Plant Protein versus Dairy Proteins: A pH-Dependency Investigation on Their Structure and Functional Properties

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.

Structural dynamics of camel milk proteins during digestion: Insights from 2D homo correlation and 2D hetero-correlation spectroscopy

This study investigates camel milk protein structural dynamics during digestion using Fourier Transform Infrared (FTIR) spectroscopy and Two-Dimensional Infrared (2D-IR) homo-correlation and hetero-correlation analysis. The synchronous 2DIR homo-correlation map reveals that NH bending and C-N stretching vibrations (amide II) are sensitive to digestion, indicating significant impacts on secondary structures. The asynchronous 2DIR homo-correlation indicates a stepwise process, where initial disruptions in NH interactions precede changes in CO stretching vibrations (amide I), highlighting the sequence of structural alterations during protein unfolding and degradation. 2DIR hetero-correlation spectroscopy, which examines the correlations between amide A (NH stretching vibrations) and amide I, II, and III bands, offers deeper insights into hydrogen bonding dynamics and its influence on protein conformation. This approach elucidates hydrogen bond dynamics by correlating the fast-changing NH stretching vibrations with the slower amide band vibrations, hetero-correlation reveals how initial hydrogen bond disruptions lead to broader structural changes in the protein backbone. It also elucidates the conformational stability and flexibility by indicating how variations in hydrogen bond intensity correlate with the strength and flexibility of different secondary structural elements, providing a nuanced understanding of the protein's behavior during digestion. These findings indicate the potential of FTIR combined with 2D-IR for monitoring digestive processes.

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.

pH-dependent emulsifying properties of pea protein isolate: Investigation of the structure - Function relationship

This study investigated the relationship between pea protein isolates (PPI) emulsifying properties and their structural, interfacial, and physicochemical characteristics at various pH values (native pH, 7, 5, and 3). Emulsion characteristics including emulsifying activity and stability, droplet size, flocculation index (FI) and coalescence index (CI) were examined. Additionally, physicochemical properties such as solubility, zeta potential, surface hydrophobicity, interfacial protein adsorption and protein conformation were analyzed. Results revealed significant pH-dependent variations in emulsifying performance. The poorest emulsifying performance was observed at pH 5, with the largest droplet size (28.84 μm) and highest CI (38.94 %). Optimal emulsifying properties were noticed at native pH, with the smallest droplet size (7.73 μm) and lowest CI (4.69). At pH 3, good emulsifying ability with the highest physical stability (5.43) were observed, associated with increased surface hydrophobicity and the presence of some aggregates contributing to the formation of cohesive interfacial film. Structural elements, particularly β-sheets and random coils, were positively correlated with emulsifying activity and stability, while β-turns had a negative impact. These findings provide insights into the pH-dependent emulsifying behavior of PPI, highlighting the complex relationship between protein structure and functionality, enabling the optimization of the use of PPI as an emulsifier in food applications.

Impact of pH on the Physicochemical, Structural, and Techno-Functional Properties of Sesame Protein Isolate

Sesame protein isolate (SPI) is a highly nutritious plant protein distinguished by its essential amino acid profile. This study investigates the influence of pH on SPI's physicochemical, structural, and techno-functional properties, highlighting its potential as a sustainable protein source for various food applications. Our findings revealed that SPI had a protein content of 90.60% and a protein extraction yield of 77.2%. The density is measured at 0.72 g/mL, with a critical compressibility index of 19.22, indicating excellent flowability for weaning foods. Notably, the ζ-potential shifts from +39 mV at pH 3.0 to 0 at the isoelectric point (pI, 5-5.5) and becomes negative at higher pH levels. We observed a direct correlation between solubility, fluorescence intensity, and functional characteristics of SPI, with peak solubility and functional properties at acidic and alkaline pH levels and lowest values at the pI. Structural analyses confirmed the relationship between electrical charge, hydrophobicity, and functional attributes, with the highest surface hydrophobicity observed at pH 2.0. In conclusion, our findings underscore the critical role of pH in modulating the physicochemical properties of sesame protein isolate, enhancing its applicability in food formulations. SPI demonstrates significant potential as a versatile ingredient in the functional food product development.

The effect of pH shifting on the calcium-fortified milk analogue with chickpea protein

Milk alternative attracts more attention due to nutrition benefits, but the low solubility and the calcium deficiency of plant protein hinder the development of milk alternatives. Therefore, pH shifting was optimized to improve chickpea protein solubility and calcium fortification while ensuring good digestibility. The results showed that pH shifting reduced the particle size from 2197.67 ± 178.2 nm to 80.2 ± 2 nm, and increased the net ζ potential from -0.48 ± 0.24 to -21.27 ± 0.65 due to the unfolding of secondary protein structure, by which chickpea protein bring better solution stability. Additionally, the whiteness of the solution with chickpea protein increased. The calcium addition kept the solution stable with small particle size despite a slight increase. The microstructure of chickpea protein during digestion was well disrupted even with fortifying calcium. This study provides proof of the positive effect of pH shifting on chickpea protein stability and calcium fortification.

Structure and functionality of Pleurotus geesteranus protein isolate as a function of pH

Edible mushroom proteins hold great potential for food applications, but those extracted using the alkaline extraction-acid precipitation method typically exhibit poor solubility in neutral water, with the structural changes during acid precipitation remaining unclear. In this study, Pleurotus geesteranus protein isolate (PGPI) with high water solubility was prepared with alkaline extraction, followed by dialysis and freeze-drying, and the effects of pH on the structural and functional properties of PGPI were systematically investigated. PGPI was enriched in essential and aromatic amino acids, and the molecular weight of bands in the sodium dodecyl sulfate-polyacrylamide gel electrophoresis profile was mainly distributed below 45 kDa. The zeta potential of PGPI changed from +16.84 to 17.58 mV when the pH increased from 2 to 9, with a pI of 4.3. At pH 7, PGPI showed a size of 232.7 nm. Away from pH 7, the particle size of PGPI increased. When the pH decreased from 7 to 2, PGPI exhibited a lower α-helix structure content and a higher β-sheet content and a gradual decrease in fluorescence intensity. In addition, as the pH approached 4, H0 and the content of SS group increased to a peak. These results indicated that lowering the pH induced the development of more ordered protein structure, which could be the primary reason for the poor water solubility of P. geesteranus protein obtained through alkaline extraction and acid precipitation. Additionally, these structural changes result in alterations to its functional properties, including water-holding capacity, oil-holding capacity, foaming capacity, foaming stability, emulsion activity index, and emulsion stability index.

Probiotic Milk Enriched with Protein Isolates: Physicochemical, Organoleptic, and Microbiological Properties

Incorporating plant protein isolates into milk can enhance probiotic culture growth by providing essential nutrients and altering the physicochemical properties of fermented milk. This study investigated the effects of adding 1.5% or 3.0% soy, pea, and whey protein isolates on the growth of Lacticaseibacillus casei and Lactobacillus johnsonii monocultures, as well as the physicochemical (acidity, syneresis, color) and organoleptic properties of fermented milk during 21 days of refrigerated storage. The results showed that 1.5% SPI and WPI did not significantly alter milk acidity compared to controls. Still, pH increased with 1.5% and 3.0% PPI. Storage time significantly affected pH in L. casei fermented milk. The initial addition of WPI at 1.5% and 3.0% reduced syneresis in L. casei fermented milk compared to other samples. Color components were significantly influenced by isolates. Initial L. casei cell counts were lower with SPI (LCS1.5 and LCS3) and 1.5% PPI (LCP1.5) compared to controls. Increasing isolate concentration from 1.5% to 3% enhanced L. johnsonii growth in WPI-milk but reduced L. casei in LCW3 compared to LCW1.5. Only increased pea protein concentration significantly increased L. casei growth. Probiotic populations generally were reduced during extended storage. Moreover, isolates impacted milk organoleptic evaluation. This research demonstrates the potential of protein isolates in creating health-promoting and diverse fermented products and offers insights into their interaction with probiotic cultures to advance functional food technologies.

Impact of pH on the structure, interfacial and foaming properties of pea protein isolate: Investigation of the structure - Function relationship

This study explored the relationship between pea protein foaming properties and their structure and physicochemical properties under neutral and acidic pH. Results showed that pH modified the zeta potential, particle size and surface tension due to electrostatic changes. FT-MIR and fluorescence spectra revealed pH-induced conformational changes, exposing hydrophobic groups and increasing sulfhydryl content, promoting protein aggregation. At pH 3, the highest foaming capacity (1.273) and lowest foam expansion (6.967) were observed, associated with increased surface hydrophobicity and net charges, ideal for creating light foams with high liquid incorporation for acidic beverages or fruit-based mousses. Pea protein isolate generated stable foams with foam volume stability between 86.662 % and 94.255 %. Although neutral pH conditions showed the highest foam volume stability, their air bubbles increased in size and transitioned from spherical to polyhedral shape, suitable for visual-centric applications, like cappuccino foam and beer-head retention. Foams at pH 5 exhibited the smallest bubbles and maintained their spherical shape, enhancing drainage resistance, beneficial for whipped toppings. Strong correlations (Pearson correlation coefficient higher than 0.600) were noted between the structure, surface and foaming properties, providing crucial insights into optimizing pea protein functionality across various pH conditions, enabling the development of plant-based foamed products with tailored properties.

Physicochemical property characterization, amino acid profiling and sensory evaluation of plant-based ice cream incorporated with soy, pea and milk proteins

This study examined the effects of incorporating milk protein concentrate (MPC), pea or soy proteins isolates (PPI and SPI) on the physicochemical, sensorial properties, and amino acid composition of ice creams containing 7% protein, in comparison to dairy ice cream as a reference. As protein ingredients, PPI exhibited higher water and oil holding capacity but lower surface hydrophobicity than SPI and MPC. Viscosity of the mixes were proportional to the firmness of ice cream, and both were highest with use of PPI. MPC ice cream had most similar physical and sensory properties to reference. PPI and SPI ice cream mixes showed higher extent of fat coalescence than MPC and reference. PPI and SPI conferred structural stability to ice cream with lower melting rate and better shape retention, and ability to delay ice recrystallization during temperature flocculation as compared with SMP and MPC. Confocal laser scanning microscope images indicated that higher extent of protein aggregation and more air cells were found in PPI ice cream. Sensory and amino acid profile results revealed that PPI and SPI ice creams were inferior in taste, texture, and essential amino acids like methionine. This study offers insights for the development of high protein frozen desserts.

A comparison of the quality of UHT milk and its plant-based analogs

The aim of this study was to compare selected physical (density) and physicochemical (color, pH, titratable acidity) properties and the fatty acid profile of dairy UHT milk and its plant-based analogs, i.e., almond, soy, rice, oat, and coconut beverages. Ten products of each type were analyzed in each group. UHT milk was characterized by higher values of color lightness (L*) and titratable acidity than all plant-based milk alternatives, higher yellowness (b*) than rice drink, higher density than almond drink, and higher pH than rice and coconut drinks. In comparison with UHT milk, all plant-based beverages were characterized by higher redness (a*), soy drink was characterized by higher values of b* and chroma (C*), and almond and soy drinks had higher pH values. In the group of non-dairy beverages, the values of b* and C* were highest in soy drink, and the value of a* was highest in almond drink. Almond drink had the highest pH value, and soy and coconut drinks had the highest titratable acidity. Rice drink had higher density than oat, soy and almond drinks. The indicators characterizing the nutritional value of fat were considerably lower in coconut drink and dairy milk than in the remaining products. The values of UFA/SFA, MUFA/SFA, and DFA/OFA ratios and the indicator of nutritional value were highest in rice drink. The PUFA/SFA ratio and the total content of EFAs were highest in soy drink, and the n-6/n-3 PUFA ratio was highest in almond drink.

Ultrasonication-Assisted Green Synthesis and Physicochemical and Cytotoxic Activity Characterization of Protein-Based Nanoparticles from Moringa oleifera Seeds

Moringa oleifera (M. oleifera) is globally recognized for its medicinal properties and offers high-quality, protein-rich seeds. This study aimed to explore the potential of M. oleifera seeds as a significant source of protein-based nanoparticles (PBNPs) using the ultrasonication technique after desolvation and to evaluate their cytotoxicity in the human leukemia cell line (THP-1) for the first time. The properties of the PBNPs were confirmed by dynamic light scattering (DLS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR). The extracted protein from moringa seed cake flour had a significant protein content of 54.20%, and the resulting PBNPs had an average size of 134.3 ± 0.47 nm with a robust zeta potential of -43.15 mV. Notably, our study revealed that PBNPs exhibited cytotoxic potential at high concentrations, especially against the THP-1 human leukemia cell line, which is widely used to study immunomodulatory properties. The inhibitory effect of PBNPs was quantitatively evidenced by a cytotoxicity assay, which showed that a concentration of 206.5 μg mL-1 (log conc. 2.315) was required to inhibit 50% of biological activity. In conclusion, our findings highlight the potential of M. oleifera seeds as a valuable resource in the innovative field of eco-friendly PBNPs by combining traditional medicinal applications with contemporary advancements in protein nanotechnology. However, further studies are required to ensure their biocompatibility.

A comparison of the quality of plain yogurt and its analog made from coconut flesh extract

The aim of this study was to compare the quality of plain yogurt made from cow milk (n = 10) and its plant-based analog made from coconut flesh extract (n = 14). Coconut yogurt alternatives were divided into 2 experimental groups based on differences in their color, which were noted after the packages had been opened. The first group included products with a typical white color (n = 8), and the second group comprised products with a grayish pink color (n = 6) that developed as a result of oxidative processes. In comparison with its plant-based analog, plain yogurt was characterized by higher values of lightness (L*), yellowness (b*) and chroma (C*), higher titratable acidity, a higher content of retinol and α-tocopherol, higher nutritional value of fat, and lower values of water-holding capacity (WHC) and redness (a*). Plain yogurt had lower volatile acidity than its plant-based analog with a grayish pink color. A comparison of yogurt analogs with different colors revealed that the product with a grayish pink color was characterized by a lower value of L*, and higher values of a*, b*, C*, and pH. An analysis of its fatty acid profile demonstrated that it also had a higher proportion of C14:0 and C18:1 cis-9; higher total monounsaturated fatty acids content; a lower proportion of C10:0, C12:0, and C18:2; a lower total content of polyunsaturated fatty acids (PUFA) and essential fatty acids; and a lower ratio of PUFA to saturated fatty acids. The yogurt analog with a grayish pink color had a lower total content of tocopherol isoforms than the remaining products. The yogurt analog with a white color had the highest WHC and γ-tocopherol content. Consumers should be aware of the fact that coconut yogurt alternatives may have nonstandard quality attributes. The differences between such products and yogurt made from cow milk should be explicitly communicated to consumers so that they could make informed purchasing decisions.

Oral Astringency in Plant Proteins: An Underestimated Issue in Formulating Next-Generation Plant-Based Foods

Ensuring the supply of affordable, palatable, healthy, and sustainable nutrients to feed the growing population without transgressing the planetary boundaries remains a key challenge in the food science community. A dietary transition toward low-emission, plant-based foods, with less reliance on animal agriculture, is advocated for sustainability, health, and ethical reasons. A major hurdle for mainstream adoption of plant-based foods is their poor sensorial performance, such as nonjuicy and astringent textures as well as various off-flavors. This review presents the current understanding of astringency and oral friction of plant-based foods. It focuses on plant proteins and their application in plant-based meat and dairy analogs. In addition, the latest advances in the quantitative characterization of astringency using tribology, electrochemistry, and cellular tools are covered. Finally, we examine factors influencing astringency and propose easy-to-implement colloidal strategies that may mitigate astringency issues, thereby underpinning the design of the next generation of sustainable and pleasurable plant-based foods.

Heat-Induced Gelation of Chickpea and Faba Bean Flour Ingredients

This study aimed to investigate the gelling behavior of faba bean (FB) and chickpea (CP) flour between 10 and 20% (w/w) concentration at pH 3.0, 5.0, and 7.0. Both sources formed at pH 3.0 and 5.0 self-standing gels with 12% (w/w) of flour, while 16% (w/w) of flour was required to obtain a gel at pH 7.0. During gelling between 40 and 70 °C, a sharp increase of the elastic modulus G' was observed in both flours, mainly due to water absorption and swelling of the starch, one of the major constituents in the ingredients. Increasing the temperature at 95 °C, G' increased due to the denaturation of globulins and therefore the exposure of their internal part, which allowed more hydrophobic interactions and the formation of the gel. After cooling, both FB and CP gels displayed a solid-like behavior (tan δ ranging between 0.11 and 0.18) with G' values at pH 3.0 and 5.0 significantly (p < 0.05) higher than those at pH 7.0, due to the lower electrostatic repulsions at pHs far from the isoelectric point. The rheological properties were supported by the water binding capacity values, confirming the better gels' strength described by rheological analysis. These results will enhance our understanding of the role of legume flours in formulating innovative and sustainable food products as alternatives to animal ones.

Supercritical CO2 Treatment to Modify Techno-Functional Properties of Proteins Extracted from Tomato Seeds

Tomato seeds are a rich source of protein that can be utilized for various industrial food purposes. This study delves into the effects of using supercritical CO2 (scCO2) on the structure and techno-functional properties of proteins extracted from defatted tomato seeds. The defatted meal was obtained using hexane (TSMH) and scCO2 (TSMC), and proteins were extracted using water (PEWH and PEWC) and saline solution (PESH and PESC). The results showed that scCO2 treatment significantly improved the techno-functional properties of protein extracts, such as oil-holding capacity and foaming capacity (especially for PEWC). Moreover, emulsifying capacity and stability were enhanced for PEWC and PESC, ranging between 4.8 and 46.7% and 11.3 and 96.3%, respectively. This was made possible by the changes in helix structure content induced by scCO2 treatment, which increased for PEWC (5.2%) and decreased for PESC (8.0%). Additionally, 2D electrophoresis revealed that scCO2 hydrolyzed alkaline proteins in the extracts. These findings demonstrate the potential of scCO2 treatment in producing modified proteins for food applications.

Study of the Technological Properties of Pedrosillano Chickpea Aquafaba and Its Application in the Production of Egg-Free Baked Meringues

Aquafaba is a by-product derived from legume processing. The aim of this study was to assess the compositional differences and the culinary properties of Pedrosillano chickpea aquafaba prepared with different cooking liquids (water, vegetable broth, meat broth and the covering liquid of canned chickpeas) and to evaluate the sensory characteristics of French-baked meringues made with the different aquafaba samples, using egg white as a control. The content of total solids, protein, fat, ash and carbohydrates of the aquafaba samples were quantified. Foaming and emulsifying capacities, as well as the foam and emulsions stabilities were determined. Instrumental and panel-tester analyses were accomplished to evaluate the sensory characteristics of French-baked meringues. The ingredients added to the cooking liquid and the intensity of the heat treatment affected the aquafaba composition and culinary properties. All types of aquafaba showed good foaming properties and intermediate emulsifying capacities; however, the commercial canned chickpea's aquafaba was the most similar to egg white. The aquafaba meringues showed less alveoli, greater hardness and fracturability and minimal color changes after baking compared with egg white meringues; the meat and vegetable broth's aquafaba meringues were the lowest rated by the panel-tester and those prepared with canned aquafaba were the highest scored in the sensory analysis.