Gel properties and structural characteristics of soy protein isolate treated with different salt ions before spray drying combined with dynamic high-pressure micro-fluidization

Structural and gelation properties of soy protein isolates-Sesbania gum gels: effects of ultrasonic pretreatment and CaSO4 concentration

This study aimed to investigate the influence of ultrasound treatment on the structural and gelation properties of soy protein isolate (SPI)-Sesbania gum (SG) composite gels induced by varying concentrations of CaSO4. The results showed that ultrasound treatment at amplitudes ranging from 20 % to 60 % for 10 min improved protein solubility, rheological properties and gel strength. The addition of CaSO4 (15 to 35 mM) further increased gel hardness but caused a decline in the water-holding capacity (WHC). Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) demonstrated that ultrasound treatment promoted the formation of a more homogenous and compact network in SPI-SG gels, improving WHC. Although higher concentrations of CaSO4 resulted in an uneven network with larger pores and reduced WHC, ultrasound treatment mitigated the loss. Moreover, analysis of intermolecular forces revealed that ultrasound treatment enhanced hydrophobic interactions and disulfide bonds within the mixed gels induced by CaSO4, leading to a stronger gel network. These findings provided a novel strategy for improving SPI-based gel properties and offer a theoretical basis for the application of SPI-SG complex in food processing.

Ultrasonic Treatment of Soybean Protein Isolate: Unveiling the Mechanisms for Gel Functional Improvement and Application in Chiba Tofu

Soybean protein isolate (SPI) cannot meet the needs of modern food production due to various shortcomings. By change of its structural characteristics, its application in the food field may be increased. This study explored the impact of ultrasonic treatment on the structural and gelation properties of the SPI dispersions. By subjecting SPI to ultrasonic treatment at 0-800 W for 10 min, it was found that this treatment significantly reduced the particle size of SPI to 196 nm and caused an increase in its solubility, surface hydrophobicity, and sulfhydryl content as well as significant changes in the protein structure. At an optimal ultrasonic power of 200 W, SPI gels demonstrated an enhanced gelling ability, strength, and water-holding capacity, forming a more uniform and compact structure. Application in Chiba tofu showed that water retention, elasticity, and sensory quality were optimized at 200 W. The findings highlight that a sonication power of 200 W significantly improves the physicochemical and structural properties of SPI, resulting in a denser and more functional gel suitable for Chiba tofu production.

Impact of pilot-scale microfluidization on soybean protein structure in powder and solution

The effect of microfluidization treatment on the primary, secondary, and tertiary structure of soybean protein isolate (SPI) was investigated. The samples were treated with and without controlling the temperature and circulated in the system 1, 3, and 5 times at high pressure (137 MPa). Then, the treated samples were freeze-dried and reconstituted in water to check the impact of the microfluidization on two different states: powder and solution. Regarding the primary structure, the SDS-PAGE analysis under reducing conditions showed that the protein bands remained unchanged when exposed to microfluidization treatment. When the temperature was controlled for the samples in their powder state, a significant decrease in the quantities of β-sheet and random coil and a slight reduction in α-helix content was noticed. The observed decrease in β-sheet and the increase in β-turns in treated samples indicated that microfluidization may lead to protein unfolding, opening the hydrophobic regions. Additionally, a lower amount of α-helix suggests a higher protein flexibility. After reconstitution in water, a significant difference was observed only in α-helix, β-sheet and β-turn. Related to the tertiary structure, microfluidization increases the surface hydrophobicity. Among all the conditions tested, the samples where the temperature is controlled seem the most suitable.

The role of fermentation with lactic acid bacteria in quality and health effects of plant-based dairy analogues

The modern food industry is undergoing a rapid change with the trend of production of plant-based food products that are more sustainable and have less impact on nature. Plant-based dairy analogues have been increasingly popular due to their suitability for individuals with milk protein allergy or lactose intolerance and those preferring a plant-based diet. Nevertheless, plant-based products still have insufficient nutritional quality, undesirable structure, and earthy, green, and bean-like flavor compared to dairy products. In addition, most plant-based foods contain lesser amounts of essential nutrients, antinutrients limiting the bioavailability of some nutrients, and allergenic proteins. Novel processing technologies can be applied to have a homogeneous and stable structure. On the other hand, fermentation of plant-based matrix with lactic acid bacteria can provide a solution to most of these problems. Additional nutrients can be produced and antinutrients can be degraded by bacterial metabolism, thereby increasing nutritional value. Allergenic proteins can be hydrolyzed reducing their immunoreactivity. In addition, fermentation has been found to reduce undesired flavors and to enhance various bioactivities of plant foods. However, the main challenge in the production of fermented plant-based dairy analogues is to mimic familiar dairy-like flavors by producing the major flavor compounds other than organic acids, yielding a flavor profile similar to those of fermented dairy products. Further studies are required for the improvement of the flavor of fermented plant-based dairy analogues through the selection of special microbial cultures and formulations.

Metal cation-induced conformational changes of soybean protein isolate/soybean soluble polysaccharide and their effects on high-internal-phase emulsion properties

BACKGROUND

Metal ions commonly inevitably appear in food products and have adverse effects on high-internal-phase emulsions (HIPEs) foods, but conformational conversion of soybean protein isolate (SPI)/soybean soluble polysaccharide (SSPS) on the interface layer of HIPEs influenced by different metal ions has rarely been reported.

RESULTS

Here, the conformational conversion of SPI/SSPS induced by Na+ , K+ , Ca2+ , Mg2+ and Fe3+ ions and its effects on HIPEs were investigated. After adding the ions to SPI and SPI/SSPS dispersions, the particle size and zeta potential results showed different degrees of flocculation; the zeta potential and Fourier transform infrared spectra indicated that SPI and SPI/SSPS changes in structure involve electrostatic interactions and hydrogen bonding. Moreover, Raman spectra showed that the content of β-sheet of SPI/SSPS HIPEs increased with the addition of Ca2+ , Mg2+ and Fe3+ , suggesting that SPI molecules at the interface formed a more orderly structure. The ultraviolet and fluorescence results showed that the hydrophobic environment of tryptophan and tyrosine residues inside protein molecules played a vital role in the emulsifying stability of SPI.

CONCLUSION

These findings suggested that the SPI/SSPS complexes for food applications were not susceptible to ions, thus ensuring complex stability, showing potential for commercial application in the production of emulsions. © 2023 Society of Chemical Industry.

Effect of High-Pressure Homogenization on the Properties and Structure of Cold-Induced Chiba Tofu Gel in Soy Protein Isolate

In the actual production process of soy protein isolate (SPI), most of the homogeneous operating pressure is controlled below 20 MPa due to the consideration of production safety and the limitation of the pressure control capability of homogeneous equipment. In order to improve the functional properties of SPI and adapt it to actual production, the effects of different homogeneous pressures (4, 8, 10, 12, and 14 MPa) on the structure and gel properties of SPI were studied from the perspective of production control. Compared to the control group, the modified SPI improved the hardness, springiness, cohesiveness, chewiness, and water holding capacity (WHC) of the protein gel (p < 0.05). Rheological analysis shows that both G' and G″ increase with increasing frequency, reaching a maximum at 12 MPa. The gel intermolecular force results show that the disulfide bond, hydrophobic interaction, and non-disulfide bond are important molecular forces for gel formation. The particle size distribution uniformity of modified SPI was high, and scanning electron microscopy (SEM) analysis showed that the protein gel with a continuous uniform and dense network structure could be formed by high-pressure homogeneous modification. Overall, high-pressure homogenization technology has the potential to improve SPI gel structure and WHC, and 12 MPa modified SPI gel has the most significant effect.

Transglutaminase-induced soybean protein isolate cold-set gels treated with combination of ultrasound and high pressure: Physicochemical properties and structural characterization

Soybean protein isolate (SPI) was treated by the combined exposure to ultrasound and high pressure and then subjected to transglutaminase (TGase)-catalyzed cross-linking to prepare SPI cold-set gels. The effects of combined treatments on physicochemical and structural properties of TGase-induced SPI cold-set gels were investigated. The combination of ultrasound and high pressure promoted the covalent disulfide bonds and ε-(γ-glutaminyl) lysine isopeptide bonds as well as non-covalent hydrophobic interactions, which further improved the gelation properties of SPI compared to ultrasound or high pressure alone. In particular, the 480 W ultrasound followed by high pressure treatment of gels led to higher strength (120.53 g), water holding capacity (95.39 %), immobilized water (93.92 %), lightness (42.18), whiteness (51.03), and elasticity (G' = 407 Pa), as well as more uniform and compact microstructure, thus resulting in the improved gel network structure. The combination of two treatments produced more flexible secondary structure, tighter tertiary conformation and higher denaturation degree of protein in the gels, leading to more stable gel structure. The structural modifications of SPI contributed to the improvement of its gelation properties. Therefore, the combined application of ultrasound and high pressure can be an effective method for improving the structure and properties of TGase-induced SPI cold-set gels.

Improvement of kefir fermentation on rheological and microstructural properties of soy protein isolate gels

Soy protein isolate (SPI) has become a promising plant-based material as an animal protein products alternative. However, its application was limited due to the weak gelling properties. To investigate the effect of kefir fermentation on SPI gels properties, SPI-polysaccharide gels was produced by unfermented and kefir-fermented SPI using different concentration of KGM, chitosan, and calcium chloride in this study. Characterization of fermented SPI gels showed that fermentation by kefir grains can be applied to improve the textural strength, mechanical structure, and thermal characteristics of SPI gels. Compared to unfermented SPI gels, the water-holding capacity was remarkably enhanced to 63.11% and 65.71% in fermented SPI-chitosan gels. Moreover, the hardness of fermented SPI-KGM gels were significantly increased to 13.43 g and 27.11 g. And the cohesiveness and resilience of fermented-KGM gels were also improved than unfermented samples. Results of rheological characterization and thermogravimetric analysis revealed the strengthened mechanical features and higher thermal stability of fermented SPI gels. Additionally, the main role of hydrophobic interactions and secondary structure variations of SPI gels were demonstrated by intermolecular force measurements, Fourier-transform infrared spectroscopy, and X-ray diffraction. Moreover, the network structure was observed more compact and homogeneous performed by microstructural images in fermented SPI gels. Therefore, this research provided a novel approach combining multi-species fermentation with protein gelation to prepare SPI gel materials with improved nutrition and structural properties.

Gel Properties and Structural Characteristics of Composite Gels of Soy Protein Isolate and Silver Carp Protein

Problems with silver carp protein (SCP) include a strong fishy odor, low gel strength of SCP surimi, and susceptibility to gel degradation. The objective of this study was to improve the gel quality of SCP. The effects of the addition of native soy protein isolate (SPI) and SPI subjected to papain-restricted hydrolysis on the gel characteristics and structural features of SCP were studied. The β-sheet structures in SPI increased after papain treatment. SPI treated with papain was crosslinked with SCP using glutamine transaminase (TG) to form a composite gel. Compared with the control, the addition of modified SPI increased the hardness, springiness, chewiness, cohesiveness, and water-holding capacity (WHC) of the protein gel (p < 0.05). In particular, the effects were most significant when the degree of SPI hydrolysis (DH) was 0.5% (i.e., gel sample M-2). The molecular force results demonstrated that hydrogen bonding, disulfide bonding, and hydrophobic association are important molecular forces in gel formation. The addition of the modified SPI increases the number of hydrogen bonds and the disulfide bonds. Scanning electron microscopy (SEM) analysis showed that the papain modifications allowed the formation of a composite gel with a complex, continuous, and uniform gel structure. However, the control of the DH is important as additional enzymatic hydrolysis of SPI decreased TG crosslinking. Overall, modified SPI has the potential to improve SCP gel texture and WHC.

Effects of different mechanical processes on the structural and powdery properties of insoluble undenatured type II collagen

This study aimed to investigate the effects of dynamic high-pressure homogenization (DHPH), dynamic high-pressure microfluidization (DHPM), and wet media milling (WMM) processes on the particle size, microstructure, triple helix structure, wettability and suspension stability of insoluble undenatured type II collagen (IUC-II). The structural and powdery properties were regulated by different processes and parameters. By contrast, WMM-treated IUC-II showed smallest particle size (15.70 μm), highest wetting rate (216.94 mm/h) and best suspension stability. However, individual mechanical processes caused partial disruption of IUC-II triple helix structure. Low-acyl gellan gum (LAGG) could bind to IUC-II through hydrogen bonds and hydrophobic interactions, which protected the triple helix structure and further enhanced powdery properties of IUC-II treated by WMM process, but restrained the soluble transition during digestion. These results demonstrated that WMM process was more suitable for enhancing powdery properties of IUC-II, while the triple helix structure of IUC-II could be effectively protected by LAGG.

Effect of high-pressure homogenization on Ca2+ -induced gel formation of soybean 11 S globulin

BACKGROUND

High-pressure homogenization (HPH) is commonly used as a non-thermal processing technique for soybean and soy protein products, and the preparation of soy protein gel products often requires the synergistic effect of HPH and heat treatment. The dissociative association behavior of 11 S is the key to the protein gel formation state. In this study, therefore, 11 S thermal gels were prepared by high-pressure homogenization and co-induction (90 °C, 30 min) (adding Ca²⁺ to promote gel formation before heat treatment), and the effects of different high-pressure homogenization pressures (0-100 MPa) and co-treatment on the dissociative association behavior of 11 S protein, gel properties, and microstructure of 11 S gels were investigated.

RESULTS

The results showed that HPH at higher pressures led to the breaking of disulfide bonds of aggregates and disrupted non-covalent interactions in protein aggregates, leading to collisions between protein aggregates and the reduction of large protein aggregates. High-pressure homogenization treatment at 60 MPa improved the gel properties of 11 S more. The HPH combined with heating changed the binary and tertiary structure of 11 S soy globulin and enhanced the hydrophobic interaction between 11 S molecules, thus improving the gel properties of 11 S. The change in intermolecular forces reflected the positive effect of HPH treatment on the formation of denser and more homogeneous protein gels.

CONCLUSION

In conclusion, high-pressure homogenization combined with heating can improve the properties of 11 S gels by changing the structure of 11 S protein, providing data and theoretical support for soy protein processing and its further applications. © 2022 Society of Chemical Industry.

Modulation of soy protein isolate gel properties by a novel "two-step" gelation process: Effects of pre-aggregation with different divalent sulfates

A novel pre-aggregation process prior to gelation was applied to modulate the aggregation and gelation pathway of soy protein isolate (SPI). SPI dispersions were pre-aggregated with CaSO₄, MgSO₄ or ZnSO₄ at 0-15 mM and then gelled by adding CaSO₄ up to a final salt concentration of 35 mM. Compared with the sample without pre-aggregation, the storage modulus of SPI gels pre-aggregated with 10 mM CaSO₄, 10 mM MgSO₄, and 2.5 mM ZnSO₄ were increased by 50.5%, 35.7%, and 63.6%, respectively. The fracture stress, texture profile analysis parameters, and water holding capacity were markedly improved by an appropriate level of pre-aggregation. To a certain extent, pre-aggregation could promote the formation of uniform structure with thicker strands, whereas over-aggregation resulted in a coarser network, which was correlated with the volume-mean diameter (D_4,3) of pre-aggregated SPI particles. The results are of great value for further understanding of gelation mechanism of proteins.