Changes in the physico-chemical characteristics of a protein solution in the presence of magnetic field and the consequences on the ultrafiltration performance

Enhancement of hydrogen bonds between proteins and polyphenols through magnetic field treatment: Structure, interfacial properties, and emulsifying properties

In food systems, proteins and polyphenols typically coexist in a non-covalent manner. However, the inherent rigid structure of proteins may hinder the binding sites of polyphenols, thereby limiting the strength of their interaction. In the study, magnetic field (MF) treatment was used to enhance non-covalent interactions between coconut globulin (CG) and tannic acid (TA) to improve protein flexibility, enhancing their functional properties without causing oxidation of polyphenols. Based on protein structure results, the interaction between CG and TA caused protein structure to unfold, exposing hydrophobic groups. Treatment with a MF, particularly at 3 mT, further promoted protein unfolding, as evidenced by a decrease in α-helix structure and an increase in coil random. These structural transformations led to the exposure of the internal binding site bound to TA and strengthening the CG-TA interaction (polyphenol binding degree increased from 62.3 to 68.2%). The characterization of molecular forces indicated that MF treatment strengthened hydrogen bonding-dominated non-covalent interactions between CG and TA, leading to improved molecular flexibility of the protein. Specifically, at a MF treatment at 3 mT, CG-TA colloidal particles with small size and high surface hydrophobicity exhibited optimal interfacial activity and wettability (as evidenced by a three-phase contact angle of 89.0°). Consequently, CG-TA-stabilized high internal phase Pickering emulsions (HIPPEs) with uniform droplets and dense gel networks at 3 mT. Furthermore, the utilization of HIPPEs in 3D printing resulted in consistent geometric shapes, uniform surface textures, and distinct printed layers, demonstrating superior printing stability. As a result, MF treatment at 3 mT was identified as the most favorable. This research provides novel insights into how proteins and polyphenols interact, thereby enabling natural proteins to be utilized in a variety of food applications.

Low-frequency alternating magnetic field and CaCl2 influence the physicochemical, conformational and gel characteristics of low-salt myofibrillar protein

In this study, the improvement mechanism of low-frequency alternating magnetic field (LF-AMF, 5 mT, 3 h) combined with calcium chloride (CaCl2, 0-100 mM) on the gel characteristics of low-salt myofibrillar protein (MP) was investigated. LF-AMF combined with 80 mM CaCl2 treatment increased solubility (32.71%), surface hydrophobicity (40.86 μg), active sulfhydryl content (22.57%), water-holding capacity (7.15%). Besides, the combined treatment decreased turbidity, particle size and intrinsic fluorescence strength of MP. Fourier transform infrared spectroscopy (FT-IR) results indicated that the combined treatment altered the secondary structure of MP by increasing β-sheet and β-turn, and reducing α-helix and random coil. The combined treatment also induced a high G' value and shortened T2 relaxation time for forming a homogeneous and compact gel structure. These results revealed that LF-AMF combined CaCl2 treatment could as a potential approach for modifying the gel characteristics of low-salt MP.

A versatile theranostic magnetic polydopamine iron oxide NIR laser-responsive nanosystem containing doxorubicin for chemo-photothermal therapy of melanoma

Theranostics nanoparticles (NPs) have recently received much attention in cancer imaging and treatment. This study aimed to develop a multifunctional nanosystem for the targeted delivery of photothermal and chemotherapy agents. Fe3O4 NPs were modified with polydopamine, bovine serum albumin, and loaded with DOX via a thermal-cleavable Azo linker (Fe3O4@PDA@BSA-DOX). The size of Fe3O4@PDA@BSA NPs was approximately 98 nm under the desired conditions. Because of the ability of Fe3O4 and PDA to convert light into heat, the temperature of Fe3O4@PDA@BSA NPs increased to approximately 47 °C within 10 min when exposed to an 808 nm NIR laser with a power density of 1.5 W/cm2. The heat generated by the NIR laser leads to the breaking of AZO linker and drug release. In vivo and in vitro results demonstrated that prepared NPs under laser irradiation successfully eradicated tumor cells without any significant toxicity effect. Moreover, the Fe3O4@PDA@BSA NPs exhibited the potential to function as a contrasting agent. These NPs could accumulate in tumors with the help of an external magnet, resulting in a significant enhancement in the quality of magnetic resonance imaging (MRI). The prepared novel multifunctional NPs seem to be an efficient system for imaging and combination therapy in melanoma.

Effect of low-frequency alternating magnetic fields on the physicochemical, conformational and rheological properties of myofibrillar protein after iterative freeze-thaw cycles

In this work, the effects of low-frequency alternating magnetic fields (LF-AMF) on the physicochemical, conformational, and functional characteristics of myofibrillar protein (MP) after iterative freeze-thaw (FT) cycles were explored. With the increasing LF-AMF treatment time, the solubility, active sulfhydryl groups, surface hydrophobicity, emulsifiability, and emulsion stability of MP after five FT cycles evidently elevated and then declined, and the peak value was obtained at 3 h. Conversely, the moderate LF-AMF treatment time can significantly reduce the average particle size, carbonyl content, and endogenous fluorescence intensity of MP. The rheology results showed that various LF-AMF treatment times would elevate the G' value of MP after iterative FT cycles. The FTIR spectroscopy results suggested that LF-AMF influenced the secondary structure of MP after multiple FT cycles, resulting in a depression in α-helix content and an increment in β-folding proportion. Moreover, LF-AMF treatment induced the gradually lighter and wider myosin heavy chain bands of MP, implying that LF-AMF accelerated the degradation of macromolecular aggregates. Therefore, the LF-AMF treatment efficaciously ameliorates the structural and functional deterioration of MP after iterative FT cycles and could be used as a potential quality-improving technology in the frozen meat industry.

Effect of magnetic field modification on oxidative stability of myoglobin in sarcoplasm systems

This study aimed to investigate the effect of magnetic fields (0, 3, 6, 12 mT) on the oxidation characteristics of myoglobin (Mb) in the sarcoplasmic protein (SP) system and to understander the underlying mechanism. The metmyoglobin content, Soret band of heme iron porphyrin, protein conformation and molecular weight distribution were measured in different Mb and SP samples. The results showed that the primary oxidation site of hydroxyl radical on Mb was likely to be the porphyrin ring structure and the side chain group of protein rather than the central iron atoms, what's more, 12 mT magnetic field treatment had an inhibitory effect on the oxidative damage induced by hydroxyl radical.

Improvement of gelation properties of Penaeus vannamei surimi by magnetic field-assisted freezing in combination with curdlan

Traditional methods of freezing and thawing may harm the quality of meat products. In order to reduce the negative impact of freezing on surimi products, the magnetic field-assisted freezing method is combined with various curdlan ratios to enhance the gelation characteristics of Penaeus vannamei surimi in this study. The results showed that the magnetic field-assisted freezing technique significantly improved the quality of thawed surimi compared with soaking freezing (SF), whereas the addition of curdlan further improved the gelation properties, and the gel strength, water-holding capacity, textural properties, whiteness, and G' value were significantly improved when its content was increased to 0.6 %. However, excessive amounts of curdlan interfered with protein covalent cross-linking, leading to a decrease in gel quality. Additionally, the addition of magnetic field and curdlan encouraged the shift of the α-helix to the random coil and β-sheet transition, which stimulated the growth of myofibril molecules, exposed the hydrophobic groups and thiols, improved protein-molecule interactions, and promoted systematic gathering of proteins, leading to the formation of the microstructure of dense and small pores. It also resulted in a drop in water release, an increase in the proton density and a shift in the water condition from free water to more immobile water, which had higher sensory qualities. These effects together resulted in a reduction in thawing and cooking loss to 11.41 % and 13.83 %, respectively. These results also help to clarify the gelation process of shrimp surimi and help to regulate the gelation characteristics of shrimp surimi products.

Magnetic field-assisted cascade effects of improving the quality of gels-based meat products: A mechanism from myofibrillar protein gelation

Physics-assisted processing technologies have huge potential in the meat processing industry. By modeling two essential procedures (pickling and preheating) of gels-based meat products, this work investigated the cascade effects of a new physical technology (magnetic field) on the conformational structures and gel properties of myofibrillar proteins (MPs). Samples were subjected with four magnetic field (MF)-assisted treatments (group A, both processes without MF; group B, pickling without MF combining with preheating with 4.5 mT MF; group C, pickling with 3.0 mT MF combining with preheating without MF; group D, pickling with 3.0 mT MF combining with preheating with 4.5 mT MF). The result showed that MF-assisted treatments significantly improved water holding capacity (WHC) of MP gels compared with group A (46.9%), reaching the maximum value of 52.1% in group D.According to the low-field nuclear magnetic results, group D decreased the percentages of P₂₂ (6.97%) and increased the percentages of P₂₁ (93%), which showed that water molecules were more tightly bound to each other. Meanwhile, the unfolding of α-helix and the formation of random coil of MF-assisted treatments resulted in more exposure of internal groups, leading to the formation of a dense network. These findings would provide new insights to improve the quality of gels-based meat products via the MF.

Magnetic field-driven biochemical landscape of browning abatement in goat milk using spatial-omics uncovers

Influence of magnetic field (MF) treatment on the glycation of goat milk proteins is yet to be elucidated. Proteomic and metabolomic analyses of brown goat milk samples with and without MF treatment were performed. Assessed glycation degree and structural modification of proteins explained that MF treatment dramatically down-regulated the glycation of brown goat milk protein, possibly due to the aggregation behavior induced by MF treatment, which consumed additional glycation sites as well as altered their accessibility and preference. Integrated datasets uncovered that the energy metabolism-related biological events including carbohydrate metabolism, glycerophospholipid metabolism, TCA cycle may mainly account for the browning abatement mechanism of MF. In addition, MF treatment enhanced both the quality and flavor of brown goat milk. This study suggests the feasibility of MF treatment to reduce glycation in brown goat milk for producing high-quality dairy ingredients and products.

Optimization of ultrasonic assisted membrane strategy for saponins from Gynostemma Pentaphyllum with response surface methodology

Gynostemma pentaphyllum saponin has a variety of biological properties. Classic separation methods of saponin, such as resin absorption and preparative chromatography are limited by environmental pollution and high cost. In the study, ultrasonic assisted membrane separation was firstly used to purify saponin from Gynostemma pentaphyllum. Total proteins, polysaccharides, saponin, gypenoside A and rutin were selected as indexes to optimize the pretreatment and purification parameters by response surface methodology. The fitted models were significant (p < 0.05) and the optimal conditions were: (1) removing protein and polysaccharides by MWCO 10,000 Da, ultrasonic power 400 W and pH 7.8; (2) separation flavonoids from saponin by MWCO 1000 Da, ultrasonic power 300 W and pH 7.9. The difficulty in separating saponin from flavonoids was solved by releasing flavonoids from micelles with ultrasonic assisted membrane method. The saponin content in Gynostemma pentaphyllum extracts reached 82.81%, which was more than four times of that obtained with resin adsorption method. The protective effect of saponins on SH-SY5Y cells injury induced by H2O2 was better than that of Gynostemma pentaphyllum extracts. The study suggested that ultrasonic assisted membrane method would be widely applied in the preparation of food materials.

Biomimetic synthesis of iron oxide nanoparticles from Bacillus megaterium to be used in hyperthermia therapy

The suitable structural characteristics of magnetic nanoparticles have resulted in their widespread use in magnetic hyperthermia therapy. Moreover, they are considered a proper and operational choice for pharmaceutical nanocarriers. Using the biomimetic method, we were able to produce iron oxide magnetic nanoparticles from the bacterial source of PTCC1250, Bacillus megaterium, for therangostic diagnosis systems and targeted drug delivery. Some of the benefits of this method include mitigated environmental and biological dangers, low toxicity, high biocompatibility, cheap and short-term mass production possibilities in each synthesis round compared to other biological sources, simple equipment required for the synthesis; and the possibility of industrial-scale production. Bacillus megaterium is a magnetotactic bacteria (MTB) that has a magnetosome organelle capable of orienting based on external magnetic fields, caused by the mineralization of magnetic nanocrystals. Utilizing this capability and adding an iron nitrate solution to the bacterial suspension, we synthesized iron oxide nanoparticles. The extent of synthesis was measured using UV–visible spectrophotometry. The morphology was evaluated using FESEM. The crystallized structure was characterized using RAMAN and XRD. The size and distribution of the nanoparticles were assessed using DLS. The surface charge of the nanoparticles was measured using zeta potential. The synthesis of iron oxide nanoparticles was confirmed using FT-IR, and the magnetic property was measured using VSM. This study is continued to identify industrial and clinical applications.

Improvement of tangential microfiltration of gelatin solution using a permanent magnetic field

Membrane technology is an interesting alternative to conventional gelatin clarification methods, resulting in the elimination of refining chemical agents. In this work, the application of a permanent magnetic field as a pre-treatment of the gelatin solutions was proposed as a strategy to improve the microfiltration (MF) performance. Filtration tests were performed using a 1.5% swine gelatin solution at 40 °C through cellulose acetate membranes in a tangential flow module. Prior to the filtrations, the feed solutions were pretreated by the circulation of the solution through magnetic fields with different flux densities, 0.7 T and 1.34 T, for 2 h. The magnetic induction of the solution significantly increased the permeate flux and the recovery of hydraulic permeance by 63% and 122%, respectively, showing the application of the magnetic field in the solution of gelatin is an attractive alternative to improve the performance of the process.

Effect of high intensity ultrasound on the gelation properties of wooden breast meat with different NaCl contents

The current study was conducted to investigate the effect of different high intensity ultrasound (HIU) amplitudes on the gelation properties of wooden breast (WB) meat batter prepared with 1% and 2% NaCl. Results indicated that HIU effectively enhanced the water holding capacity (WHC) of WB at 1% and 2% NaCl, and enabled WB to obtain better WHC than the normal. The thermal stability of WB was affected by HIU, and the difference of G'_end between WB and normal was reduced at 2% NaCl. HIU continuously decreased the particle size of WB at 1% NaCl, whereas opposite trends were observed at 2% NaCl. In addition, HIU transformed α-helix structure of WB to random coil at 1% NaCl, whereas to β-sheet structure at 2% NaCl. Overall, HIU can be utilized to improve the gelation properties of WB meat with the potential to produce low- and common-salt gel-type meat products.