Insight into ultrasound-assisted phosphorylation on the structural and emulsifying properties of goose liver protein

Efficacy, physicochemical and processing properties of oat peptides prepared via ultrasonication-assisted organic acid hydrolysis

Currently, the low efficiency and pollution issues associated with biological and chemical methods for the preparation of functional peptides continue to pose challenges, restricting the large-scale production and utilization of functional peptides. This study has found that the ultrasound-assisted organic acid-surfactant system is an efficient and green method for the preparation of functional peptides. The probe ultrasonication-assisted tartaric acid system successfully degraded oat globulins into peptides with a degree of hydrolysis (DH) of 22.8 %. The addition of glyceryl monostearate increased the instantaneous burst rate of the bubble (with a D-value of 16 %), thereby elevating the DH to as high as 36 %. The resulting oat peptide particles exhibited high hydrophobicity, and consequently demonstrated strong foaming capacity (99.6 %), oil holding capacity (399.4 %), emulsifying ability (Emulsifying activity index = 50.5 m2/g, stability index = 108 min), and hydroxyl radical scavenging capacity of 98.9 % (at a concentration of 5 mg/mL), holding great promise for application in the field of food processing. These findings deepen our understanding of the enhanced ultrasonic hydrolysis ability of surfactants and pave a new way to produce functional peptides.

Impact of phosphorus on the functional properties of extracellular polymeric substances recovered from sludge

Extracellular Polymeric Substances (EPS) are ubiquitous in biological wastewater treatment (WWT) technologies like activated sludge systems, biofilm reactors, and granular sludge systems. EPS recovery from sludge potentially offers a high-value material for the industry. It can be utilized as a coating in slow-release fertilizers, as a bio-stimulant, as a binding agent in building materials, for the production of flame retarding materials, and more. P recovered within the extracted EPS is an intrinsic part of the recovered material that potentially influences its properties and industrial applications. P is present in EPS in different speciation (e.g., P esters, poly-P, ortho-P, etc.). Such P species are already intensively used in the chemical industry to enhance thermal stability, viscoelasticity, emulsification, water-holding capacity, and many other properties of some natural and petroleum-derived polymers. The translation of this knowledge to EPS is missing which prevents the full utilization of phosphorus in EPS. This knowledge could allow us to engineer EPS via phosphorus for specific target properties and applications. In this review, we discuss how P could affect EPS properties based on experiences from other industries and reflect on how these P species could be influenced during the EPS extraction process or in the WWTPs.

Effect of transglutaminase cross-linking on the structure and emulsification performance of heated black bean protein isolate

BACKGROUND

Transglutaminase (TGase) is a heat-resistant biocatalyst with strong catalytic activity, which functions effectively under moderate temperature and pH conditions, and is used widely in protein cross-linking and recombination. Transglutaminase cross-linking is a novel and specific modification method for black bean protein isolate (BBPI). This article investigates the effect of transglutaminase cross-linking on the structure and emulsification performance of heated BBPI.

RESULTS

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that heated BBPI with TGase had a higher molecular weight than heated BBPI without TGase, and the protein bands widened with increasing enzyme activity, indicating that TGase cross-linking promoted protein molecule aggregation. A high molecular weight polymer can better stabilize the oil-water interface, preventing the emulsion from layering. Fourier transform infrared (FTIR) spectroscopy showed that the α-helix content decreased from 15.64% to 13.75%, and the β-sheet content increased from 48.13% to 54.08%. The decrease in α-helix content and increase in β-sheet content could make the structure more stable and improve the emulsifying properties of heated BBPI. When TGase was 20 U g-1, the protein emulsification activity index (EAI) reached its highest value of 1.87 m2 g-1, and the emulsification stability index (ESI) value was 0.27 min (P < 0.05); these figures were 0.19 m2 g-1, and 0.07 min higher, respectively, than in the sample without added TGase.

CONCLUSION

In summary, transglutaminase cross-linking has a positive effect on the structure and emulsification performance of heated BBPI and can be used as an effective method for BBPI modification. © 2024 Society of Chemical Industry.

Apolar oil favored interfacial curcumin complexation onto goose liver protein improves the high internal phase emulsion templated oleogel characters

The curcumin complexation onto goose liver protein (GLP) at interface for high internal phase emulsions (HIPEs) property enhancement as well as plant oil (sunflower oil, corn oil and flaxseed oil) based oleogels stabilization were elucidated. Interfacial pressure and rheology showed that oily dispersed curcumin and its complexation strengthened the GLP adsorption and intermolecular assembly, especially for apolar flaxseed oil. Frequency sweep and micromorphology of HIPEs suggested that flaxseed oil and curcumin complexation rendered the highest droplet packing density with least size dimension (40.25 ± 0.77 μm) ascribed to the most elevated GLP interfacial property. The oleogel with flaxseed oil incorporation and curcumin complexation exhibited also the largest shear resistance due to sufficient GLP interfacial networking that better entrapped the oil droplets, as was also indicated by thermogravimetric analysis, X-ray diffraction and Fourier infrared spectroscopy. Consequently, this oleogel gave the most favored oil holding (90.15 ± 1.05 %) as well as the highest oxidation stability with least oil unsaturation to saturation transformation for 10 days storage. This study provided an alternative for oleogel synthesis via facile oil inclusion with the phenol and potentiated the application of fat replacer using the by-product protein with synergistic curcumin complexation.

Structural and functional changes induced by different ultrasound-frequency-assisted xylose-glycation inhibits lysinoalanine formation in Tenebrio molitor protein

We explored the effects of sonication-assisted xylose (Xyl) grafting on the structure and functionality of Tenebrio molitor protein (MP). Different ultrasound frequencies (20, 25, 28, 20/25, 20/28, 25/28, 20/25/28 kHz) were used, and the inhibition mechanism of ultrasound-assisted Xyl grafting on the formation of lysinoalanine (LAL) was explored. The results suggested that the turbidity and browning products of MP significantly increase, with MP-Xyl-20 kHz exhibiting the highest grafting degree (43.78 %). Compared with MP, the total sulfhydryl content of MP-Xyl and MP-Xyl-20 kHz was significantly improved by 21.90 % and 98.80 % (P < 0.05). Circular Dichroism, Fourier Transform Infrared Spectroscopy, SEM, and AFM analysis showed changes in MP conformation following various frequencies ultrasound-assisted glycosylation. Notably, emulsifying capacity, stability, and foaming ability of MP-Xyl-20 kHz were significantly enhanced by 97.08 %, 48.03 %, and 55.01 %, respectively, compared with MP. The glycol-conjugated MP treated with ultrasound-assisted glycosylation (MP-Xyl-25/28 kHz) had the lowest LAL content (7.19 μg/mg), representing a 56.56 % and 46.70 % decrease compared to the control MP and MP-Xyl, respectively. The content of LAL exhibited a positive correlation with surface hydrophobicity, whereas it demonstrated a negative correlation with sulfhydryl and carbonyl groups. These findings indicated that sonication-assisted xylose improved the functional characteristics of MP, and the inhibition effect on LAL formation. The outcome of the study could be very beneficial in the modification of MP for food industrial applications.

Pickering emulsions stabilized by ultrasound-assisted phosphorylated cantaloupe seed protein isolate -chitosan: Preparation, characterization and stability

Cantaloupe seed protein isolate (CSPI) has attracted the attention of its low cost, easy digestion and balanced composition of essential amino acids. However, due to the low solubility of CSPI, its application in the food industry is limited. Therefore, the present study investigated the effect of ultrasound-assisted phosphorylation on the solubility of CSPI and the structural properties were characterized. The solubility of cantaloupe seed protein increased from 9.17 % to 63.27 % by ultrasound assisted phosphorylation, and resulting in an increase in the absolute value of CSPI potential, a decrease in particle size, and a stable structure, which could be used for the construction of the food emulsification system. The modified CSPI was combined with chitosan (CS) to prepare stabilized Pickering emulsion for subsequent stability study. The results showed that stable Pickering emulsions could be prepared with CSPI at pH 7, CS 0.5 % and oil phase fraction 55 %. Ultrasound-assisted phosphorylation enhanced electrostatic interaction between CS's -NH3 groups and CSPI's -COO-groups which improved the storability of stabilized Pickering emulsion. This will help to broaden the application range of CSPI and provide a theoretical basis for CPI stable Pickering emulsion.

The improved gel properties of myofibrillar protein under low salt condition by ultrasound-assisted sodium tripolyphosphate

Excessive salt intake is associated with increased risks of cardiovascular disease, while directly reducing salt content significantly decreased the quality of meat. The objective of this study was to investigate the synergistic effects of sodium tripolyphosphate (STP) and ultrasound treatment on the gel properties of MP under low-salt conditions (0.3 M NaCl). The results of FTIR spectra showed that P3O105- group of STP bound to -NH2 or -OH group of MP form C-N-P or C-O-P bond, indicating the STP was successfully introduced to MP. The addition of STP significantly increased the absolute value of Zeta-potential, suggesting that the presence of STP increased the electrostatic interaction of MP-MP. Importantly, STP combined with ultrasound treatment under low salt condition (STP-U0.3) significantly increased solubility and decreased particle size of MP. Besides, STP-U0.3 treatment also promoted the exposure of hydrophobic groups and improved the rheological behavior of MP, resulting in the highest gel strength (37.78 ± 0.71 g) and the lowest cooking loss (26.73 ± 0.90 %) especially in 10 mM STP combined 100 W ultrasound treatment. These results corresponded by the gradually increases of α-helix content and the decrease of tryptophan fluorescence intensity. Furthermore, results of SEM illustrated that STP-U0.3 treatment contributed to formation of more homogeneous and dense gel network of MP gel. The above results displayed that the STP-U treatment under 0.3 M NaCl resulted in an equivalent effect to control group of 0.6 M NaCl, indicating that the combined application of STP and ultrasound has a promising potential in the low-salt meat processing industry.

Ultrasonic treatment of emulsion gels with different soy protein-hemp protein composite ratios: Changes in structural and physicochemical properties

To improve the emulsion gel system of single soybean isolate protein (SPI) and to broaden the application field of hemp protein isolate (HPI), ultrasonic treatment and HPI were introduced to improve the properties of SPI emulsion gel and to explore the mechanism. The results showed that the gel strength (218.6 g) and water-holding capacity (86.24 %) of the emulsion gels were improved under ultrasonic treatments when the ratio of SPI:HPI was >6:4, and the reticulation structure of the gels was enhanced. When the ratio of SPI:HPI was <6:4, the gel structure was loose and formless. Ultrasonic treatment has a significant effect on the emulsion gel with the ratio of SPI:HPI was >6:4. Appropriate ultrasonic treatment (400 W) changed the protein structure, improved the rheological properties of emulsion gels to form the protein-oil-coated network structure. However, excessive ultrasonic treatment (600 W) will destroy the conformation of the protein, reducing the stability of the structure. The effect of ultrasonic treatment on emulsion gels with the ratio of SPI:HPI was <6:4 is low, but improved the gel protein digestibility. This study provides a theoretical basis for the application of ultrasonic in composite protein emulsion gels systems and the development and application of HPI.

Potential mechanisms and effects of ultrasound treatment combined with pre- and post-addition of κ-carrageenan on the gelling properties and rheological behavior of myofibrillar proteins under low-salt condition

This study investigated the effect of ultrasound (US) combined with pre- and post-addition of κ-carrageenan (KC) on the gelling properties, structural characteristics and rheological behavior of myofibrillar proteins (MP) under low-salt conditions. The results showed that US combined with either pre- or post-addition of KC rendered higher gel strength and water holding capacity (WHC) of MP gels than those treated with US alone and added with KC alone (P < 0.05). US combined with pre-addition of KC facilitated the binding between MP and KC, which enhanced the gel strength and WHC of the mixed MP gels and significantly improved the rheological behavior of MP. This was also confirmed by the highest surface hydrophobicity, disulfide bonds and β-sheet content of the MP gels with US combined with pre-addition of KC. Moreover, microstructural results reflected a denser structure for the pre-addition of KC in combination with US. However, US combined with post-addition of KC resulted in limited MP unfolding and relatively weak hydrophobic interactions in the composite gels, which were less effective in improving the gel properties of the MP gels. This study provides potential strategies for enhancing the gelling properties of low-salt meat products via application of US and KC.

Effects of low-frequency magnetic field on solubility, structural and functional properties of soy 11S globulin

BACKGROUND

Soy 11S globulin has high thermal stability, limiting its application in the production of low-temperature gel foods. In this study, the low-frequency magnetic field (LF-MF, 5 mT) treatment (time, 30, 60, 90, and 120 min) was used to improve the solubility, conformation, physicochemical properties, surface characteristics, and gel properties of soy 11S globulin.

RESULTS

Compared with the native soy 11S globulin, the sulfhydryl content, emulsifying capacity, gel strength, water-holding capacity, and absolute zeta potential values significantly increased (P < 0.05) after LF-MF treatment. The LF-MF treatment induced the unfolding of the protein structure and the fracture of disulfide bonds. The variations in solubility, foaming properties, viscosity, surface hydrophobicity, and rheological properties were closely related to the conformational changes of soy 11S globulin, with the optimum LF-MF modification time being 90 min.

CONCLUSION

LF-MF treatment is an effective method to improve various functional properties of native soy 11S globulin, and this study provides a reference for the development of plant-based proteins in the food industry. © 2024 Society of Chemical Industry.

The gelling properties of fish gelatin as improved by ultrasound-assisted phosphorylation

This study investigated the effects of ultrasound-assisted phosphorylation on gelling properties of fish gelatin (FG). Ultrasound-assisted phosphorylation (UP) for 60, 90, and 120 min resulted in >6.54% increase of phosphorylation degree and decreased zeta potential of FG. Atomic force microscopy revealed that UP-FGs showed larger aggregates than P-FGs (normal phosphorylation FGs). Low frequent-NMR and microstructure analysis revealed that phosphorylation enhanced water-binding capability of FG and improved the gel networks. However, UP60 had the highest gel strength (340 g), gelling (17.96 °C) and melting (26.54 °C) temperature while UP90 and UP120 showed slightly lower of them. FTIR analysis indicated thatβ-sheet and triple helix content increased but random coil content decreased in phosphorylated FGs. Mass spectrometry demonstrated phosphate groups mainly bound to serine, threonine and tyrosine residues of FG and UP-FG exhibited more phosphorylation sites. The study showed that mild phosphorylation (UP60) could be applied to improve FG gel properties.

Goose liver protein emulsion with enhanced interfacial stabilization by facile core-shell curcumin complexation

The role of facile curcumin dispersion and its hydrophobic complexation onto GLP, in the form of shell (GLPC-E), core (GLPE-C) and with synergy (GLP-ECE), on the protein interfacial and emulsion stabilization was investigated. Turbiscan instability index, microrheological elasticity, viscosity and solid-liquid balance values showed that the O/W emulsion stability was in the order of GLP-E < GLPC-E < GLPE-C < GLP-ECE. GLP-ECE also gave the most reduced D [4, 3] (8.11 ± 0.14 μm) with lowest indexes of flocculation (2.80 ± 0.05 %) and coalescence (2.83 ± 0.10 %) at day 5. Interfacial shear rheology suggested the GLP-curcumin complexation fortified the GLP interfacial gelling and then the efficiency as steric stabilizer, especially of core-shell complexation (14.2 mN/m) that showed the most sufficient in-plane protein interaction against strain. Dilatational elasticity and desorption observation revealed the synergistic curcumin complexation facilitated GLP unfolding and macromolecular association at O/W interface, as was also verified from SEM image and surface hydrophobicity (from 36.23 to 76.04). Overall, this study firstly reported the facile curcumin bi-physic dispersion and GLP complexation in improving the emulsion stabilizing efficiency of the protein by advancing its interfacial stabilization.

Mechanism for improving the in vitro digestive properties of coconut milk by modifying the structure and properties of coconut proteins with monosodium glutamate

In this paper, the effect of monosodium glutamate (MSG) on coconut protein (CP) solubility, surface hydrophobicity, emulsification activity, ultraviolet spectroscopy and fluorescence spectroscopy was investigated. Meanwhile, the changes in the in vitro digestive properties of coconut milk were also further analyzed. MSG treatment altered the solubility and surface hydrophobicity of CP, thereby improving protein digestibility. Molecular docking showed that CP bound to pepsin and trypsin mainly through hydrogen bonds and salt bridges. And MSG increased the cleavable sites of pepsin and trypsin on CP, thus further improving the protein digestibility. In addition, MSG increased the Na+ concentration in coconut milk, promoted flocculation and aggregation between coconut milk droplets, which prevented the binding of lipase and oil droplets and inhibited lipid digestion. These findings may provide new ideas and insights to improve the digestive properties of plant-based milk.

Phosphate type dependent phosphorylation on the interfacial and emulsion stabilizing behaviors of goose liver protein: Perspective of protein charging

Elucidation on the emulsifying behaviors of goose liver protein (GLP) from interfacial perspective was scarce when protein charging was altered. This work aimed to elucidate the role of phosphorylation on the interfacial associative interaction and then emulsion stabilizing properties of GLP using three structurally relevant phosphates of sodium trimetaphosphate (STMP), sodium tripolyphosphate (STPP) and sodium pyrophosphate (TSPP). A monotonic increment of protein charging treated from STMP, STPP to TSPP caused progressively increased particle de-aggregation, surface hydrophobicity and structural flexibility of GLP. Compared with STMP and TSPP, STPP phosphorylation rendered the most strengthened interfacial equilibrium pressure (11.98 ± 0.24 mN/m) due to sufficient unfolding but moderated charging character conveyed. Desorption curve and interfacial protein microstructure indicated that STPP phosphorylation caused the highest interfacial connectivity between proteins adsorbed onto the same droplet, as was also verified by interfacial elastic modulus (10.3 ± 0.21 mN/m). STPP treated GLP also yielded lowest droplet size (8.16 ± 0.10 μm), flocculation (8.18%) and Turbiscan stability index (8.78 ± 0.36) of emulsion but most improved microrheological properties. Overall, phosphorylation functioned itself in fortifying the intradroplet protein-protein interaction but restraining the interdroplet aggregation, and STPP phosphorylation endowed the protein with most enhanced interfacial stabilization and emulsifying efficiency.

Phenolic structure dependent interaction onto modified goose liver protein enhanced by pH shifting: Modulations on protein interfacial and emulsifying properties

The appropriateness of animal by-product proteins as emulsifiers is barely explored compared to their meat counterparts. This paper focused on improving interfacial and emulsifying properties of modified goose liver protein using three structurally relevant polyphenols either enhanced by pH shifting (P-catechin, P-quercetin and P-rutin) or not (catechin, quercetin and rutin). Due to its high hydrophobicity and limited steric hindrance, quercetin was more sufficient to hydrophobically interact (ΔH > 0, ΔS > 0) with MGLP than catechin and rutin. Results showed that polyphenol interactive affinity was positively correlated to surface hydrophobicity but negatively to size and aggregation extent of MGLP. Interfacial pressure and dilatational elastic modulus implied that synergistic polyphenol interaction and pH shifting favored the interfacial adsorption and macromolecular association of MGLP, particularly for P-quercetin with the values reached to 19.9 ± 2.0 mN/m and 22.9 ± 1.2 mN/m, respectively. Emulsion stabilized by P-quercetin also maintained highest physical and oxidative stabilities regarding the lowest D [4,3] (3.78 ± 0.27 μm) and creaming index (8.38 ± 0.43 %), together with highest mono- (19.51 %) and polyunsaturated fatty acid content (29.39 %) during storage. Overall, chemical structure of polyphenols may be determining in fabricating MGLP-polyphenol complexes with improved emulsion stabilization efficiency.

Improvement in the gelling properties of myofibrillar protein from the razor clam (Sinonovacula constricta) through phosphorylation and structural characterization of the modified protein

This study investigated the modification of myofibrillar protein (MP) from the razor clam through phosphorylation by using various phosphate salts, namely, sodium tripolyphosphate (STPP), sodium trimetaphosphate (STMP), sodium polyphosphate (STTP) and sodium pyrophosphate (TSPP), and their mechanisms of action for functional and gelling properties. Fourier transform infrared spectrometry (FTIR) showed that MP introduced phosphate groups during phosphorylation; these phosphates changed the secondary structure. Moreover, MP after phosphorylation led to an increase in solubility, which was more evident in the case of TSPP phosphorylation, leading to the improvement of gel properties. Therefore, TSPP was the phosphate with the best gel properties in the modification of MP, showing the highest phosphorus content, which resulted in better gelling properties owing to its relatively shorter chains. These results showed that phosphate was able to improve protein cross-linking through ion interactions and electrostatic interactions, which ultimately improved the gelling properties of the razor clam protein.

Ultrasound-assisted phosphorylation of goose myofibrillar proteins: improving protein structure and functional properties

BACKGROUND

Goose meat is rough and embedded with dense connective tissue, impairing protein solubility. Therefore, to improve the functional properties of goose myofibrillar protein (GMP), ultrasound was used to assist the phosphorylation of GMP.

RESULTS

The fact that GMP attached covalently with the phosphate group of sodium tripolyphosphate (GMP-STP) was disclosed directly by Fourier transform infrared spectroscopy. Furthermore, ultrasound significantly improved the hydrophobicity and solubility of GMP-STP, which could be attributed to the conversion of α-helix to β-sheet, β-turns, and random coils by sonication. The spatial stabilization of the protein phosphorylation process was boosted by ultrasound, making the droplets more dispersed, and thus an improvement in the functional properties of GMP-STP was observed. Water-holding capacity, oil-binding capacity, and emulsifying and foaming properties were best at an ultrasound power of 400 W.

CONCLUSION

Ultrasound-assisted phosphorylation has great potential to modulate the structure-function relationship of proteins. © 2023 Society of Chemical Industry.

Study on the Structure, Function, and Interface Characteristics of Soybean Protein Isolate by Industrial Phosphorylation

The impacts of industrial phosphorylation on the structural changes, microstructure, functional, and rheological features of soybean protein isolate (SPI) were spotlighted. The findings implied that the spatial structure and functional features of the SPI changed significantly after treatment with the two phosphates. Sodium hexametaphosphate (SHMP) promoted aggregation of SPI with a larger particle size; sodium tripolyphosphate (STP) modified SPI with smaller particle size. SDS-polyacrylamide gel electrophoresis (SDS-PAGE) results showed insignificant alterations in the structure of SPI subunits. Fourier transform infrared (FTIR) and endogenous fluorescence noted a decline in α-helix quantity, an amplification in β-fold quantity, and an increase in protein stretching and disorder, indicating that phosphorylation treatment fluctuated the spatial structure of the SPI. Functional characterization studies showed that the solubility and emulsion properties of the SPI increased to varying degrees after phosphorylation, with a maximum solubility of 94.64% for SHMP-SPI and 97.09% for STP-SPI. Emulsifying activity index (EAI) and emulsifying steadiness index (ESI) results for STP-SPI were better than those for SHMP-SPI. Rheological results showed that the modulus of G' and G″ increased and the emulsion exhibited significant elastic behavior. This affords a theoretical core for expanding the industrial production applications of soybean isolates in the food and various industries.

Functional properties of glutelin from Camellia oleifera seed cake: Improvement by alkali-assisted phosphorylation through changes in protein structure

To explore the effect and its mechanism of alkali-assisted phosphorylation on the functional properties of Camellia Oleifera seeds cake glutelin (CSCG), CSCG was treated with different concentration of sodium trimetaphosphate (STMP, 1.0, 2.0, 3.0, 4.0, and 5%, w/v) in different pH environment (3.0, 5.0, 7.0, 9.0, and 11.0). The results showed that alkali assist improved the phosphorylation degree of CSCG, and the optimum pH value is 9.0. FT-IR and XPS confirmed the successful modification of phosphate groups on CSCG through covalent interaction. Alkali-assisted phosphorylation decreased the particle size and increased electronegativity of CSCG, as well as changed in its surface hydrophobicity, crystallinity, and intrinsic fluorescence. All these changes of protein structure triggered by alkali-assisted phosphorylation led to the improvement of water solubility, water/oil absorption capacity, emulsifying ability, foamability, and in vitro digestibility of CSCG. This work could provide a theoretical basis for industrial production of CSCG with excellent functional properties.

Ultrasound-Assisted Extraction of Artocarpus heterophyllus L. Leaf Protein Concentrate: Solubility, Foaming, Emulsifying, and Antioxidant Properties of Protein Hydrolysates

The impact of ultrasound-assisted extraction (UAE) was evaluated on the functionality of jackfruit leaf protein hydrolysates. Leaf protein concentrate was obtained by ultrasound (LPCU) and conventional extractions by maceration (LPCM). LPCM and LPCU were hydrolyzed with pancreatin (180 min), and hydrolysates by maceration (HM) and ultrasound (HU) were obtained. The composition of amino acids, techno-functional (solubility, foaming, and emulsifying properties), and antioxidant properties of the hydrolysates were evaluated. A higher amount of essential amino acids was found in HU, while HM showed a higher content of hydrophobic amino acids. LPCs exhibited low solubility (0.97–2.89%). However, HM (67.8 ± 0.98) and HU (77.39 ± 0.43) reached maximum solubility at pH 6.0. The foaming and emulsifying properties of the hydrolysates were improved when LPC was obtained by UAE. The IC50 of LPCs could not be quantified. However, HU (0.29 ± 0.01 mg/mL) showed lower IC50 than HM (0.32 ± 0.01 mg/mL). The results reflect that the extraction method had a significant (p < 0.05) effect on the functionality of protein hydrolysates. The UAE is a suitable method for enhancing of quality, techno-functionality, and antioxidant properties of LPC.

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

The most important factors restricting research and application in the food industry are the poor solubility and emulsification of pea protein isolate (PPI). This study investigates the effect of high-intensity ultrasound (HIU, 0-600 W) and pH-shifting treatment, alone or combined, on the structure, solubility, and emulsification of PPI, as well as its potential mechanism. The results revealed that the PPI solubility significantly increases when treated with the combination, corresponding to a decrease in the protein particle size, especially at 500 W of HIU power (p < 0.05). Correspondingly, the emulsion prepared from it was less prone to phase separation during storage. According to the structural analysis, the structural changes caused by protein unfolding (i.e., the exposure of hydrophobic and polar sites and the loss of the α-helix) seemed to be the primary reasons for increased PPI solubility. In addition, confocal laser scanning microscopy indicated that the combination treatment accelerated the adsorption of PPI at the oil/water interface and strengthened the compactness of the interface film. Improved interfacial properties and intermolecular forces played a critical role in the resistance to droplet coalescence in PPI emulsion. In conclusion, ultrasound and pH-shifting treatments have a synergistic effect on improving the solubility and emulsification of PPI.

Casein-hempseed protein complex via cross-link catalyzed by transglutaminase for improving structural, rheological, emulsifying and gelation properties

In present study, microbial transglutaminase (MTGase) was applied to strengthen the interaction between casein and hempseed protein (HPI) through crosslinking. The structural and functional characteristics of this heteropolymers were investigated. Both homologous and heterologous crosslinking were achieved by adding MTGase in casein-HPI system, and thus enhanced zeta potential, surface hydrophobicity, viscosity, emulsifying and gelation properties of the complex. However, HPI hindered the crosslinking due to unbalanced Lys/Gln ratios. Emulsifying and gelling properties were significantly correlated with the secondary structures. When MTGase activity was < 30 U/g or treatment time was < 2 h, the α-helix content decreased by 9% while the β-sheet content increased by 12%, respectively, with MTGase activity and treatment time increase. The structural alterations resulted in the better emulsifying activity, gel networks and water holding capacity of the complex. This work represents a novel interaction mode between casein and HPI via MTGase to elevate functional properties of complex.

The Effect of Glycosylated Soy Protein Isolate on the Stability of Lutein and Their Interaction Characteristics

Lutein is a natural fat-soluble carotenoid with various physiological functions. However, its poor water solubility and stability restrict its application in functional foods. The present study sought to analyze the stability and interaction mechanism of the complex glycosylated soy protein isolate (SPI) prepared using SPI and inulin-type fructans and lutein. The results showed that glycosylation reduced the fluorescence intensity and surface hydrophobicity of SPI but improved the emulsification process and solubility. Fluorescence intensity and ultraviolet–visible (UV–Vis) absorption spectroscopy results showed that the fluorescence quenching of the glycosylated soybean protein isolate by lutein was static. Through thermodynamic parameter analysis, it was found that lutein and glycosylated SPI were bound spontaneously through hydrophobic interaction, and the binding stoichiometry was 1:1. The X-ray diffraction analysis results showed that lutein existed in the glycosylated soybean protein isolate in an amorphous form. The Fourier transform infrared spectroscopy analysis results revealed that lutein had no effect on the secondary structure of glycosylated soy protein isolate. Meanwhile, the combination of lutein and glycosylated SPI improved the water solubility of lutein and the stability of light and heat.

Recent advances in modified food proteins by high intensity ultrasound for enhancing functionality: Potential mechanisms, combination with other methods, equipment innovations and future directions

High intensity ultrasound (HIU) is an efficient and green technology that has recently received enormous research attention for modification of food proteins. However, there are still several knowledge gaps in the possible mechanisms, synergistic effects of HIU with other strategies and improvement of HIU equipment that contribute to its application in the food industry. This review focuses on the recent research progress on the effects and potential mechanisms of HIU on the structure (including secondary and tertiary structure) and functionality (including solubility, emulsibility, foamability, and gelability) of proteins. Furthermore, the combination methods and innovations of HIU equipment for proteins modification in recent years are also detailed. Meanwhile, the possible future trends of food proteins modification by HIU are also considered and proposed.

Effect of Phosphorylation on the Structure and Emulsification Properties of Different Fish Scale Gelatins

This study aimed to investigate the effect of phosphorylation on the structure and emulsification of Coregonus peled, Esox lucius and Grass carp scale gelatin. Fourier transform infrared spectroscopy (FTIR) and endogenous fluorescence spectra showed that the structures of the three fish scale gelatins changed. Additionally, the surface hydrophobicity index of the three fish scale gelatins increased by 36.72, 31.42 and 111.67, respectively, after 1 h of phosphorylation, and the surface tension decreased by 17.27, 32.58 and 18.7 mN/m, respectively. The emulsification activity index increased by 115.86, 155.22 and 45.52 m²/g, and the emulsification stability index increased by 98.37, 256.77 and 169.61 min, respectively. The structure of fish scale gelatin changed after phosphorylation, which resulted in the improvement of emulsification. This work will provide useful information to understand the relationship between the structure and function of gelatin.