Abundant proteins associated with lecithin in soy protein isolate

Fabrication of soy protein-polyphenol covalent complex nanoparticles with improved wettability to stabilize high-oil-phase curcumin emulsions

BACKGROUND

Recent studies have shown that the wettability of protein-based emulsifiers is critical for emulsion stability. However, few studies have been conducted to investigate the effects of varying epigallocatechin gallate (EGCG) concentrations on the wettability of protein-based emulsifiers. Additionally, limited studies have examined the effectiveness of soy protein-EGCG covalent complex nanoparticles with improved wettability as emulsifiers for stabilizing high-oil-phase (≥ 30%) curcumin emulsions.

RESULTS

Soy protein isolate (SPI)-EGCG complex nanoparticles (SPIEn) with improved wettability were fabricated to stabilize high-oil-phase curcumin emulsions. The results showed that EGCG forms covalent bonds with SPI, which changes its secondary structure, enhances its surface charge, and improves its wettability. Moreover, SPIEn with 2.0 g L -1 EGCG (SPIEn-2.0) exhibited a better three-phase contact angle (56.8 ± 0.3o) and zeta potential (-27 mV) than SPI. SPIEn-2.0 also facilitated the development of curcumin emulsion gels at an oil volume fraction of 0.5. Specifically, the enhanced network between droplets as a result of the packing effects and SPIEn-2.0 with inherent antioxidant function was more effective at inhibiting curcumin degradation during long-term storage and ultraviolet light exposure.

CONCLUSION

The results of the present study indicate that SPIEn with 2.0 g L -1 EGCG (SPIEn-2.0) comprises the optimum conditions for fabricating emulsifiers with improved wettability. Additionally, SPIEn-0.2 can improve the physicochemical stability of high-oil-phase curcumin emulsions, suggesting a novel strategy to design and fabricate high-oil-phase emulsion for encapsulating bioactive compounds. © 2024 Society of Chemical Industry.

Effect of preheating-induced denaturation of proteins and oleosomes on the structure of protein and soymilk properties

In this paper, effects of preheating-induced denaturation of proteins and oleosomes on protein structure and soymilk quality were studied. The protein in soybeans baked at 55 °C (B-55) and 85 °C (B-85) showed an increase of β-sheet content by 3.2 % and a decrease of α-helix content by 3.3 %, indicating that proteins were gradually unfolded while oleosomes remained intact. The protein resisted thermal denaturation during secondary heating, and soymilks were stable as reflected by a small d3,2 (0.4 μm). However, raw soymilk from soybeans baked at 115 °C (B-115), steamed for 1 min (ST-1) and 5 min (ST-5) presented oleosomes destruction and lipids aggregates. The proteins were coated around the oil aggregates. The β-turn content from soybeans steamed for 10 min (ST-10) increased by 9.5 %, with a dense network where the OBs were tightly wrapped, indicating the serious protein denaturation. As a result, the soymilks B-115 or steamed ones were unstable as evidenced by the serious protein aggregation and larger d3,2 (5.65-12.48 μm). Furthermore, the soymilks were graininess and the protein digestion was delayed due to the formation of insoluble protein aggregates. The flavor and early-stage lipid digestion of soymilk from steamed soybeans was improved owing to lipid release.

Structural Characterization and Properties of Modified Soybean Meal Protein via Solid-State Fermentation by Bacillus subtilis

Soybean meal (SBM) is a high-quality vegetable protein, whose application is greatly limited due to its high molecular weight and anti-nutritional properties. The aim of this study was to modify the protein of soybean meal via solid-state fermentation of Bacillus subtilis. The fermentation conditions were optimized as, finally, the best process parameters were obtained, namely fermentation temperature of 37 °C, inoculum amount of 12%, time of 47 h, and material-liquid ratio of 1:0.58, which improved the content of acid-soluble protein. To explore the utilization of modified SBM as a food ingredient, the protein structure and properties were investigated. Compared to SBM, the protein secondary structure of fermented soybean meal (FSBM) from the optimal process decreased by 8.3% for α-helix content, increased by 3.08% for β-sheet, increased by 2.71% for β-turn, and increased by 2.51% for random coil. SDS-PAGE patterns showed that its 25-250 KDa bands appeared to be significantly attenuated, with multiple newborn peptide bands smaller than 25 KDa. The analysis of particle size and zeta potential showed that fermentation reduced the average particle size and increased the absolute value of zeta potential. It was visualized by SEM and CLSM maps that the macromolecular proteins in FSBM were broken down into fragmented pieces with a folded and porous surface structure. Fermentation increased the solubility, decreased the hydrophobicity, increased the free sulfhydryl content, decreased the antigenicity, improved the protein properties of SBM, and promoted further processing and production of FSBM as a food ingredient.

Ethanol as a switch to induce soybean lipophilic protein self-assembly and resveratrol delivery

Protein-based nanoparticles or nanocarriers of emulsion systems have piqued the interest of nutrition and health care goods. As a result, this work examines the characterisation of ethanol-induced soybean lipophilic protein (LP) self-assembly for resveratrol (Res) encapsulation, particularly the influence on emulsification. By varying the ethanol content ([E]) in the range of 0-70% (v/v), the structure, size, and morphology of LP nanoparticles may be adjusted. Similarly, the self-assembled LPs have a strong [E] dependency on the encapsulation efficiency of Res. For [E] = 40% (v/v), Res had the highest encapsulation efficiency (EE) and load capacity (LC) of 97.1% and 141.0 μg/mg nanoparticles, respectively. Most of the Res was encapsulated by the hydrophobic core of LP. Moreover, for [E] = 40% (v/v), LP-Res showed significantly improved emulsifying properties, independent of low-oil or high-oil emulsion systems. Furthermore, the ethanol-induced production of appropriate aggregates increased emulsion system stability, hence increasing Res retention during storage.

Investigation of soybean lipophilic proteins as carriers for vitamin B12: Focus on interaction mechanism, physicochemical functionality, and digestion characteristics

This study aimed to explore the interaction mechanism between soybean lipophilic protein (LP) and vitamin B₁₂ and the potential of LP as a vitamin B₁₂ carrier. The results of spectroscopy indicated that the interaction between vitamin B₁₂ and LP changed the conformation of LP and exposed hydrophobic groups largely. The results of molecular docking revealed that vitamin B₁₂ interacted with LP through a hydrophobic pocket embedded on the surface of LP. With the enhancement of the interaction between LP and vitamin B₁₂, the particle size of the LP-vitamin B₁₂ complex gradually decreased to 588.31 nm and the absolute value of zeta potential gradually increased to 26.82 mV. Meanwhile, the LP-vitamin B₁₂ complex showed excellent physicochemical properties and digestive characteristics. The present work enriched the means of vitamin B₁₂ protection and provided a theoretical basis for applying the LP-vitamin B₁₂ complex in food systems.

Control of Beany Flavor from Soybean Protein Raw Material in Plant-Based Meat Analog Processing

The development of plant-based meat analogs is currently hindered by the beany flavor generated by raw soybean protein and extrusion processing. Wide concern has led to extensive research on the generation and control of this unwanted flavor, as an understanding of its formation in raw protein and extrusion processing and methods through which to control its retention and release are of great significance for obtaining ideal flavor and maximizing food quality. This study examines the formation of beany flavor during extrusion processing as well as the influence of interaction between soybean protein and beany flavor compounds on the retention and release of the undesirable flavor. This paper discusses ways to maximize control over the formation of beany flavor during the drying and storage of raw materials and methods to reduce beany flavor in products by adjusting extrusion parameters. The degree of interaction between soybean protein and beany compounds was found to be dependent on conditions such as heat treatment and ultrasonic treatment. Finally, future research directions are proposed and prospected. This paper thus provides a reference for the control of beany flavor during the processing, storage, and extrusion of soybean raw materials used in the fast-growing plant-based meat analog industry.

Stability and digestibility of encapsulated lycopene in different emulsion systems stabilized by acid-modified soybean lipophilic protein

BACKGROUND

Owing to the harsh acidic environment of the stomach, acid-resistant emulsion products have wide-ranging applications in the food industry. Herein, natural soybean lipophilic protein (LP) was used to establish coarse emulsions, nanoemulsions, emulsion gels, and high internal phase Pickering emulsions (HIPPE) under acidic conditions. Furthermore, the carrying characteristics of the acid-resistant emulsion system with lycopene were explored.

RESULTS

Comparisons of particle sizes, potentials, microstructures, and rheology of the four carrier systems revealed that HIPPE has a single particle-size distribution, the largest zeta potential, and an elastic gel-like network structure. Comparison of encapsulation rates indicated that HIPPE had the best effect on encapsulating lycopene, reaching approximately 90%. The pH stability, storage stability, and simulated in vitro digestion experiments showed that the four emulsions that were stable under acidic conditions had good acid resistance. Among them, the acid-induced LP-stabilized HIPPE had the best storage stability and superior compatibility with the harsh acidic environment of the stomach, which not only achieved the purpose of delaying the release of lipids but also conferred better protection to lycopene in the gastric tract; moreover, it achieved the best bioavailability.

CONCLUSION

LP-stabilized HIPPE has the best stability and can yield better absorption and utilization of lycopene by the body. The results of this study are helpful for the development of acid-resistant functional emulsion foods that are conducive to the absorption of lycopene. © 2022 Society of Chemical Industry.

Bacterial cellulose/soybean protein isolate composites with promoted inflammation inhibition, angiogenesis and hair follicle regeneration for wound healing

Soybean protein, as a safe and low-cost alternative to animal protein, attracts increasing attention in wound healing. In the present study, beta-conglycinin (7S) and glycinin (11S) with high solubility were obtained through separation of soybean protein. Afterward, 7S or 11S modified bacterial cellulose (BC) composites were produced by self-assembly method. Results confirmed the successful self-assembly of soybean protein isolates on the nanofibers of BC. The surface roughness and hydrophilicity of BC/7S and BC/11S decreased compared with native BC. Soybean protein could be steadily released from BC/7S and BC/11S and BC/11S released more soybean proteins than BC/7S. In vitro, BC/7S and BC/11S supported fibroblasts attachment and promoted fibroblasts proliferation and type I collagen expression. In vivo, BC/7S and BC/11S facilitated wound healing and collagen deposition, enhanced angiogenesis and hair follicle regeneration, as well as reduced scar formation and inflammation in full-thickness skin wounds of rats. Moreover, wounds treated with BC/11S showed a faster wound healing rate and more collagen depositions than those of BC/7S, which may be attributed to the larger considerable amount of soybean protein released by BC/11S. These results indicate that BC/7S and BC/11S are potential candidates for wound dressings.

In Vitro and in Silico Analyses of the Adiponectin Receptor Agonistic Action of Soybean Tripeptides

The Tyr-Pro (YP) dipeptide can serve as an adiponectin receptor 1 (AdipoR1) agonist. We thus investigated the AdipoR1-agonistic potential of YP-related tripeptides in the soybean protein sequence. Among the 17 soybean candidate tripeptides, those elongated at the C-terminus of YP (0.1 μM YPG, 140 ± 16%; 0.1 μM YPE, 141 ± 22%; 0.1 μM YPP, 145 ± 19%; 0.1 μM YPQ, 143 ± 20%; p < 0.05) significantly promoted glucose uptake by L6 muscle myotubes, comparable to the effect of 0.1 μM AdipoRon (163 ± 52%, p < 0.05). The knockdown of AdipoR1 expression in L6 cells abrogated this effect of YPG and YPP, indicating that the two tripeptides had an AdipoR1 agonistic effect. CHARMM-GUI-aided molecular dynamics simulation in a virtual phospholipid membrane revealed that YPG and YPP were stably positioned at the binding pockets of AdipoR1 (binding free energy < -10 kcal/mol). These findings demonstrate that the tripeptides YPG and YPP, with AdipoR1 agonistic YP sequences, have alternative adiponectin-like potential via their preferential binding to AdipoR1.

Antihypertensive Effect of Dietary β-Conglycinin in the Spontaneously Hypertensive Rat (SHR)

Dietary β-conglycinin has been shown to increase plasma adiponectin concentration and decrease visceral adipose tissue weight in rats. Since adiponectin is one of the factors regulating blood pressure, as well as modulating lipid metabolism, we examined whether dietary β-conglycinin affects blood pressure in spontaneously hypertensive rats. The experimental diets were prepared according to the AIN-93G formula containing 20% protein, either casein (Control) or casein replaced with soy protein isolate (SOY) or β-conglycinin (β-CON) at the proportion of 50%. Male rats (SHR/Izm, 6 wk-old) were fed the diets for 7 weeks. The SOY compared with the Control significantly suppressed the blood pressure both at week 4 (p = 0.011, Control vs. SOY) and thereafter, and β-CON had even higher suppression (p = 0.0002, Control vs. β-CON). SOY and β-CON increased plasma adiponectin concentration followed by an increase in plasma nitric oxide and possibly a decreasing trend of gene expressions of angiotensinogen in the liver and renin in the kidney. The results indicated suppression by β-conglycinin of increasing blood pressure through an enhancement of plasma adiponectin, probably in combination with a regulation of the renin–angiotensin system in spontaneously hypertensive rats.

Dynamic gastric stability and in vitro lipid digestion of soybean protein isolate and three storage protein-stabilized emulsions: Effects of ultrasonic treatment

The emulsification of vegetable protein is closely related to solubility. The purpose of this study was to evaluate the effect of ultrasound on protein emulsification and to provide a prospective method for assessing the digestive properties of emulsions. In this article, we investigate the emulsion stability of ultrasonic pretreated soy protein isolate (SPI), and its three storage proteins, namely β-conglycinin (7S), lipophilic protein (LP), and glycinin (11S), under dynamic gastric conditions. The effects of these emulsions on lipolysis during digestion in the small intestine are also assessed using an in vitro dynamic human stomach simulator and a small intestine model. Particle size and ζ-potential measurements, as well as confocal laser scanning microscopy, revealed that during dynamic gastric digestion, the flocculation degree and floc size of 7S and soybean LP emulsions are larger than that of 11S and SPI emulsions. Meanwhile, ultrasound pretreatment of the proteins was found to prevent the agglomeration of the emulsion in a dynamic gastric environment. Moreover, enhanced flocculation delayed oil droplet delivery to the small intestine and subsequently retarded the release of lipophilic nutrients. The droplet size, molecular weight, and protein secondary structures of the ultrasonicated proteins were conducive to relatively higher rates and degrees of lipolysis in intestinal digestion than those of unsonicated proteins. Additionally, the slow-release effect of LP was superior to that of 11S and SPI, whereas 7S was comparatively more difficult to digest. The present study elucidated the fate of soy protein in the digestive tract and may facilitate microstructural food design to regulate physiological responses during digestion.

A Diet Including Red Bell Pepper Juice and Soy Protein Suppress Physiological Markers of Muscle Atrophy in Mice

Although muscle atrophy can be caused by disuse and lifestyle-related syndromes, it may be possible to prevent this condition through dietary intervention. We hypothesized that a diet including red bell pepper juice (RBPJ) and soy protein isolate (SPI) would prevent muscle atrophy. Accordingly, an experimental diet containing RBPJ and/or SPI was administered for 18 d to normal C57BL/6J mice. The control group was administered a casein diet. Four days before the end of the test period, denervation-induced muscle atrophy and/or sham operation were performed. Anterior tibialis muscle samples were then obtained to assess muscle degradation and perform metabolome analysis. Under the denervation condition, the 20% SPI diet did not alter the mRNA expression levels of muscle atrophy marker genes compared with the 20% casein group. Although the diet comprising RBPJ and 20% casein did not prevent muscle atrophy compared with the control group, the diet containing RBPJ and 20% SPI did. Metabolome analysis revealed that a diet including RBPJ and SPI induced a greater than 1.5-fold change in the levels of 20 muscle atrophy-related metabolites. In particular, the level of S-adenosylmethionine, which concerned with energy metabolism and lifespan, showed a strong positive correlation with the muscle atrophy marker. These findings suggest that a diet including RBPJ and soy protein suppress gene expressions related with muscle atrophy. Further research in humans is needed to confirm whether a combination of RBPJ and SPI can indeed prevent muscle atrophy.

Natural Compounds Attenuate Denervation-Induced Skeletal Muscle Atrophy

The weight of skeletal muscle accounts for approximately 40% of the whole weight in a healthy individual, and the normal metabolism and motor function of the muscle are indispensable for healthy life. In addition, the skeletal muscle of the maxillofacial region plays an important role not only in eating and swallowing, but also in communication, such as facial expressions and conversations. In recent years, skeletal muscle atrophy has received worldwide attention as a serious health problem. However, the mechanism of skeletal muscle atrophy that has been clarified at present is insufficient, and a therapeutic method against skeletal muscle atrophy has not been established. This review provides views on the importance of skeletal muscle in the maxillofacial region and explains the differences between skeletal muscles in the maxillofacial region and other regions. We summarize the findings to change in gene expression in muscle remodeling and emphasize the advantages and disadvantages of denervation-induced skeletal muscle atrophy model. Finally, we discuss the newly discovered beneficial effects of natural compounds on skeletal muscle atrophy.

Gel properties of transglutaminase-induced soy protein isolate-polyphenol complex: influence of epigallocatechin-3-gallate

BACKGROUND

Traditional soy protein isolate (SPI)-based gel products, such as tofu, are generally produced by heating and by addition of metal salt ions to adjust the hydrophobicity and electrostatic force of soybean protein to facilitate the formation of a uniform network structure. However, the gelation rate of the soy protein gel network structure is difficult to control. Theoretically, epigallocatechin-3-gallate (EGCG) could be used to alter the surface hydrophobicity of thermally induced SPI to improve its gelation rate and form a more uniform network structure, thus improving SPI-based gel properties (hardness, water holding capacity and rheological properties).

RESULTS

An SPI-EGCG complex (SPIE) was prepared, and properties of the resulting gel, following induction of transglutaminase (TG), were evaluated. Results showed that EGCG is bound to thermally induced SPI primarily via hydrophobic and hydrogen bonding, thus altering the secondary structure composition and reducing surface hydrophobicity of proteins in thermally induced SPI. Furthermore, the optimum amount of EGCG required to improve the gel strength, water holding capacity and rheological properties was ≤0.04:1 (SPI 1 g L^-1 ; EGCG:SPI, w/w). Thermal stability analysis further indicated that EGCG in SPIE was more stable than free EGCG after heating.

CONCLUSION

This study demonstrated that EGCG can improve the gel properties of TG-crosslinked SPIE, while EGCG in SPIE exhibits enhanced thermal stability. Additionally, the results of this study provide a novel strategy for the development of SPI-based gel foods with improved gel properties and that are enriched with bioactive compounds. © 2020 Society of Chemical Industry.

Simultaneous induction of mutant alleles of two allergenic genes in soybean by using site-directed mutagenesis

BACKGROUND

Soybean (Glycine max) is a major protein crop, because soybean protein has an amino acid score comparable to that of beef and egg white. However, many allergens have been identified among soybean proteins. A decrease in allergenic protein levels would be useful for expanding the market for soybean proteins and processed foods. Recently, the CRISPR/Cas9 system has been adopted as a powerful tool for the site-directed mutagenesis in higher plants. This system is expected to generate hypoallergenic soybean varieties.

RESULTS

We used two guide RNAs (gRNAs) and Agrobacterium-mediated transformation for simultaneous site-directed mutagenesis of two genes encoding the major allergens Gly m Bd 28 K and Gly m Bd 30 K in two Japanese soybean varieties, Enrei and Kariyutaka. We obtained two independent T0 Enrei plants and nine T0 Kariyutaka plants. Cleaved amplified polymorphic sequence (CAPS) analysis revealed that mutations were induced in both targeted loci of both soybean varieties. Sequencing analysis showed that deletions were the predominant mutation type in the targeted loci. The Cas9-free plants carrying the mutant alleles of the targeted loci with the transgenes excluded by genetic segregation were obtained in the T2 and T3 generations. Variable mutational spectra were observed in the targeted loci even in T2 and T3 progenies of the same T0 plant. Induction of multiple mutant alleles resulted in six haplotypes in the Cas9-free mutants derived from one T0 plant. Immunoblot analysis revealed that no Gly m Bd 28 K or Gly m Bd 30 K protein accumulated in the seeds of the Cas9-free plants. Whole-genome sequencing confirmed that a Cas9-free mutant had also no the other foreign DNA from the binary vector. Our results demonstrate the applicability of the CRISPR/Cas9 system for the production of hypoallergenic soybean plants.

CONCLUSIONS

Simultaneous site-directed mutagenesis by the CRISPR/Cas9 system removed two major allergenic proteins from mature soybean seeds. This system enables rapid and efficient modification of seed components in soybean varieties.

Proteolytic activity of selected commercial Lactobacillus helveticus strains on soy protein isolates

Soy protein isolates were fermented by three commercial Lactobacillus helveticus strains for a maximum of seven days to investigate the resulting proteolysis. The proteolytic activity of the most active strain (LH88) was further analyzed (LC-MS/MS and GC-MS) and it was shown that the β-conglycinin α subunit 1, β-conglycinin α' subunit, glycinin G1, and 2S albumin were specifically degraded. Peptigram analysis and visualization of the crystal structure showed that the hydrolysis sites of β-conglycinin α subunit, α' subunit, and the glycinin G1 were located on the surface of the molecule or at the mobile disordered region, hence being highly accessible for the proteinase of LH88. The proteins were partially further degraded to free amino acids, and subsequently catabolized to volatile compounds. However, most of the proteins remained native, even after seven days of fermentation, thus additional modification of protein structure or adjustment of fermentation conditions are required for effective generation of flavor compounds.

Stability and in vitro simulated release characteristics of ultrasonically modified soybean lipophilic protein emulsion

Natural emulsifiers such as soybean lipophilic protein (SLP) show potential as delivery systems for hydrophobic bioactive components such as vitamin E; however, the solubility of SLP is limited by its high lipid content. This study evaluated the effects of various ultrasonic conditions on the structure and properties of SLP. Using an emulsion of modified SLP, the carrier properties and in vitro digestion and release properties for vitamin E were evaluated. Biochemical and spectroscopic analyses indicated that the ultrasonic treatment mainly changed the secondary and tertiary structures of SLP. Furthermore, appropriate ultrasonic conditions significantly improved the solubility and emulsifying properties of SLP, with the highest emulsion stability and SLP encapsulation efficiency obtained using an ultrasonic power of 240 W for 20 min. An in vitro digestion simulation revealed that the emulsion prepared by ultrasonic modification of SLP was an effective delivery system for vitamin E. In particular, the emulsion protected the biological activity of vitamin E while significantly increasing the rate of lipid digestion and the bioavailability of vitamin E. These results indicate that the ultrasonically modified SLP can be used to prepare a stable emulsion for encapsulating vitamin E, which provides a new approach for the delivery of hydrophobic bioactive components.

The effect of pH on the stabilization and digestive characteristics of soybean lipophilic protein oil-in-water emulsions with hypromellose

The development of functional foods requires a detailed understanding of the behavior of lipophilic protein (LP) in the presence of emulsion stabilizers at different pH conditions. In this study, we examined the interaction between hydroxypropyl methylcellulose (hypromellose, HPMC) and soybean lipophilic protein. To that end, we examined the stabilities of LP-HPMC emulsions at pH 3, 5, and 7, as well as the oil-release behavior of LP-HPMC emulsions during digestion. Fluorescence data showed that HPMC binds to LP with quenching at a single binding site that did not change with pH. Atomic-force microscopy, emulsification, and oxidation-stability analyses showed that HPMC improves the pH stability of the LP-HPMC emulsions, while simulated in-vitro digestion experiments showed that added HPMC delayed the release of lipids to varying degrees. The results of this study will aid in the development of emulsion-based functional foods, pharmaceutical carriers with controlled-release or sustained-release functional ingredients.

The effect on the surface activity and the structure of SPI caused by cleavage of disulfide bonds and by subsequent glucose modification

The main purpose of this study was to investigate the effects on the molecular structure and the properties of soybean proteins isolate (SPI) after two modifications: (1) peracetic acid oxidative cleavage of its disulfide bonds and (2) the subsequent addition of covalently bonded glucose to the SPI containing the cleaved disulfide bonds. An appropriate amount of peracetic acid will be capable of enhancing the surface properties of SPI significantly; however, excessive oxidation can obtain undesirable results. When the concentration of peracetic acid was 0.4%, following by 35.5% of the disulfide bond cleavage, compared with those of natural SPI, the foaming capacity (FC), foaming stability (FS), emulsifying capacity (EC), and emulsifying stability (ES) of oxidized-SPI were increased by 82.0%, 65.8%, 58.5%, and 41.5%, respectively. The surface activity of oxidized-SPI could be promoted by glucose modification, and the FC, FS, EC, and ES of oxidized-SPI have further risen to 146.8%, 96.0%, 131.4%, and 40.3%, respectively, after the further glucose modification. Particle size measurements showed bimodality for the SPI that was modified with glucose with a portion of smaller sizes seen. Fluorescence spectroscopy and circular dichroism measurements demonstrate that extensibility increases; flexibility is enhanced; and glycosylation occurs more readily due to the oxidation of SPI. When grafted with glucose, these oxidized soybean protein products produce more ideal foaming and display better emulsification properties.

Proteomic study of bioactive peptides from tempe

Tempe is a traditional Indonesian fermented soybean mostly produced in small industries and sold locally throughout the country. Studies on the bioactive peptides in tempe are rare. Here, we studied bioactive peptides in samples from three tempe producers with different degrees of sanitation. The peptide sub-fractions of tempe from each producer were collected following water extraction, ultrafiltration (<3 kDa), gel filtration chromatography, and reversed phase-high performance liquid chromatography (RP-HPLC) separation followed by liquid chromatography-mass spectrometry (LC-MS). The MS spectra were then predicted using FindPept tools, and their biofunctionalities were confirmed with BIOPEP databases. There were few similar peptides found in tempe from the three producers. Peptides Val-His and Ala-Leu-Glu-Pro were found in tempe from all producers. Producers having a good sanitation level had more bioactive peptides than those with moderate or poor sanitation levels (58%, 43% and 35%, from good to poor sanitation). This work showed that the tempe from the three producers had antihypertensive, antidiabetic, antioxidative and antitumor peptides.

Effects of heat treatment under low moisture conditions on the protein and oil in soybean seeds

The effects of autoclave and microwave heating on the protein and oil in soybean seeds were investigated under low moisture conditions. The nitrogen solubility index (NSI) decreased on heating. The reduction in the NSI was accompanied by an increase in the size and deformation of the oil bodies in the cellular tissue of soybean seeds. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that lipoxygenase was susceptible to heat denaturation, but 7S and 11S globulins were only partially denatured. The partial denaturation of the proteins was confirmed by Fourier transform infrared spectroscopy measurements. The ratio of oil to protein peaks increased with increasing heating, suggesting the exudation of oil to the surface or outside of oil bodies. Microwave heating is more efficient in changing the oil distribution in soybean seeds than autoclave heating. On the other hand, the degree of protein denaturation is lower after microwave heating.

Absolute quantification of the α, α', and β subunits of β-conglycinin from soybeans by liquid chromatography/tandem mass spectrometry using stable isotope-labelled peptides

β-Conglycinin, a major protein in soybeans, shows improvement effect of lipid metabolism. Moreover, this protein influences the processing properties of soybeans. β-Conglycinin is a hetero-trimer constituted by α, α', and β subunits. In this work, a method for the selective quantification of these subunits was developed by means of protein absolute quantification (AQUA) technology using liquid chromatography/tandem mass spectrometry with the stable isotope-labelled internal standard peptides LQSGDALR[13C6,15N4], NILEASYDTK[13C6,15N2], and NPIYSNNFGK[13C6,15N2]. This method exhibited linear relationships (r2 > 0.99) in the concentration range of 1.2-300 fmol/μL for LQSGDALR[13C6,15N4] and NILEASYDTK[13C6,15N2], and of 4.7-300 fmol/μL for NPIYSNNFGK[13C6,15N2]. As a result, the content of these subunits in β-conglycinin-rich and both α and α' subunit-deficient soybean cultivars was successfully determined. This quantitative assay is promising for the evaluation of the food functionality and processing properties of soybeans.

Identification of the 7S and 11S globulins as percutaneously sensitizing soybean allergens as demonstrated through epidermal application of crude soybean extract

Cutaneous exposure to food allergens can predispose individuals to food allergies. Soybean, a major allergenic food, is an ingredient in various cosmetic products. However, the types of soybean proteins that are percutaneously sensitizing in humans or animal models remain unknown. In this study, BALB/c mice were dorsally shaved and epicutaneously exposed to a crude soybean extract including sodium dodecyl sulfate or distilled water alone. Specific IgEs secreted in response to 7S globulin (Gly m 5), 11S globulin (Gly m 6), Gly m 3, and Gly m 4 were measured using enzyme-linked immunosorbent assays or immunoblots. Exposure to soybean extract elicited the secretion of soybean-specific IgEs. Of the soybean proteins, 7S and 11S globulins acted as percutaneous sensitizers in 6/9 mice (67%). Additionally, IgE bound specifically and preferentially to the 7S globulin β subunit. In conclusion, this is the first report to identify percutaneously sensitizing soybean allergens in a mouse model.

Detection of plant protein adulterated in fluid milk using two-dimensional gel electrophoresis combined with mass spectrometry

The illegal or unlabelled addition of plant protein in milk can cause serious anaphylaxis. For sustainable food security, it is therefore important to develop a methodology to detect non-milk protein in milk products. This research aims to differentiate milk adulterated with plant protein using two-dimensional gel electrophoresis (2-DE) coupled with mass spectrometry. According to the protein spots highlighted on the gel of adulterated milk, β-conglycinin and glycinin were detected in milk adulterated with soy protein, while legumin, vicilin, and convicilin indicated the addition of pea protein, and β-amylase and serpin marked wheat protein. These results suggest that a 2-DE-based protein profile is a useful method to identify milk adulterated with soy and pea protein, with a detection limit of 4% plant protein in the total protein.

Improvement of glucose and lipid metabolism via mung bean protein consumption: clinical trials of GLUCODIA™ isolated mung bean protein in the USA and Canada

The aim of the present study was to confirm the effects of a commercially available mung bean protein isolate (GLUCODIA™) on glucose and lipid metabolism. The main component of GLUCODIA™ is 8S globulin, which constitutes 80 % of the total protein. The overall structure of this protein closely resembles soyabean β-conglycinin, which accounts for 20 % of total soya protein (soya protein isolate; SPI). Many physiological beneficial effects of β-conglycinin have been reported. GLUCODIA™ is expected to produce beneficial effects with fewer intakes than SPI. We conducted two independent double-blind, placebo-controlled clinical studies. In the first (preliminary dose decision trial) study, mung bean protein was shown to exert physiological beneficial effects when 3·0 g were ingested per d. In the second (main clinical trial) study, mung bean protein isolate did not lower plasma glucose levels, although the mean insulin level decreased with consumption of mung bean protein. The homeostatic model assessment of insulin resistance (HOMA-IR) values significantly decreased with mung bean protein. The mean TAG level significantly decreased with consumption of mung bean protein isolate. A significant increase in serum adiponectin levels and improvement in liver function enzymes were observed. These findings suggest that GLUCODIA™ could be useful in the prevention of insulin resistance and visceral fat accumulation, which are known to trigger the metabolic syndrome, and in the prevention of liver function decline.