Synergistic modification of pea protein structure using high-intensity ultrasound and pH-shifting technology to improve solubility and emulsification

Effects of different thermal sterilization conditions on the quality of ready-to-eat shrimp based on specific sterilization intensity

The effects of different thermal sterilization conditions on the quality and digestibility of ready-to-eat (RTE) shrimp were investigated. Compared with the high-temperature (121 °C) and short-time (6 min and 8 min) sterilization, the low-temperature (110 and 115 °C) and long-time (>20 min) sterilization significantly promoted the Maillard and browning reactions and changed the color of the RTE-shrimp. The high sterilization temperature promoted shrimp protein oxidation, resulting in increased carbonyl group, disulfide bond, and free radical content, while the free sulfhydryl group content decreased. This oxidation and tissue destruction at high temperature led to reduced texture properties and altered water distribution within the shrimp's muscles. However, sterilized shrimp exhibited superior digestive properties in an in vitro simulated digestion experiment. High-temperature and short-time sterilization is more effective in mitigating the quality deterioration of RTE-shrimp compared to low-temperature and long-time sterilization.

A comprehensive review on the recent trends in extractions, pretreatments and modifications of plant-based proteins

Plant-based proteins offer sustainable and nutritious alternatives to animal proteins with their techno-functional attributes influencing product quality and designer food development. Due to the inherent complexities of plant proteins, proper extraction and modifications are vital for their effective utilization. This review highlights the emerging sources of plant-based proteins, and the recent statistics of the techniques employed for pretreatment, extraction, and modifications. The pretreatment, extraction and modification approach to modify plant proteins have been classified, addressed, and the recent applications of such methodologies are duly indicated. Furthermore, this study furnishes novel perspectives regarding the potential impacts of emerging technologies on the intricate dynamics of plant proteins. A thorough review of 100 articles (2018-2024) shows the researchers' keen interest in investigating novel plant proteins and how they can be used; seeds being the main source for protein extraction, followed by legumes. Use of by-products as a protein source is increasing rapidly, which is noteworthy. Protein studies still lack knowledge on protein fraction, antinutrients, and pretreatments. The use of physical methods and their combination with other techniques are increasing for effective and environmentally friendly extraction and modification of plant proteins. Several studies explore the effect of protein changes on their function and nutrition, especially with a goal of replacing ingredients with plant proteins that have improved or enhanced qualities. However, the next step is to investigate the sophisticated modification methods for deeper insights into food safety and toxicity.

Enhancing the usability of pea protein in emulsion applications through modification by various approaches: A comparative study

The extensive utilization in food industry of pea protein is often impeded by its low water solubility, resulting in poor functional properties. Various methods, including pH-shifting (PS), ultrasonication (US), high-pressure micro-fluidization (MF), pH-shifting combined with ultrasonication (PS-US), and pH-shifting with micro-fluidization (PS-MF), were utilized to modify pea protein isolate (PPI) in order to enhance its functionality in emulsion formulation. The physicochemical properties and structural changes of the protein were investigated by assessing solubility, particle size, surface charge, protein profile, surface hydrophobicity, free sulfhydryl groups, and secondary structure content. The extent of modification induced by each treatment method on PPI-stabilized emulsions was compared based on parameters such as adsorbed interfacial protein concentration, particle size, zeta potential, and microstructure of the prepared emulsions. All modification increased the solubility of pea protein in the sequence of PS (4-fold) < MF (7-fold) < US (11-fold) < PS-US (13-fold) < PS-MF (14-fold). For single treatments, proteins dissolved more readily under US, resulting in the most uniform emulsions with small particle. The combined processes of PS-US and PS-MF further improved solubility, decreased emulsions particle size, promoted uniformity of emulsions. PS-US-stabilized emulsions displayed more smaller droplet size, narrower size distribution, and slightly higher stability than those prepared by PS-MF. The relatively higher emulsifying capacity of PPI treated by PS-US than those by PS-MF may be attributed to its higher surface hydrophobicity.

Encapsulation of Lactobacillus plantarum in W1/O/W2 double emulsions stabilized with the high-intensity ultrasound-treated pea protein and pectin

This study focuses on developing a water-in-oil-in-water (W1/O/W2) double emulsion system using high-intensity ultrasound (HIU)-treated pea protein isolate (HIU-PPI) and pectin to encapsulate Lactobacillus plantarum (L. plantarum). The effects of ultrasound treatment on pea protein isolate (PPI) characteristics such as solubility, particle size, emulsification, surface hydrophobicity, and surface free sulfhydryl group were examined, determining optimal HIU processing conditions was 400 W for 10 min. The developed W1/O/W2 double emulsion system based on HIU-PPI demonstrated effective encapsulation and protection of L. plantarum, especially at the HIU-PPI concentration of 4 %, achieving an encapsulation efficiency of 52.65 %. Incorporating both HIU-PPI and pectin as emulsifiers increased the particle size and significantly enhanced the emulsion's viscosity. The highest bacterial encapsulation efficiency of the emulsion, 59.94 %, was attained at a HIU to pectin concentration ratio of 3:1. These emulsions effectively encapsulate and protect L. plantarum, with the concentration of HIU-PPI being a critical factor in enhancing probiotic survival under simulated gastrointestinal digestion. However, the concurrent utilization of pectin and HIU-PPI as emulsifiers did not provide a notable advantage compared to the exclusive use of HIU-PPI in enhancing probiotic viability during in vitro simulated digestion. This research offers valuable perspectives for the food industry on harnessing environmentally friendly, plant-based proteins as emulsifiers in probiotic delivery systems. It underscores the potential of HIU-modified pea protein and pectin in developing functional food products that promote the health benefits of probiotics.

Unraveling the effect of combined heat and high-pressure homogenization treatment on the improvement of chickpea protein solubility from the perspectives of colloidal state change and structural characteristic modification

Chickpea protein (CP) is a promising plant protein ingredient, but the poor solubility has limited its broad application. In this study, heating followed by high-pressure homogenization (HPH) was used to improve the solubility of CP. The results showed that combined heat (80℃, 30 min) and HPH (80 MPa, 2 cycles) treatment exhibited an additive effect in improving the solubility of CP. This improvement could be attributed to the dissociation and the rearrangement of large insoluble protein aggregates into small-sized soluble protein aggregates, the increased exposure of hydrophobic residues and reactive sulfhydryl groups, the transformation of α-helices to β-sheets and β-turns. Moreover, the 11S subunits of CP could form reinforced disulfide covalent cross-links under heating + HPH, which may provide steric hindrance preventing the reassembly of large protein bodies. This work proposes an interesting approach to enhance the physicochemical properties of CP for tailoring techno-functional plant protein ingredients in food formulations.

Liposomes decorated with β-conglycinin and glycinin: Construction, structure and in vitro digestive stability

Liposomes were modified with different proportions of β-conglycinin (7S) and glycinin (11S) to form Lip-7S and Lip-11S. The morphology, interaction and in vitro simulated digestion of liposomes were studied. The particle size of Lip-7S was smaller than that of Lip-11S. When the values of Lip-7S and Lip-11S were 1:1 and 1:0.75, respectively, the ζ-potential had the maximum absolute value and the dispersion of the system was good. The results of multispectral analysis showed that hydrogen-bond and hydrophobic interaction dominated protein-modified liposomes, the protein structure adsorbed on the surface of liposomes changed, the content of α-helix decreased, and the structure of protein-modified liposomes became denser. The surface hydrophobicity and micropolarity of liposomes decreased with the increase of protein ratio, and tended to be stable after Lip-7S (1:1) and Lip-11S (1:0.75). Differential scanning calorimetry showed that Lip-7S had higher phase transition temperature (≥170.5 °C) and better rigid structure. During simulated digestion, Lip-7S (22.5 %) released less Morin than Lip (40.6 %) and Lip-11S (26.2 %), and effectively delayed the release of FFAs. The environmental stability of liposomes was effectively improved by protein modification, and 7S had better modification effect than 11S. This provides a theoretical basis for 7S and 11S modified liposomes, and also provides a data reference for searching for new materials for stabilization of liposomes.

Pea protein-inulin conjugate prepared by atmospheric pressure plasma jet combined with glycosylation: structure and emulsifying properties

Pea protein is one of plant proteins with high nutritional value, but its lower solubility and poor emulsifying properties limit its application in food industry. Based on wet-heating glycosylation of pea protein and inulin, effects of discharge power of atmospheric pressure plasma jet (APPJ) on structure, solubility, and emulsifying ability of pea protein-inulin glycosylation conjugate were explored. Results indicated that the APPJ discharge power did not affect the primary structure of pea protein. However, changes in secondary and spatial structure of pea protein were observed. When APPJ discharge power was 600 W, the solubility of glycosylation conjugate was 75.0% and the emulsifying stability index was 98.9 min, which increased by 14.85 and 21.95% than that of only glycosylation sample, respectively. These findings could provide technical support for APPJ treatment combination with glycosylation to enhance the physicochemical properties of plant-based proteins.

High internal phase Pickering emulsions stabilized by the complexes of ultrasound-treated pea protein isolate/mung bean starch for delivery of β-carotene

High internal phase Pickering emulsions (HIPPEs) stabilized by edible colloid particles have gained great interest. In this study, ultrasound-treated pea protein isolate and mung bean starch complexes (UPPI/MS) were prepared and used in stabilization of HIPPEs. The emulsifying properties of UPPI/MS were found to be superior to those of pea protein isolate (PPI), as evidenced by a smaller particle size and higher surface hydrophobicity. HIPPEs stabilized by UPPI/MS displayed a higher viscoelastic and gel-like structure. Low-Field NMR (LF-NMR) revealed that HIPPEs stabilized by UPPI60/MS (UPPI60/MS-HIPPEs) showed better ability to restrict the mobility of water. UPPI60/MS-HIPPEs also revealed the best environmental stability attributed a stronger three-dimensional network structure. Encapsulation of β-carotene within HIPPEs resulted in improving stability, with UPPI60/MS-HIPPEs exhibiting the highest retention rate of 73.58 %. Moreover, β-carotene encapsulated in HIPPEs displayed enhanced bioaccessibility, with UPPI60/MS-HIPPEs achieving the highest value of 25.37 %. This research highlighted the potential of UPPI60/MS complexes as effective stabilizers for HIPPEs and provided new insights on HIPPEs in nutrient delivery systems.

Pea protein [Pisum sativum] as stabilizer for oil/water emulsions

A map of stability for various water/oil/pea protein compositions has been plotted from the numerous reported results. Two clear regions of stability were identified. High internal oil phase emulsions with 70-80%, v/v oil content stabilized by total pea protein concentration <2.5%, w/v showed stability. Low oil content of 10-30%, v/v for a range of total pea protein concentrations >0.5%, w/v have also been identified as stable. Intermediate oil content and pea protein concentrations >4% w/v are unexplored regions and are likely to be areas of fruitful future research. The wide range of stability suggests that different stabilization mechanisms could be important for different compositions and careful consideration has to be taken to avoid oversimplification. Both stabilization with particles, i.e. Pickering emulsions, and protein unfolding have been suggested as mechanisms. The diverse way of describing stability makes it difficult to intercompare results in different studies. A summary of different oil types used have been presented and several properties such as dynamic viscosity, density, the dielectric constant and interfacial tension have been summarized for common vegetable oils. The type of vegetable oil and emulsion preparation techniques were seen to have rather little effect on emulsion stability. However, the different extraction methods and processing of the pea material had more effect, which could be attributed to changing composition of different proteins and to the states of aggregation and denaturing. Careful consideration has to be taken in the choice of extraction method and an increased understanding of what contributes to the stability is desirable for further progress in research and eventual product formulation.

Structure and functionality of whey protein, pea protein, and mixed whey and pea proteins treated by pH shift or high-intensity ultrasound

Three modifications (pH shift, ultrasound, combined pH shift and ultrasound) induced alterations in pure whey protein isolate (WPI), pea protein isolate (PPI), and mixed whey and pea protein (WPI-PPI) were investigated. The processing effect was related to the protein type and technique used. Solubility of WPI remained unchanged by various treatments. Particle size was enlarged by pH shift while reduced by ultrasound and combined approach. All methods exposed more surface hydrophobic groups on WPI, while pH shift and joint processing was detrimental to its emulsifying activity. The PPI and mixture exhibited similar responses toward the modifications. Solubility of PPI and the blend enhanced in the sequence of pH shift and ultrasound > ultrasound > pH shift. Individual approach expanded while co-handling diminished the particle diameter. Treatments also caused more disclosure of hydrophobic regions in PPI and WPI-PPI and emulsifying activity was ameliorated in the order of pH shift and ultrasound > ultrasound > pH shift.

Combination of pH-shifting, ultrasound, and heat treatments to enhance solubility and emulsifying stability of rice protein isolate

Rice protein isolates (RPI) are promising plant-protein sources but present low solubility and poor surface activity in neutral conditions. Improving these characteristics is a crucial challenge to capitalize on them. This is the first work performing pH-shifting, ultrasound, and heat treatments on a commercial RPI. The combined approaches increased the protein solubility (from ∼2.7% to ∼91.8%) and surface hydrophobicity (up to ∼283%) and induced the formation of less compact and more dispersed protein aggregates. The pH-shifting induced the unfolding of protein molecules and aggregates making them available for modification by both ultrasound and heating, which are supposed to induce further protein unfolding, exposure of buried hydrophobic amino acid, and protein hydrolysis. Also, the combined approaches generated modified RPI able to form oil-in-water emulsions with reduced particle size and enhanced stability than the untreated RPI. Therefore, this work presents an effective combined approach to enhance the techno-functional properties of rice proteins.

Influence of varying oil phase volume fractions on the characteristics of flaxseed-derived diglyceride-based Pickering emulsions stabilized by modified soy protein isolate

This research aimed to create Pickering emulsions using modified soy protein isolate (SPI) as a stabilizer and flaxseed-derived diglyceride (DAG) as an oil phase. The SPI was modified through a process involving both heating and ultrasound treatment. The result indicated that the droplet size of emulsions increased with the increase in oil content (p < 0.05). For instance, the largest droplet size (23 µm) was observed at an oil-to-SPI dispersion ratio of 4:1 ratio (φ = 80), whereas the smallest droplet size (6.39 µm) was noticed at the 1:4 ratio. During the 7-day storage period, the emulsions with a 4:1 ratio (φ = 80) showed the lowest droplet size increase (from 23 µm to 25.58 µm). In contrast, the emulsions with a 1:1 ratio displayed the highest increase (from 19.39 µm to 74.29 µm). Creaming index results revealed that emulsions with a 4:1 ratio (φ = 80) showed no signs of creaming and phase separation than all other treatments (p < 0.05). Backscattering fluctuations (ΔBS) and turbiscan stability index (TSI) showed that emulsions with 4:1, 2:1, and 1:1 oil-to-SPI dispersion ratios had consistent ΔBS curves with higher and TSI curves with lower values. Optical microscopy, confocal laser scanning, and cryo-scanning electron microscopy revealed that emulsions with oil-to-SPI dispersion ratios of 4:1 and 2:1 had well-organized structures with no visible coalescence. Macromorphological and microrheological investigations demonstrated that emulsions with 80% oil content had the highest viscosity, both moduli, elasticity index, macroscopic viscosity index, and the lowest fluidity index and solid-liquid balance values. Moreover, these emulsions were more resistant to centrifugation and storage environments. In conclusion, the study determined that flaxseed-derived DAG-based high internal phase Pickering emulsions (φ = 80) had superior stability, improved viscoelasticity, and better rheological properties.

Improvement of the emulsifying properties of Zanthoxylum seed protein by ultrasonic modification

The influence of ultrasonic treatment (100-500 W, 30 min) on the molecular structures and emulsifying properties of Zanthoxylum seed protein (ZSP) was explored for the first time in this work. Research results indicated that the all ultrasonic treatments at different power levels decreased the particle size but increased the surface charge of ZSP. In addition, the ultrasonic treatments induced the structural unfolding of the ZAP, as indicated by the increase in α-helix, ultraviolet-visible absorbance, surface hydrophobicity and the amount of surface free sulfhydryl groups, as well as the decrease in β-sheet and intrinsic fluorescence intensity. As a result, the significantly (p < 0.05) increased emulsifying activity index (EAI) and emulsion stability index (ESI) of ZSP were observed after ultrasonic treatment. In addition, the emulsion prepared by ultrasonically treated ZSP exhibited the smaller and more uniform droplets with significantly improved stability against environmental stress (temperature, salt concentration, pH), creaming and oxidation due to the increased ratio of interfacially adsorbed ZSP. Furthermore, ultrasonic treatment at 400 W was found to be the optimum condition for modification. These findings will provide a theoretical foundation for the utilization of ultrasound in enhancing the emulsifying properties of ZSP and promoting its application in the field of food processing.

Evaluation of sono-physico-chemical and processing effects in the mixed sarcoplasmic protein/soy protein isolate system

Since it may be employed to guide the production of high-quality plant protein as a partial substitute for animal protein using sono-physico-chemical effects, it is important to investigate the mixing of animal and plant protein in ultrasound (UID)-assisted processing systems. A study group of sono-physico-chemical processing with five distinct soy protein isolate (SPI)/ sarcoplasmic protein (SPN) ratios was developed in this work. The results showed that adding additional SPN to the mixed protein can increase its sono-physico-chemical impact, and this effect is greatest when the ratio of SPI to SPN is 1:3. The high SPN group's grafting rate rose from 39.13% to 55.26% in comparison to the high SPI content group. Quercetin (Que) may more readily modify SPN than SPI in the "dual protein" system used in this work, highlighting the critical function of plant protein in controlling the effects of UID-assisted processing in the "dual protein" system. Changes in apparent viscosity and microstructure are the primary parameters that affect the severity of sono-physico-chemical effects in SPI/SPN mixed protein systems, in addition to structural variables.

Optimization of ultrasound-assisted cellulase degradation method on the extraction of mulberry leaf protein and its effect on the functional characteristics

The mulberry leaf protein extracted by ultrasound-assisted cellulase degradation (UACD) method was optimized with the protein dissolution amount (PDA) as the index. The Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy of extracted mulberry leaf protein were measured. The functional characteristics of protein extracted by the UACD method were evaluated. Results showed that the extraction condition was optimized and adjusted to the following parameters: pH value of 7.20, ultrasound temperature of 35.00 °C, enzyme dosage of 4.20% and ultrasound time of 10.00 min. Under these optimized conditions, the experimental verification value of PDA was 13.87 mg/mL, which was approaching to the predicted value of 13.54 mg/mL. The analysis results of FTIR showed that after extraction by the UACD method, the mulberry leaf protein with the vibrational peak of ester carbonyl (C = O) absorption peak (1734.66 cm-1) disappeared. The α-helix content of protein extracted by the UACD decreased by 8.13%, and the β-turn and random coil content of protein increased by 20.22% and 18.79%, respectively, compared to that of the blank. The microstructure of mulberry leaf protein showed that the UACD method could break the dense structure of protein raw materials, reduce the average size of proteins and increase the specific surface area and roughness of proteins. According to the results of functional characteristics, the mulberry leaf protein extracted by the UACD method presented the highest enzymolysis properties and solubility, which was beneficial for the application in the food industry. In conclusion, the UACD method was a very effective way to extract protein from mulberry leaf.

Functionalization of pine kernel protein by pH-shifting combined with ultrasound treatments: Further improvement with increasing acidity

As a novel plant protein, developing various aspects of pine kernel protein (PKP) functionality is essential to meet the demand for protein-rich foods. To achieve this, the PKP was functionalized by a combination of pH-shifting and ultrasound techniques. The solubility, emulsification and droplet stability of the PKP in the pH range suitable to food (pH 3 to 7) were further investigated. The pH 12-shifting was an effective strategy to increase the solubility of PKP under extreme acidic and neutral conditions, characterized by a higher content of β-sheets and random coils, a greater exposure of free sulfhydryl and hydrophobic groups. Furthermore, appropriate ultrasonic power (250 W) further improved the solubility of PKPs by disrupting intermolecular hydrogen and hydrophobic bonds. As the ambient acidity increased, the emulsions exhibited higher viscoelasticity and stronger protein interactions. Especially at pH 3, the oil droplets stabilized by U250-PKP-12 (PKP treated with 250 W ultrasound-assisted pH 12-shifting) were homogeneously dispersed and surrounded by dense protein, maintaining small particle size and large electrostatic repulsion, and there was no apparent creaming or phase separation in the emulsions after 10 days of storage. Thus, the functionality of PKP after pH-shifting combined with ultrasonic treatments is further enhanced by increasing the environmental acidity.

Intestine-targeted high internal phase Pickering emulsion formulated using silkworm pupa protein via ultrasonic treatment

High internal phase Pickering emulsions (HIPPEs) stabilized by food grade particles have received much attention as deliver vehicles for bioactives in recent years. In this study, ultrasonic treatment was conducted to regulate the size of silkworm pupa protein (SPP) particles, fabricating oil-in-water (O/W) HIPPEs with intestinal releasability. Briefly, the pretreated SPP and SPP-stabilized HIPPEs were characterized, and the targeting release was investigated using in vitro gastrointestinal simulations and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Results revealed ultrasonic treatment time was the key factor regulating emulsification performance and stability of HIPPEs. Optimized SPP particles were obtained based on their size and zeta potential of 152.67 nm and 26.77 mV, respectively. With ultrasonic treatment, the hydrophobic groups in the secondary structure of SPP were exposed, facilitating the formation of a stable oil-water interface for HIPPEs. Additionally, SPP-stabilized HIPPE showed high stable against the gastric digestion. The SPP with 70 kDa molecular weight, which was the major interfacial proteins of the HIPPE, can be hydrolyzed by intestinal digestive enzymes, enabling the intestine-targeted release of the emulsion. Overall, in the present study, a facile method was developed to stabilize HIPPEs using solo SPP with ultrasonic treatment to protect and deliver hydrophobic bioactive ingredients.

Preparation and characterization of soy protein isolate films by pretreatment with cysteine

The effect of cysteine concentration on the viscosity of soy protein isolate (SPI)-based film-forming solution (FFS) and physicochemical properties of SPI films was investigated. The apparent viscosity of FFS decreased after adding 1 mmol/L cysteine but did not change after adding 2-8 mmol/L cysteine. After treatment with 1 mmol/L cysteine, the film solubility decreased from 70.40% to 57.60%, but the other physical properties did not change. The water vapor permeability and contact angle of SPI films increased as cysteine concentration increased from 4 mmol/L to 8 mmol/L, whereas the film elongation at break decreased. Based on scanning electron microscopy and X-ray diffraction results, cysteine crystallization could be aggregated on the surface of SPI films treated with 4 or 8 mmol/L cysteine. In conclusion, pretreatment with approximately 2 mmol/L cysteine could reduce the viscosity of SPI-based FFS, but did not change the physicochemical properties of SPI films.

Characteristics of enzymolysis of silkworm pupa protein after tri-frequency ultrasonic pretreatment: kinetics, thermodynamics, structure and antioxidant changes

As a by-product of the sericulture industry, the utilization rate of silkworm pupa resources is currently not high. Proteins are converted into bioactive peptides through enzymatic hydrolysis. Not only can it solve the utilization problem, but it also creates more valuable nutritional additives. Silkworm pupa protein (SPP) was pretreated with tri-frequency ultrasonic (22/28/40 kHz). Effects of ultrasonic pretreatment on enzymolysis kinetics, enzymolysis thermodynamics, hydrolysate structure as well as hydrolysate antioxidant of SPP were investigated. Ultrasonic pretreatment significantly increased the hydrolysis efficiency, showing a 6.369% decrease in k _m and a 16.746% increase in k _A after ultrasonic action (p < 0.05). The SPP enzymolysis reaction followed a second-order rate kinetics model. Evaluation of enzymolysis thermodynamics revealed that Ultrasonic pretreatment markedly enhanced the SPP enzymolysis, leading to a 21.943% decrease in E _a. Besides, Ultrasonic pretreatment significantly increased SPP hydrolysate's surface hydrophobicity, thermal stability, crystallinity, and antioxidant activities (DPPH radical scavenging activity, Fe²⁺ chelation ability, and reducing power). This study indicated that tri-frequency ultrasonic pretreatment could be an efficient approach to enhancing the enzymolysis and improving the functional properties of SPP. Therefore, tri-frequency ultrasound technology can be applied industrially to enhance enzyme reaction process.

Legume protein/polysaccharide food hydrogels: Preparation methods, improvement strategies and applications

For the development of innovative foods and nutritional fortification, research into food gel is essential. As two types of rich natural gel material, both legume proteins and polysaccharides have high nutritional value and excellent application potential, attracting wide attention worldwide. Research has focused on combining legume proteins with polysaccharides to form hybrid hydrogels as their combinations show improved texture and water retention compared to single legume protein or single polysaccharide gels, and these properties can be tailored for specific applications. This article reviews hydrogels of common legume proteins and discusses heat induction, pH induction, salt ion induction, and enzyme-induced assembly of legume protein/polysaccharide mixtures. The applications of these hydrogels in fat replacement, satiety enhancement, and delivery of bioactive ingredients are discussed. Challenges for future work are also highlighted.

Incorporation of α-Tocopherol into Pea Protein Edible Film Using pH-Shifting and Nanoemulsion Treatments: Enhancing Its Antioxidant Activity without Negative Impacts on Mechanical Properties

The aim of this study is to develop an antioxidant film based on pea protein isolate (PPI) without sacrificing the packaging properties. To achieve this, α-tocopherol was incorporated to impart antioxidant activity to the film. We investigated the effects on film properties resulting from the addition of α-tocopherol in a nanoemulsion form and pH-shifting treatment of PPI. The results revealed that direct addition of α-tocopherol into un-treated PPI film disrupted film structure and formed a discontinuous film with rough surface, and thereby significantly decreasing the tensile strength and elongation at break. However, pH-shifting treatment in combination with the α-tocopherol nanoemulsion, formed a smooth and compact film, which greatly improved the mechanical properties. It also significantly changed the color and opacity of PPI film, but had little effects on film solubility, moisture content, and water vapor permeability. After the addition of α-tocopherol, the DPPH scavenging ability of PPI film was greatly improved and the release of α-tocopherol was mainly within the first 6 h. Additionally, pH-shifting and nanoemulsion did not affect the film's antioxidant activity nor the release rate. In conclusion, pH-shifting combined with nanoemulsion is an effective method to incorporate hydrophobic compounds such as α-tocopherol into protein-based edible films without negative impacts on film mechanical properties.

High Internal Phase Emulsions Stabilized by Pea Protein Isolate Modified by Ultrasound Combined with pH-Shifting: Micromorphology, Rheology, and Physical Stability

In this study, the interfacial behavior of high internal phase emulsions (HIPEs), stabilized by ultrasound combined with pH-shifting modified pea protein isolate (MPPI), was investigated, and its emulsification process and stabilization mechanism were discussed. The effects of MPPI concentration on the micromorphology, droplet size, rheology, and stability of HIPEs were investigated. As the MPPI concentration increased, the appearance of HIPEs gradually changed from a relatively fluid state to a plastic solid-like state with detailed texture. There occurred a gradual decrease in droplet size, the cohering of an orderly and tight arrangement, in addition to the formation of a bilayer elastic interface layer. The macro- and microrheological assessments confirmed that the apparent viscosity, storage modulus, elasticity index, and macroscopic viscosity index increased gradually. Furthermore, it was demonstrated that 5 wt% MPPI-stabilized HIPEs had the potential to be used as 3D printing inks. Stability evaluation showed that the TURBISCAN stability index decreased and centrifugal stability increased. The appearance and microstructure remained highly stable after heating at 80 °C for 30 min and storage at 4 ℃ for 90 days. These findings confirm that MPPI improves the rheological behavior and stability of HIPEs by modulating the interfacial adsorption and network structure.

Sonochemical Effects on the Preparation, Structure and Function of Gliadin-(-)-Epigallo-Catechin 3-Gallate Conjugates

It is essential to understand the mechanism of action of ultrasound synergistic free radical oxidation to promote covalent reactions between proteins and polyphenols. (-)-epigallo-catechin 3-gallate (EGCG) with rich bioactivity could be used to increase the functional properties of cereal protein-gliadin (GL). This study systematically explored the role of ultrasound treatment (US) on the binding mechanisms of GL and EGCG. Electrophoresis and high-performance liquid chromatography (HPLC) confirmed the greater molecular mass of the covalent complexes in the ultrasound environment. Quantitative analysis by the phenol content revealed that the ultrasound environment increased the EGCG content in the covalent complex by 15.08 mg/g of protein. The changes in the spatial structure of the proteins were indicated by Fourier infrared and ultraviolet spectroscopy. Additionally, scanning electron microscopy (SEM) and atomic force microscopy (AFM) found that US disrupted the aggregation of GL and the clustered structure of the covalent complexes. The results demonstrated that the water solubility of ultrasonic conjugates was significantly increased by 8.8-64.19%, the digestion rate was more efficient, and the radical scavenging capacity was twice that of GL. This research contributes to the theoretical basis for broadening the application of polyphenols in modifying protein.

Effects of dual succinylation and ultrasonication modification on the structural and functional properties of ovalbumin

In this study, the functional properties of ovalbumin (OVA) were improved through dual modification with succinylation (succinylation degrees of 32.1 % [S1], 74.2 % [S2], and 95.2 % [S3]) and ultrasonication (ultrasonication durations of 5 min [U1], 15 min [U2], and 25 min [U3]), and the changes in protein structures were explored. Results showed that as the succinylation degree was increased, the particle size and surface hydrophobicity of S-OVA decreased by the maximum values of 2.2 and 2.4 times, respectively, causing emulsibility and emulsifying stability to increase by 2.7 and 7.3 times, respectively. After ultrasonic treatment, the particle size of succinylated-ultrasonicated OVA (SU-OVA) had decreased by 3.0-5.1 times relative to that of S-OVA. Moreover, the net negative charge of S3U3-OVA had increased to the maximum value of - 35.6 mV. These changes contributed to the further enhancement in functional indicators. The unfolding of the protein structure and the conformational flexibility of SU-OVA were illustrated and compared with those of S-OVA via protein electrophoresis, circular dichroism spectroscopy, intrinsic fluorescence spectroscopy, and scanning electron microscopy. The dually modified OVA emulsion (S3U3-E) presented small droplets (243.33 nm), reduced viscosity, and weakened gelation behavior that were indicative of even distribution, which was visually proven by confocal laser scanning microscopy images. Furthermore, S3U3-E exhibited favorable stability, a particle size that was almost unchanged, and a low polydispersity index (<0.1) over 21 days of storage at 4 °C. The above results demonstrated that succinylation combined with ultrasonic treatment could be an effective dual modification method for enhancing the functional performance of OVA.

Modifications of Thermal-Induced Northern Pike (Esox lucius) Liver Ferritin on Structural and Self-Assembly Properties

Ferritin, as an iron storage protein, regulates iron metabolism and delivers bioactive substances. It has been regarded as a safe, new type of natural iron supplement, with high bioavailability. In this paper, we extracted and purified ferritin from northern pike liver (NPLF). The aggregation stabilities, assemble properties, and structural changes in NPLF were investigated using electrophoresis, dynamic light scattering (DLS), circular dichroism (CD), UV–Visible absorption spectroscopy, fluorescence spectroscopy, and transmission electron microscopy (TEM) under various thermal treatments. The solubility, iron concentration, and monodispersity of NPLF all decreased as the temperature increased, and macromolecular aggregates developed. At 60 °C and 70 °C, the α-helix content of ferritin was greater. The content of α-helix were reduced to 8.10% and 1.90% at 90 °C and 100 °C, respectively, indicating the protein structure became loose and lost its self-assembly ability. Furthermore, when treated below 80 °C, NPLF maintained a complete cage-like shape, according to the microstructure. Partially unfolded structures reassembled into tiny aggregates at 80 °C. These findings suggest that mild thermal treatment (80 °C) might inhibit ferritin aggregation while leaving its self-assembly capacity unaffected. Thus, this study provides a theoretical basis for the processing and use of NPLF.