Modifications of soy protein isolates using combined extrusion pre-treatment and controlled enzymatic hydrolysis for improved emulsifying properties

TGase-induced crosslinking of mulberry leaf protein particles as stabilizer of high-internal-phase Pickering emulsions: characterization and stability

BACKGROUND

Mulberry leaf protein (MLP) is a high-quality protein with significant nutritional value and functional properties. Enzymatic modification of proteins can enhance their functional properties by using proteases to covalently crosslink or hydrolyze proteins. This study investigates the potential of transglutaminase (TGase)-induced crosslinked MLP as an emulsifier in the formation of high-internal-phase Pickering emulsions.

RESULTS

Crosslinked MLP samples were prepared with TGase concentrations ranging from 0 to 25 U g-1. High-internal-phase Pickering emulsions (80% v/v) were formed at pH 8, with a crosslinking temperature of 50 °C, a TGase concentration of 20 U g-1 and an optimal crosslinking time of 60 min. As the enzyme concentration increased, the content of exposed sulfhydryl groups progressively increased, while the total free sulfhydryl content remained relatively stable. After varying crosslinking durations, both total free and exposed sulfhydryl group contents initially increased before declining. Additionally, the content of free amino groups in MLP gradually decreased with higher enzyme dosages and longer crosslinking times. The surface hydrophobicity of crosslinked MLP increased initially, followed by a decrease, reflecting changes in the spatial structure of MLP. SDS-PAGE analysis confirmed the formation of polymer masses after TGase-catalyzed crosslinking. Under optimal crosslinking conditions, the high-internal-phase Pickering emulsion prepared with TGase-induced crosslinked MLP exhibited a relatively uniform droplet distribution.

CONCLUSION

TGase-induced crosslinking enhances both the emulsifying activity and stability of MLP emulsions. © 2025 Society of Chemical Industry.

Enzymatic hydrolysis of grape seed protein: In vitro digestibility, functional, and structural insights as effected by enzyme concentration and enzymolysis time

This study investigated the production of grape seed protein hydrolysate by studying the influence of various enzymatic hydrolysis conditions on grape seed proteins. The hydrolysate was characterized in terms of functional, structural, antioxidant properties and in vitro digestibility. The findings revealed that enzymatic hydrolysis led to structural modifications, which enhanced the functional properties of grape seed proteins. Enzymatic hydrolysis of grape seed protein with enzyme alcalase concentration @ 4 % (v/v) and 6 h resulted in the highest degree of hydrolysis, highest antioxidant activity, emulsifying capacity and solubility, and the lowest turbidity value. Enzymatic hydrolysis treatment reduced particle size, and turbidity, while improving DPPH radical scavenging activity, solubility. FTIR analysis indicated structural and conformational changes in the protein. X-ray diffraction results demonstrated reduced crystallinity in all the grape seed protein hydrolysates. The conformational as well as structural alterations contributed to improved antioxidant properties, and in-vitro digestibility of grape seed protein hydrolysate.

Modification of plum seed protein isolate via enzymatic hydrolysis, polyphenol conjugation and polysaccharide complexation to enhance emulsification and encapsulation of essential oils

Partial or limited hydrolysis, polyphenol conjugation, and polysaccharide complexation are widely used methods to improve emulsifying properties of plant proteins. These modifications enable proteins to encapsulate essential oils more effectively, thereby expanding their potential applications. In this study, plum seed protein isolate (PSPI) was modified by enzymatic hydrolysis (Alcalase, pepsin, and flavourzyme), followed by conjugation with polyphenols (catechin, curcumin, and proanthocyanidin), complexation with polysaccharides (gum Arabic, sodium alginate, and wolfberry polysaccharides) to evaluate their effects on PSPI's structure and functional properties. The results showed that all three methods significantly improved PSPI's emulsifying and encapsulating properties by modulating its structure, solubility, surface hydrophobicity, and interfacial tension. These modification methods significantly affected stability of essential oil emulsions and physicochemical properties of the resulting capsules. Hydrolysis with Alcalase, coacervation with gum Arabic, and conjugation with catechin produced emulsions with excellent storage, thermal, and ionic stability. The resulting capsules exhibited higher encapsulation efficiency, improved dispersion, greater thermal stability, enhanced antioxidant and antibacterial activities, and a slower release rate. These findings suggest that PSPI hydrolysates, conjugates, and complexes could serve as preservatives, flavor enhancers, and antimicrobial agents, with potential applications in food packaging, oral care products (chewing gum, mouthwashes, and toothpaste), and niche pharmaceutical formulations.

Modification mechanism of potato protein by twin-screw extrusion from the perspective of temperature variation

Potato protein has attracted much attention due to its unique nutritional and structural properties. In this study, the twin-screw extrusion technology was employed to modify potato protein, while the modification mechanism was investigated from the perspective of temperature variation. Results indicated that extruded potato protein (EPP) led to the extremely significantly decreased surface hydrophobicity (1350 to 307-396) and foaming capacity (41.08 % to 11.32-22.95 %). Solubility, emulsifying capacity, hydrophobic amino acids and the maintained forces of protein conformation varied greatly with the changes of extrusion temperature. Sufficient evidences could be found in SEM, DSC, SDS-PAGE and secondary/tertiary structures of EPP, possessing the higher crosslinking degree and highly distinct structures. The potential modification mechanism was revealed in a vivid schematic diagram. Results demonstrated that twin-screw extrusion provided more possibilities for modifying the highly heterogeneous structure of potato protein, highlighting a promising strategy for its high-value application in food production.

Enhancement of Emulsifying Activity in Soy-Protein-Based Products by Partial Substitution with Zein Hydrolysates and Transglutaminase Addition

Partially substituting other proteins in soy-protein-based products is an effective method to meet nutritional and application requirements. However, the emulsifying properties of soybean protein isolates (SPI) when partially substituted with zein hydrolysates (ZH) remain unknown. In the present work, protein blend (0 h-SPI/ZH) from SPI and ZH with a ratio of 3.5: 1 (w/w) was treated by transglutaminase (TGase) for 0, 0.5, 1.0, and 1.5 h, respectively. SDS-PAGE analysis results indicate protein polymers were generated in SPI/ZH conjugates. Emulsifying activity of the conjugates (1.5 h-SPI/ZH) was significantly increased from 23.69 to 28.13 m2 g-1 in comparison with SPI, and there was no statistically significant difference (p < 0.05) in emulsion stability. The apparent viscosity, surface hydrophobicity of the SPI/ZH conjugates were significantly increased. Emulsion droplet size and zeta potential stabilized by 1.5 h-SPI/ZH were also increased; the values were 64.73 to 80.79 r.nm and -21.8 to -29.9 mV, respectively. CLSM results indicate that 1.5 h-SPI/ZH conjugates stabilized the emulsion and had a thicker adsorption layer. Overall, high values of negative zeta potential and suitable molecular weight distribution of the SPI/ZH conjugates might be responsible for the improved emulsifying property. This study provides insights for the preparation of soy-protein-based products as a promising food emulsifier.

Food utility potential of protease obtained from insect-commensal Bacillus subtilis AU-2

BACKGROUND

Bacillus subtilis AU-2, isolated from the gut of Tribolium castaneum, was used for protease production. The purified protease was evaluated for its potential in food-related applications including meat tenderization, milk coagulation, and the preparation of enzymatic soybean hydrolysates. Enzymatic hydrolysis of soy protein is an effective method for producing protein hydrolysates with optimal techno-functional properties.

RESULTS

This study confirmed that B. subtilis AU-2 is a commensal with T. castaneum, within the insect gut flora. The purified protease obtained from B. subtilis AU-2 exhibited meat tenderization activity and an ability to promote milk coagulation within a 20 min timeframe. Soybean hydrolysate prepared using the protease exhibited a relatively higher degree of hydrolysis (20.1%) than pepsin, trypsin, and papain. The sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) peptide fragmentation pattern of the enzymatically prepared soy protein hydrolysate revealed the disappearance of ~35 kDa protein bands after 4 h protease treatment. The prepared soy protein hydrolysate showed improved emulsifying capacity (EC) (705 mL g-1) and exhibited significant 2,2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant activity (77.89%) and hydroxyl (OH) radical scavenging activity (97.23%).

CONCLUSIONS

The protease obtained from the newly isolated B. subtilis AU-2 strain exhibited potential for food-related applications, including meat tenderization, milk clotting, and soybean hydrolysate preparation. Its accessibility opens avenues for utilization in the food processing industry. © 2024 Society of Chemical Industry.

Tyrosinase-Catalyzed Soy Protein and Tannic Acid Interaction: Effects on Structural and Rheological Properties of Complexes

This study investigated the structural, rheological, and microstructural properties of soy protein isolate (SPI) induced by tyrosinase-catalyzed crosslinking with tannic acid (TA) at 25 °C under neutral conditions at pH 6.5. The particle size and polydispersity index of modified SPI progressively increased with rising TA concentrations. Tyrosinase-induced polymerization significantly impacted the conformational structure of SPI, evidenced by a notable decrease in intrinsic fluorescence, a pronounced red shift, and a remarkable reduction in surface hydrophobicity. FTIR analysis further revealed that, compared to control SPI, the amide I, II, and III bands of SPI incubated with TA and tyrosinase exhibited varying degrees of red-shift or blue-shift. These observations suggested a substantial alteration in the secondary structure of SPI after incubation with TA and tyrosinase. The apparent viscosity, G', and G″ of the modified SPI increased with higher TA concentrations, indicating that the modification of SPI by TA in the presence of tyrosinase resulted in enhanced covalent crosslinking. Microstructural observations confirmed that higher TA levels promoted the formation of denser and more uniform gel-like networks. The findings demonstrated that tyrosinase-mediated crosslinking improved the functionality of SPI, making it a promising approach for food applications.

Innovative strategies for valorization of byproducts from soybean industry: A review on status, challenges, and sustainable approaches towards zero-waste processing systems

The agro-food supply chain generates significant quantities of waste and byproducts globally, influenced by regional socioeconomic conditions, policy frameworks, and environmental concerns. The soybean industry generates various byproducts during the production processes of oil, soy milk, tofu, soy yogurt, edamame, miso, tempeh, natto, and soy sauce, presenting both challenges and opportunities for sustainable valorization. The review aims to outline the composition, status, and potential applications of key byproducts within the soybean industry including soy okara, soy whey, soy hull, soy meal, and lecithin, elucidating innovative strategies for their comprehensive valorization. The goal is to establish a sustainable zero-waste processing system by effectively utilizing these byproducts. This review explores emerging biotechnological advancements and eco-friendly processes aimed at maximizing resource recovery through the valorization of these soy byproducts. Various commercially viable products derived from repurposing the carbohydrate and protein fractions of diverse soy byproducts are highlighted. Additionally, a cutting-edge framework is proposed, advocating for the establishment of a zero-waste system within the soybean processing sector, emphasizing integrated biorefinery technologies, circular economy strategies, and sustainability principles. The framework proposed encompasses maximizing okara utilization, extracting value-added products, and implementing a closed-loop byproduct management approach within collaborative supply chains. Despite promising prospects, challenges such as anti-nutrients, viscosity and solubility of soy powder, and environmental impact must be addressed. This study could inspire further research into innovative technologies for the comprehensive and integrated valorization of soy byproducts, aiming to mitigate food waste and enhance the sustainability of the soybean industry.

Interaction of soy protein isolate with vitamin B12 during digestion: Focus on the binding mechanism, structure, and functional properties

This study investigated the release mechanism and digestive characteristics of soy protein isolate (SPI)-loaded vitamin B12 during digestion. According to the molecular docking results, vitamin B12 interacted with the SPI through a hydrophobic pocket on the SPI surface. Spectroscopy revealed that the fluorescence intensity of the SPI and complex system increased with the digestion time. The maximum emitted wavelength was red-shifted in gastric digestion and blue-shifted in intestinal digestion. Moreover, volume exclusion chromatography unveiled that high-molecular-weight proteins in the SPI and complex system gradually decomposed with an increase in the digestion time. The molecular weight progressively shifted from 100 kDa (macromolecules) to 30-50 kDa (small molecules). The present study clarified the digestive mechanism of the SPI with vitamin B12 and offered a theoretical basis for applying the SPI-vitamin B12 complex in food systems.

Production of fermented milk analogs using subcritical water extraction of rice by-products and investigation of its physicochemical, microbial, rheological, and sensory properties

Rice milling by-products extract and Persian grape syrup (Persian grape molasses), as the proper alternatives for milk ingredients and sucrose, respectively, can be considered a promising way to produce functional milk analogs. In this study, we studied the production of rice milling by-product extracts via the subcritical water extraction method, as a green method. The optimum extract was then fermented by Lactobacillus casei and Lactobacillus plantarum, and the different physicochemical, sensory, and rheological properties and the viability of these lactic acid bacteria were assessed during fermentation and certain intervals of 28-day storage. Considering rheological properties, the optimum rice milling by-product extract was recognized based on DOE analysis and the rheological curves of fermented drinks and Persian grape molasses were fitted by Herschel-Bulkley and Bingham models, respectively. The extract and also milk analog had excellent fitness with Herschel-Bulkley model, and this fermented milk analog showed a drop in the consistency index, flow behavior, and yield stress during the 28-day storage. According to the results, the viable cell count of Lactobacillus plantarum and Lactobacillus casei remained at 106-108 colony forming unit/mL after 28-day storage, which showed a combination of rice milling by-product ingredients and inulin had a positive effect on the survival rate of lactic acid bacteria. An increase in values of total phenolic compounds, as well as antioxidant activity observed during fermentation; however, these compounds dropped considerably during storage as a result of degradation and interaction with other compounds. Moreover, in terms of sensory evaluation, Lactobacillus plantarum drinks provided the highest overall acceptability among other samples on the 28th day.

Technological advances in protein extraction, structure improvement and assembly, digestibility and bioavailability of plant-based foods

Plant-based foods are being considered seriously to replace traditional animal-origin foods for various reasons. It is well known that animals release large amounts of greenhouse gases into the environment during feeding, and eating animal-origin foods may also cause some health problems. Moreover, animal resources will likely be in short supply as the world population grows. It is highly likely that serious health problems ascribed to insufficient protein intake in some areas of the world will occur. Studies have shown that environmentally friendly, abundant, and customizable plant-based foods can be an effective alternative to animal-based foods. However, currently, available plant-based foods lack nutrients unique to animal-based foods. Innovative processing technologies are needed to improve the nutritional value and functionality of plant-based foods and make them acceptable to a wider range of consumers. Therefore, protein extraction technologies (e.g., high-pressure extraction, ultrasound extraction, enzyme extraction, etc.), structure improvement and assembly technologies (3D printing, micro-encapsulation, etc.), and technologies to improve digestibility and utilization of bioactive substances (microbial fermentation, physical, etc.) in the field of plant-based foods processing are reviewed. The challenges of plant-based food processing technologies are summarized. The advanced technologies aim to help the food industry solve production problems using efficient, environmentally friendly, and economical processing technologies and to guide the development of plant-based foods in the future.

Direct hydrolysis of einkorn whole grain flour proteins for the generation of bioactive peptides using various proteases

In this study, it was aimed to investigate the direct release of BAPs from einkorn flour in one-step process. Thus, the protein extraction step was eliminated, thereby reducing processing cost. Commercial proteases (Alcalase, Flavourzyme, Neutrase, and Trypsin), and crude enzyme from Bacillus mojavensis sp. EBTA7 were used for hydrolyzing einkorn flour (30 %, w/v) solutions at 50-60 °C. The supernatants after centrifugation were used for bioactivity and techno-functionality tests. All hydrolysates demonstrated significant antioxidant capacities, with values ranging from 17.7 to 33.0 μmol TE/g for DPPH, 107 to 190 μmol TE/g for ABTS, and 0.09 to 3.08 mg EDTA/g for ion-chelating activities. Alcalase and Flavourzyme hydrolysis had the highest DPPH activities, while Bacillus mojavensis sp. EBTA7 enzyme yielded relatively high ABTS and ion-chelating activities. Notably, Bacillus mojavensis sp. EBTA7 crude enzyme hydrolysates demonstrated higher oil absorption capacity (2.94 g oil/g hydrolysate), robust emulsion (227 min), and foam stability (94 %) compared to commercial enzymes. FTIR spectroscopy confirmed variations in the secondary structure of peptides. All hydrolysates exhibited negative zeta potentials. The SDS-PAGE showcased MW ranged from 14 to 70 kDa, which was influenced by both the enzyme type and the degree of hydrolysis. Overall, Bacillus mojavensis sp. EBTA7 hydrolysates revealed considerable bio and techno-functional characteristics.

Effect of synergism of sucrose ester and xanthan gum on the stability of walnut milk

BACKGROUND

Single emulsifiers have an effect on the stability of plant protein drinks, giving some improvement. Emulsifiers are more effective in maintaining emulsion stability when combined with polysaccharides such as xanthan gum. In this paper, we studied the food-grade emulsifier sucrose ester and measured the average particle size, polydispersity value, zeta potential, microrheological properties, microstructure and creaming index related to walnut protein emulsion by constructing a walnut protein emulsion simulation system. SDS-PAGE and low-field NMR were used to analyze the relative molecular masses of emulsions and the water distribution of emulsions, respectively, to further investigate the synergistic effects of sucrose esters and xanthan gum on the ease of emulsification and intrinsic mechanisms of different molecular weight proteins of walnut protein emulsions.

RESULTS

The results indicate that the synergistic effect of sucrose esters and xanthan gum was to stabilize emulsions better than single emulsifiers. Xanthan gum and protein may form protein-polysaccharide complexes, as well as the hydrophobic interaction between sucrose ester and xanthan gum. The properties of xanthan gum can improve the stability of the emulsion by affecting the mechanical properties of walnut protein emulsion, and the combination of sucrose ester and xanthan gum can better stabilize large protein molecules.

CONCLUSION

The results not only provide a theoretical basis for the stability of plant protein emulsion systems, but also provide technical support for the production and processing of large-molecule plant proteins into emulsions in this field for improving their stability, and also provide more possibilities for other types of emulsions. © 2023 Society of Chemical Industry.

Electron beam irradiation induced aggregation, structural and functional changes of soybean 11S globulin

This study investigated the effects of different irradiation doses of an electron beam (e-beam) (0, 2, 4, 6, 8, and 10 kGy) on the structure, emulsification, foaming, and rheological and gel properties of soybean 11S globulin. The irradiation treatment at 4 and 6 kGy significantly increased the solubility, surface hydrophobicity, disulfide bonding, and ζ-potential of 11S globulin, decreased the particle size of the protein solution, and effectively improved the emulsifying activity and foaming stability of the protein solution. Moreover, irradiation induced moderate cross-linking and aggregation of the proteins, thereby increasing the apparent viscosity and shear stress of the protein solution. In addition, the low-field NMR and microstructure analysis results revealed that protein gels formed a dense and homogeneous three-dimensional mesh structure after irradiation (6 kGy), along with increased content of bound water (T2b) and water not readily flowable (T21) and a decrease content of free water (T22). Overall, our results confirmed that e-beam irradiation could significantly improve the physicochemical properties of soybean 11S globulin. Our study thus provides a new technical means for the application of electron beam irradiation technology toward protein modification and broadens the high-value utilization of soybean 11S globulin in the food processing industry.

Physicochemical properties and stability of oil-in-water emulsions stabilized by soy protein isolate and xanthan gum

The aim of this work was to determine rheological and disperse characteristics and stability of oil-in-water emulsions stabilized by soy protein isolate (SPI) and xanthan gum (XG), as natural components. The effects of their combination on emulsion stabilization have not been investigated yet. The existence of interactions between the two macromolecules were indicated by the influence of XG on SPI surface hydrophobicity and surface tension values. Increase in SPI concentration from 1 to 3 % shift of distribution curves towards smaller particle size, while the opposite effects of further increase of SPI was obtained. The emulsions stabilized by SPI showed shear-thinning flow behavior, which changed to thixotropic at 5 % of SPI concentration. The presence of XG in emulsions at low concentrations did not affect the size distribution of the droplets, while at 0.1 % of XG Sauter mean diameter value raised and distribution curves were shifted towards a higher particle size. The presence of XG at higher concentration resulted in thixotropic flow behavior of emulsions. Also, increase in XG concentration led to the increase in consistency index and extent of non-Newtonian behavior of emulsions and enhanced the influence of the elastic modulus and creaming stability of the systems.

Plant protein solubility: A challenge or insurmountable obstacle

Currently, there is an increasing focus on comprehending the solubility of plant-based proteins, driven by the rising demand for animal-free food formulations. The solubility of proteins plays a crucial role in impacting other functional properties of proteins and food processing. Consequently, understanding protein solubility in a deeper sense may allow a better usage of plant proteins. Herein, we discussed the definition of protein solubility from both thermodynamic and colloidal perspectives. A range of factors affecting solubility of plant proteins are generalized, including intrinsic factors (amino acids composition, hydrophobicity), and extrinsic factors (pH, ionic strength, extraction and drying methods). Current methods to enhance solubility are outlined, including microwave, high intensity ultrasound, hydrostatic pressure, glycation, pH-shifting, enzymatic hydrolysis, enzymatic cross-linking, complexation and modulation of amino acids. We base the discussion on diverse modified methods of nitrogen solubility index available to determine and analyze protein solubility followed by addressing how other indigenous components affect the solubility of plant proteins. Some nonproteinaceous constituents in proteins such as carbohydrates and polyphenols may exert positive or negative impact on protein solubility. Appropriate protein extraction and modification methods that meet consumer and manufacturers requirements concerning nutritious and eco-friendly foods with lower cost should be investigated and further explored.

Replacing animal proteins with plant proteins: Is this a way to improve quality and functional properties of hybrid cheeses and cheese analogs?

The growing emphasis on dietary health has facilitated the development of plant-based foods. Plant proteins have excellent functional attributes and health-enhancing effects and are also environmentally conscientious and animal-friendly protein sources on a global scale. The addition of plant proteins (including soy protein, pea protein, zein, nut protein, and gluten protein) to diverse cheese varieties and cheese analogs holds the promise of manufacturing symbiotic products that not only have reduced fat content but also exhibit improved protein diversity and overall quality. In this review, we summarized the utilization and importance of various plant proteins in the production of hybrid cheeses and cheese analogs. Meanwhile, classification and processing methods related to these cheese products were reviewed. Furthermore, the impact of different plant proteins on the microstructure, textural properties, physicochemical attributes, rheological behavior, functional aspects, microbiological aspects, and sensory characteristics of both hybrid cheeses and cheese analogs were discussed and compared. Our study explores the potential for the development of cheeses made from full/semi-plant protein ingredients with greater sustainability and health benefits. Additionally, it further emphasizes the substantial chances for scholars and developers to investigate the optimal processing methods and applications of plant proteins in cheeses, thereby improving the market penetration of plant protein hybrid cheeses and cheese analogs.

Recent advances in soybean protein processing technologies: A review of preparation, alterations in the conformational and functional properties

Currently, growing concerns about sustainable development and health awareness have driven the development of plant-based meat substitutes. Soybean proteins (SPs) are eco-friendly and high-quality food sources with well-balanced amino acids to meet consumer demand. The functionality and physicochemical attributes of SPs can be improved by appropriate processing and modification. With the burgeoning advances of modern processing technologies in the food industry, a multitude of functional foods and ingredients can be manufactured based on SPs. This review mainly highlights the conformational changes of SPs under traditional and emerging processing technologies and the resultant functionality modifications. By elucidating the relationship between processing-induced structural and functional alterations, detailed and systematic insights are provided regarding the exploitation of these techniques to develop different nutritional and functional soybean products. Some popular methods to modify SPs properties are discussed in this paper, including thermal treatment, fermentation, enzyme catalysis, high hydrostatic pressure, high-intensity ultrasound, atmospheric cold plasma, high-moisture extrusion, glycosylation, pulsed ultraviolet light and interaction with polyphenols. Given these processing technologies, it is promising to expand the application market for SPs and boost the advancement of the soybean industry.

Relation of amino acid composition, hydrophobicity, and molecular weight with antidiabetic, antihypertensive, and antioxidant properties of mixtures of corn gluten and soy protein hydrolysates

New mixed Alcalase-hydrolysates were developed using corn gluten meal (CP) and soy protein (SP) hydrolysates, namely CPH, SPH, SPH30:CPH70, SPH70:CPH30, and SPH50:CPH50. Amino acid profile, surface hydrophobicity (H 0), molecular weight (MW) distribution, antioxidant activity, angiotensin-converting enzyme (ACE), α-amylase, and α-glucosidase inhibitory activities, and functional characteristics of hydrolysates were determined. Hydrolysis changed the amount of hydrophilic and hydrophobic amino acid composition and significantly increased the H 0 values of hydrolysates, especially for CPH. The DPPH radical scavenging activity (RSA) was higher for CPH, SPH30:CPH70, and SPH50:CPH50 than SPH and SPH70:CPH30. Moreover, SPH, SPH70:CPH30, and SPH50:CPH50 showed lower MW than CPH, and this correlated with the higher hydrophilicity, and ABTS and hydroxyl RSA values obtained for SPH and the mixed hydrolysates with predominantly SPH. SPH70:CPH30 exhibited higher ACE, α-glucosidase, and α-amylase inhibitory activities among all samples due to its specific peptides with high capacity to interact with amino acid residues located at the enzyme active site and also low binding energy. At 15% degree of hydrolysis, both SPH and CPH showed enhanced solubility at pH 4.0, 7.0 and 9.0, emulsifying activity, and foaming capacity. Taken together, SPH70:CPH30 displayed strong antioxidant, antihypertensive, and antidiabetic attributes, emulsifying activity and stability indexes, and foaming capacity and foaming stability, making it a promising multifunctional ingredient for the development of functional food products.

Soy Protein Hydrolysates Affect the Structural and Mechanical Properties of Soy Protein-Wheat Gluten Extrudates Using High Moisture Extrusion

This study aimed to investigate the effect of hydrolyzed soy protein isolate (HSPI) as a plasticizer in the soy protein mixture-wheat gluten (SP-WG) extrudates on its structural and mechanical properties during high moisture extrusion. Those SP were prepared by mixing soy protein isolate (SPI) and HSPI with different ratios. HSPI primarily consisted of small molecular weight peptides measured with size exclusion chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The elastic modulus of SP-WG blends decreased with increased HSPI contents through the closed cavity rheometer. Adding HSPI at low concentrations (≤30 wt% of SP) enhanced a fibrous appearance and higher mechanical anisotropy while adding more HSPI resulted in a compact and brittle structure and tended to be isotropic. It can be concluded that the partial addition of HSPI as a plasticizer can promote the formation of a fibrous structure with enhanced mechanical anisotropy.

Effects of ultrasound assisted cell wall disruption on physicochemical properties of camellia bee pollen protein isolates

Camellia bee pollen protein isolates were extracted by cell wall disruption using ultrasonication, freeze-thawing, enzymatic hydrolysis, and their combinations. The effects of these methods on microstructure of cell wall, protein release, protein yield, physiochemical properties and structure of proteins were investigated. As compared with physical treatments (ultrasonication, freeze-thawing and their combination), the enzymatic hydrolysis significantly improved the yield of proteins, because it not only promoted the release of proteins from the inside of pollen, but also released proteins in pollen wall. The proteins extracted by enzymatic hydrolysis method also exhibited better solubility, emulsifying and gelation properties due to the partial hydrolysis of proteins by protease. In addition, when ultrasound was combined with freeze-thawing or enzymatic hydrolysis, it could further improve the yield of proteins and the functional properties of proteins, which was mainly related to the changes of protein structure induced by cavitation effect of ultrasound.

Decolorization and detoxication of plant-based proteins using hydrogen peroxide and catalase

The gap between the current supply of meat and its predicted future demand is widening, increasing the need to produce plant-based meat analogs. Despite ongoing technical developments, one of the unresolved challenges of plant-based meat analogs is to safely and effectively decolor plant proteins that originally exhibit yellow-brown or strong brown color. This study aimed to develop an effective and safe decoloring system for soy-based protein products using food-grade hydrogen peroxide and catalase. First, soy-based protein isolate (PI) and textured vegetable protein (TVP) were treated with hydrogen peroxide, and then the residual hydrogen peroxide was degraded using catalase. This process caused notable decolorization of PI and TVP, and residual hydrogen peroxide was not detected in these products. These findings indicate that this process could safely and effectively decolorize soy-based proteins. Interestingly, this decoloring process enhanced the solubility, water- and oil-holding capacities, foaming capacity, and emulsifying stability of decolored soy-based PI. Additionally, cooking loss and juiciness of decolored TVP-based foods were improved compared to those of non-treated foods. These findings indicate that the decoloring process also enhances the physical properties of soy-based protein products.

Extrusion Modification: Effect of Extrusion on the Functional Properties and Structure of Rice Protein

Modification of rice protein by extrusion technology can broaden the range of processing and applications for food and feed raw materials. In this study, rice protein was extruded at different screw speeds (100–250 rpm), extrusion temperatures (90–150 °C), and moisture contents (25–40%). Compared with an unextruded protein, the functional properties and structural properties of textured rice protein were evaluated. The results showed that, after extrusion, the solubility of protein was improved, by up to 19.76%, which was 45.23% higher than pre-extrusion; the water holding capacity of extruded rice protein was highest at 200 rpm, 130 °C, and 25%, which could be enhanced by 37.74%; the emulsion stability was enhanced by 152.82% at 200 rpm, 130 °C, and 35%. Under extrusion, the content of sulfhydryl and disulfide bonds of rice protein decreased significantly; the hydrogen bond content increased, and the ionic bond content decreased; the hydrophobic effect decrease, except at 200 rpm, 130 °C, and 40%. The microstructure changed significantly after extrusion, producing protein aggregates with a tight structure. No new characteristic peaks appeared after extrusion, but transformation occurred between the components of the secondary structure: β-sheet and β-turn angles to an α-helix structure toward the transformation, but β-sheet was still the main component. As a safe and efficient modification method, extrusion cooking can effectively improve the functional properties of rice protein to enrich the application of rice protein resources.

Peptide profiles and antioxidant capacity of extensive hydrolysates of milk protein concentrate

Milk protein concentrate was hydrolyzed using one-step enzymatic hydrolysis. Both the peptide profiles and antioxidant activities of the resulting extensive hydrolysates of milk protein concentrate (EMPH) were analyzed using a peptidomics approach based on liquid chromatography-tandem mass spectrometry. The results demonstrated that the degrees of hydrolysis of the 4 EMPH by Alcalase-Protamex, Alcalase-Protease A 2SD, Alcalase-Flavorzyme, and Alcalase-ProteAXH were 12.02%, 16.85%, 15.87%, and 15.77%, respectively. Using size exclusion chromatography, 99.85% of the peptides in the Alcalase-Protease A 2SD hydrolysate were shown to have a molecular weight of <3 kDa. A total of 33 common peptides were identified in the EMPH by liquid chromatography-tandem mass spectrometry, 16 of which were identified as bioactive peptides using bioinformatics. The peptide profiles and the coverage of master proteins of the 4 EMPH were different. The EMPH also exhibited strong free radical scavenging capacity, as indicated by the results of the 1,1-diphenyl-2-picrylhydrazyl radical, 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid), hydroxyl radical, and reducing power assays. The results of this study provided useful information on the peptide profiles and antioxidant activity of EMPH.

Micronization using combined alkaline protease hydrolysis and high-speed shearing homogenization for improving the functional properties of soy protein isolates

The present study aimed to investigate the functional properties of soybean protein isolate (SPI) treated with alkaline protease and high-speed shearing homogenization. Alkaline protease-hydrolyzed SPIs that were characterized by varying degrees of hydrolysis between 0 and 6% were treated with high-speed shearing homogenization to obtain different micro-particulate proteins. The results showed that this combined treatment could significantly reduce the particle size of SPI by markedly degrading the structure of both the 7S and 11S subunits, thereby resulting in a significantly reduced content of β-sheet and β-turn structures. The surface hydrophobicity increased considerably for samples with hydrolysis below the threshold of 2% and then declined gradually above this threshold. Furthermore, the combination of hydrolysis and homogenization significantly improved the emulsion stability of SPI hydrolysates. It also significantly improved the foaming properties of SPI. These results demonstrated that alkaline protease hydrolysis combined with high-speed shearing homogenization represents a promising approach for improving the functional and structural properties of SPI.

Recent application of protein hydrolysates in food texture modification

The demand for clean labels has increased the importance of natural texture modifying ingredients. Proteins are unique compounds that can impart unique textural and structural changes in food. However, lack of solubility and extensive aggregability of proteins have increased the demand for enzymatically hydrolyzed proteins, to impart functional and structural modifications to food products. The review elaborates the recent application of various proteins, protein hydrolysates, and their role in texture modification. The impact of protein hydrolysates interaction with other food macromolecules, the effect of pretreatments, and dependence of various protein functionalities on textural and structural modification of food products with controlled enzymatic hydrolysis are explained in detail. Many researchers have acknowledged the positive effect of enzymatically hydrolyzed proteins on texture modification over natural protein. With enzymatic hydrolysis, various textural properties including foaming, gelling, emulsifying, water holding capacity have been effectively improved. It is evident that each protein is unique and imparts exceptional structural changes to different food products. Thus, selection of protein requires a fundamental understanding of its structure-substrate property relation. For wider applicability in the industrial sector, more studies on interactions at the molecular level, dosage, functionality changes, and sensorial attributes of protein hydrolysates in food systems are required.

Soy Protein Isolate/Sodium Alginate Microparticles under Different pH Conditions: Formation Mechanism and Physicochemical Properties

The effects of sodium alginate (SA) and pH value on the formation, structural properties, microscopic morphology, and physicochemical properties of soybean protein isolate (SPI)/SA microparticles were investigated. The results of ζ-potential and free sulfhydryl (SH) content showed electrostatic interactions between SPI and SA, which promoted the conversion of free SH into disulfide bonds within the protein. The surface hydrophobicity, fluorescence spectra, and Fourier transform infrared spectroscopy data suggested that the secondary structure and microenvironment of the internal hydrophobic groups of the protein in the SPI/SA microparticles were changed. Compared with SPI microparticles, the surface of SPI/SA microparticles was smoother, the degree of collapse was reduced, and the thermal stability was improved. In addition, under the condition of pH 9.0, the average particle size of SPI/SA microparticles was only 15.92 ± 0.66 μm, and the distribution was uniform. Rheological tests indicated that SA significantly increased the apparent viscosity of SPI/SA microparticles at pH 9.0. The maximum protein solubility (67.32%), foaming ability (91.53 ± 1.12%), and emulsion activity (200.29 ± 3.38 m²/g) of SPI/SA microparticles occurred at pH 9.0. The application of SPI/SA microparticles as ingredients in high-protein foods is expected to be of great significance in the food industry.

Faba bean protein: A promising plant-based emulsifier for improving physical and oxidative stabilities of oil-in-water emulsions

Faba bean is a protein-rich, sustainable, but understudied legume. Faba bean protein isolates (FBPIs) can serve as promising emulsifiers. This review aims to summarize the research on FBPIs as emulsifiers and various modification methods to improve the emulsifying functionalities. The emulsifying activities of FBPIs depend on several physiochemical characteristics (e.g. solubility, surface hydrophobicity, surface charge, interfacial activity). Physical modifications, especially via linking FBPIs electrostatically to polysaccharides can effectively increase the interfacial layer thickness/compactness and maintain the interfacial protein adsorption. Chemical modifications of FBPIs (e.g. acetylation and Maillard reaction) could improve the interfacial activity and affect the droplet-size distribution. Enzymatic modifications, usually either via hydrolysis or cross-linking, help to optimize the molecular size, solubility, and surface hydrophobicity of FBPIs. It is critical to consider the lipid/protein oxidative stability and physical stability when optimizing the emulsifying functionality of FBPIs. With suitable modifications, FBPI can serve as a promising emulsifier in food production.

Self-Assembled Micellar Nanoparticles by Enzymatic Hydrolysis of High-Density Lipoprotein for the Formation and Stability of High Internal Phase Emulsions

In this study, the influence of pH on the conformational state of EHT, which was obtained from the enzymatic hydrolysis of trypsin, and the stabilizing properties of high internal phase emulsions have been demonstrated. Critical micelle concentration and transmission electron microscopy results exhibited the formation of micellar nanoparticles with mean diameters ranging from 108 to 1359.5 nm. The results of solubility, surface hydrophobicity, and conformations indicated that EHT tended to act as particulate emulsifiers at pH 3, 5, and 7, while at alkaline pH, it was more like a polymeric emulsifier, which could be proven by confocal laser scanning microscopy. The EHT at pH 7 exhibited better stabilizing properties than those at pH 9 and 11 as influenced by storage, temperature, and ionic strength. These findings might be of great importance for broadening the range of sustainable applications of amphiphilic peptides in foods and pharmaceuticals.

Enhancing the functional characteristics of soy protein isolate via cross-linking catalyzed by Bacillus subtilis transglutaminase

BACKGROUND

Although Streptomyces mobaraense transglutaminase (MTG) has been extensively applied to enhance the functional characteristics of soy protein isolate (SPI) through cross-linking, various transglutaminases (TGs) in nature may provide more choice in the food industry. Previous research reported that TG derived from Bacillus subtilis (BTG) exhibited better pH stability and thermostability than MTG.

RESULTS

An attempt was made to study the influence of BTG induced cross-linking on the properties of SPI. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) results indicated that almost all protein constituents (α', α, β, AS, and BS) in SPI could be cross-linked with BTG treatment. The BTG treatment also resulted in a significant increase (*P < 0.05) in SPI mean particle size. Emulsifying activity and stability were improved from 0.11535 m²  g^-1 and 48.3% for native SPI to 0.13252 m²  g^-1 and 83.9% for SPI treated with BTG at 6 h. Similarly, the modified SPI showed better foam activity (1.32 mL) and stability (87.6%) than the original SPI (0.93 mL and 56.8%). The water-holding capacity of SPI gel was found to increase with time, with a value of 95.43% at 6 h. Furthermore, SPI gel's texture profiles were greatly improved by adding BTG (*P < 0.05).

CONCLUSION

The results of the present study indicated that BTG could be a promising cross-linking agent for improving the functional characteristics of SPI. As a substitute for MTG, BTG could thus potentially be used for food structure engineering to enhance the functional characteristics of multiple proteins to advance the development of food chemistry. © 2020 Society of Chemical Industry.

Effect of two-step enzymatic hydrolysis on the antioxidant properties and proteomics of hydrolysates of milk protein concentrate

Food protein and peptides are generally considered a source of dietary antioxidants. The antioxidant activity and peptide profiles of four extensive hydrolysates of milk protein concentrate (MPC) were examined using the two-step enzymatic method. The hydrolysis combinations were Alcalase-Flavourzyme (AE), Alcalase-ProteAXH (AH), Alcalase-Protamex (AX) and Alcalase-Protease A 2SD (AD). The results showed that highest degree of hydrolysis corresponded to the AE sample (20.41%). High-efficiency gel-filtration chromatography results indicated that the relative proportions of extensive hydrolysates with molecular weights < 3 kDa were 99.89%, 99.57%, 99.93%, and 99.89% for AX, AE, AD and AH, respectively. The hydrolysates of the MPC exhibited increased radical-scavenging capacity, as evidenced through an analysis with 1,1-diphenyl-2-pycryl-hydrazyl (DPPH), 2,2-azinobis (3-ethylbenzothiazo-line-6-sulfonic acid) diammonium salt (ABTS), reducing power and hydroxyl-radical scavenging activity testing. The main bioactive peptides were identified through EASY-nLC-orbitrap MS/MS and bioinformatics. The study may provide useful information regarding the antioxidant properties of extensive hydrolysates of MPC.