Effects of high-pressure treatment on some physicochemical and functional properties of soy protein isolates

Performance and protein conformation of thermally treated silver carp (Hypophthalmichthys molitrix) and scallop (Argopecten irradians) blended gels

BACKGROUND

The quality of surimi-based products can be improved by combining the flesh of different aquatic organisms. The present study investigated the effects of incorporating diverse ratios of unwashed silver carp (H) and scallop (A) and using various thermal treatments on the moisture, texture, microstructure, and conformation of the blended gels and myofibrillar protein of surimi.

RESULTS

A mixture ratio of A:H = 1:3 yielded the highest gel strength, which was 60.4% higher than that of scallop gel. The cooking losses of high-pressure heating and water-bath microwaving were significantly higher than those of other methods (P < 0.05). Moreover, the two-step water bath and water-bath microwaving samples exhibited a more regular spatial network structure compared to other samples. The mixed samples exhibited a microstructure with a uniform and ordered spatial network, allowing more free water to be trapped by the internal structure, resulting in more favorable gel properties. The thermal treatments comprehensively modified the tertiary and quaternary structures of proteins in unwashed mixed gel promoted protein unfurling, provided more hydrophobic interactions, enhanced protein aggregation and improved the gel performance.

CONCLUSION

The findings of the present study improve our understanding of the interactions between proteins from different sources. We propose a new method for modifying surimi's gel properties, facilitating the development of mixed surimi products, as well as enhancing the efficient utilization of aquatic resources. © 2024 Society of Chemical Industry.

Effects of High-Pressure Homogenization on the Structure and Functional Properties of Solenaia oleivora Proteins

Solenaia oleivora, a rare freshwater shellfish with high protein quality, is unique to China. However, the poor hydrosolubility and functional properties of Solenaia oleivora proteins hinder their utilization in food products. Herein, the alkaline dissolution-isoelectric precipitation method was used for the extraction of Solenaia oleivora proteins. Furthermore, the impact of high-pressure homogenization (HPH) treatment varying from 0 to 100 MPa on the structure and functional properties of Solenaia oleivora proteins was investigated. The obtained results indicated that HPH treatment decreased the α-helix content and enhanced the β-sheet and random coil content. Furthermore, the HPH caused the unfolding of protein structure, exposing aromatic amino acids, increasing the free thiol group content, and enhancing surface hydrophobicity. As the homogenization pressure increased from 0 to 100 MPa, the particle size of Solenaia oleivora proteins decreased from 899 to 197 nm with the polymer dispersity index (PDI) value decreased from 0.418 to 0.151, the ζ-potential increased from -22.82 to -43.26 mV, and the solubility increased from 9.54% to 89.96%. Owing to the significant changes in protein structure and solubility, the emulsifying, foaming, and digestive properties of Solenaia oleivora proteins have been significantly improved after treatment with HPH.

The Effect of High Hydrostatic Pressure (HHP) Induction Parameters on the Formation and Properties of Inulin-Soy Protein Hydrogels

The aim of this study was to determine the effect of high hydrostatic pressure (HHP) induction parameters on the formation and properties of inulin-soy protein hydrogels. Solutions containing 20 g/100 g of inulin and 3 or 6 g/100 g of soy protein isolate (3 SPI; 6 SPI) were subjected to HHPs of 150, 300, or 500 MPa for 5, 10, or 20 min. The HHP parameters had no significant impact on the effectiveness of hydrogel formation. In most cases, the time of solution pressurization had no significant effect on the characteristics of hydrogels. However, increasing the induction pressure from 150 to 300 MPa resulted in hydrogels with different characteristics being obtained, e.g., more flattened microstructure; higher stability (only 3 SPI); higher yield stress, firmness, and adhesiveness; and lower spreadability. These changes were more noticeable in the hydrogels with lower protein content. An increase in the induction pressure (to 500 MPa) did not result in a significant strengthening of the hydrogel structure. However, in the case of 6 SPI hydrogels, induction with a pressure of 500 MPa had an unfavorable effect on their stability. The results indicate that HHP (300 MPa) can be used as an effective method for strengthening the structure of inulin-protein hydrogels.

Analyzing changes in volatile flavor compounds of soy protein isolate during ultrasonic-thermal synergistic treatments using electronic nose and HS-SPME-GC-MS combined with chemometrics

The beany flavor of soy protein isolate (SPI) creates barriers to their application in food processing. This study investigated the effect of ultrasonic-thermal synergistic treatments, combined with vacuum degassing, on the removal of volatile compounds from SPI. The results revealed that ultrasonic-thermal synergistic treatments altered protein secondary structure and increased fluorescence intensity and surface hydrophobicity, which affected the flavor-binding ability of protein, resulting in reduced electronic nose sensor response values. At synergistic treatment (350 W, 120 ℃ and 150 s), the content of hexanal, (E)-2-hexenal, and 1-octen-3-ol reduced by 70.60 %, 95.60 % and 61.23 %. (E)-2-nonenal and 2-pentylfuran were not detected. Chemometric analysis indicated significant flavor differences between control and treated SPI. Furthermore, α-helix, β-sheet, β-turn, and surface hydrophobicity highly correlated with volatile compounds through correlation analysis, indicating that altered protein structure affected interactions with volatile compounds. The study reduced beany flavor and further expanded the range of applications of plant protein in food industry.

A promising Artemisia capillaris Thunb. Leaf proteins with high nutrition, applicable function and excellent antioxidant activity

The nutritional and functional properties of leaf proteins is a decisive factor for their use in food. This work was aimed to extract defatted Artemisia capillaris Thunb. (ACD) leaf proteins (ACLP), and assess ACLP nutritional quality, functional properties and in vitro antioxidant activity, as well characterize the structure. ACLP had a balanced amino acid profile and high bioavailability (protein digestibility corrected amino acid score (PDCAAS) 99.29 %). Solubility, foaming capacity and emulsifying ability of ACLP correlated positively with pH. Water and oil holding capacity were increased with temperature. Gel electrophoresis shown the protein molecular size was mainly ∼25 kDa, and random coil was the mainly secondary structure while β-sheet was dominant regular conformation as indicated by circular dichroism (CD). ACLP performed in vitro antioxidant activity which was better after digestion. All data implied ACLP met the WHO/FAO protein quality expectations and had application potential in food.

Investigating Texture and Freeze-Thaw Stability of Cold-Set Gel Prepared by Soy Protein Isolate and Carrageenan Compounding

In this study, the purpose was to investigate the effects with different concentrations of carrageenan (CG, 0-0.30%) on the gel properties and freeze-thaw stability of soy protein isolate (SPI, 8%) cold-set gels. LF-NMR, MRI, and rheology revealed that CG promoted the formation of SPI-CG cold-set gel dense three-dimensional network structures and increased gel network cross-linking sites. As visually demonstrated by microstructure observations, CG contributed to the formation of stable SPI-CG cold-set gels with uniform and compact network structures. The dense gel network formation was caused when the proportion of disulfide bonds in the intermolecular interaction of SPI-CG cold-set gels increased, and the particle size and zeta potential of SPI-CG aggregates increased. SG20 (0.20% CG) had the densest gel network in all samples. It effectively hindered the migration and flow of water, which decreased the damage of freezing to the gel network. Therefore, SG20 exhibited excellent gel strength, water holding capacity, freeze-thaw stability, and steaming stability. This was beneficial for the gel having a good quality after freeze-thaw, which provided a valuable reference for the development of freeze-thaw-resistant SPI cold-set gel products.

Structural modification of oat protein by thermosonication combined with high pressure for O/W emulsion and model salad dressing production

Oat protein is becoming an important ingredient in beverages and formulated foods owing to its high nutritive value and bland flavor; yet, its functionality remains largely unexplored. This study sought to enhance the surface activity of oat protein isolate (OPI) through high-intensity ultrasound (HIU; at 20 or 60 °C) combined with high pressure homogenization (HP; 30 MPa) treatments. Sonication disturbed the protein conformation and significantly improved surface hydrophobicity (19.7%) and ζ-potential (15.7%), which were further augmented by subsequent HP (P < 0.05). Confocal microscopy revealed a uniform oil droplet distribution in emulsions prepared with HIU+HP combination treated OPI, and the oil droplet size decreased up to 35.6% when compared to that of non-treated OPI emulsion (d = 1718 nm). Emulsifying activity was greater for HIU+HP than for HIU, and the viscosity followed a similar trend. Moreover, while emulsions prepared with HIU or HP treated OPI were more stable than control, the 60 °C HIU+HP combination treatment yielded the maximum stability. In corroboration, a model salad dressing prepared from HIU+HP treated OPI displayed a homogenous oil droplet distribution and an improved viscosity. Therefore, thermosonication combined with high pressure homogenization may be suitable for salad dressings and other oil-imbedded food products.

Effects of direct addition of curdlan on the gelling characteristics of thermally induced soy protein isolate gels

In this study, the effects of the direct addition of curdlan on the physicochemical, structural, and functional properties of heat-induced soy protein isolate (SPI) gels were evaluated. Results demonstrated that the direct incorporation of curdlan enhanced the gel-forming performance, water-holding capacity, and gel strength of heat-induced SPI gels. The presence of curdlan reduced the free water molecules and α-helix content in the SPI structure and contributed to the construction of stable SPI gels with uniform and compact network structures, as visually proven by microstructure observations. Moreover, compared with the SPI gel alone, the curdlan-SPI composite gels presented a more pronounced viscoelastic property and thermal stability mainly due to the intermolecular hydrogen bonding interaction between curdlan and the SPI molecules. Our findings suggest that the direct incorporation of curdlan can effectively ameliorate the gelling characteristics of heat-induced SPI gels, indicating its potential application as a promising gel improver in the food industry.

Smart antimicrobial system based on enzyme-responsive high methoxyl pectin-whey protein isolate nanocomplex for fresh-cut apple preservation

The increase in pectin methylesterase (PME) activity on fresh-cut apple surface can smartly trigger the controlled release of bactericidal agents encapsulated within intelligent responsive Pickering emulsions. In this study, we developed a PME-responsive nanocomplex (W-H-II) to stabilize Pickering emulsion containing thyme essential oil (TEO), preserving fresh-cut apples. W-H-II, formed by heat-induced whey protein isolate (WPI) and high methoxyl pectin (HMP) (pH 4.5, 85 °C, 15 min, WPI:HMP ratio 1:2), exhibited good pH stability due to the stabilizing effects of hydrophobic, hydrogen bonding, and electrostatic interactions. The presence of PME triggered the demethylation of HMP within W-H-II, conferring PME response characteristics. Subsequently, a bacteriostasis experiment with pectinase-producing Bacillus subtilis provided evidence of PME-triggered TEO release from W-H-II-stabilized Pickering emulsion. Furthermore, microscopy techniques were employed to verify the demulsification behavior of the emulsion when PME activity ranged from 0.25 to 2.50 U mL-1. Finally, the PME-responsive TEO Pickering emulsion effectively preserved fresh-cut apples. Stored for 6 days at 5 °C and 10 °C, as the PME activity on the apple surface increased, the decay rate of the coated group was 0 %, with a total colony count below 3.0 log CFU g-1. This study introduces a novel intelligent preservation strategy for storing fresh-cut apples.

Influence of heat treatment before and/or after high-pressure homogenization on the structure and emulsification properties of soybean protein isolate

This study investigates the effects of heat treatment before high-pressure homogenization (HHPH) and heat treatment after high-pressure homogenization (HPHH) at different pressures (20, 60, and 100 MPa) on the structural and emulsification properties of soy protein isolate (SPI). The results indicate that HHPH treatment increases the surface hydrophobicity (H0) of the SPI, reduces β-fold and irregular curls, leading to the formation of soluble aggregates, increased adsorbed protein content, and subsequent improvements in emulsification activity index (EAI) and emulsion stability index (ESI). In contrast, the HPHH treatment promoted the exchange of SH/SS bonds between protein molecules and facilitated the interaction of basic peptides and β-subunits, leading to larger particle sizes of the soluble aggregates compared to the HHPH-treated samples. However, excessive aggregation in HPHH-treated aggregates leads to decreased H0 and adsorbed protein content, and increased interfacial tension, negatively affecting the emulsification properties. Compared to the HPHH treatment, HHPH treatment at homogenization pressures of 20 to 100 MPa increases EAI and ESI by 5.81-29.6 % and 5.31-25.9 %, respectively. These findings provide a fundamental basis for soybean protein manufacturers to employ appropriate processing procedures aimed at improving emulsification properties.

Enhancing pea protein isolate functionality: A comparative study of high-pressure homogenization, ultrasonic treatment, and combined processing techniques

Pea protein has attracted widespread attention due to its high nutritional value, low allergenicity, non-GMO status, and broad availability. However, compared to animal proteins, pea protein has inferior functional properties, which limits its application in the food industry. This study used pea protein isolate (PPI) as the main raw material and investigated the effects of high-pressure homogenization (HPH), ultrasonic treatment (US), and the combination of the two in different orders on the structure and function of PPI. The results showed that HPH or US promoted the transformation of PPI insoluble suspension into a uniform protein dispersion, significantly reducing particle size, unfolding the spatial structure, exposing more amino acid residues. These structural changes resulted in a substantial increase in the solubility, foaming capacity and emulsifying activity of PPI. Moreover, the combined treatments further impacted the properties of PPI, largely depending on the order of the processing steps; the combination of HPH-US exhibited the best functional characteristics.

Influence of atmospheric pressure plasma jet on the structural, functional and digestive properties of chickpea protein isolate

Chickpea protein (CPI) is a promising dietary protein and potential substitute for soy protein in food product development due to its high protein content and low allergenicity. However, CPI possesses denser tertiary and quaternary structures and contains certain amount of anti-nutritional factors, both of which constrain its functional properties and digestibility. The objective of this study was to assess the effectiveness of atmospheric pressure plasma jets (APPJ) as a non-thermal method for enhancing the functional characteristics and digestibility of CPI. In this study, the reactive oxygen and nitrogen species generated by the APPJ treatment led to protein oxidation and increased carbonyl and di-tyrosine contents. At the same time, the secondary, tertiary and microstructural structures of CPI were changed. The solubility, water holding capacity, fat absorption capacity, emulsifying capacity and foaming capacity of CPI were significantly improved after 30 s APPJ treatment, and a higher storage modulus in rheology was observed. Additionally, it was observed that the in vitro protein digestibility (IVPD) of APPJ-treated CPI increased significantly from 44.85 ± 0.6 % to 50.2 ± 0.59 % following in vitro simulated gastric and intestinal digestion, marking a noteworthy improvement of 11.93 %. These findings indicate that APPJ processing can enhance the functional and digestive properties of CPI through structural modification and expand its potential applications within the food industry.

Effects of ultrasonic treatment on the structural, functional properties and beany flavor of soy protein isolate: Comparison with traditional thermal treatment

This research explored the influences of ultrasonic and thermal treatments on the structure, functional properties, and beany flavor of soy protein isolate (SPI). In comparison with traditional thermal treatment, ultrasonic treatment effectively induced protein structural unfolding and exposure of hydrophobic groups, which reduced relative content of α-helix, increased relative content of β-turn, β-sheet and random coil, and improved the solubility, emulsifying and foaming properties of SPI. Both treatments significantly decreased the species and contents of flavor compounds, such as hexanal, (E)-2-nonenal, (Z)-2-heptenal and (E)-2-hexenal in SPI. The relative content of hexanal in the major beany flavor compound decreased from 11.69% to 6.13% and 5.99% at 350 W ultrasonic power and 150 s thermal treatment procedure, respectively. After ultrasonic treatment, structural changes in SPI were significantly correlated with functional properties but showed a weak correlation with flavor. Conversely, the opposite trend was observed for thermal treatment. Thus, using ultrasonic treatment to induce and stabilise the denatured state of proteins is feasible to improve the functional properties and beany flavor of SPI.

Study on potential antigenicity and functional properties of whey protein treated by high hydrostatic pressure based on structural analysis

High hydrostatic pressure (HHP) is extensively utilized in the field of food processing due to its remarkable ability to preserve the freshness of food. The potential antigenicity of β-lactoglobulin (β-LG) in whey protein isolate (WPI, 3%) treated by HHP was detected by enzyme linked immunosorbent assay (ELISA) using monoclonal antibodies. Furthermore, the impact of pressure-induced structural alterations on the emulsification properties and antioxidant activity of WPI was investigated. The findings revealed that pressures exceeding 300 MPa resulted in molecular aggregation, the formation of inter-molecular disulfide bonds, and an increase in surface hydrophobicity (H0). The percentage of β-sheet decreased along with the pressure. The results showed the increment of α-helix and β-turn with pressure. ELISA demonstrated a significant reduction in the antigenicity of β-LG following HHP treatment (100-600 MPa), with a slight recovery observed at 300 MPa. These spatial structural modifications led to the unfolding of the β-LG molecule, thereby enhancing its digestibility. Moreover, HHP treatment substantially improved the antioxidant properties, with the exposure to hydrophobic amino acids contributing to increased antioxidant properties and emulsion stability.

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.

Effects of electric field intensity regulation on protein aggregation behaviour and foaming property of soybean 7S globulin

In this study, the aggregation behaviour of soybean 7S globulin after moderate electric field (MEF) treatment was investigated, and the influence of the electric field and temperature field on the structure and foaming property of the aggregates were analysed and compared with conventional water bath (COV). The results showed that MEF treatment enhanced the properties of the aggregates. The properties of the treated aggregates were significantly better than those of native 7S globulin. At an electric field strength of 8 V/cm, the solubility, turbidity, and particle size increased from 95.81 % to 99.37 %, 0.097 to 0.189 and 61.97 nm to 113.21 nm, respectively, and the absolute value of potential decreased from 23.56 mV to 22.12 mV. The SDS-PAGE and size exclusion chromatography (SEC) results showed that the electric field had a positive effect on the aggregate formation of the Fourier-transform infrared spectroscopy (FTIR), fluorescence spectroscopy, surface hydrophobicity (H0) and total sulfhydryl (SHT) results indicated that the spatial structure of the protein was changed by MEF treatment. The protein β-sheet content was reduced, and the Try that was originally buried inside the molecule was exposed, resulting in an increase in H0 and a decrease in SHT. The foaming property of the 7S globulin aggregates was improved by MEF treatment.

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

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

Protein-Stabilized Emulsion Gels with Improved Emulsifying and Gelling Properties for the Delivery of Bioactive Ingredients: A Review

In today's food industry, the potential of bioactive compounds in preventing many chronic diseases has garnered significant attention. Many delivery systems have been developed to encapsulate these unstable bioactive compounds. Emulsion gels, as colloidal soft-solid materials, with their unique three-dimensional network structure and strong mechanical properties, are believed to provide excellent protection for bioactive substances. In the context of constructing carriers for bioactive materials, proteins are frequently employed as emulsifiers or gelling agents in emulsions or protein gels. However, in emulsion gels, when protein is used as an emulsifier to stabilize the oil/water interface, the gelling properties of proteins can also have a great influence on the functionality of the emulsion gels. Therefore, this paper aims to focus on the role of proteins' emulsifying and gelling properties in emulsion gels, providing a comprehensive review of the formation and modification of protein-based emulsion gels to build high-quality emulsion gel systems, thereby improving the stability and bioavailability of embedded bioactive substances.

Effects of high pressure synergistic enzymatic physical state and concentration on the denaturation of polyphenol oxidase

The synergistic effect of the initial state of the enzyme and pressure level on the denaturation of PPO has not been clear yet, but it significantly affects the application of high hydrostatic pressure (HHP) in the enzyme-containing food processing. Solid (S-) and low/high concentration liquid (LL-/HL-) polyphenol oxidase (PPO) was used as the study object, and the microscopic conformation, molecular morphology and macroscopic activity of PPO under HHP treatments (100-400 MPa, 25 °C/30 min) were investigated by spectroscopic techniques. The results show that the initial state has a significant effect on the activity, structure, active force and substrate channel of PPO under pressure. The effec can be ranked as follows: physical state > concentration > pressure, S-PPO > LL-PPO > HL-PPO. High concentration has a weakening effect on the pressure denaturation of the PPO solution. Under high pressure, the α-helix and concentration factors play a crucial role in stabilizing the structure.

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.

Impacts of Industrial Modification on the Structure and Gel Features of Soy Protein Isolate and its Composite Gel with Myofibrillar Protein

Native soy protein isolate (N-SPI) has a low denaturation point and low solubility, limiting its industrial application. The influence of different industrial modification methods (heat (H), alkaline (A), glycosylation (G), and oxidation (O)) on the structure of SPI, the properties of the gel, and the gel properties of soy protein isolate (SPI) in myofibril protein (MP) was evaluated. The study found that four industrial modifications did not influence the subunit composition of SPI. However, the four industrial modifications altered SPI's secondary structure and disulfide bond conformation content. A-SPI exhibits the highest surface hydrophobicity and I_850/830 ratio but the lowest thermal stability. G-SPI exhibits the highest disulfide bond content and the best gel properties. Compared with MP gel, the addition of H-SPI, A-SPI, G-SPI, and O-SPI components significantly improved the properties of the gel. Additionally, MP-ASPI gel exhibits the best properties and microstructure. Overall, the four industrial modification effects may impact SPI's structure and gel properties in different ways. A-SPI could be a potential functionality-enhanced soy protein ingredient in comminuted meat products. The present study results will provide a theoretical basis for the industrialized production of SPI.

Multi-dimensional analysis of heat-induced soybean protein hydrolysate gels subjected to ultrasound-assisted pH pretreatment

This study aimed to evaluate the gelation characteristics of soybean protein hydrolysate (SPH) extracted by enzyme-assisted aqueous extraction. Specifically, the changes in gelation behaviors for heat-induced (95 °C, 20 min) SPH dispersions treated with pH (pH 3, 5, 9; pH 7 as control) and ultrasound (U; 240 W, 30 min) were investigated. The results showed that typical gel behavior with high elastic nature in the viscoelasticity and network structures were observed during the heating process, where the disulfide bond played a dominant role in the gel network formation of all the samples. Notably, the heat-induced aggregation in the SPH gels was mainly formed by the association of the basic B polypeptide in 11S and β subunit in 7S. The most superior SPH gel was formed at pH 7 when assisted by ultrasonication during the heating process. This as-synthesized gel showed a uniform filamentous structure and exhibited the more excellent textural, rheological and thermal properties than those of the samples formed under acidic and alkaline conditions. These results are of great value in revealing the gelation mechanism of SPH.

Effects of Heating Treatment on Functional and Structural Properties of Liquid Whole Egg

Liquid whole egg (LWE) products have many advantages such as convenient transportation, easy production and are safe. However, LWE has a short shelf life and high thermal sensitivity, so suitable heating treatment is the key to the production of LWE products. The aim of this study is to investigate the effects of heating treatments conditions (at 55–67 °C for 0–10 min) on the emulsification, foaming activity and rheological properties of LWE. The results indicated that the emulsifying activity of LWE had no significant change after 55–64 °C heating treatment, while it decreased significantly after heating treatment at 67 °C. The foaming property of LWE increased significantly after 55 °C to the 64 °C heating treatment; while the foaming property showed a downward trend with the increase in heat treatment temperature, it can significantly improve the foam stability of LWE. The heating treatment thoroughly changed the molecular weight distribution of LWE protein, thus promoted the protein surface hydrophobicity, hydrophobicity activity and rheological properties. The heating treatment at 61 °C for 6 min had a better effect on the functional properties than that of the other heating groups. In addition, the results of this study provide the change in rules of LWE under different heating treatment conditions and provide theoretical guidance for the production and processing of LWE.

Correlation between interfacial layer properties and physical stability of food emulsions: current trends, challenges, strategies, and further perspectives

Emulsions are thermodynamically unstable systems that tend to separate into two immiscible phases over time. The interfacial layer formed by the emulsifiers adsorbed at the oil-water interface plays an important role in the emulsion stability. The interfacial layer properties of emulsion droplets have been considered the cutting-in points that influence emulsion stability, a traditional motif of physical chemistry and colloid chemistry of particular significance in relation to the food science and technology sector. Although many attempts have shown that high interfacial viscoelasticity may contribute to long-term emulsion stability, a universal relationship for all cases between the interfacial layer features at the microscopic scale and the bulk physical stability of the emulsion at the macroscopic scale remains to be established. Not only that, but integrating the cognition from different scales of emulsions and establishing a unified single model to fill the gap in awareness between scales also remain challenging. In this review, we present a comprehensive overview of recent progress in the general science of emulsion stability with a peculiar focus on interfacial layer characteristics in relation to the formation and stabilization of food emulsions, where the natural origin and edible safety of emulsifiers and stabilizers are highly requested. This review begins with a general overview of the construction and destruction of interfacial layers in emulsions to highlight the most important physicochemical characteristics of interfacial layers (formation kinetics, surface load, interactions among adsorbed emulsifiers, thickness and structure, and shear and dilatational rheology), and their roles in controlling emulsion stability. Subsequently, the structural effects of a series of typically dietary emulsifiers (small-molecule surfactants,proteins, polysaccharides, protein-polysaccharide complexes, and particles) on oil-water interfaces in food emulsions are emphasized. Finally, the main protocols developed for modifying the structural characteristics of adsorbed emulsifiers at multiple scales and improving the stability of emulsions are highlighted. Overall, this paper aims to comprehensively study the literature findings in the past decade and find out the commonality of multi-scale structures of emulsifiers, so as to deeply understand the common characteristics and emulsification stability behaviour of adsorption emulsifiers with different interfacial layer structures. It is difficult to say that there has been significant progress in the underlying principles and technologies in the general science of emulsion stability over the last decade or two. However, the correlation between interfacial layer properties and physical stability of food emulsions promotes revealing the role of interfacial rheological properties in emulsion stability, providing guidance on controlling the bulk properties by tuning the interfacial layer functionality.

Effect of High Pressure Homogenization-Modified Soy 11S Globulin on the Gel and Rheological Properties of Pork Myofibrillar Protein

The changes in texture and rheological characteristics, water holding capacity, and microstructure of pork myofibrillar protein with high-pressure homogenization-modified (0-150 MPa) soy 11S globulin were studied. The cooking yield, whiteness values, texture properties, shear stress, initial apparent viscosity, storage modulus (G'), and loss modulus (G″) of pork myofibrillar protein with high-pressure homogenization-modified soy 11S globulin were significantly increased (p < 0.05) compared with the sample of 0 MPa, and centrifugal yield was significantly decreased, except for the sample of 150 MPa. Therein, the sample of 100 MPa had the largest values. Meanwhile, the water and proteins bonded more tightly because the initial relaxation times of T_2b, T₂₁ and T₂₂ from pork myofibrillar protein with high-pressure homogenization-modified soy 11S globulin were shorter (p < 0.05). Overall, the water-holding capacity, gel texture and structure, and rheological properties of pork myofibrillar protein could improve when adding soy 11S globulin treated with 100 MPa.

Dithiothreitol-induced reassembly of soybean lipophilic protein as a carrier for resveratrol: Preparation, structural characterization, and functional properties

We employed dithiothreitol (DTT) to reassemble soy lipophilic protein (LP) and increased its solubility for encapsulating resveratrol (Res); we subsequently added hydroxypropyl methylcellulose (HPMC) to further stabilize Res. Physicochemical characterization, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and spectral analysis revealed that DTT triggered the breakage and reassembly of the disulfide bond. Consequently, the solubility of LP increased from 38.64 % to 71.49 %, and the number of free sulfhydryl groups increased to 7.84 mol·g-1. Furthermore, the encapsulation efficiency and structure of reassembled LP nanoparticles loaded with Res were found to be closely related to the DTT concentration used for induction. When HPMC was added, the LP-Res complex demonstrated spontaneous self-assembly, and the pH and temperature stability of the Res in the nanoparticles improved. An in vitro digestion simulation revealed that the reassembled LP was an efficient carrier for Res delivery. Particularly, HPMC improved the bioavailability and sustained release of Res.

Study of ultrasonic treatment on the structural characteristics of gluten protein and the quality of steamed bread with potato pulp

Physicochemical properties and microstructure of gluten protein, and the structural characteristics of steamed bread with 30 % potato pulp (SBPP) were investigated by ultrasonic treatments. Results showed that 400 W ultrasonic treatment significantly (P < 0.05) increased the combination of water and substrate in the dough with 30 % potato pulp (DPP). The contents of wet gluten, free sulfhydryl (SH), and disulfide bond (SS) were influenced by ultrasonic treatment. Moreover, UV-visible and fluorescence spectroscopy demonstrated that the conformation of gluten protein was changed by ultrasonic treatment (400 W). Fourier transform infrared (FT-IR) illustrated that the β-sheet content was significantly (P < 0.05) increased (42 %) after 400 W ultrasonic treatment, and the surface hydrophobicity of gluten protein in SBPP increased from 1225.37 (0 W ultrasonic treatment) to 4588.74 (400 W ultrasonic treatment). Ultrasonic treatment facilitated the generation of a continuous gluten network and stabilized crumb structure, further increased the specific volume and springiness of SBPP to 18.9 % and 6.9 %, respectively. Those findings suggested that ultrasonic treatment would be an efficient method to modify gluten protein and improve the quality of SBPP.

Valorization of Local Legumes and Nuts as Key Components of the Mediterranean Diet

Legumes and nuts are components of high importance in the diet of many countries, mainly those in the Mediterranean region. They are also very versatile and culturally diverse foods found all over the world, acting as a basic protein source in certain countries. Their genetic diversity is needed to sustain the food supply and security for humans and livestock, especially because of the current loss of habitats, species, and genetic diversity worldwide, but also because of the ever present need to feed the increasing human population. Even though both legumes and nuts are considered as high-protein food and environmentally friendly crops, developed countries have lower consumption rates when compared to Asia or Africa. With a view to increasing the consumption of legumes and nuts, the objective of this review is to present the advantages on the use of autochthonous varieties from different countries around the world, thus providing a boost to the local market in the area. The consumption of these varieties could be helped by their use in ready-to-eat foods (RTE), which are now on the rise thanks to today's fast-paced lifestyles and the search for more nutritious and sustainable foods. The versatility of legumes and nuts covers a wide range of possibilities through their use in plant-based dairy analogues, providing alternative-protein and maximal amounts of nutrients and bioactive compounds, potential plant-based flours for bakery and pasta, and added-value traditional RTE meals. For this reason, information about legume and nut nutrition could possibly increase its acceptance with consumers.

Effects of high-pressure homogenization on physicochemical and functional properties of enzymatic hydrolyzed soybean protein concentrate

This paper investigates the effect on the physicochemical and functional properties of soybean protein concentrate (SPC) by using Alcalase protease and high-pressure homogenization (HPH) (0, 20, 40, 60, 80, and 100 MPa) for the combined modification. The results showed that the degree of hydrolysis of SPC was 4.1% and the antigen protein was degraded after Alcalase hydrolysis, when the homogenization pressure (HP) was 6 0Mpa, the particle size of the SPC was the smallest, the zate potential absolute value up to 33.45 mV, the secondary structure has the lowest β-sheet content, the highest random coil content, and the highest surface hydrophobicity (H0), the size of protein fragments on the microstructure surface is the smallest, the lowest denaturation temperature (T d ) and enthalpy (△H) are 72.59°C and 1.35 J/g, the highest solubility is 80.54%, and the highest water and oil holding capacities are 7.73 g/g and 6.51 g/g, respectively. The best emulsifying activity and emulsifying stability were 43.46 m2/g and 190.35 min, the most even distribution of emulsion droplets. This indicates that the HPH treatment destroys the structure of enzymatic hydrolyzed SPC, changes its physicochemical properties, and improves its functional properties. In this study, SPC was modified by HPH and enzyme combined treatment, in order to improve the functionality and application range of SPC, and provide a theoretical basis for its high-value utilization in the food field.

Effect of high hydrostatic pressure processing on the structure, functionality, and nutritional properties of food proteins: A review

Proteins are important food ingredients that possess both functional and nutritional properties. High hydrostatic pressure (HHP) is an emerging nonthermal food processing technology that has been subject to great advancements in the last two decades. It is well established that pressure can induce changes in protein folding and oligomerization, and consequently, HHP has the potential to modify the desired protein properties. In this review article, the research progress over the last 15 years regarding the effect of HHP on protein structures, as well as the applications of HHP in modifying protein functionalities (i.e., solubility, water/oil holding capacity, emulsification, foaming and gelation) and nutritional properties (i.e., digestibility and bioactivity) are systematically discussed. Protein unfolding generally occurs during HHP treatment, which can result in increased conformational flexibility and the exposure of interior residues. Through the optimization of HHP and environmental conditions, a balance in protein hydrophobicity and hydrophilicity may be obtained, and therefore, the desired protein functionality can be improved. Moreover, after HHP treatment, there might be greater accessibility of the interior residues to digestive enzymes or the altered conformation of specific active sites, which may lead to modified nutritional properties. However, the practical applications of HHP in developing functional protein ingredients are underutilized and require more research concerning the impact of other food components or additives during HHP treatment. Furthermore, possible negative impacts on nutritional properties of proteins and other compounds must be also considered.

High moisture extrusion cooking of meat analogs: A review of mechanisms of protein texturization

High-moisture extrusion cooking (HMEC) is an efficient method for converting proteins and polysaccharides into fibrous structure that is used in the industrial production of meat analogs. The purpose of this review is to systematically evaluate current knowledge regarding the modification of protein structure including denaturation and reassembly upon extrusion processing and to correlate this understanding to the structure of the final products. Although there is no consensus on the relative importance of a certain type of bond on extrudates' structure, literature suggests that, regardless of moisture level, these linkages and interactions give rise to distinctive hierarchical order. Both noncovalent and disulfide bonds contribute to the extrudates' fibrous structure. At high water levels, hydrogen and disulfide bonds play a dominant role in extrudates' texture. The process parameters including cooking temperature, screw speed, and moisture content have significant albeit different levels of impact on the texturization process. Their correlation with the ingredients' physiochemical properties provides a greater insight into the process-structure-function relationship of meat analogs. The tendency of protein and polysaccharide blends to phase separate rather than produce a homogeneous mix is a particularly important aspect that leads to the formation of fibrous layers when extruded. This review shows that systematic studies are required to measure and explain synergistic and competitive interactions between proteins and other ingredients such as carbohydrates with a focus on their incompatibility. The wide range of plant protein source can be utilized in the HMEC process to produce texturized products, including meat analogs.

Characteristics and structure of a soy protein isolate-lutein nanocomplex produced via high-pressure homogenization

BACKGROUND

In recent years, nanocarriers for transporting active substances have attracted attention. This study was to explore the soy protein isolate (SPI) after high-pressure homogenization (HPH) (0, 30, 60, 90 and 120 MPa) as potential lutein carriers.

RESULTS

The load amount (LA) and encapsulation efficiency (EE) of the SPI-lutein nanocomplexes at a homogenization pressure of 60 MPa were the highest (2.32 mg mL^-1 and 92.85%, respectively), and the average particle size and ζ-potential of the SPI-lutein nanocomplexes were 192.1 nm and -30.06 mV, respectively. The DPPH (2,2-diphenyl-1-picrylhydrazyl) and hydroxyl-antioxidant activities of the complex increased from 12.4% and 23.3% to 52.7% and 61.07%, respectively, after the protein was treated with HPH. The surface hydrophobicity of the SPI and the SPI-lutein nanocomplexes increased with increasing homogenization pressure treatment. Fourier transform-infrared spectrophotometry analyses suggested that the homogenization treatments resulted in partial unfolding of the protein molecules, and the addition of lutein can also lead to the change of protein secondary structure. The fluorescence emission of SPI was quenched by lutein through the static quenching mechanism. Fluorescence experiments revealed that SPI and lutein had the strongest binding ability through hydrophobic interaction at a homogenization pressure of 60 MPa.

CONCLUSION

After HPH, the combination of SPI and lutein was beneficial, and the stability of lutein also improved after the combination. This study is conducive to expanding the application of soybean protein in the food industry. © 2022 Society of Chemical Industry.

Antioxidant potential and molecular docking of bioactive compound of Camellia sinensis and Camellia assamica with cytochrome P450

Camellia sinensis and Camellia assamica are well known for their medicinal and therapeutic potential. The purpose of this work is to assess the flavonoid content and antioxidant potential of methanol extracts of C. sinensis (MES) and acetone extract of C. assamica (AEA) experimentally and computationally. Qualitative analysis was done to assess the presence of flavonoids. Further, the antioxidant potential of MES and AEA was done by ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)) and superoxide free radical-scavenging activity. The profiling of functional groups was analyzed by FT-IR analysis. The bioactive compounds n-heptadecanol-1 of MES and 2',6'-dihydroxyacetophenone, bis(trimethylsilyl) ether of AEA were procured from our previous study to analyze their antioxidant potential computationally (Auto-dock Vina). Both the extracts showed their potential to neutralize free radicals with variable potency. The study of the molecular interactions revealed that both the extracts MES and AEA interacted to the active site with higher binding energy. This work deduced that n-heptadecanol-1 and 2',6'-dihydroxyacetophenone, bis(trimethylsilyl) ether have good potential to inhibit and scavenge the free radicals.