing performance of the meat slurry. Collectively, gels with appropriate hardness and WHC may have the favorable printing adaptability, and the combined use of TNP, TG, and CaCl2 is an effective way to enhance the 3D printing precision and gel texture of low-sodium meat slurry.

A comparative study of different soybean oil forms on the physicochemical properties of surimi myofibrillar protein gel: The role of soybean protein isolate and κ-carrageenan

Natural soybean oil, Pickering emulsion, high-internal-phase emulsion (HIPE), and emulsion gel were prepared to investigate their effects on the physicochemical properties of surimi myofibrillar protein gels. Their effects on gel strength ranked as: emulsion gel > Pickering emulsion > HIPE > soybean oil. At the same oil content, the emulsion gel exhibited higher G' than the other forms whereas natural oil exhibited the lowest G', and T22 was smaller in the emulsion gel group, indicating that the emulsion gel enhanced the interaction between water molecules and protein macromolecules. FT-IR testified that 9 % natural oil reduced the β-sheet content to 26.34 %, whereas Pickering emulsion, HIPE, and emulsion gel recovered the β-sheet content to 31.30 %, 36.17 %, and 32.69 %, respectively. Emulsion gel led to fewer voids, and the oil droplets in emulsion gel were more regularly spherical and homogeneously dispersed in the gel matrix, which might be attributed to the filling effects as well as “bridging action” of soybean protein isolate and κ-carrageenan within surimi proteins. In conclusion, we demonstrated emulsion gel as a good replacer to mitigate the negative effect of oil on the texture and structure of surimi gels, which would be a promising approach for oil supplementation in surimi production.

Characterization of ulvan polysaccharide extracted from Ulva pertusa and its effect on thermal, rheological, and gelling properties of rice flour

Three ulvan fractions (UPs 1–3) were extracted from Ulva pertusa via hot-water extraction. UP1 exhibited a molecular weight of 729,151 Da, while UPs 2 and 3 ranged from 19,952 to 750,384 Da. These fractions differed in monosaccharide, uronic acid, and sulfate levels. Zeta potentials for polysaccharide solutions (0.2–0.6 % w/v) ranged from −34.4 to −25.1, all demonstrating shear-thinning behavior. Incorporating UPs 1–3 solutions (0.2–0.6 % w/v) with rice flour increased gelatinization temperatures and modified pasting properties, increasing peak time, peak viscosity, and trough viscosity while reducing breakdown, final, and setback viscosities. Ulvan polysaccharide improved the viscous behavior of rice flour paste, indicated by increased loss modulus and tan δ (p > 0.05). Furthermore, ulvan polysaccharide improved the microstructure and texture of rice flour gel, with UP1 (0.6 % w/v) forming denser matrices and better texture. Molecular docking analysis suggested that hydrogen bonding is the primary interaction between rice glutelin and ulvan components.

Extraction technology determines the properties of bamboo shoots dietary fiber concentrate and its application in chicken mince gels: Systematic analysis

This study investigated how physical, chemical, and enzymatic extraction technologies affected the physicochemical properties of bamboo shoot insoluble dietary fiber (IDF). Additionally, the effects of IDF extracted by these techniques on the gel properties, water retention, microstructure, and digestibility of chicken mince gels were evaluated. Results showed that IDFs extracted by physical (P-IDF), chemical (C-IDF), and enzymatic (E-IDF) exhibited a typical cellulose polysaccharide structure and strong water and oil retention capabilities, with the highest values reaching 14.18 g/g and 6.74 g/g, respectively. Compared to P-IDF, C-IDF and E-IDF displayed a rougher porous structure and stronger adsorption capacities for glucose (409.91 mg/g and 604.95 mg/g), cholesterol (54.46 mg/g and 64.06 mg/g), sodium cholate, and nitrite. The addition of IDF improved the water retention, water stability, texture, and rheological properties of chicken mince gels, and had no negative effect on the digestion of chicken mince proteins. On the one hand, the hydrophilic groups exposed in IDF absorb water and fill the gel networks, reducing the formation of water channels in the gel and improving water stability. Furthermore, the hydrophilic groups on the glucose unit that makes up the IDF interacts with the proteins through the hydrogen bond and the transformation of protein β-structure to α-structure, promoting the formation of gel network structure and improving gel texture and rheological properties. E-IDF and C-IDF showed better overall gel performances, but E-IDF had better dry matter digestibility, protein digestibility, and gastrointestinal digestive effects. Therefore, IDF prepared by enzymatic hydrolysis is more suitable for chicken mince processing.

Ultrasound treatment improved gelling and emulsifying properties of myofibrillar proteins from Antarctic krill (Euphausia superba)

Antarctic krill is a promising source of marine proteins with abundant biomass and excellent nutritional profile, but has poor technological properties. Ultrasonic treatment at power levels of 0, 100, 200, 300, 400 and 500 W was applied to improve the technological properties of Antarctic krill meat, and the changes in physicochemical properties of myofibrillar proteins (MPs) were investigated. The results indicated that proper ultrasonic treatment significantly improved the gelling properties of Antarctic krill meat, in terms of a more uniform and stable gel texture and better water holding capacity, which were related to better cross-linking of MPs. Ultrasonic treatment promoted the conversion of MPs’ secondary structures from α-helix and random coil to β-sheet and β-turn, thereby making the molecular structure soft and loose. In addition, at tertiary structure level, ultrasonic treatment exposed the hydrophobic groups and sulfhydryl groups within MPs, thereby improving the emulsifying properties by changing the intermolecular interactions and interface properties. Furthermore, the particle size of MPs decreased and exhibited a more uniform distribution, aligning with the enhanced interactions observed between MPs and oil. These results provide an insight into the efficient development of Antarctic krill by elucidating how the ultrasonic treatment improves the gelling and emulsifying properties based on structure modulation of myofibrillar proteins.

Effects of galactomannans of varied structural features on the functional characteristics and in vitro digestibility of wheat starch

This study explores the effects of four natural galactomannans (GMs) with varying degrees of branching (fenugreek gum, guar gum, tara gum and locust bean gum) on the functional properties and in vitro digestibility of wheat starch (WS). Results from rapid viscosity analysis (RVA) and low-field nuclear magnetic resonance (LF-NMR) analysis revealed that GMs with lower branching degrees were correlated with higher paste viscosity, peak viscosity, and greater water-holding capacity in the WS-GM mixtures. Additionally, these lower branching GMs more effectively inhibited amylose leaching during starch gelatinization, leading to a softer gel texture and increased transparency of the mixtures. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analysis demonstrated that starch mixtures containing lower branching GMs exhibited reduced relative crystallinity and enthalpy values during aging. Furthermore, the incorporation of lower branching GMs resulted in decreased starch digestibility in vitro, thereby enhanced resistant starch content. These findings highlight the potential of selectively branched GMs to modulate the functional properties and nutritional profile of WS, providing a promising approach for the development of starch-based products with improved health benefits.

Lactic acid bacteria fermentation-induced egg white protein structure deformation influencing gelling properties, with membrane concentration as a strategy to improve texture.

Egg white (EW), a rich protein source, holds promise for creating a high-protein, low-fat gel product. However, browning issues during heating and sterilization have hindered its wider application. In this study, lactic acid bacteria fermentation was employed to eliminate reducing sugar in EW, and its impact on the molecular structure and gelling properties was explored. The results revealed that fermentation would trigger protein structural unfolding and aggregation, evident from higher fluorescence intensity and enlarged protein particle diameters, resulting in the decrease in gelling hardness. In comparison, Streptococcus thermophilus-fermented EW (under 6×108CFU/mL incubation rate, fermented for 6h) exhibited the highest gel hardness, ascribed to the relatively weaker structure transformation, with high water holding capacity and stronger intermolecular hydrophobic interaction. To further enhance the gelling properties of fermented EW, membrane concentration treatment was applied, exhibiting superior characteristics in appearance, aroma, and taste. In summary, lactic acid bacteria fermentation and concentration are feasible solutions to improve appearance and texture of EW gels simultaneously. The research findings offer eco-friendly and practical strategies for enhancing the quality of EW gels, providing valuable theoretical insights for the development of innovative, texture-rich, and healthy nutritional foods.

Pea protein soften surimi gels and improve in vitro digestibility: Potential high protein foods for elderly

As the fastest growing fraction of the global population, the creation of high protein foods for the elderly has become increasingly urgent and important. While surimi gels are a good source of concentrated myofibrillar proteins, their elastic texture makes swallowing of these gels difficult, which current studies have focused on maintaining or enhancing. As such this study aimed to better understand how to reduce surimi gelation which would allow us to better control gel texture by partially replacing surimi with pea proteins. With an increasing proportion of pea proteins, the hardness, cohesiveness and adhesiveness of the gels was progressively reduced. This was due to the increase in pea protein aggregate formation, as characterised by the increase in β-structures and hydrophobic interactions which reduced the viscoelasticity and time stability of the gels. When comprising of less than 60% pea proteins, pea aggregates were dispersed within the continuous crosslinked surimi gel network, but above that the aggregates dominated the gels, disrupting the network structure, forming coarse gels with larger pores. Hence, mixed protein gels with 60% and above pea proteins had modified textures suitable for consumption by those with swallowing difficulties. Gel structure and texture also positively influenced the in vitro digestibility of the gels, as the higher pea protein ratio and softer texture allowed for increased proteolysis, solubilisation, and amino acid release. Thus, this study provides a basis for modulating the texture of mixed surimi and pea protein gels by understanding protein interactions and their effects on gel structure and digestibility.

The impact of κ-carrageenan on the pea protein gelation by high pressure processing and the gelling mechanisms study

The transition toward sustainable and health-conscious diets has intensified plant-based proteins, particularly pea protein. This research explored the gelation mechanisms of pea protein with κ-carrageenan by high-pressure processing (HPP) as an alternative to traditional thermal methods. Suspensions containing 15% pea protein with 0.1–1% κ-carrageenan were subjected to HPP at 100–600 MPa for 5–30 min. Increasing κ-carrageenan concentration reduced the pressure required to obtain good gels, rendering HPP more energy efficient. Pea protein gels with 1% κ-carrageenan at 600 MPa demonstrated a 27-fold increase in compressive strength compared to 15% pea protein alone by HPP and over 5 times the strength of heat-induced counterparts. Gel textures could be tailored by modulating HPP conditions and κ-carrageenan concentrations. Fourier transform infrared spectroscopy, confocal laser scanning microscopy, and scanning electron microscopy characterized protein unfolding, phase separation, and network formation to study the gelation mechanisms. Results revealed that HPP induced protein tertiary structure unfolding, facilitating phase separation and uniform submicron κ-carrageenan particle distribution in the protein matrix. This, along with a more compact protein network induced by HPP, enhanced gel strength, compensating for limited cysteine in pea protein for disulfide bonds. Higher pressures intensified protein unfolding and aggregation, with κ-carrageenan particles evenly distributing into smaller particles, further strengthening gel structures. Conversely, heating-induced gelation caused more random protein aggregation, leading to coarser and weaker gel networks. This research highlights HPP's effectiveness over traditional heating methods in preparing strong pea protein gels with minimal κ-carrageenan and provides preliminary insights into tailoring HPP and κ-carrageenan for desirable gel textures.

Exploring the effects of spontaneous and solid-state fermentation on the physicochemical, functional and structural properties of whole wheat flour (Triticum aestivum L.)

The effects of fermentation on various physicochemical and functional properties of whole wheat flour (Triticum aestivum L.) were investigated in this study. Firstly, changes in pH and total titratable acidity (TTA) were observed during spontaneous and solid-state fermentation. Spontaneous and solid-state fermentation led to a decrease in pH and a rapid increase in TTA, indicating effective acidification due to organic acid production. Both fermentation approaches significantly influenced the total starch and amylose content of wheat. The total starch content was decreased accompanied by a significant increase in apparent amylose content. This phenomenon was attributed to starch hydrolysis facilitated by microbial enzymes and organic acids, resulting in a higher amylose/amylopectin ratio. Chemical composition and mineral content of whole wheat flour were also affected. Fermentation led to reductions in moisture, crude fat, and crude protein content, while ash content increased. Furthermore, fermentation significantly impacted the soluble and total dietary fiber content of whole wheat flour, with an increase in soluble dietary fiber and a decrease in total dietary fiber. These changes were attributed to increased synthesis of non-cellulosic polysaccharides and β-glucans during fermentation. Moreover, fermentation resulted in reductions in gluten content, alterations in functional properties such as water and oil absorption capacity, changes in protein solubility, and modifications in gel texture properties. Finally, X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed minimal changes in the crystalline structure and morphology of starch granules during fermentation, with some signs of surface erosion and degradation, particularly in solid-state fermented samples. The results highlight the potential benefits of fermentation for improving the properties of whole wheat flour. This study contributes to a better understanding of the effects of fermentation on whole wheat flour, offering insights for the development of novel and improved whole wheat flour-based food products.

The dynamic changes in physicochemical properties, functionalities, and gel properties of the starch-konjac gum mixture during the melting process: Based on three typical melting temperatures of DSC

The present study focuses on investigating the effect of typical melting temperatures (To, Tp, and Tc from DSC) on the dynamic changes of physicochemical properties, functionalities, and gel properties of starch-konjac gum mixture (PS/KGM). The typical melting treatments (HTo, HTp, and HTc) significantly enhanced the PS/KGM synergism, as indicated by the increased thermal stability, and the improved pasting and gel properties. The work suggested that the typical melting effectively stabilized the aqueous mixture system of PS/KGM, showing no phase separation in the water phase system, even after storage for 12 h. The PLM and SEM show that melting at HTo, HTp, and HTc causes partial melting with the loss of birefringence of starch granules, and the granules conglomerate into large clusters with rough surfaces, surrounded by smaller matrices. DSC demonstrated that typical melting significantly raised the To of composite to approximately 77 from 59.10 °C for native. RVA suggested that the melting significantly increased the FV of PS/KGM from 3363 to approximately 8000 mPa s, while the BD decreased from 5009 to approximately 400 mPa·s. Especially in which there is no BD recorded when melted by HTp and HT. The PS/KGM melted by HTo and HTp had more acidic, salty, and shear stability during the thermal process with improved gel texture and freeze-thaw stability than HTc. Partial melting of starch and chain rearrangement is critical for enhancing PS/KGM synergism. As RC% and DM% controlling at approximately 30–35% are the most effective for promoting PS/KGM interaction (HTp > HTo > HTc).

Investigating the effects of oil type, emulsifier type, and emulsion particle size on textured fibril soy protein emulsion-filled gels and soybean protein isolate emulsion-filled gels.

The effects of oil type, emulsifier type, and emulsion particle size on the texture, gel strength, and rheological properties of SPI emulsion-filled gel (SPI-FG) and TFSP emulsion-filled gel (TFSP-FG) were investigated. Using soybean protein isolate or sodium caseinate as emulsifiers, emulsions with cocoa butter replacer (CBR), palm oil (PO), virgin coconut oil (VCO), and canola oil (CO) as oil phases were prepared. These emulsions were filled into SPI and TFSP gel substrates to prepare emulsion-filled gels. Results that the hardness and gel strength of both gels increased with increasing emulsion content when CBR was used as the emulsion oil phase. However, when the other three liquid oils were used as the oil phase, the hardness and gel strength of TFSP-FG decreased with the increasing of emulsion content, but those of SPI-FG increased when SPI was used as emulsifier. Additionally, the hardness and gel strength of both TFSP-FG and SPI-FG increased with the decreasing of mean particle size of emulsions. Rheological measurements were consistent with textural measurements and found that compared with SC, TFSP-FG, and SPI-FG showed higher G' values when SPI was used as emulsifier. Confocal laser scanning microscopy (CLSM) observation showed that the distribution and stability of emulsion droplets in TFSP-FG and SPI-FG were influenced by the oil type, emulsifier type and emulsion particle size. SPI-stabilized emulsion behaved as active fillers in SPI-FG reinforcing the gel matrix; however, the gel matrix of TFSP-FG still had many void pores when SPI-stabilized emulsion was involved. In conclusion, compared to SPI-FG, the emulsion filler effect that could reinforce gel networks became weaker in TFSP-FG.

Soy Protein Isolate Gel Subjected to Freezing Treatment: Influence of Methylcellulose and Sodium Hexametaphosphate on Gel Stability, Texture and Structure.

Freezing affects texture and induces the loss of gel quality. This study investigated the effects of methylcellulose (MC) (0.2%, 0.4%, 0.6%) and sodium hexametaphosphate (SHMP) (0.15%, 0.3%) on the gel textural and structural properties of SPI gels before and after freezing, and explores the synergistic enhancement of gel texture and the underlying mechanisms resulting from the simultaneous addition of SHMP and MC to SPI gels. It was revealed that MC improved the strength of SPI gels through its thickening properties, but it could not inhibit the reduction of SPI gels after freezing. The 0.4% MC-SPI gel exhibited the best gel strength (193.2 ± 2.4 g). SHMP inhibited gel reduction during freezing through hydrogen bonding and ionic interactions; it enhanced the freezing stability of SPI gels. The addition of 0.15% SHMP made the water-holding capacity in SPI gels reach the highest score after freezing (58.2 ± 0.32%). The synergistic effect of MC and SHMP could improve the strength and the freezing stability of SPI gels. MC facilitated the release of ionizable groups within SPI, causing negatively charged SHMP groups to aggregate on the SPI and inhibit the freezing aggregation of proteins. These results provide a strong basis for the improvement of cryogenic soy protein gel performance by SHMP and MC.