Plant protein solubility: A challenge or insurmountable obstacle

Enhancing bioavailability and functionality of plant peptides and proteins: A review of novel strategies for food and pharmaceutical applications

Plant-derived peptides and proteins are emerging as versatile bioactive ingredients in functional food and pharmaceutical sectors due to their diverse health benefits. However, their practical applications are often limited by poor bioavailability and functional instability. This review evaluates key determinants of plant peptide/protein bioactivity, including physicochemical properties, anti-nutritional components, food matrix interactions, and gastrointestinal digestion conditions. Strategies to enhance their functionality and bioavailability are systematically discussed, focusing on absorption enhancers, structural modifications, protease inhibitors, and colloidal delivery systems (e.g., liposomes, emulsions, nanoparticles). Recent advancements highlight targeted enzymatic hydrolysis and fermentation as effective methods to generate bioactive peptides with improved therapeutic properties. Additionally, physical/chemical modifications enhance stability against proteolysis and improve functional performance. Innovations in plant-derived protein-based delivery systems, such as nanoparticles, demonstrate promise in protecting bioactive compounds and optimizing bioavailability. Collectively, these approaches provide a roadmap for developing next-generation plant-protein products, addressing challenges in bioactivity retention and gastrointestinal absorption.

Modulation of protein glutaminase α-helix and disulfide bonds in a sunflower pollen microgel microenvironment: A strategy to enhance enzyme activity and stability

Protein glutaminase (PGase) can improve plant protein solubility, but its activity tends to decline under the influence of external factors. Here, we developed a novel PGase-stabilizing agent (sunflower pollen microgel, SPMG) and investigated the mechanism for its stabilizing effect on PGase. Alkali treatment could regulate the physicochemical microenvironment of SPMG, and its ability to stabilize PGase declined with prolonged treatment time. SPMG increased PGase activity by a maximum of 49.24 %, while enhanced its storage stability by 30.61 %, 21.64 %, and 26.00 % at 4 °C, 25 °C, and 37 °C, respectively. SPMG improved PGase properties through hydrophobic interaction, resulting in the burying of inner hydrophobic groups and enhancement of intermolecular hydrogen bonding, which promoted the α-helix content from 23.28 % to 26.19 %. Additionally, these interactions facilitated the sulfhydryl-disulfide bond exchange reaction between PGase molecules, significantly increasing the disulfide bond content by nearly 80 %. This compact structure ultimately enhanced the activity and stability of PGase.

Assessing the Functional and Structural Properties of Peanut Meals Modified by Transglutaminase-Coupled Glycation

To increase the added value of peanut meal (PM, protein content of 46.17%) and expand its application in food processing, cold-pressed PM was modified via transglutaminase (TGase)-coupled glycation to enhance its functional properties. The effects of the modification conditions (i.e., PM concentration, PM/glucose mass ratio, temperature, and time) on the functional properties of PM were investigated, and its structural properties were evaluated using water contact angle measurements, fluorescence spectroscopy, and Fourier-transform infrared spectroscopy. It was found that TGase-coupled glycation modification altered the secondary structure of PM and increased both the water contact angle and the surface hydrophobicity, thereby significantly affecting its functional properties. Additionally, superior emulsification, foaming, and oil-absorbing properties were achieved for the modified PM, which were named EPM, FPM, and OPM, respectively (specimens under different modification conditions). Notably, the emulsification activity of the EPM sample was enhanced by 69.8% (i.e., from 18.48 to 31.38 m2/g); the foaming capacity of the FPM specimen was increased by 84.00% (i.e., from 21.00 to 46.00%); and the oil-absorbing capacity of the OPM sample was enhanced by 359.57% (i.e., from 1.41 to 6.48 g/g protein).

Recent progress in fabrication, characterization and application of functional protein aggregates derived from plant proteins

This review highlights recent advancements in fabrication, characterization, and applications of functional plant protein aggregates, emphasizing their growing importance in the food industry because of their sustainability as well as cost-effectiveness compared to animal proteins. While native plant proteins often exhibit limited technofunctional properties, the formation of protein aggregates offers a promising solution. This review explores various aggregation methods, including physical methods (e.g., heat treatment, ultrasonication), chemical modifications (e.g., glycation, acylation), and biological processes (e.g., enzymatic hydrolysis, fermentation), and structural and functional properties changes after these treatments. Advanced characterization techniques such as spectroscopy, microscopy, and rheological methods, are discussed to assess microstructures and key properties like emulsification, gelation, and foaming. Applications of these aggregates in products like beverages, mayonnaise, and whipped cream are highlighted. The review concludes with future research directions to enhance industrial applications and nutritional benefits, providing insights into the potential of plant protein aggregates for developing innovative and sustainable plant-based food and non-food products.

Baru Proteins: Extraction Methods and Techno-Functional Properties for Sustainable Nutrition and Food Innovation

Global population growth raises concerns about the availability of safe and nutritious food, along with its environmental and social impacts. In this context, plant-based foods have emerged as a promising solution, offering sustainable and affordable alternatives. Baru almonds (Dipteryx alata Vogel), a native Brazilian species, represent a viable and eco-friendly protein source with significant potential for food applications. This review discusses the nutritional composition, protein extraction methods and techno-functional properties of baru almonds, highlighting both advantages and limitations for food application. Baru proteins exhibit a high protein content (23-30%, w/w), a balanced essential amino acid profile, and valuable functional properties, including emulsifying capacity, foam stability, and moderate water- and oil-holding capacities. However, despite their potential, the lack of research on the gelation properties of baru proteins restricts their application in structured plant-based food formulations, where protein gelation is crucial for texture, water retention, and overall product stability. Further research is needed to evaluate their gel-forming ability and allergenic potential. Additionally, this review explores emerging protein extraction techniques that could improve protein quality and functionality, expanding their applicability in the food industry. By promoting biodiversity conservation and regional development, baru almonds contribute to the growing demand for sustainable protein sources.

Exploring Camellia oleifera Abel seed cake as sustainable source of protein for food applications: A review

The demand for sustainable plant-based protein is rising due to concerns over the environmental impact of animal-based protein. One promising yet overlooked protein source is the seed cake generated from Camellia oleifera oil extraction (COSC), which contains 14-20 % crude protein. COSC protein (COSCP) exhibit excellent nutritional and functional properties making it a promising ingredient for innovative food products. However, its adoption remains limited. This review discusses COSCP extraction methods, functional properties, and food applications to promote its broader utilization. It also examined how oil extraction methods influence COSCP functional characteristics and explores modification techniques to enhance its functionality. COSCP has excellent functional properties, making it suitable for use as emulsifier, foaming, and gelling agents in food systems. However, cross-linking of COSCP with saponins and phenolics during seed processing compromise the protein yield, purity, and functionality and need to be addressed to fully unlock the potential of COSCP in food applications.

Cysteine-induced disulfide cleavage enhances the solubility of alkali-treated pea protein and its elasticity contribution in low-salt hybrid meat gels

This study investigated the effectiveness of cysteine in improving the functional properties of pea proteins within low-salt myofibrillar protein (MP) gels. Cysteine treatment, at a concentration of 3.3 mM/g protein, cleaved 71-82 % of the disulfide bonds in native and pH-shifted pea protein isolates (PPIN and PPIpH), which increased the solubility and hydrophobicity of PPIpH. PPIN showed slight changes, primarily an increase in tryptophan fluorescence. The cleavage of disulfide bonds improved the hardness, elastic component (G'), and network integrity of hybrid gels. When combined with transglutaminase, the MP + PPIpH gel reached its maximum hardness (0.38 N) at a cysteine concentration of 1.7 mM/g protein. SDS-PAGE patterns and gels treated with additional N-ethylmaleimid confirmed the involvement of cysteine-treated PPI in the gel matrix. Consequently, cysteine-mediated disulfide bond disruption effectively modifies pea proteins, rendering them a more suitable functional ingredient for enhancing the texture of low-salt meat products.

The effect of enzymatic deamidation on the solubility and emulsifying properties of walnut protein isolate

BACKGROUND

Alkaline-extracted walnut protein isolates (WPI) exhibit limited solubility, which poses challenges for their application in the food industry. The present study investigated the effects of protein-glutaminase (PG) deamidation on the physicochemical characteristics, solubility and emulsifying properties of WPI.

RESULTS

The deamidation process of WPI was monitored by assessing the release of free ammonia and the reduction in solution turbidity. PG deamidation significantly increased the surface charge of WPI and modified its surface hydrophobicity with increasing deamidation degree (DD), resulting in a gradual improvement in solubility by approximately 50-70%. Furthermore, the emulsifying capacity of deamidated WPI (DeWPI), specifically at 0.25 h (DeWPI0.25, DD 7%) and 9 h (DeWPI9, DD 23%), was evaluated for stabilizing low internal phase emulsions (LIPEs) and high internal phase emulsions (HIPEs). LIPEs stabilized by WPI and DeWPI0.25 exhibited significant flocculation of oil droplets, leading to decreased stability against heat, salt treatment and storage compared to those stabilized by DeWPI9. DeWPI-stabilized HIPEs showed a 2-2.5-fold higher storage modulus compared to those stabilized by WPI. However, HIPEs stabilized by DeWPI0.25 displayed higher flow stress and flow strain compared to DeWPI9-stabilized HIPEs. Overall, DeWPI-stabilized HIPEs demonstrated relatively high physical stability against storage, heat treatment and high ionic strength.

CONCLUSION

PG deamidation significantly enhanced the solubility and influenced the emulsifying properties of WPI in a manner dependent on the DD. © 2024 Society of Chemical Industry.

Dephenolization Methods, Quality Characteristics, Applications, and Advancements of Dephenolized Cottonseed Protein: Review

Dephenolized cottonseed protein is a high-protein product obtained through the further dephenolization of cottonseed meal or by removing the lint and shell of cottonseed, extracting the oil at a low temperature, and subsequently eliminating toxic substances (gossypol). This paper presents a review of the latest advancements in the dephenolization methods, quality characteristics, and application domains of dephenolized cottonseed protein. It focuses on enhanced dephenolization methods, and summarizes the composition, structural characteristics, functional properties, and recent research developments. Additionally, it identifies challenges, opportunities, and new directions for future research on dephenolized cottonseed protein, which will contribute to advancing the field of dephenolized cottonseed protein research.

Structure-property relationship of pea protein microgels as fat analogues in Pickering oil-in-water emulsions: effect of salt addition

BACKGROUND

The design of plant-based microgels provides a platform for food ingredients to enhance palatability and functionality. This work aimed to explore the modifying effect of salt addition (KCl) on the structure of pea protein microgel particles (PPI MPs), on the interfacial adsorption and characteristics of formed emulsions as fat analogues.

RESULTS

Salt addition (0-200 mmol L-1) promoted a structural transformation from α-helix to β-sheet, increased the surface hydrophobicity (from 1160.8 to 2280.7), and increased the contact angle (from 56.73° to 96.47°) of PPI MPs. The electrostatic shielding effect led to the tighter packing of MPs with irregular structures and lowered the adsorption energy barrier. Notably, salt-treated PPI MPs could adjust their adsorption state at the interface. The discernible adsorption of PPI MPs with 200 mmol L-1 salt addition that possessed enhanced anti-deformation ability dominated the interfacial stabilization, whereas a relatively rougher stretched continuous interfacial film formed after spreading and deformation of 0 mmol L-1 MPs. A tribological test suggested that emulsion stabilized by MPs at 0 (0.0053) and 80 mmol L-1 (0.0068) had similar friction coefficients to commercial mayonnaise (0.0058), whereas a higher salt concentration (200 mmol L-1) lowered its oral sensation due to the adsorption layer and enhanced the resistance to droplet coalescence during oral processing.

CONCLUSION

Salt could be a modifier to tune the structure of microgels, and further promote the formation and attributes of emulsions. This study would improve application attributes of PPI MPs in the design of realistic fat analogues. © 2024 Society of Chemical Industry.

Elucidating the role of compositional and processing variables in tailoring the technological functionalities of plant protein ingredients

Although various plant protein (PP) ingredients are available on the market, their application in foods is not trivial, and food companies are struggling to identify PP ingredients fitting the intended use. To fill this gap, abundant literature has appeared but data are hardly comparable due to the absence of a recognized classification of PP ingredients accounting not only for protein purity but also for the process history, and of standardised protocols for technological functionality assessment. In this review, a comprehensive analysis of comparable literature data was thus carried out to elucidate the effect of composition and processing variables on PP technological functionalities. The review presents four sections describing: (i) the approach followed for the construction of a database of PP ingredient functionalities; (ii) the composition and processing factors relevant to PP ingredients; (iii) PP ingredient functional properties and methods used for their determination; (iv) the effect of composition and processing factors on PP ingredient functionalities. This analysis showed legume proteins to present the highest solubility and interfacial properties while pseudocereal ones the highest water-holding capacity. Although pure ingredients show higher functionalities, non-protein components could contribute to interfacial properties. Alkaline extraction, isoelectric precipitation and freeze-drying is the process mostly used in academic research to obtain PP ingredients. However, other extraction, purification, and drying methods can be properly combined, resulting in specific PP ingredient functionalities. Overall, this review highlights that, besides protein purity and source, knowledge of the processing history is required to select PP ingredients with desired functionalities.

Whipping Creams: Advances in Molecular Composition and Nutritional Chemistry

Whipping cream (WC) is an oil-in-water (O/W) emulsion used in food industry that can be transformed into aerated foam. The cream market has expanded significantly, driven by consumer demands for healthier and higher-quality products, leading to significant scientific research and innovation. This review focuses on formulation challenges related to ingredients such as fats, emulsifiers, and stabilizers, and how these components interact to form a stable emulsion and foam structure. Many studies have aimed to enhance the physicochemical, functional, and nutritional characteristics of WC by fine-tuning formulation parameters. A major focus was to address the health concerns linked to the high saturated fat content in milk fat (MF) by developing healthier alternatives. These include modifying the fat content, developing low-fat formulations, and introducing plant-based substitutes for dairy creams. The participation of additives to improve the properties of whipping cream was also investigated in many recent studies. The use of plant proteins, hydrocolloids, and emulsifiers has been explored, highlighting their effectiveness in enhancing emulsifying and foaming properties. This review summarizes recent advancements in whipping cream formulation, emphasizing the role of additives and alternative ingredients in meeting consumer preferences for healthier, more sustainable whipping cream products with enhanced functional, sensory, and nutritional properties.

Design and characterization of EGCG conjugated walnut protein cold-set gels for quercetin encapsulation

While heat treatment is a conventional method for the gelation of alkaline-extracted walnut protein isolates (AWPI), it can limit the incorporation of heat-sensitive ingredients. This study explored a novel approach to fabricate cold-set gels from epigallocatechin-3-gallate (EGCG) conjugated AWPI (AWPI-EGCG). EGCG conjugation effectively inhibited the thermal gelation of AWPI while promoting the formation of soluble aggregates upon heat treatment. AWPI-EGCG cold-set gels were then successfully fabricated through acidification with glucono-δ-lactone (GDL). The rheological study revealed that the storage modulus and yield stress of the cold-set gels were positively correlated with the GDL concentration and the EGCG conjugation degree. However, higher concentrations of GDL were associated with the reduced yield strain of the gels. Texture analysis indicated an increase in gel hardness with increasing GDL concentration, accompanied by a decrease in springiness. Microstructural examination by scanning electron microscopy revealed that the AWPI-EGCG cold-set gels with 0.3 % GDL exhibited smaller pores with thinner and smoother internal walls, while those with 0.9 % GDL exhibited relatively larger pores with thicker and denser walls. In addition, the AWPI-EGCG cold-set gels showed promising quercetin encapsulation capacities and controlled release properties.

Industrial Production of Functional Foods for Human Health and Sustainability

Functional foods significantly affect social stability, human health, and food security. Plants and microorganisms are high-quality chassis for the bioactive ingredients in functional foods. Characterised by precise nutrition and the provision of both nutritive and medicinal value, functional foods serve a as key extension of functional agriculture and offer assurance of food availability for future space exploration efforts. This review summarises the main bioactive ingredients in functional foods and their functions, describes the strategies used for the nutritional fortification and industrial production of functional foods, and provides insights into the challenges and future developments in the applications of plants and microorganisms in functional foods. Our review aims to provide a theoretical basis for the development of functional foods, ensure the successful production of new products, and support the U.N. Sustainable Development Goals, including no poverty, zero hunger, and good health and well-being.

Deciphering the mechanism underlying poor aqueous solubility of extracted quinoa proteins

This study aimed to decipher the mechanisms underlying poor solubility of quinoa proteins by investigating the form of quinoa proteins dispersed in water and how protein-protein interactions influenced the kinetic stability of proteins in the dispersions. Specifically, the relative solubility and the forms of quinoa proteins in 1-5 w/w% protein dispersions were determined by separating proteins via centrifugation and/or ultrafiltration. The kinetic stability of quinoa proteins in the supernatants over a 3-week storage period was characterized by determining the changes of concentration, composition and physicochemical properties of quinoa proteins and predicting protein-protein interactions. The results showed that quinoa proteins existed mainly as differently-sized protein aggregates in the dispersions, leading to low relative solubility. The coagulation of protein aggregates in the supernatants caused severe precipitation during the first week of storage whereas they were disassociated simultaneously. With further storage, the remaining proteins in the supernatants reached kinetic stability, which was contributed by stronger electrostatic repulsion and lower surface hydrophobicity. Moreover, 11S globulin and 2S albumin were precipitated and solubilized together during storage, which was ascribed to intermolecular interactions driven by multiple sites between 11S globulin and/or 2S albumin. This study lays a foundation for extensive utilization of quinoa proteins.

Toward Diverse Plant Proteins for Food Innovation

This review highlights the development of plant proteins from a wide variety of sources, as most of the research and development efforts to date have been limited to a few sources including soy, chickpea, wheat, and pea. The native structure of plant proteins during production and their impact on food colloids including emulsions, foams, and gels are considered in relation to their fundamental properties, while highlighting the recent developments in the production and processing technologies with regard to their impacts on the molecular properties and aggregation of the proteins. The ability to quantify structural, morphological, and rheological properties can provide a better understanding of the roles of plant proteins in food systems. The applications of plant proteins as dairy and meat alternatives are discussed from the perspective of food structure formation. Future directions on the processing of plant proteins and potential applications are outlined to encourage the generation of more diverse plant-based products.

Exploring the Impact of Solid-State Fermentation on Fava Bean Flour: A Comparative Study of Aspergillus oryzae and Rhizopus oligosporus

Fava bean (Vicia faba L.) is a protein-rich pulse with high nutritional value, but its functional and sensory characteristics limit its application in foods. Solid-state fermentation (SSF) can modify the composition of plant proteins, modulate its functionality, and enhance the sensory aspects. In this study, fava bean flour (FB) was fermented with Aspergillus oryzae and Rhizopus oligosporus to produce FBA and FBR, respectively, ingredients with distinct nutritional, functional, and aroma characteristics. The protein content increased by 20% in FBA and 8% in FBR, while fat levels rose more significantly in FBR (+40%). The overall content of fermentable oligo-, di-, mono-saccharides, and polyols (FODMAPs) decreased by 47% (FBA) and 57% (FBR), although polyol production by A. oryzae was observed. SSF improved the nutritional profile of FBA and FBR, with a notable increase in the concentration of essential amino acids observed, and a reduction in most antinutrients, with the exception of trypsin inhibitors. SSF resulted in the formation of aggregates, which increased the particle size and reduced protein solubility. Emulsions prepared with the fermented ingredients separated faster, and the foaming capacity of both FBA and FBR was decreased, but an increase in water-holding capacity was observed. SSF resulted in the production of predominantly savoury-associated aroma compounds, with compounds characteristic of metallic and mouldy aromas reduced. These results indicate the potential of SSF to transform FB with enhanced nutritional value and improved sensory and functional properties.

Yeast Proteins: Proteomics, Extraction, Modification, Functional Characterization, and Structure: A Review

Proteins are essential for human tissues and organs, and they require adequate intake for normal physiological functions. With a growing global population, protein demand rises annually. Traditional animal and plant protein sources rely heavily on land and water, making it difficult to meet the increasing demand. The high protein content of yeast and the complete range of amino acids in yeast proteins make it a high-quality source of supplemental protein. Screening of high-protein yeast strains using proteomics is essential to increase the value of yeast protein resources and to promote the yeast protein industry. However, current yeast extraction methods are mainly alkaline solubilization and acid precipitation; therefore, it is necessary to develop more efficient and environmentally friendly techniques. In addition, the functional properties of yeast proteins limit their application in the food industry. To improve these properties, methods must be selected to modify the secondary and tertiary structures of yeast proteins. This paper explores how proteomic analysis can be used to identify nutrient-rich yeast strains, compares the process of preparing yeast proteins, and investigates how modification methods affect the function and structure of yeast proteins. It provides a theoretical basis for solving the problem of inadequate protein intake in China and explores future prospects.

Insight into the improvement mechanism of gel properties of pea protein isolate based on the synergistic effect of cellulose nanocrystals and calcium ions

Here, the influence and potential mechanism by which cellulose nanocrystals (CNC) collaborated with Ca2+ enhancing the heat-induced gelation of pea protein isolate (PPI) were investigated. It was found that the combination of 0.45% CNC and 15 mM Ca2+ synergistically increased the gel strength (from 14.18 to 65.42 g) and viscoelasticity of PPI while decreased the water holding capacity. The improved particle size, turbidity, and thermostability as well as the reduced solubility, crystallinity, and gel porosity were observed in CNC/CaCl2 composite system. CNC fragments bind to specific amino acids in 11S legumin and 7S vicilin mainly through hydrogen bonding and van der Waals forces. Moreover, changes in the protein secondary structure and enhancement of the molecular interaction induced by CNC and Ca2+ could favor the robust gel network. The results will provide a new perspective on the functional regulation of pea protein and the creation of pea protein gel-based food.

Incorporation of Locust Bean Gum and Solid Lipid Microparticles as Strategies to Improve the Properties and Stability of Calcium-Rich Soy Protein Isolate Gels

The present study aimed to investigate the properties of calcium-rich soy protein isolate (SPI) gels (14% SPI; 100 mM CaCl2), the effects of incorporating different concentrations locust bean gum (LBG) (0.1-0.3%, w/v) to the systems and the stability of the obtained gels. Also, the incorporation of solid lipid microparticles (SLMs) was tested as an alternative strategy to improve the system's stability and, therefore, potential to be applied as a product prototype. The gels were evaluated regarding their visual aspect, rheological properties, water-holding capacities (WHCs) and microstructural organizations. The CaCl2-induced gels were self-supported but presented low WHC (40.0% ± 2.2) which was improved by LBG incorporation. The obtained mixed system, however, presented low stability, with high syneresis after 10 days of storage, due to microstructural compaction. The gels' stability was improved by SLM incorporation, which decreased the gelled matrices' compaction and syneresis for more than 20 days. Even though the rheological properties of the emulsion-filled gels (EFGs) were very altered due to the ageing process (which may affect the sensory perception of a future food originated from this EFG), the incorporation of SLMs increased the systems potential to be applied as a calcium-rich product prototype.