Near-infrared spectroscopy to quantify overall thermal process intensity during high-moisture extrusion of soy protein concentrate.

High-moisture extrusion (HME) is widely used to produce meat analogues. During HME the plant-based materials experience thermal and mechanical stresses. It is complicated to separate their effects on the final products because these effects are interrelated. In this study we hypothesize that the intensity of the thermal treatment can explain a large part of the physicochemical changes that occur during extrusion. For this reason, near-infrared (NIR) spectroscopy was used as a novel method to quantify the thermal process intensity during HME. High-temperature shear cell (HTSC) processing was used to create a partial least squares (PLS) regression curve for processing temperature under controlled processing conditions (root mean standard error of cross-validation (RMSECV) = 4.00 °C, coefficient of determination of cross-validation (R2CV) = 0.97). This PLS regression model was then applied to HME extrudates produced at different screw speeds (200-1200 rpm) and barrel temperatures (100-160 °C) with two different screw profiles to calculate the equivalent shear cell temperature as a measure for thermal process intensity. This equivalent shear cell temperature reflects the effects of changes in local temperature conditions, residence time and thermal stresses. Furthermore, it can be related to the degree of texturization of the extrudates. This information can be used to gain new insights into the effect of various process parameters during HME on the thermal process intensity and extrudate quality.

Differential effects of heating modes on the immunogenic potential of soy-derived peptides released after in vitro infant digestion.

During production of soy-based infant formula, soy protein undergoes heating processes. This study investigated the differential impact of heating modes on the immunogenic potential of peptides in soy protein digests. Wet or dry heating was applied, followed by in vitro gastrointestinal infant digestion. The released peptides were analyzed by LC-MS/MS. Bioinformatics tools were utilized to predict and identify potential linear B-cell and T-cell epitopes, as well as to explore cross-reactivity with other legumes. Subsequently, the peptide intensities of the same potential epitope across different experimental conditions were compared. As a result, we confirmed the previously observed enhancing effect of wet heating on infant digestion and inhibitory effect of dry heating. A total of 8,546 peptides were detected in the digests, and 6,684 peptides were with a score over 80. Among them, 29 potential T-cell epitopes and 27 potential B-cell epitopes were predicted. Cross-reactivity between soy and other legumes, including peanut, pea, chickpea, lentil, kidney bean, and lupine, was also detected. Overall, heating and digestion time could modulate the potential to trigger peptide-induced immune responses.

Characterization of high-internal-phase emulsions based on soy protein isolate with varying concentrations of soy hull polysaccharide and their capabilities for probiotic delivery: In vivo and in vitro release and thermal stability.

In this study, the impact of soy hull polysaccharide (SHP) concentration on high-internal-phase emulsions (HIPEs) formation and the gastrointestinal viability of Lactobacillus plantarum within HIPEs were demonstrated. Following the addition of SHP, competitive adsorption with soy protein isolate (SPI) occurred, leading to increased protein adhesion to the oil-water interface and subsequent coating of oil droplets. This process augmented viscosity and enhanced HIPEs stability. Specifically, 1.8 % SHP had the best encapsulation efficiency and delivery efficiency, reaching 99.3 % and 71.1 %, respectively. After 14 d of continuous zebrafishs feeding, viable counts of Lactobacillus plantarum and complex probiotics in the intestinal tract was 1.1 × 107, 1.3 × 107, respectively. In vitro experiments further proved that HIPEs' ability to significantly enhance probiotics' intestinal colonization and provided targeted release for colon-specific delivery. These results provided a promising strategy for HIPEs-encapsulated probiotic delivery systems in oral food applications.

Soybean isolate protein complexes with different concentrations of inulin by ultrasound treatment: Structural and functional properties.

The effects of ultrasound and different inulin (INU) concentrations (0, 10, 20, 30, and 40 mg/mL) on the structural and functional properties of soybean isolate protein (SPI)-INU complexes were hereby investigated. Fourier transform infrared spectroscopy showed that SPI was bound to INU via hydrogen bonding. All samples showed a decreasing and then increasing trend of α-helix content with increasing INU concentration. SPI-INU complexes by ultrasound with an INU concentration of 20 mg/mL (U-2) had the lowest content of α-helix, the highest content of random coils and the greatest flexibility, indicating the proteins were most tightly bound to INU in U-2. Both UV spectroscopy and intrinsic fluorescence spectroscopy indicated that it was hydrophobic interactions between INU and SPI. The addition of INU prevented the exposure of tryptophan and tyrosine residues to form a more compact tertiary structure compared to SPI alone, and ultrasound caused further unfolding of the structure of SPI. This indicated that the combined effect of ultrasound and INU concentration significantly altered the tertiary structure of SPI. SDS-PAGE and Native-PAGE displayed the formation of complexes through non-covalent interactions between SPI and INU. The ζ-potential and particle size of U-2 were minimized to as low as -34.94 mV and 110 nm, respectively. Additionally, the flexibility, free sulfhydryl groups, solubility, emulsifying and foaming properties of the samples were improved, with the best results for U-2, respectively 0.25, 3.51 µmoL/g, 55.51 %, 269.91 %, 25.90 %, 137.66 % and 136.33 %. Overall, this work provides a theoretical basis for improving the functional properties of plant proteins.

Molecular modification of low-dissolution soy protein isolates by anionic xanthan gum, neutral guar gum, or neutral konjac glucomannan to improve the protein dissolution and stabilize fish oil emulsion.

Herein, the effects of anionic xanthan gum (XG), neutral guar gum (GG), and neutral konjac glucomannan (KGM) on the dissolution, physicochemical properties, and emulsion stabilization ability of soy protein isolate (SPI)-polysaccharide conjugates were studied. The SPI-polysaccharide conjugates had better water dissolution than the insoluble SPI. Compared with SPI, SPI-polysaccharide conjugates had lower ß-sheet (39.6 %-56.4 % vs. 47.3 %) and α-helix (13.0 %-13.2 % vs. 22.6 %) percentages, and higher ß-turn (23.8 %-26.5 % vs. 11.0 %) percentages. The creaming stability of SPI-polysaccharide conjugate-stabilized fish oil-loaded emulsions mainly depended on polysaccharide type: SPI-XG (Creaming index: 0) > SPI-GG (Creaming index: 8.1 %-21.2 %) > SPI-KGM (18.1 %-40.4 %). In addition, it also depended on the SPI preparation concentrations, glycation times, and glycation pH. The modification by anionic XG induced no obvious emulsion creaming even after 14-day storage, which suggested that anionic polysaccharide might be the best polysaccharide to modify SPI for emulsion stabilization. This work provided useful information to modify insoluble proteins by polysaccharides for potential application.

Soy Protein Concentrate Diets Inversely Affect LPS-Binding Protein Expression in Colon and Liver, Reduce Liver Inflammation, and Increase Fecal LPS Excretion in Obese Zucker Rats.

Dietary soy protein and soy isoflavones have anti-inflammatory properties. Previously, we reported that feeding soy protein concentrate diet (SPC) with low or high isoflavone (LIF or HIF) to young (seven-week-old) obese (fa/fa) Zucker rats inhibits lipopolysaccharide (LPS) translocation and decreases liver inflammation compared to a casein control (CAS) diet. The current study investigated whether SPC-LIF and SPC-HIF diets would reduce liver inflammation in adult obese Zucker rats fed a CAS diet. A total of 21 six-week-old male obese (fa/fa) Zucker rats were given CAS diet for 8 weeks to develop obesity then randomly assigned to CAS, SPC-LIF, or SPC-HIF (seven rats/group) diet for an additional 10 weeks. The expression of LPS-translocation, inflammation, and intestinal permeability markers were quantified by qPCR in liver, visceral adipose tissue (VAT), and colon. LPS concentration was determined in both the colon content and fecal samples by a Limulus amebocyte lysate (LAL) test. SPC-LIF and SPC-HIF diets significantly decreased liver LPS-binding protein (LBP) expression compared to CAS diet (p < 0.01 and p < 0.05, respectively). SPC-HIF diet also significantly decreased liver MCP-1 and TNF-α expression (p < 0.05) and had a trend to decrease liver iNOS expression (p = 0.06). In the colon, SPC-HIF diet significantly increased LBP expression compared to CAS diet (p < 0.05). When samples from all three groups were combined, there was a negative correlation between colon LBP expression and liver LBP expression (p = 0.046). SPC diets did not alter the expression of intestinal permeability markers (i.e., occludin, claudin 3, and zonula occludens-1) in the colon or inflammation markers (i.e., TNF-α and iNOS) in VAT or the colon. LPS levels in the colon content did not differ between any groups. Fecal LPS levels were significantly higher in the SPC-LIF and SPC-HIF groups compared to the CAS group (p < 0.01). In conclusion, SPC, particularly SPC with HIF, reduces liver LBP expression and inflammation makers (i.e., TNF-α and MCP-1 expression) in adult obese Zucker rats, likely by reducing LPS translocation.

A self-healing crosslinked-xanthan gum/soy protein based film containing halloysite nanotube and propolis with antibacterial and antioxidant activity for wound healing.

Traumatic multidrug-resistant bacterial infections are the most threat to wound healing. Lower extremity wounds under diabetic conditions display a significant delay during the healing process. To overcome these challenges, the utilization of protein-based nanocomposite dressings is crucial in implementing a successful regenerative medicine approach. These dressings hold significant potential as polymer scaffolds, allowing them to mimic the properties of the extracellular matrix (ECM). So, the objective of this study was to develop a nanocomposite film using dialdehyde-xanthan gum/soy protein isolate incorporated with propolis (PP) and halloysite nanotubes (HNTs) (DXG-SPI/PP/HNTs). In this protein-polysaccharide hybrid system, the self-healing capability was demonstrated through Schiff bonds, providing a favorable environment for cell encapsulation in the field of tissue engineering. To improve the properties of the DXG-SPI film, the incorporation of polyphenols found in PP, particularly flavonoids, is proposed. The synthesized films were subjected to investigations regarding degradation, degree of swelling, and mechanical characteristics. Additionally, halloysite nanotubes (HNTs) were introduced into the DXG-SPI/PP nanocomposite films as a reinforcing filler with varying concentrations of 3 %, 5 %, and 7 % by weight. The scanning electron microscope (SEM) analysis confirmed the proper embedding and dispersion of HNTs onto the DXG-SPI/PP nanocomposite films, leading to functional interfacial interactions. The structure and crystallinity of the synthesized nanocomposite films were characterized using Fourier Transform Infrared Spectrometry (FTIR) and X-ray diffraction (XRD), respectively. Moreover, the developed DXG-SPI/PP/HNTs nanocomposite films significantly improved cell growth of NIH-3T3 fibroblast cells in the presence of PP and HNTs, indicating their cytocompatibility. The antibacterial activity of the nanocomposite was evaluated against Escherichia coli (E. Coli) and Staphylococcus aureus (S. Aureus), which are commonly associated with wound infections. Overall, our findings suggest that the synthesis of DXG-SPI/PP/HNTs nanocomposite scaffolds holds great promise as a clinically relevant biomaterial and exhibits strong potential for numerous challenging biomedical applications.

Homologous Overexpression of Tyrosinase in Trichoderma reesei and Its Application in Glycinin Cross-Linking.

Tyrosinase is capable of oxidizing tyrosine residues in proteins, leading to intermolecular protein cross-linking, which could modify the protein network of food and improve the texture of food. To obtain the recombinant tyrosinase with microbial cell factory instead of isolation tyrosinase from the mushroom Agaricus bisporus, a TYR expression cassette was constructed in this study. The expression cassette was electroporated into Trichoderma reesei Rut-C30 and integrated into its genome, resulting in a recombinant strain C30-TYR. After induction with microcrystalline cellulose for 7 days, recombinant tyrosinase could be successfully expressed and secreted by C30-TYR, corresponding to approximately 2.16 g/L tyrosinase in shake-flask cultures. The recombinant TYR was purified by ammonium sulfate precipitation and gel filtration, and the biological activity of purified TYR was 45.6 U/mL. The purified TYR could catalyze the cross-linking of glycinin, and the emulsion stability index of TYR-treated glycinin emulsion was increased by 30.6% compared with the untreated one. The cross-linking of soy glycinin by TYR resulted in altered properties of oil-in-water emulsions compared to emulsions stabilized by native glycinin. Therefore, cross-linking with this recombinant tyrosinase is a feasible approach to improve the properties of protein-stabilized emulsions and gels.

Effect of montmorillonite (MMT) on the properties of soybean meal protein isolate-based nanocomposite film loaded with debittered kinnow peel powder.

The synthetic, non-renewable nature and harmful effects of plastic packaging have led to the synthesis of eco-friendly renewable bio-nanocomposite film. The present work was aimed at the formulation and characterization of bio-nanocomposite film using soybean meal protein, montmorillonite (MMT), and debittered kinnow peel powder. The composition of film includes protein isolate (5% w/v), glycerol (50% w/w), peel powder (20% w/w), and MMT (0.5-2.5% w/w). Incorporation of MMT in soybean meal protein-based film loaded with kinnow peel powder showed lesser solubility (16.76-26.32%), and swelling ability (142.77-184.21%) than the film prepared without MMT (29.41%, & 229.41%, respectively). The mechanical properties like tensile strength of nanocomposite film improved from 9.41 to 38.69% with the increasing concentration of MMT. The water vapor transmission rate of the nanocomposite film was decreased by 3.45-17.85% when the MMT concentration increased. Fourier-transform infrared spectroscopy and X-ray diffraction analysis showed no considerable change in the structural properties of the film after the addition of MMT. Differential scanning colorimeter analysis revealed the increment in melting temperature (85.33-92.67 °C) of the film with a higher concentration of MMT. Scanning electron microscopy analysis indicated an increased distributed area of MMT throughout the film at higher concentrations. The antimicrobial activity of the film was remarkably increased by 4.96-17.18% with the addition of MMT. The results obtained in the current work confirmed that MMT incorporation in soybean meal protein-based film can augment its properties and can be utilized for enhancing the storage period of food products.

pH-regulated Tannic acid and soybean protein isolate adhesive for enhanced performance in plant-based meat analogues.

A food adhesive comprising tannic acid (TA) and soybean protein isolate (SPI) was developed to establish a cohesive bond between soy protein gel and simulated fat. The impact of varying TA concentrations and pH levels on the adhesive's rheology, thermal stability, chemical structure, and tensile strength were investigated. Rheological results revealed a gradual decrease in adhesive viscosity with increasing TA content. Differential scanning calorimetry (DSC) and thermal gravimetric (TG) results indicated that the stability of the adhesive improved with higher TA concentrations, reaching its peak at 0.50% TA addition. The incorporation of TA resulted in the cross-linking of amino group in unfolded SPI molecules, forming a mesh structure. However, under alkaline conditions (pH 9), adhesive viscosity and stability increased compared to the original pH. This shift was due to the disruption of the SPI colloidal charge structure, an increase in the stretching of functional groups, further unfolding of the structure, and an enhanced binding of SPI to TA. Under the initial pH conditions, SPI reacted with TA's active site to form covalent crosslinked networks and hydrogen bonds. In alkaline condition, beyond hydrogen and ionic bonding, the catechol structure was oxidized, forming an ortho-quinone that crosslinked SPI and created a denser structure. Tensile strength measurements and freeze-thaw experiments revealed that the adhesive exhibited maximum tensile strength and optimal adhesion with 0.75% TA at pH 9, providing the best overall performance. This study provides a new formulation and approach for developing plant-based meat analogues adhesives.

Exploring simple ways to avoid collecting highly 137Cs-contaminated Aralia elata buds for the revival of local wild vegetable cultures.

Collection and cooking of wild vegetables have provided seasonal enjoyments for Japanese local people as provisioning and cultural ecosystem services. However, the Fukushima Daiichi Nuclear Power Plant accident in March 2011 caused extensive radiocesium contamination of wild vegetables. Restrictions on commercial shipments of wild vegetables have been in place for the last 10 years. Some species, including buds of Aralia elata, are currently showing radiocesium concentrations both above and below the Japanese reference level for food (100 Bq/kg), implying that there are factors decreasing and increasing the 137Cs concentration. Here, we evaluated easy-to-measure environmental variables (dose rate at the soil surface, organic soil layer thickness, slope steepness, and presence/absence of decontamination practices) and the 137Cs concentrations of 40 A. elata buds at 38 locations in Fukushima Prefecture to provide helpful information on avoiding collecting highly contaminated buds. The 137Cs concentrations in A. elata buds ranged from 1 to 6,280 Bq/kg fresh weight and increased significantly with increases in the dose rate at the soil surface (0.10-6.50 µSv/h). Meanwhile, the 137Cs concentration in A. elata buds were not reduced by decontamination practices. These findings suggest that measuring the latest dose rate at the soil surface at the base of A. elata plants is a helpful way to avoid collecting buds with higher 137Cs concentrations and aid in the management of species in polluted regions.

Localization of G1A1a Allergenic Domain Destroyed by Thermal Processing.

Glycinin is an important allergenic protein. A1a is the acidic chain of the G1 subunit in glycinin (G1A1a), and it has strong allergenicity. In this study, we used phage display technology to express the protein of G1A1a and its overlapping fragments and an indirect enzyme-linked immunosorbent assay (iELISA) to determine the antigenicity and allergenicity of the expressed protein. After three rounds of screening, it was determined that fragment A1a-2-B-I (151SLENQLDQMPRRFYLAGNQEQEFLKYQQEQG181) is the allergenic domain of G1A1a destroyed by thermal processing. In addition, three overlapping peptides were synthesized from fragments A1a-2-B-I, and a linear epitope was found in this domain through methods including dot blot and iELISA. Peptide 2 (157DQMPRRFYLANGNQE170) showed allergenicity, and after replacing it with alanine, it was found that amino acids D157, Q158, M159, and Y164 were the key amino acids that affected its antigenicity, while Q158, M159, R162, and N168 affected allergenicity.

Preparation and characterization of vitamin E/calcium/soy protein isolate nanoparticles for soybean milk beverage fortification.

Soybean milk is a rich plant-based source of protein, and phenolic compounds. This study compared the nutritional value of soybean milk, flour, soy protein isolate (SPI) and evaluated the impact of prepared vitamin E/calcium salt/soy protein isolate nanoparticles (ECSPI-NPs) on fortification of developed soybean milk formulations. Results indicated that soybean flour protein content was 40.50 g/100 g, that fulfills 81% of the daily requirement (DV%), the unsaturated fatty acids (USFs), oleic and linoleic content was 21.98 and 56.7%, respectively, of total fatty acids content. In soybean milk, essential amino acids, threonine, leucine, lysine achieved 92.70, 90.81, 77.42% of amino acid scores (AAS) requirement values respectively. Ferulic acid was the main phenolic compound in soybean flour, milk and SPI (508.74, 13.28, 491.78 µg/g). Due to the moisture content of soybean milk (88.50%) against (7.10%) in soybean flour, the latest showed higher nutrients concentrations. The prepared calcium (20 mM/10 g SPI) and vitamin E (100 mg/g SPI) nanoparticles (ECSPI-NPs) exhibited that they were effectively synthesized under transmission electron microscope (TEM), stability in the zeta sizer analysis and safety up to IC50 value (202 ug/mL) on vero cell line. ECSPI-NPs fortification (NECM) enhanced significantly phenolic content (149.49 mg/mL), taste (6.10), texture (6.70) and consumer overall acceptance (6.54). Obtained results encourage the application of the prepared ECSPI-NPs for further functional foods applications.

Conformation-Activity Mechanism of Alcalase Hydrolysis for Reducing In Vitro Allergenicity of Instant Soy Milk Powder.

Effective reduction of the allergenicity of instant soy milk powder (ISMP) is practically valuable for expanding its applications. This study optimized the enzymolysis technology of ISMP using single-factor experiments and response surface methodology, combined serological analysis, cellular immunological models, bioinformatics tools, and multiple spectroscopy techniques to investigate the effects of alcalase hydrolysis on allergenicity, spatial conformation, and linear epitopes of ISMP. Under the optimal process, special IgE and IgG1 binding abilities and allergenic activity to induce cell degranulation of alcalase-hydrolyzed ISMP were reduced by (64.72 ± 1.76)%, (56.79 ± 3.72)%, and (73.3 ± 1.19)%, respectively (P < 0.05). Moreover, the spatial conformation of instant soy milk powder hydrolysates (ISMPH) changed, including decreased surface hydrophobicity, a weaker peak of amide II band, lower contents of α-helix and ß-sheet, and an enhanced content of random coil. Furthermore, the linear epitopes of major soy allergens, 9 from glycinin and 13 from ß-conglycinin, could be directionally disrupted by alcalase hydrolysis. Overall, the structure-activity mechanism of alcalase hydrolysis to reduce ISMP allergenicity in vitro was preliminarily clarified. It provided a new research direction for the breakthrough in the desensitization of ISMP and a theoretical basis for revealing the potential mechanism of alcalase enzymolysis to reduce the allergenicity of ISMP.

Deciphering the interaction mechanism between soy protein isolate and fat-soluble anthocyanin on experiments and molecular simulations.

In this work, the acylated anthocyanin (Ca-An) was prepared by enzymatic modification of black rice anthocyanin with caffeic acid, and the binding mechanism of Ca-An to soybean protein isolate (SPI) was investigated by experiments and computer simulation to expand the potential application of anthocyanin in food industry. Multi-spectroscopic studies revealed that the stable binding of Ca-An to SPI induced the folding of protein polypeptide chain, which transformed the secondary structure of SPI trended to be flexible. The microenvironment of protein was transformed from hydrophobic to hydrophilic, while tyrosine played dominant role in quenching process. The binding sites and forces of the complexes were determined by computer simulation for further explored. The protein conformation of the 7S and 11S binding regions to Ca-An changed, and the amino acid microenvironment shifted to hydrophilic after binding. The results showed that more non-polar amino acids existed in the binding sites, while in binding process van der Waals forces and hydrogen bonding played a major role hydrophobicity played a minor role. Based on MM-PBSA analysis, the binding constants of 7S-Ca-An and 11S-Ca-An were 0.518 × 106 mol-1 and 5.437 × 10-3 mol-1, respectively. This information provides theoretical guidance for further studying the interaction between modified anthocyanins and biomacromolecules.

Ultrasound viscous reduction effects on the proteolysis of soy protein isolate at a limited degree of hydrolysis: Changes in the functional characteristics and protein structure.

High-concentration soy protein isolate was subjected to ultrasonication for viscosity reduction to assist the process of limited enzymatic hydrolysis. Ultrasonication (20 kHz, 10 min, 160 W/L) effectively reduced the viscosity of soy protein isolate at a comparatively high concentration of 14 % (w/v) and promoted the limited enzymatic hydrolysis (controlled degree of hydrolysis of 12 %) with a higher peptide yield than that of the conventional method. The correlations between substrate viscosity and peptide yield, as well as the viscosities of the resulting hydrolysates, were studied. The findings revealed positive correlations between the viscosities of the substrate and hydrolysate, underscoring the potential impact of altering substrate viscosity on the final product. Furthermore, the utilization of ultrasonic viscosity reduction-assisted proteolysis has shown its capability to improve the functional and physicochemical properties, as well as the protein structure of the hydrolysate, while maintaining the same level of hydrolysis. It is worth noting that there were significant alterations in particle size (decrease), ß-sheet content (increase), ß-turn content (increase), and random coil content (increase). Interestingly, ultrasonication unexpectedly impeded the degradation of molecular mass in proteins during proteolysis, while increasing the hydrophobic properties of the hydrolysate. These findings aligned with the observed reduction in bitterness and improvement in emulsifying properties and water-holding capacity.

Integrated Transcriptome and Proteome Analyses of ß-Conglycinin-Induced Intestinal Damage in Piglets.

ß-conglycinin (ß-CG) induces intestinal damage in piglets; however, its regulatory mechanisms are not fully understood. This study aimed to investigate the molecular mechanisms by which ß-CG regulates intestinal injury in piglets through downstream genes and proteins. Our findings revealed that ß-CG significantly reduced villus height while increasing the crypt depth. In addition, we analyzed the transcriptome and proteome of jejunum tissues after the ß-CG treatment. In total, 382 differentially expressed genes (DEGs) and 292 differentially expressed proteins (DEPs) were identified between the treatment and the control groups. The expression levels of DEGs and DEPs were validated by using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blotting, respectively. The findings revealed a consistent correlation between their expression levels and transcriptomic and proteomic data. In addition, Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses of DEGs and DEPs revealed their enrichment in oxidation-related GOs, as well as in lysosome-related pathways. A protein-protein interaction (PPI) regulatory network was constructed based on the DEPs. The integration of transcriptomic and proteomic analyses identified six genes that were significantly different at both the transcript and the protein levels. This study provides valuable insights into the molecular mechanisms underlying ß-CG-induced intestinal injury in piglets.

Anti-Obesity Effect and Signaling Mechanism of Potassium Poly-γ-Glutamate Produced by Bacillus subtilis Chungkookjang in High-Fat Diet-Induced Obese Mice.

The purpose of this work was to examine the effects of potassium poly-γ-glutamate (PGA-K) on mice fed a high-fat diet consisting of 60% of total calories for 12 weeks. PGA-K administration reduced the increase in body weight, epididymal fat, and liver weight caused by a high-fat diet compared to the obese group. The triglyceride, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol levels, which are blood lipid indicators, were significantly increased in the obese group but were significantly decreased in the PGA-K-treated group. The administration of PGA-K resulted in a significant inhibition of pro-inflammatory cytokines, including tumor necrosis factor α and interleukin 6. Moreover, the levels of leptin and insulin, which are insulin resistance indicators, significantly increased in the obese group but were significantly decreased in the PGA-K-treated group. These results suggest that PGA-K exhibits a protective effect against obesity induced by a high-fat diet, underscoring its potential as a candidate for obesity treatment.

Modification mechanism of soybean protein isolate-soluble soy polysaccharide complex by EGCG through covalent and non-covalent interaction: Structural, interfacial, and functional properties.

Soybean protein isolate was modified with polysaccharides and polyphenols to prepare a natural emulsifier with antioxidant capacity. Physicochemical, structural, interfacial, and functional properties of SPI-SSPS complex were investigated after covalent and non-covalent interacted with EGCG. SPI-SSPS-EGCG ternary complex with low EGCG concentrations (0.0625 and 0.125 mg/mL) showed a significant increase in absolute potential value and a decrease in turbidity. EGCG destroyed the original rigid structure of SPI-SSPS complex, and the covalent complexes had an ordered structure, while the non-covalent interaction resulted in disordered. The ternary complex with high EGCG concentrations (0.25 and 0.5 mg/mL) exhibited stronger EGCG binding capacity and lower surface hydrophobicity, which in turn affected its interfacial properties. The EAI and ESI of SPI-SSPS-EGCG covalent complex increased significantly, while the non-covalent complex had a significant change in EAI but no significant change in ESI with increasing EGCG concentration. The ternary complex showed significantly enhanced antioxidant capacity. The SPI-SSPS-EGCG ternary complex, with excellent antioxidant capacity and emulsifying property, making it suitable for emulsion delivery systems.

Rapid quantitative analysis of soybean protein isolates secondary structure by two-dimensional correlation infrared spectroscopy through pH perturbation.

The infrared spectroscopy (IR) signal of protein is prone to being covered by impurity signals, and the accuracy of the secondary structure content calculated using spectral data is poor. To tackle this challenge, a rapid high-precision quantitative model for protein secondary structure was proposed. Firstly, a two-dimensional correlation calculation was performed based on 60 groups of soybean protein isolates (SPI) infrared spectroscopy data, resulting in a two-dimensional correlation infrared spectroscopy (2DCOS-IR). Subsequently, the optimal characteristic bands of the four secondary structures were extracted from the 2DCOS-IR. Ultimately, partial least squares (PLS), long short-term memory (LSTM), and bidirectional long short-term memory (BILSTM) algorithms were used to model the extracted characteristic bands and predict the content of SPI secondary structure. The findings suggested that BILSTM combined with 2DCOS-IR model (2DCOS-BILSTM) exhibited superior predictive performance. The prediction sets for α-helix, ß-sheet, ß-turn, and random coil were designated as 0.9257, 0.9077, 0.9476, and 0.8443, respectively, and their corresponding RMSEP values were 0.26, 0.48, 0.20, and 0.15. This strategy enhances the precision of IR and facilitates the rapid identification of secondary structure components within SPI, which is vital for the advancement of protein industrial production.