Driving forces of disaggregation and reaggregation of peanut protein isolates in aqueous dispersion induced by high-pressure microfluidization

Impact of pilot-scale microfluidization on soybean protein structure in powder and solution

The effect of microfluidization treatment on the primary, secondary, and tertiary structure of soybean protein isolate (SPI) was investigated. The samples were treated with and without controlling the temperature and circulated in the system 1, 3, and 5 times at high pressure (137 MPa). Then, the treated samples were freeze-dried and reconstituted in water to check the impact of the microfluidization on two different states: powder and solution. Regarding the primary structure, the SDS-PAGE analysis under reducing conditions showed that the protein bands remained unchanged when exposed to microfluidization treatment. When the temperature was controlled for the samples in their powder state, a significant decrease in the quantities of β-sheet and random coil and a slight reduction in α-helix content was noticed. The observed decrease in β-sheet and the increase in β-turns in treated samples indicated that microfluidization may lead to protein unfolding, opening the hydrophobic regions. Additionally, a lower amount of α-helix suggests a higher protein flexibility. After reconstitution in water, a significant difference was observed only in α-helix, β-sheet and β-turn. Related to the tertiary structure, microfluidization increases the surface hydrophobicity. Among all the conditions tested, the samples where the temperature is controlled seem the most suitable.

Effect of dynamic high-pressure microfluidization treatment on soybean protein isolate-rutin non-covalent complexes

In this investigation, soybean protein isolate-rutin (SPI-RT) complexes were treated using dynamic high-pressure microfluidization (DHPM). The effects of this process on the physicochemical and thermodynamic properties of SPI were investigated at different pressures. Fourier-transform infrared spectroscopy and fluorescence spectroscopy provided evidence that the SPI structure had been altered. The binding of SPI to RT resulted in a decrease in the percentage of α-helices and random curls as well as an increase in the percentage of β-sheets. In particular, the α-helix content decreased from 29.84 % to 26.46 %, the random curl content decreased from 17.45 % to 15.57 %, and the β-sheet content increased from 25.37 % to 26.53 %. Moreover, fluorescence intensity decreased, and the emission peak of the complex was red-shifted by 6 nm, exposing the internal groups. Based on fluorescence quenching analysis, optimal SPI-RT complexation was achieved after 120-MPa DHPM treatment, and molecular docking analysis verified the interaction between SPI and RT. The minimum particle size, maximum absolute potential, and total phenolic content of the complexes were 78.06 nm, 21.4 mV and 74.35 nmol/mg protein, respectively. Furthermore, laser confocal microscopy revealed that the complex particles had the best microstructure. Non-covalent interactions between the two were confirmed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Moreover, the hydrophobicity of the complex particle's surface increased to 16,045 after 120-MPa DHPM treatment. The results of this study suggest that DHPM strongly promotes the improvement of the physicochemical properties of SPI, and provide a theoretical groundwork for further research.

Microfluidized hemp protein isolate: an effective stabilizer for high-internal-phase emulsions with improved oxidative stability

BACKGROUND

Hemp protein isolates (HPIs), which provide a well-balanced profile of essential amino acids comparable to other high-quality proteins, have recently garnered significant attention. However, the underutilized functional attributes of HPIs have constrained their potential commercial applications within the food and agriculture field. This study advocates the utilization of dynamic-high-pressure-microfluidization (DHPM) for the production of stable high-internal-phase emulsions (HIPEs), offering an efficient approach to fully exploit the potential of HPI resources.

RESULTS

The findings underscore the effectiveness of DHPM in producing HPI as a stabilizing agent for HIPEs with augmented antioxidant activity. Microfluidized HPI exhibited consistent adsorption and anchoring at the oil-water interface, resulting in the formation of a dense and compact layer. Concurrently, the compression of droplets within HIPEs gave rise to a polyhedral framework, conferring viscoelastic properties and a quasi-solid behavior to the emulsion. Remarkably, HIPEs stabilized by microfluidized HPI demonstrated superior oxidative and storage stability, attributable to the establishment of an antioxidative barrier by microfluidized HPI particles.

CONCLUSION

This study presents an appealing approach for transforming liquid oils into solid-like fats using HPI particles, all without the need for surfactants. HIPEs stabilized by microfluidized HPI particles hold promise as emerging food ingredients for the development of emulsion-based formulations with enhanced oxidative stability, thereby finding application in the food and agricultural industries. © 2023 Society of Chemical Industry.

Dynamic microfluidic-assisted transglutaminase modification of soy protein isolate-chitosan: Effects on structural and functional properties of the adduct and its antioxidant activity after in vitro digestion

In this study, soy protein isolate (SPI)-chitosan (CS) adducts were prepared by using dynamic microfluidic-assisted transglutaminase (TGase) modification. It was shown that the solubility and degree of binding of SPI-CS adducts prepared by dynamic microfluidic-assisted TGase modification were better. After the samples were treated twice at 400 bar, the degree of binding for SPI-CS adducts increased to 31.97 ± 1.31%, and the solubility increased to 66.25 ± 1.10%. With the increase of microfluidic pressure, the exposed free sulfhydryl groups increased, the particle size reduced, and the surface hydrophobicity first increased and then decreased. Under the action of the pressure generated by microfluidics, the structure of the protein in the SPI-CS adduct was unfolded and transformed from an ordered structure to a disordered one. The SPI-CS adducts prepared with assisted dynamic microfluidic treatment showed significantly higher ABTS radical scavenging rate, DPPH radical scavenging rate and reducing power after in vitro digestion compared with that of SPI-CS adducts prepared with TGase alone. This result indicated that appropriate dynamic microfluidic treatment improved the structural and functional properties of TGase-modified SPI-CS adducts and significantly increased the antioxidant activity after in vitro digestion.

Effects of ultrasound treatment on the morphological characteristics, structures and emulsifying properties of genipin cross-linked myofibrillar protein

Genipin is a natural crosslinker that improves the functional properties of proteins by modifying its structures. This study aimed to investigate the effects of sonication on the emulsifying properties of different genipin concentration-induced myofibrillar protein (MP) cross-linking. The structural characteristics, solubility, emulsifying properties, and rheological properties of genipin-induced MP crosslinking without sonication (Native), sonication before crosslinking (UMP), and sonication after crosslinking (MPU) treatments were determined, and the interaction between genipin and MP were estimated by molecular docking. The results demonstrated that hydrogen bond might be the main forces for genipin binding to the MP, and 0.5 μM/mg genipin was a desirable concentration for protein cross-linking to improve MP emulsion stability. Ultrasound treatment before and after crosslinking were better than Native treatment to improve the emulsifying stability index (ESI) of MP. Among the three treatment groups at the 0.5 μM/mg genipin treatment, the MPU treatment group showed the smallest size, most uniform protein particle distribution, and the highest ESI (59.89%). Additionally, the highest α-helix (41.96%) in the MPU + G5 group may be conducive to the formation of a stable and multilayer oil-water interface. Furthermore, the free groups, solubility, and protein exposure extent of the MPU groups were higher than those of UMP and Native groups. Therefore, this work suggests that the treatment of cross-linking followed by ultrasound (MPU) could be a desirable approach for improving the emulsifying stability of MP.

Effects of Ultra-High-Pressure Jet Processing on Casein Structure and Curdling Properties of Skimmed Bovine Milk

Ultra-high-pressure jet processing (UHPJ) is a new non-thermal processing technique that can be employed for the homogenization and the sterilization of dairy products. However, the effects on dairy products are unknown when using UHPJ for homogenization and sterilization. Thus, this study aimed to investigate the effects of UHPJ on the sensory and curdling properties of skimmed milk and the casein structure in skimmed milk. Skimmed bovine milk was treated with UHPJ using different pressures (100, 150, 200, 250, 300 MPa) and casein was extracted by isoelectric precipitation. Subsequently, the average particle size, Zeta potential, contents of free sulfhydryl and disulfide bonds, secondary structure, and surface micromorphology were all used as evaluation indicators to explore the effects of UHPJ on the structure of casein. The results showed that with an increase of pressure, the free sulfhydryl group content changed irregularly, while the disulfide bond content increased from 1.085 to 3.0944 μmol/g. The content of α-helix and random coil in the casein decreased, while the β-sheet content increased at 100, 150, 200 MPa pressure. However, treatment with higher pressures of 250 and 300 MPa had the opposite effect. The average particle size of the casein micelles first decreased to 167.47 nm and then increased up to 174.63 nm; the absolute value of Zeta potential decreased from 28.33 to 23.77 mV. Scanning electron microscopy analysis revealed that the casein micelles had fractured into flat, loose, porous structures under pressure instead of into large clusters. After being ultra-high-pressure jet-processed, the sensory properties of skimmed milk and its fermented curd were analyzed concurrently. The results demonstrated that UHPJ could alter the viscosity and color of skimmed milk, shortening curdling time from 4.5 h to 2.67 h, and that the texture of the curd fermented with this skimmed milk could be improved to varying degrees by changing the structure of casein. Thus, UHPJ has a promising application in the manufacture of fermented milk due to its ability to enhance the curdling efficiency of skimmed milk and improve the texture of fermented milk.

Dynamic high pressure treatments: current advances on mechanistic-cum-transport phenomena approaches and plant protein functionalization

Dynamic high pressure treatment (DHPT) either by high pressure homogenization or microfluidisation, is an emerging concept used in the food industry for new products development through macromolecules modifications in addition to simple mixing and emulsification action. Mechanistic understanding of droplets breakup during high pressure homogenization is used to understand how these compact and high molecular weight-sized globular plant proteins are affected during DHPTs. Plant protein needs to be functionalized for advanced use in food formulation. DHPTs brought changes in plant proteins' secondary, tertiary, and quaternary structures through alterations in intermolecular and intramolecular interactions, sulfhydryl groups, and disulfide bonds. These structural changes in plant proteins affected their functional and physicochemical properties like solubility, oil and water holding capacity, gelation, emulsification, foaming, and rheological properties. These remarkable changes made utilization of this concept in novel food system applications like in plant-based dairy analogues. Overall, this review provides a comprehensive and critical understanding of DHPTs on their mechanistic and transport approaches for droplet breakup, structural and functional modification of plant macromolecules. This article also explores the potential of DHPT for formulating plant-based dairy analogues to meet healthy and sustainable food consumption needs. HIGHLIGHTSIt critically reviews high pressure homogenization (HPH) and microfluidisation (DHPM).It explores the mechanistic and transport phenomena approaches of HPH and DHPMHPH and DHPM can induce conformational and structural changes in plant proteins.Improvement in the functional properties of HPH and DHPM treated plant proteins.HPH and DHPM are potentially applicable for plant based dairy alternatives food system.

Aggregation and deaggregation: The effect of high-pressure homogenization cycles on myofibrillar proteins aqueous solution

Myofibrillar proteins (MPs) have not been fully used for a long time due to its poor solubility in low ionic strength solutions. The study explored the effect of high pressure homogenization (HPH) cycles under two pressures on the solubility of MPs. The MPs solubility increased with HPH cycles (p < 0.05), the results of turbidity, appearance, droplet size indicated that the increase of solubility was due to MPs depolymerization, excessive HPH cycles (25k psi for 11 cycles) would lead to protein re-aggregation but does not affect solubility (p>0.05). SDS-PAGE suggested that myosin formed soluble polymers with different molecular weights through disulfide bonds during HPH cycles, the polymer consisted of myosin subunits of different molecular weights. Endogenous fluorescence spectra, intermolecular chemical forces, isoelectric point analysis and free amino acids (FAAs) indicated that the dissolution of polymers in low ionic strength media was dominated by polar environment and intermolecular steric hindrance, but not to FAAs.

Purification and characterization of antioxidant peptides from hairtail surimi hydrolysates and their effects on beef color stability

The antioxidant peptides extracted from plants or animals have shown great potential in preventing food quality deterioration caused by oxidization. Here, peptide fractions obtained from hairtail surimi hydrolysates (HSH) were investigated for structure and color-protective effect. The results showed the <3 kDa fraction obtained from HSH by ultrafiltration could be separated into five major fractions (A-E) by gel chromatography, among which fraction A possessed the highest antioxidant activities. This fraction A could be further separated into two fractions (A₁ and A₂ ) by the reversed-phase high-performance liquid chromatography, and fraction A₂ with lower α-helix content exhibited the higher antioxidant activities. The amino acids sequence of fraction A₂ was identified as DLYANTVLSGGTTMYPGIADR (2214.0627 Da). The synthetic peptide with this sequence was also found to exhibit obvious antioxidant activity. Moreover, both HSH, fractions A₁ and A₂ , and synthetic peptide demonstrated color-protective effects during the beef preservation. Taken together, the results obtained showed that the natural antioxidant peptides could be isolated from HSH, which can be used in meat preservation for inhibiting color deterioration. PRACTICAL APPLICATION: This study demonstrated the potential of hairtail surimi hydrolysates (HSH) as a source of antioxidant peptides. Furthermore, these antioxidant peptides purified from HSH exhibited the potential for prevention of beef color deterioration of beef, providing a potential application for meat preservation. Particularly, using the antioxidant peptides sourced from fish surimi for meat preservation may not only ease the safety concerns about artificial preservatives but also create a unique selling proposition, especially in far eastern Asian countries, since consumers in these countries believe "umami" is the combination of "fish" and "meat."

Characteristics of rice dreg protein isolate treated by high-pressure microfluidization with and without proteolysis

The characteristics of rice dreg protein isolate (RDPI) treated by microfluidization (0, 40, 80, 120, and 160 MPa) with or without proteolysis were investigated. Alcalase, Neutrase, and the combination of the two (Alcalcase:Neutrase = 1:1 [w/w]) were adopted for hydrolysis. The surface hydrophobicity and solubility of RDPI were increased. As pressure increased, different structures of RDPI exhibited disaggregation (<120 MPa) and reaggregation (160 MPa), and the effect on proteolysis was significant. The solubility of Neutrase and combined enzyme hydrolysates was improved after microfluidization. Additionally, the optimum choice of microfluidization (40 MPa) and Neutrase was efficient for improving the DPPH radical scavenging activity. The results indicate that both pressure level and enzyme type synergistically determine the functionality and antioxidant activities of products. This work may provide an alternative methodology for improving the utilization of RDPI in the food industry through desirable modifications.

Latest developments in the applications of microfluidization to modify the structure of macromolecules leading to improved physicochemical and functional properties

Microfluidization is a unique high-pressure homogenization technique combining various forces such as high-velocity impact, high-frequency vibration, instantaneous pressure drop, intense shear rate, and hydrodynamic cavitation. Even though it is mainly used on emulsion-based systems and known for its effects on particle size and surface area, it also significantly alters physicochemical and functional properties of macromolecules including hydration properties, solubility, viscosity, cation-exchange capacity, rheological properties, and bioavailability. Besides, the transformation of structure and conformation due to the combined effects of microfluidization modifies the material characteristics that can be a base for new innovative food formulations. Therefore, microfluidization is being commonly used in the food industry for various purposes including the formation of micro- and nano-sized emulsions, encapsulation of easily degradable bioactive compounds, and improvement in functional properties of proteins, polysaccharides, and dietary fibers. Although the extent of modification through microfluidization depends on processing conditions (e.g., pressure, number of passes, solvent), the nature of the material to be processed also changes the outcomes significantly. Therefore, it is important to understand the effects of microfluidization on each food component. Overall, this review paper provides an overview of microfluidization treatment, summarizes the applications on macromolecules with specific examples, and presents the existing problems.

Study on condition of ultrasound-assisted thermo-alkali-modified peanut protein embedding curcumin for nanoparticles

This study investigated the effects of ultrasound-assisted thermo-alkali modification on the molecular structure of peanut protein. Further, the preparation conditions involved in embedding curcumin by the modified pea protein were also studied. It was found that within the pH range of 7 < pH < 11, with an increase in pH, the content of free sulfhydryl group in peanut protein isolate gradually increased from 10.35 ± 0.63 μmol/g (pH = 7) to 18.26 ± 0.93 μmol/g (pH = 10); and the content of disulfide bonds decreased from 44.62 ± 0.48 μmol/g (pH = 7) to 34.26 ± 2.03 μmol/g (pH = 11). In the ultrasonic power range (P < 300 W), with an increase in power, the content of free mercapto group in peanut protein isolate gradually increased from 12.44 ± 0.73 μmol/g to 19.46 ± 0.24 μmol/g (P = 250 W); and the content of disulfide bonds decreased from 42.29 ± 1.24 μmol/g to 33.28 ± 0.64 μmol/g (P = 300 W). Within the temperature range of 70 °C < T < 90 °C, with an increase in temperature, the content of free sulfhydryl group in peanut protein isolate gradually increased from 10.35 ± 0.94 μmol/g (T = 70 °C) to 19.67 ± 0.68 μmol/g (T = 90 °C), and the content of disulfide bonds decreased from 45.02 ± 2.84 μmol/g (T = 70 °C) to 34.26 ± 2.03 μmol/g (T = 90 °C). Response surface test was used to optimize the preparation conditions of nanoparticles from curcumin. The results showed that the optimum parameters of ultrasonic-assisted modification of peanut protein embedding curcumin were pH = 9.8, heating temperature T = 90 °C, ultrasonic power Q = 225 W, and heating time S = 21 min. Under these conditions, the embedding rate of curcumin reached 83.27 + 1.06%, the ABTS⁺ scavenging activity generally decreases with time over the 2 days period measured in PPI solution and PPI nanoparticles (PPN), the ABTS⁺ scavenging activity decreased from 40.8%, 52.2% and 67.3% to 27.1%, 39.0% and 60.5%, respectively. Compared with pure curcumin, the antioxidant activity was increased at presence of PPI.