Low pH-shifting treatment would improve functional properties of black turtle bean (Phaseolus vulgaris L.) protein isolate with immunoreactivity reduction

Unveiling the potential of bean proteins: Extraction methods, functional and structural properties, modification techniques, physiological benefits, and diverse food applications

Bean proteins, known for their sustainability, versatility, and high nutritional value, represent a valuable yet underutilized resource, receiving less industrial attention compared to soy and pea proteins. This review examines the structural and molecular characteristics, functional properties, amino acid composition, nutritional value, antinutritional factors, and digestibility of bean proteins. Their applications in various food systems, including baked goods, juice and milk substitutes, meat alternatives, edible coatings, and 3D printing inks, are discussed. The physiological benefits of bean proteins, such as antidiabetic, cardioprotective, antioxidant, and neuroprotective effects, are also presented, highlighting their potential for promoting well-being. Our review emphasizes the diversity of bean proteins and highlights ultrasound as the most effective extraction method among available techniques. Beyond their physiological benefits, bean proteins significantly enhance the structural, technological, and nutritional properties of food systems. The functionality can be further improved through various modification techniques, thereby expanding their applicability in the food industry. While studies have explored the impact of bean protein structure on their nutritional and functional properties, further research is needed to investigate advanced modification techniques and the structure-function relationship. This will enhance the utilization of bean proteins in innovative and sustainable food applications.

Optimizing β-Lactoglobulin antigenicity through single enzyme hydrolysis: Exploring structural changes and effects on linear epitopes

β-lactoglobulin (β-LG) is the major allergen in dairy products, but research on the optimal conditions for antigen reduction in β-LG using different enzymes remains limited. Therefore, this study aims to investigate the antigenicity, structural characteristics, and peptide distribution of advantageous protease hydrolysates capable of eliminating the allergenic epitopes of β-LG selected via bioinformatics tools. The results showed that under optimal enzymatic hydrolysis conditions, the antigen reduction rates for the four advantageous proteases acting on β-LG were 47.37 % (pepsin), 33.54 % (chymotrypsin A), 38.71 % (papain), and 45.91 % (stem bromelain), respectively. The four proteases effectively degraded β-LG, causing shorter peptide chain formation, reduced content of highly ordered α-helix, decreased fluorescence intensity, and lower surface hydrophobicity. Furthermore, they cleaved the linear epitopes of β-LG into peptides of varying sizes, leading to different antigen reduction rates among the hydrolysates. These findings provide a theoretical basis for developing targeted enzymatic hydrolysis technologies and low-allergenicity dairy-based materials.

Binding mechanism and structural characteristics of alloyed protein complex for enhanced solubility of hemp seed protein isolate

Despite the numerous health benefits and high digestibility of hemp seed protein isolate (HPI), its low solubility at neutral pH limits its utilization in the food industry. Therefore, we subjected insoluble HPI and soluble mung bean protein isolate (MBPI) to pH co-shifting under extremely alkaline conditions to form an alloyed protein complex (A-HM). At a mass ratio of HPI:MBPI of 50:50, A-HM exhibited the highest solubility (95.30 ± 0.99 %), and also had high resistance to heat treatment. Native PAGE demonstrated the formation of alloyed protein complexes, and particle size analysis revealed that A-HM exhibited small particle sizes and dispersion in water without aggregation of HPI. Owing to their small size, numerous hydrophobic residues and aromatic ring of HPI were exposed on the surface. Hydrophobic interactions predominantly governed the binding force involved in the formation of A-HM. Our findings may enhance HPI applications in the food industry, particularly in plant-based beverages.

Hofmeister ion effects induced by different acidifiers and alkalizers improve the techno-functional properties of complex rapeseed protein during pH-driven self-assembly

pH-driven method is an effective strategy to prepare complex protein. This study provides guidance on how to select acidifiers and alkalizers from view of Hofmeister ion effects. Cations and anions regulated the molecular structure (particle size, surface charge, protein folding/unfolding, structural orderliness) of complex rapeseed proteins (CRPs) mainly via electrostatic and hydrogen bond. No evident changes were found in the molecular weight distribution, but their distribution on oil/air-water interface varied greatly. Various techno-functional properties of CRPs were synergistically improved: Citrate3- and Na+ increased the emulsifying activity index of CRPs from 80 to 102.21 m2/g; Citrate3-, K+ and Na+ made the foaming stability of CRPs close to 80 % after 60 min of storage. Moreover, the oil/water-holding and gel properties of CRPs were regulated effectively. These findings demonstrate the key role of Hofmeister ion effects in improving CRPs properties, contributing to develop, select, and apply novel acidifiers and alkalizers during pH-driven treatment.

Impact of pH-Shifting and Autoclaving on the Allergenic Potential of Red Kidney Bean (Phaseolus vulgaris L.) Lectins

The ingestion of red kidney bean products is hindered by the persistent allergenicity of lectins, even after autoclaving. This study examined the modification of lectin allergenicity in red kidney beans by pH-shifting and autoclaving treatments, utilizing BALB/c mouse sensitization, in situ recirculating perfusion, and a bone marrow-derived dendritic cell (BMDC) model for allergenicity evaluation. Compared to autoclaving alone, combined pH-shifting and autoclaving reduced allergic symptoms in BALB/c mice, as evidenced by lower serum IgE, mMCPT-1, GM-CSF, HIS, IL-2, IL-4, IL-9, IL-13, and IL-17 levels and higher IgG1, IgG2a, IL-10, IFN-γ, and IFN-α cytokine release. Moreover, lectin continued to affect intestinal permeability and damaged the barrier despite undergoing pH-shifting and autoclaving treatments. Additionally, the uptake of lectin by BMDCs through mannose receptor-mediated endocytosis was diminished, with an increased susceptibility to endolysosomal degradation. The T-cell polarization was consistent with the mouse experiments, where the balance of Th1 and Th2 cells remained in lectin with pH-shifting and autoclaving treatments though the decreased abundance ratios of peptide YKYDSNAHT and increased abundance ratios of peptide ITKGNVETN in endolysosomal degradation. Therefore, the immunogenicity of lectins could be decreased by pH-shifting and autoclaving treatments, offering insights into the development of hypoallergenic legume products.

Effect of pH-Shift Treatment on IgE-Binding Capacity and Conformational Structures of Peanut Protein

Hypoallergenic processing is an area worthy of continued exploration. In the treatment of the peanut protein (PP), pH shift was applied by acidic (pH 1.0-4.0) and alkaline (pH 9.0-12.0) treatment, after which the pH was adjusted to 7.0. Following pH-shift treatment, PP showed a larger particle size than in neutral solutions. SDS-PAGE, CD analysis, intrinsic fluorescence, UV spectra, and surface hydrophobicity indicated the protein conformation was unfolded with the exposure of more buried hydrophobic residues. Additionally, the IgE-binding capacity of PP decreased after pH-shift treatment on both sides. Label-free LC-MS/MS results demonstrated that the pH-shift treatment induced the structural changes on allergens, which altered the abundance of peptides after tryptic digestion. Less linear IgE-binding epitopes were detected in PP with pH-shift treatment. Our results suggested the pH-shift treatment is a promising alternative approach in the peanut hypoallergenic processing. This study also provides a theoretical basis for the development of hypoallergenic food processing.

Structure, functional and physicochemical properties of lotus seed protein under different pH environments

BACKGROUND

The present study investigated the structure, functional and physicochemical properties of lotus seed protein (LSP) under different pH environments. The structures of LSP were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Fourier transform infrared spectroscopy (FTIR), zeta potential, particle size distributions, free sulfhydryl and rheological properties. The functional and physicochemical properties of LSP were characterized by color, foaming property, emulsification property, solubility, oil holding capacity, water holding capacity, differential scanning calorimetry analysis and surface hydrophobicity.

RESULTS

LSP was mainly composed of eight subunits (18, 25, 31, 47, 51, 56, 65 and 151 kDa), in which the richest band was 25 kDa. FTIR results showed that LSP had high total contents of α-helix and β-sheet (44.81-46.85%) in acidic environments. Meanwhile, there was more β-structure and random structure in neutral and alkaline environments (pH 7.0 and 9.0). At pH 5.0, LSP had large particle size (1576.98 nm), high emulsion stability index (91.43 min), foaming stability (75.69%) and water holding capacity (2.21 g g-1), but low solubility (35.98%), free sulfhydryl content (1.95 μmol g-1) and surface hydrophobicity (780). DSC analysis showed the denaturation temperatures (82.23 °C) of LSP at pH 5.0 was higher than those (80.10, 80.52 and 71.82 °C) at pH 3.0, 7.0 and 9.0. The analysis of rheological properties showed that LSP gel had high stability and great strength in an alkaline environment.

CONCLUSION

The findings of the present study are anticipated to serve as a valuable reference for the implementation of LSP in the food industry. © 2024 Society of Chemical Industry.

Rapid quantitative analysis of soybean protein isolates secondary structure by two-dimensional correlation infrared spectroscopy through pH perturbation

The infrared spectroscopy (IR) signal of protein is prone to being covered by impurity signals, and the accuracy of the secondary structure content calculated using spectral data is poor. To tackle this challenge, a rapid high-precision quantitative model for protein secondary structure was proposed. Firstly, a two-dimensional correlation calculation was performed based on 60 groups of soybean protein isolates (SPI) infrared spectroscopy data, resulting in a two-dimensional correlation infrared spectroscopy (2DCOS-IR). Subsequently, the optimal characteristic bands of the four secondary structures were extracted from the 2DCOS-IR. Ultimately, partial least squares (PLS), long short-term memory (LSTM), and bidirectional long short-term memory (BILSTM) algorithms were used to model the extracted characteristic bands and predict the content of SPI secondary structure. The findings suggested that BILSTM combined with 2DCOS-IR model (2DCOS-BILSTM) exhibited superior predictive performance. The prediction sets for α-helix, β-sheet, β-turn, and random coil were designated as 0.9257, 0.9077, 0.9476, and 0.8443, respectively, and their corresponding RMSEP values were 0.26, 0.48, 0.20, and 0.15. This strategy enhances the precision of IR and facilitates the rapid identification of secondary structure components within SPI, which is vital for the advancement of protein industrial production.

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.

Effects of Different pH Levels on the Structural and Functional Properties of Proteins of Phaeodactylum tricornutum

Phaeodactylum tricornutum is identified by its capacity for rapid growth, reproduction, and in vitro cultivation, as well as the presence of a range of high-value active compounds, including proteins, with potential food applications. The objective of this study was to investigate the effects of pH shift treatments (pH of 3, 5, 7, 9, and 11) on the structural and functional properties of the Phaeodactylum tricornutum protein (PTP). The molecular weight of the PTP was predominantly distributed within the following ranges: below 5 kDa, 5-100 kDa, and above 100 kDa. Compared to the acidic environment, the PTP demonstrated higher solubility and greater free sulfhydryl group content in the alkaline environment. Additionally, PTP had a smaller particle size and higher thermal stability in alkaline environments. The PTP exhibited superior foaming ability (135%), emulsification activity index (3.72 m2/g), and emulsion stability index (137.71 min) in alkaline environments. The results of this investigation provide a foundation for the future development and application of the PTP in the food industry.

Euglena gracilis Protein: Effects of Different Acidic and Alkaline Environments on Structural Characteristics and Functional Properties

Due to the growing demand for human-edible protein sources, microalgae are recognized as an economically viable alternative source of proteins. The investigation into the structural characteristics and functional properties of microalgin is highly significant for its potential application in the food industry as an alternative source of protein. In this research, we extracted protein from Euglena gracilis by using alkaline extraction and acid precipitation and investigated its structural characteristics and functional properties in different acidic and alkaline environments. The molecular weight distribution of Euglena gracilis protein (EGP), as revealed by the size exclusion chromatography results, ranges from 152 to 5.7 kDa. EGP was found to be rich in hydrophobic amino acids and essential amino acids. Fourier infrared analysis revealed that EGP exhibited higher α-helix structure content and lower β-sheet structure content in alkaline environments compared with acidic ones. EGP exhibited higher foaming properties, emulsifying activity index, solubility, free sulfhydryl, and total sulfhydryl in pH environments far from its isoelectric point, and lower fluorescence intensity (2325 A.U.), lower surface hydrophobicity, larger average particle size (25.13 µm), higher emulsifying stability index, and water-holding capacity in pH environments near its isoelectric point. In addition, X-ray diffraction (XRD) patterns indicated that different acidic and alkaline environments lead to reductions in the crystal size and crystallinity of EGP. EGP exhibited high denaturation temperature (Td; 99.32 °C) and high enthalpy (ΔH; 146.33 J/g) at pH 11.0, as shown by the differential scanning calorimetry (DSC) results. The findings from our studies on EGP in different acidic and alkaline environments provide a data basis for its potential commercial utilization as a food ingredient in products such as emulsions, gels, and foams.

The structural characteristics and physicochemical properties of mung bean protein hydrolysate of protamex induced by ultrasound

BACKGROUND

The limited physicochemical properties (such as low foaming and emulsifying capacity) of mung bean protein hydrolysate restrict its application in the food industry. Ultrasound treatment could change the structures of protein hydrolysate to accordingly affect its physicochemical properties. The aim of this study was to investigate the effects of ultrasound treatment on the structural and physicochemical properties of mung bean protein hydrolysate of protamex (MBHP). The structural characteristics of MBHP were evaluated using tricine sodium dodecylsulfate-polyacrylamide gel electrophoresis, laser scattering, fluorescence spectrometry, etc. Solubility, fat absorption capacity and foaming, emulsifying and thermal properties were determined to characterize the physicochemical properties of MBHP.

RESULTS

MBHP and ultrasonicated-MBHPs (UT-MBHPs) all contained five main bands of 25.8, 12.1, 5.6, 4.8 and 3.9 kDa, illustrating that ultrasound did not change the subunits of MBHP. Ultrasound treatment increased the contents of α-helix, β-sheet and random coil and enhanced the intrinsic fluorescence intensity of MBHP, but decreased the content of β-turn, which demonstrated that ultrasound modified the secondary and tertiary structures of MBHP. UT-MBHPs exhibited higher solubility, foaming capacity and emulsifying properties than MBHP, among which MBHP-330 W had the highest solubility (97.32%), foaming capacity (200%), emulsification activity index (306.96 m2  g-1 ) and emulsion stability index (94.80%) at pH 9.0.

CONCLUSION

Ultrasound treatment enhanced the physicochemical properties of MBHP, which could broaden its application as a vital ingredient in the food industry. © 2023 Society of Chemical Industry.

Insight of pH-shifting as an effective pretreatment to reduce the antigenicity of lectin from red kidney bean (Phaseolus vulgaris L.) combining with autoclaving treatments: The structure investigation

Combined effects of pH-shifting and an autoclaving cycle (121 °C, 15 min) on red kidney bean lectin (RKBL) were investigated using intrinsic and extrinsic fluorescence, UV, FTIR, DSC, SEC, dot-blot analysis and in vitro digestibility. Spectroscopic studies suggested that the protein refolding was stable after 3 h incubation with the hydrophobic exposure after pH-shifting, and hydrophobicity was significantly increased with the formation of more looser structure, which would influence the structural stability of known epitopes. In details, the increase of β-turn and reduction of random coil was related with the lower denaturation enthalpy, while the protein aggregation was also observed in acidic treated samples after autoclaving. Lower antigenicity and good digestibility suggested the exposure of enzyme cutting sites, and confirmed the effectivity of pH-shifting prior to the autoclaving. Then the results would be beneficial to the development of hypoallergenic kidney bean foods.

Lima bean (Phaseolus lunatus Linn.) protein isolate as a promising plant protein mixed with xanthan gum for stabilizing oil-in-water emulsions

BACKGROUND

Lima bean protein isolate (LPI) is an underutilized plant protein. Similar to other plant proteins, it may display poor emulsification properties. In order to improve its emulsifying properties, one effective approach is using protein and polysaccharide mixtures. This work investigated the structural and emulsifying properties of LPI as well as the development of an LPI/xanthan gum (XG)-stabilized oil-in-water emulsion.

RESULTS

The highest protein solubility (84.14%) of LPI was observed and the molecular weights (Mw ) of most LPI subunits were less than 35 kDa. The enhanced emulsifying activity index (15.97 m2  g-1 ) of LPI might be associated with its relatively high protein solubility and more low-Mw subunits (Mw  < 35 kDa). The effects of oil volume fraction (ϕ) on droplet size, microstructure, rheological behavior and stability of emulsions were investigated. As ϕ increased from 0.2 to 0.8, the emulsion was arranged from spherical and dispersed oil droplets to polyhedral packing of oil droplets adjacent to each other, while the LPI/XG mixtures changed from particles (in the uncrowded interfacial layer) to lamellae (in the crowded interfacial layer). When ϕ was 0.6, the emulsion was in a transitional state with the coexistence of particles and lamellar structures on the oil droplet surface. The LPI/XG-stabilized emulsions with ϕ values of 0.6-0.8 showed the highest stability during a 14-day storage period.

CONCLUSION

This study developed a promising plant-based protein resource, LPI, and demonstrates potential application of LPI/XG as an emulsifying stabilizer in foods. © 2023 Society of Chemical Industry.

Improved gelling and emulsifying properties of chicken wooden breast myofibrillar protein by high-intensity ultrasound combination with pH-shifting

The functional properties of chicken wooden breast myofibrillar protein (WBMP) are impaired. The protein structure and functional properties of WBMP are investigated using high-intensity ultrasound (HIU, 20 kHz, 200, 400, 600, and 800 W) combined with pH-shifting. HIU promoted the unfolding of WBMP, reduced the particle size of WBMP, and enhanced electrostatic repulsion. Medium-power (200 and 400 W) HIU promoted the α-helix to β-sheet transformation, while high-power (600 and 800 W) HIU significantly (P < 0.05) increased the content of the random coil. The microstructure and images after storage further showed that 400 W HIU in combination with pH-shifting made the WBMP emulsion more uniform. In addition, gel performance analysis showed that the gel strength and water-holding capacity of the protein gel increased gradually after 400 W. Scanning electron microscope images also showed the formation of a stable network structure in the protein gel. This work could help promote the utilization of inferior proteins similar to WBMP, but the utilization rate still needs to be further improved.

Common beans as a source of food ingredients: Techno-functional and biological potential

Common beans are an inexpensive source of high-quality food ingredients. They are rich in proteins, slowly digestible starch, fiber, phenolic compounds, and other bioactive molecules that could be separated and processed to obtain value-added ingredients with techno-functional and biological potential. The use of common beans in the food industry is a promising alternative to add nutritional and functional ingredients with a low impact on overall consumer acceptance. Researchers are evaluating traditional and novel technologies to develop functionally enhanced common bean ingredients, such as flours, proteins, starch powders, and phenolic extracts that could be introduced as functional ingredient alternatives in the food industry. This review compiles recent information on processing, techno-functional properties, food applications, and the biological potential of common bean ingredients. The evidence shows that incorporating an adequate proportion of common bean ingredients into regular foods such as pasta, bread, or nutritional bars improves their fiber, protein, phenolic compounds, and glycemic index profile without considerably affecting their organoleptic properties. Additionally, common bean consumption has shown health benefits in the gut microbiome, weight control, and the reduction of the risk of developing noncommunicable diseases. However, food matrix interaction studies and comprehensive clinical trials are needed to develop common bean ingredient applications and validate the health benefits over time.

Effect of processing treatments on the allergenicity of nuts and legumes: A meta-analysis

The effective food processing to reduce nuts and legumes allergenicity could not be easily and directly concluded from reading a few published reports. Therefore, we conducted a meta-analysis to investigate this issue. A literature search was conducted in eight electronic databases from January 2000 to June 11, 2021. The primary outcome of interest was the allergenicity of processed nuts or legumes determined by enzyme-linked immunosorbent assay from in vitro studies. Data with the standardized mean difference (SMD) of 95% confidence interval (CI) were pooled using a random-effect model by RevMan 5.4 software. Heterogeneity was assessed using Cochran's Q (P_Q ) and I² tests. The search strategy identified 18,793 articles. However, only 61 studies met the inclusion criteria and were included in this meta-analysis. There were 21 and 15 types of respective single and combined food processing treatments analyzed for their effects on reducing allergenicity. In single processing treatment, the extrusion and fermentation had the largest reduction in allergenicity, considering their SMD value, that is, -20.19 (95% CI: -22.22 to -18.17; the certainty of evidence: moderate) and -20.8 (95% CI: -24.10 to -17.50; the certainty of evidence: moderate), respectively. Whereas in the combination, the treatment of fermentation followed by proteolytic hydrolysis showed the most significant reduction (SMD: -53.34; 95% CI: -70.18 to -36.5) and the evidence quality of this treatment was considered moderate. In conclusion, these three food processing methods showed a desirable impact in reducing nuts or legumes allergenicity. PRACTICAL APPLICATION: Nuts and legumes play an essential role as protein sources in food consumption worldwide, but they usually contain allergens. Our study has investigated the food processing methods that effectively reduce their allergenicity by meta-analysis. The result gives valuable information for further laboratory investigation on allergens and can be used by food industries in providing foods from nuts and legumes with lower allergenicity.

The Structural and Functional Differences between Three Species of Fish Scale Gelatin and Pigskin Gelatin

In this paper, gelatin was extracted from the scales of Coregonus peled, Carp and Bighead carp by the acid method, and the structure and functional properties of the obtained scale gelatin and food-grade pigskin gelatin (FG) were compared. The results showed that all gelatins exhibited relatively high protein (86.81-93.61%), and low lipid (0.13-0.39%) and ash (0.37-1.99%) contents. FG had the highest gel strength, probably because of its high proline content (11.96%) and high average molecular weight distribution. Low β-antiparallel was beneficial to the stability of emulsion, which led FG to have the best emulsifying property. The high content of hydrophobic amino acids may be one of the reasons for the superior foaming property of Bighead carp scales gelatin (BCG). The gel strength of Carp scales gelatin (CG) and BCG, the ESI of Coregonus peled scales gelatin (CPG) and the foaming property of BCG indicate that fish gelatin has the potential to be used in food industry as a substitute for pig skin gelatin.

Identification of the Immunoglobulin E Epitope of Arginine Kinase, an Important Allergen from Crassostrea angulata

Arginine kinase (AK) was identified as an allergen in Crassostrea angulata. However, little information is available about its epitopes. In this study, AK from C. angulata was registered to the World Health Organization/International Union of Immunological Societies allergen nomenclature committee to be named as Cra a 2. The immunoglobulin G/immunoglobulin E-binding capacity of Cra a 2 was significantly reduced after chemical denaturation treatment. Further, eight linear mimotopes and five conformational mimotopes of Cra a 2 were obtained using phage panning. In addition to six linear epitopes that have been identified, two linear epitopes were verified by a synthetic peptide, of which L-Cra a 2-2 was conserved in shellfish. Four conformational epitopes were verified by site-directed mutation, among which mutation of C-Cra a 2-1 affected the structure and reduced the immunoreactivity of Cra a 2 most significantly. Overall, the identified epitopes may lay a foundation for the development of hypoallergenic oyster products through food processing.

Improved pH stability, heat stability, and functionality of phycocyanin after PEGylation

Phycocyanin (PC), a spirulina-derived protein-chromophore complex, suffers from poor techno-functional properties and is highly susceptible to aggregation and color changes upon heating and pH fluctuations. We tackled these issues by modifying PC via PEGylation. Electrophoresis and Fourier transform infrared spectroscopy proved successful conjugation of methoxy PEG (mPEG) chains on PC after PEGylation. Circular dichroism indicated highly ordered folding states adopted by PEGylated PC, which we attributed to the mPEG chains on the protein surface that sterically stabilized the protein structure. Consequently, the mPEG-PC conjugates exhibited high blue color intensity and improved thermodynamic stability. Further, benefit from an electrostatic shielding effect of mPEG chains, surface charges of PEGylated PC were neutralized over pH 2-9 and the blue hue of PC was stabilized against pH variations. Additionally, the flexible and hydrophilic mPEG polymers on the PC surface promoted protein-protein and protein-water interactions. PEGylated PC thus gained increased protein solubility, techno-functionality (emulsifying, foaming, and gelling performance), and antioxidant activities, when compared to unmodified PC. Heat-induced gels formed by mPEG-PC conjugates exhibited increased stiffness, higher water retention, and weak gel-type rheological properties. After PEGylation, the improved functional properties, bioactivity, and color stability against heat and pH fluctuations will facilitate food and pharmaceutical applications of PC.

The Impact of Dehulling and Germination on the Physiochemical, Protein Solubility and Water and Oil Holding Capacities of Yellow Eye Bean (Phaseolus vulgaris L.) Protein Concentrates

Pulse varieties including Yellow Eye (YE) beans (Phaseolus vulgaris L.) are a rich source of protein (~26.5%) that can be utilized to create value-added protein concentrates. Pre-treatments including dehulling and germination have been shown to be effective at improving the nutritional and functional properties of extracted protein concentrates. However, the composition and functionality of these protein concentrates can vary depending on the pre-treatments and the method of extraction used (salt vs. alkaline). Furthermore, little is known about the impact of combining these different processing methods on the properties of YE bean protein concentrates. The objective of this study was to evaluate how germination and dehulling pre-treatments individually and when combined influence protein extraction efficiency, physiochemical properties (surface hydrophobicity and intrinsic fluorescence), and the functionality (solubility, oil and water holding capacities) of salt and alkaline extracted protein concentrates. Compared to the salt extracted concentrates, the alkaline protein concentrates exhibited higher protein recovery yields (16–23% vs. 43–56%) respectively. Conversely, the salt extracted protein concentrates exhibited superior functional properties as observed by improved water holding capacities and less variation in their solubilities at different pH values (4 to 10). When the pre-treatments were combined, the salt extracted concentrates exhibited improved extraction efficiencies and improved hydrophobicity and intrinsic fluorescence, whereas the opposite trend was observed in the alkaline protein concentrates. These observations were attributed to differences in the protein content and composition of the salt vs. alkaline protein concentrates. Overall, these findings suggest that dehulling and germination are potential processing methods that may be used to improve the physiochemical characteristics of salt extracted protein concentrates from yellow eye beans. Future research may investigate the potential application of these ingredients in different food formulations.

Effects of Ultrasound Combined with Preheating Treatment to Improve the Thermal Stability of Coconut Milk by Modifying the Physicochemical Properties of Coconut Protein

In the food industry, coconut milk has a unique flavor and rich nutritional value. However, the poor emulsifying properties of coconut proteins restrict its development. In this study, the effect of ultrasound combined with preheating on coconut globulin and coconut milk was evaluated by physicochemical properties and structural characteristics. The results showed that ultrasound and 90 °C preheating gave coconut protein better emulsifying and thermal properties, demonstrated by higher solubility (45.2% to 53.5%), fewer free sulfhydryl groups (33.24 to 28.05 μmol/g) and higher surface hydrophobicity (7658.6 to 10,815.1). Additionally, Fourier transform infrared spectroscopy and scanning electron microscopy showed obvious changes in the secondary structure. Furthermore, the change in the physicochemical properties of the protein brought a higher zeta potential (−11 to −23 mV), decreased the thermal aggregation rate (148.5% to 13.4%) and increased the viscosity (126.9 to 1103.0 m·Pa·s) of the coconut milk, which indicates that ultrasound combined with preheating treatment provided coconut milk with better thermal stability. In conclusion, ultrasound combined with preheating will have a better influence on modifying coconut globulin and increasing the thermal stability of coconut milk. This study provides evidence that ultrasound and other modification technologies can be combined to solve the problems encountered in the processing of coconut protein products.

Insight into IgG/IgE binding ability, in vitro digestibility and structural changes of shrimp (Litopenaeus vannamei) soluble extracts with thermal processing

The effects of six kinds of thermal processing on soluble protein recovery, potential allergenicity, in vitro digestibility and structural characteristics of shrimp soluble proteins were evaluated. Obtained results confirmed soluble protein recovery and IgG/IgE reactivity of shrimp soluble extracts were markedly suppressed by various thermal treatments with enhanced digestibility depended on the extent and type of heating applied, which correlated well with the structural alterations and modification. The maximum reduction of IgG/IgE-binding capacity and digestive stability were observed in the autoclaved shrimps because of unfolding of protein and hydrophobic residues exposed. Notably, tropomyosin (TM) and sarcoplasmic calcium-binding protein (SCP) were still IgG/IgE-reactive in various heat-processed shrimps, even higher IgG reactivity were found in heat-treated shrimps TM according to TM antiserum western-blotting and indirect ELISA results. Shrimp TM and SCP maintains its IgE/IgG-binding capacity after various cooking methods, thus most probably initiating allergic sensitization to both raw and cooked shrimps.

Detection of Lectin Protein Allergen of Kidney Beans (Phaseolus vulgaris L.) and Desensitization Food Processing Technology

With the increase of food allergy events related to not properly cooked kidney beans (Phaseolus vulgaris L.), more and more researchers are paying attention to the sensitization potential of lectin, one of the major storage and defensive proteins with the specific carbohydrate-binding activity. The immunoglobulin E (IgE), non-IgE, and mixed allergic reactions induced by the lectins were inducted in the current paper, and the detection methods of kidney bean lectin, including the purification strategies, hemagglutination activity, specific polysaccharide or glycoprotein interactions, antibody combinations, mass spectrometry methods, and allergomics strategies, were summarized, while various food processing aspects, such as the physical thermal processing, physical non-thermal processing, chemical modifications, and biological treatments, were reviewed in the potential of sensitization reduction. It might be the first comprehensive review on lectin allergen detection from kidney bean and the desensitization strategy in food processing and will provide a basis for food safety control.

Identification and characterization of Crassostrea angulata arginine kinase, a novel allergen that causes cross-reactivity among shellfish

Oyster is a common food that causes allergy. However, little information is available about its allergens and cross-reactivity. In this study, arginine kinase (AK) was identified as a novel allergen in Crassostrea angulata. The primary sequence of AK was cloned which encoded 350 amino acids, and recombinant AK (rAK) was obtained. The immunodot results, secondary structure and digestive stability showed that native AK and rAK had similar IgG/IgE-binding activity and physicochemical properties. Serological analysis of 14 oyster-sensitive individuals demonstrated that AK exhibited cross-reactivity among oysters, shrimps, and crabs. Furthermore, nine epitopes in oyster AK were verified using inhibition dot blots and inhibition enzyme linked immunosorbent assay, six of which were similar to the epitopes of shrimp/crab AK. The most conserved epitopes were P5 (121-133) and P6 (133-146), which may be responsible for the cross-reactivity caused by AK. These findings will provide a deeper understanding of oyster allergens and cross-reactivity among shellfish.

Improved solubility and interface properties of pigskin gelatin by microwave irradiation

In this study, the microwave irradiation as a green approach was applied to improve the properties (mainly solubility and interface properties) of pigskin gelatin. The results showed that the solubility of pigskin gelatin was improved obviously at room temperature (25 °C) due to the destruction of polymer subunits. Furthermore, the exposure of more hydrophobic groups in microwave-irradiated gelatin increased its hydrophobicity, consequently improving the amphiphilic property and the interfacial properties of gelatin. The results of interface behavior showed that the interfacial tension of microwave-irradiated gelatin was reduced obviously with the extension of irradiation time (0-30 min), which is more beneficial to adsorption of gelatin molecules at the interface, thus resulting in a significant increase of adsorption rate (AP) from 56.13% (0 min) to 91.87% (30 min). Correspondingly, the foaming and emulsifying properties of gelatin were also improved significantly (p < 0.05). This study would promote the development of food-grade foam and emulsion based on pigskin gelatin by adjusting solubility and interface properties.