Insight into the mechanisms of combining direct current magnetic field with phosphate in promoting emulsifying properties of myofibrillar protein.

This study investigated the combined effects of direct-current magnetic field (DC-MF, 9.5 mT) and tetrasodium-pyrophosphate (TSPP, 1-5 g/L) on emulsified gel properties of porcine myofibrillar protein (MP). Results showed that MP at DC-MF and 3 g/L TSPP had decreased spectrum intensity of UV and fluorescence compared to that without DC-MF, owing to the changes of MP tertiary structure caused by DC-MF, especially tryptophan and tyrosine. The emulsion treated with DC-MF behaved better emulsifying activity and stability than that without DC-MF under such condition. And emulsion had lower creaming index and better storage stability. Gels prepared by this MP emulsion had low porosity and stable structure, accompanying with smaller size and more uniform distribution of oil droplets. Microstructure images showed that gels were covered with microporous structure, which was conducive to the good WHC of the emulsified gels (97.12%). These results showed the feasibility of DC-MF and TSPP in improving MP emulsion/emulsified gel.

Effect of magnetic field mediated CaCl2 on the edible quality of low-sodium minced pork gels.

Magnetic field combined with calcium chloride (CaCl2,) treatment is a highly promising technique for reducing sodium chloride (NaCl) in meat. Therefore, this paper investigated the effect of reducing NaCl addition (0-10%) by CaCl2 in combination with a magnetic field (3.8 mT) on the edible quality of low-salt pork mince. It is desired to drive the application of magnetic field and CaCl2 in low-sodium meat processing in this way. Results showed that the cooking yield, color, hardness, elasticity, mouthfeel, apparent texture, and orderliness of protein conformation of all minced pork were improved as compared to the control group, while the electron nose response values of their volatile sulfides and nitrogen oxides were decreased. In particular, the best edible quality and perceived salty intensity of minced pork gel was obtained by using CaCl2 in place of 5% NaCl under magnetic field mediation. In addition, energy dispersive X-ray spectroscopy scans showed that the reduced NaCl treatment by magnetic field combined with CaCl2 could increase the signal intensity of sodium in minced pork matrices to some extent. Magnetic field-mediated substitution of NaCl for CaCl2 treatment was also found to be favorable for inducing the transition of the protein secondary structure from an irregularly coiled to a ß-folded structure (demonstrated by infrared spectroscopy). In short, magnetic fields combined with CaCl2 instead of NaCl was a highly promising method of producing low-NaCl meats.

Study on the interaction and gel properties of pork myofibrillar protein with konjac polysaccharides.

BACKGROUND: Natural myofibrillar protein (MP) is sensitive to changes in the microenvironment, such as pH and ionic strength, and therefore can adversely affect the final quality of meat products. The aim of this study was to modify natural MP as well as to improve its functional properties. Therefore, the quality improvement effect of konjac polysaccharides with different concentrations (0, 1.5, 3, 4.5 and 6 g kg-1 protein) on MP gels was investigated. RESULTS: With a concentration of konjac polysaccharides of 6 g kg-1 protein, the composite gel obtained exhibited a significant improvement of water binding (water holding capacity increased by 7.71%) and textural performance (strength increased from 29.12 to 37.55 N mm, an increase of 8.43 N mm). Meanwhile, konjac polysaccharides could help to form more disulfide bonds and non-disulfide covalent bonds, which enhanced the crosslinking of MP and maintained the MP gel network structure. Then, with the preservation of α-helix structure (a significant increase of 8.11%), slower protein aggregation and formation of small aggregates, this supported the formation of a fine and homogeneous network structure and allowed a reduction in water mobility. CONCLUSION: During the heating process, konjac polysaccharides could absorb the surrounding water and fill the gel system, which resulted in an increase in the water content of the gel network and enhanced the gel-forming ability of the gel. Meanwhile, konjac polysaccharides might inhibit irregular aggregation of proteins and promote the formation of small aggregates, which in turn form a homogeneous and continuous gel matrix by orderly arrangement. © 2023 Society of Chemical Industry.

Effect and mechanism of DC magnetic field combined with calcium chloride on saltiness and flavor enhancement of low salt pork gel.

This study intended to investigate the synergistic effect of direct current magnetic field (DC-MF) and calcium chloride (CaCl2) on improving the saltiness and quality of pork gel and to explore the potential adjustment mechanisms involved. Pork mince was subjected to low-salt treatment of DC-MF for 3 h (T1), CaCl2 substitution (T2) or DC-MF combined with CaCl2 (T3) respectively under high and low salt controls (HC and LC). Heat-induced gels of pork mince were prepared and analyzed in terms of gel texture, saltiness perception, moisture status, salt release and protein structure. Results indicated that DC-MF combined with CaCl2 treatment could reduce the addition of sodium chloride by 5% while maintaining the saltiness and overall acceptability of mince as well as improving its texture and yield. Further studies revealed that DC-MF in concert with CaCl2 treatment could not only increase the moisture content of mince gel, but also enhance saltiness perception by causing gel matrix to release salt-bearing juices under external forces. The energy spectrum analysis also illustrated that co-treatment technique could avoid the salt loss of minced meat during cooking process. Finally, a possible potential regulatory mechanism was speculated that the synergistic action of DC-MF and CaCl2 could alter the gel texture and sodium salt availability by modifying protein conformation and inducing a competitive binding reaction site for calcium and sodium ions. In conclusion, synergistic treatment by DC-MF and CaCl2 was a potential strategy in meat salt reduction.

Yam Bean (Pachyrhizus erosus L. Urban) Powder Improves Grass Carp Myofibrillar Protein Gel by Forming Disulfide Bonds, Hydrogen Bonds, and Proper Microstructure.

This study aimed to analyze the impact of different additions (0-1.25%) of yam bean powder (YBP) on myofibrillar protein (MP) gel characteristics such as the structure, water-holding capacity (WHC), chemical interaction strength of grass carp MP, and texture. The results showed that the YBP exhibited a strong water absorption capacity and filled in the protein heat-induced polymerization gel network well, which enabled the gel network to capture and retain water effectively, resulting in MP gels containing YBP with excellent WHC and gel strength (0.75%). In addition, YBP induced the formation of hydrogen and disulfide bonds in proteins and inhibited the conversion of α-helices to ß-sheets and ß-turn structures, facilitating the formation of high-strength gel networks (p < 0.05). In conclusion, YBP can significantly improve the thermally induced gelling properties of grass carp MP. In particular, the addition of 0.75% YBP had the best effect in terms of filling the gel network of grass carp MP, resulting in the formation of a continuous and dense protein network, leading to the composite gel with the best WHC and texture.

Insoluble dietary fibers from Lentinus edodes stipes improve the gel properties of pork myofibrillar protein: A water distribution, microstructure and intermolecular interactions study.

This paper investigated the effects of Lentinus edodes stipes insoluble dietary fiber (LESIDF, 0%-3.0%) on the quality and microscopic properties of pork myofibrillar protein (MP) gels. The results showed that the water holding capacity and gel strength of composite gels enhanced with increasing LESIDF (1.0%-2.5%), and reached the maximum at the level of 2.5%-3.0%. Disulfide and non-disulfide covalent bonds were major chemical forces maintaining the 3D network of LESIDF-MP composite gels. LESIDF also promoted the formation of ionic and hydrogen bonds, confirmed by the self-assembly of ß-sheets to α-helices, leading to a compact gel network structure. The observation of paraffin section revealed that LESIDF could capture more water molecules in gels, which was consistent with the transformation of free water to immobilized water. Overall, the optimal addition of LESIDF was 2.5%-3.0%, which provided a good strategy for LESIDF as an agricultural by-product to improve the quality of gel meat products.

[Value of high-flow oxygen therapy after weaning for successful extubation of critical ill patients with mechanical ventilation].

OBJECTIVE: To investigate the value of high-flow oxygen therapy after weaning in successful extubation of critically ill patients with mechanical ventilation. METHODS: A retrospective study was conducted. The weaned patients who were older than 18 years old and underwent mechanical ventilation for the first time due to cerebrovascular accidents, surgical operations, cardiovascular diseases, and pneumonia admitted to the department of critical care medicine of Zhejiang Hospital from January 2018 to June 2020 were enrolled. Among the patients, 40 cases received high-flow oxygen therapy after weaning, and 37 cases received Venturi combined with the humidifier. The patient's gender, age, primary disease, severity score, duration of mechanical ventilation before weaning, heart rate (HR), blood pressure, pulse oxygen saturation (SpO2) at 0, 6, 12, 18, and 24 hours after weaning, and pH value, arterial partial pressure of oxygen (PaO2), arterial partial pressure of carbon dioxide (PaCO2) at 6, 12, 18, and 24 hours after weaning, the rate of performing mechanical ventilation after weaning, extubation time after weaning, and the rate of reintubation after extubation for 72 hours were collected. RESULTS: There was no significant difference in baseline data such as gender, age, primary disease, severity score, and duration of mechanical ventilation before weaning between the two groups. After weaning, the vital signs of the two groups were stable, and there was no significant difference in HR, systolic blood pressure (SBP), diastolic blood pressure (DBP) or SpO2 at each time point between the two groups. After weaning, the pH of arterial blood gas analysis in the two groups and the fluctuations of PaO2 and PaCO2 in the high-flow group were not obvious. In the Venturi group, PaO2 gradually decreased after weaning, PaCO2 increased significantly at 12 hours, and slowly decreased after 12 hours. The PaO2 from 6 hours and PaCO2 from 12 hours in the high-flow group were significantly lower than those in the Venturi group, and continued to 24 hours [PaO2 (mmHg, 1 mmHg ≈ 0.133 kPa): 112.34±38.25 vs. 156.76±68.44 at 6 hours, 110.92±38.66 vs. 150.64±59.07 at 12 hours, 111.12±36.77 vs. 141.30±39.05 at 18 hours, 110.82±39.37 vs. 139.65±41.50 at 24 hours; PaCO2 (mmHg): 41.30±7.51 vs. 47.42±7.54 at 12 hours, 40.97±6.98 vs. 45.83±8.63 at 18 hours, 40.10±7.06 vs. 46.14±9.15 at 24 hours, all P < 0.01]. The rate of performed mechanical ventilation after weaning and the rate of reintubation after extubation for 72 hours in the high-flow group were significantly lower than those in the Venturi group [17.5% (7/40) vs. 40.5% (15/37), 6.2% (2/32) vs. 31.8% (7/22), both P < 0.05], and the extubation time after weaning was significantly shorter than that in the Venturi group (hours: 22.43±11.72 vs. 28.07±10.42, P < 0.05). CONCLUSIONS: Using high-flow oxygen therapy to the extubation process of critically ill mechanical ventilation patients can reduce the incidence of carbon dioxide retention and the rate of performed mechanical ventilation after weaning, shorten the extubation time after weaning, and reduce the rate of reintubation after extubation for 72 hours.

Strategies to optimize the structural and functional properties of myofibrillar proteins: Physical and biochemical perspectives.

Myofibrillar protein (MP), as the main meat protein, have high nutritional value. However, the relatively poor solubility of MP at low ionic strength sometimes limits the utilization of MP to produce products rich in meat protein. Accordingly, appropriate modification of MP is needed to improve their functional properties. In general, MP modification strategies are categorized into biochemical and physical approaches. Different from other available reviews, the review focuses on summarizing the principles and applications of several techniques of physical modification, briefly depicting biochemical modification as a comparison. Modification of MP with a certain intensity of direct current magnetic field, ultrasound, high pressure, microwave, or radio frequency can improve solubility, emulsification, stability, and gel formation. Of these, magnetic field and microwave-modified MP have shown some potential in reducing salt in meat. These physical techniques can also have synergistic effects with other conditions (temperature, pH, physical or chemical techniques) to compensate for the deficiencies of individual treatment techniques. However, these strategies still need further research for practical applications.HIGHLIGHTSThe current status and findings of research on direct current magnetic field in meat processing are presented.Several physical strategies to modify the microstructure and functional properties of MPs.The synergistic effects of these techniques in combination with other methods to modify MPs are discussed.

Enzymatic extraction and functional properties of phosphatidylcholine from chicken liver.

An environmentally sustainable method to extract phosphatidylcholine (PC) from chicken liver (PCCL) and its functional properties were studied. The extraction times, enzymatic hydrolysis time, the solid-liquid ratio as well as types of enzymes (protamex proteinase and neutral proteinase) were investigated. Furthermore, the content of PCCL, emulsifying properties and solubilities of PCCL were also determined. The optimum conditions of extracting PCCL were found to be: reaction time of 3.75 h, enzymatic hydrolysis time of 85.22 min, 1: 3.15 (w/v) of solid-liquid ratio, using protamex proteinase, and the yield and concentration of PCCL was 88.92% and 0.89 mg/mL, respectively. Solubility and emulsifying properties of PCCL showed that the HLB value of PCCL was 10, and in ethanol and glycerol, the solubility of PCCL was 0.5850 g/mL and 0.0965 g/mL, respectively, which was shown to have good ethanol solubility and lipophilicity. From the perspective of green production and high-value utilization of by-products, PCCL could be used as a potential new lecithin source, providing ideas for the development and application of PC of animal origin.

Gel properties and thermal gelling mechanism in myofibrillar protein of grass carp (Ctenopharyngodon idellus) under the synergistic effects of radio frequency combined with magnetic field.

This study evaluated the effects of radio frequency (RF)-replaced water bath (WB) or/and magnetic field (MF)-assisted WB heating on various quality parameters of grass carp myofibrillar protein (GCMP) gel and to understand the thermal gelling mechanism. Compared with the control, RF-replaced 40°C WB combining MF-assisted 80°C WB heating promoted GCMP structural changes, that was random coil content observably increased from 28.87% to 32.3% at the expense of α-helix reducing from 17.93% to 15.80%, even promoting the self-assembly of exposed residues. These structural changes were conducive to form relatively smooth and loose gel network structures, thus significantly increasing immobilized and bound water and improving water holding capacity. The electrostatic repulsion between exposed residues was conducive to the stability of protein molecules and gel structure. Overall, the RF-replaced 40°C WB combining MF-assisted 80°C WB heating was a desirable thermal alternative to conventional WB heating for improving gel quality.

Highly fluorescent N doped C-dots as sensor for selective detection of Hg2+ in beverages.

In this work, nitrogen doped carbon dots (NCDs) were synthesized through one step hydrothermal reaction using citric acid and ethylenediamine as precursors. The prepared NCDs exhibit high quantum yield of 67.4%, good stability, excellent selectivity and sensitivity. It was found that the NCDs have potential as a fluorescence sensor for the detection of Hg2+. Under optimal conditions, good linearity between the change in NCDs fluorescence intensity and Hg2+ concentration was obtained in the range of 0.3 to 2.0 µM with a detection limit at 0.24 µM. The possible detection mechanism was static quenching of NCDs by Hg2+. The established method was successfully applied to the determination of Hg2+ in beverage samples. The results indicated that the NCDs-based sensor has potential for detection of Hg2+ in real beverage sample.

Effect of sarcoplasmic proteins oxidation on the gel properties of myofibrillar proteins from pork muscles.

This study investigated the influence of sarcoplasmic proteins (SPs) treated by the oxidation system (0.1 mmol/L FeCl3 , 0.1 mmol/L ascorbic acid, and 0, 1, 5, 10 mmol/L H2 O2 ) on the properties of pork myofibrillar proteins (MPs) gel. After oxidation treatment, the SPs showed an increased in carbonyl content and a decreased in total sulfhydryl content, coupled with the cross-linking of protein components by disulfide bonds and covalent bonds. The MPs gel with SPs oxidized at 1 mmol/L H2 O2 exhibited the maximal strength while the minimal water holding capacity (WHC). The WHC of MPs gel was significantly decreased with increasing SPs oxidation, leading to the increase of free water and the decrease of immobilized water in the gel system. The microstructures of MPs gels with moderately (1 mmol/L H2 O2 ) oxidized SPs showed a more compact and smaller pore gel network than MPs alone, suggesting adding oxidized SPs can expel water trapped in the gel. Furthermore, the environmental polarity of aliphatic C-H groups increased with SPs oxidation.

Radio frequency heating improves water retention of pork myofibrillar protein gel: An analysis from water distribution and structure.

This study was to explore effects of hot air assisted or not assisted radio frequency (RF, 27.12 MHz, 1.4 kW) heating with different electrode gaps (100 mm, 120 mm, and 140 mm) on the water-holding capacity (WHC) of myofibrillar protein (MP) gel and to understand the underlying mechanism through chemical forces, water distribution, and structure. The results showed that the MP gels heated by RF (100 mm) had the highest WHC and uniform gel network structure. As for RF with 100 mm electrode gap, the increased ionic and hydrogen bonds might be conducive to the WHC compared to water bath heating, which was verified by Low-field nuclear magnetic resonance results that the free water converted into the immobilized water. Raman spectroscopy results revealed that RF (100 mm) induced the self-assembly of ß-sheet to α-helix, which conduced to the stable and ordered gel network structure.

Structural changes induced by direct current magnetic field improve water holding capacity of pork myofibrillar protein gels.

The study was to investigate the role of direct current magnetic field (DC-MF) for water-holding capacity (WHC) of myofibrillar protein gels and to understand potential mechanisms. Samples were subjected to DC-MF with different intensities (3.5, 3.8, 9.5 and 10.4 mT), and DC-MF treatment significantly improved WHC compared with control (46.09%), reaching the maximum value of 50.36% at 3.8 mT. The main reason for the increase in WHC might be that DC-MF modified the protein structure via unfolding, re-crosslinking and aggregation of proteins, which was supported by the increased intensity of tyrosine, aliphatic and tryptophan residues, and reduced reactive sulfhydryl (2.97 to 1.94). And the re-crosslinking between molecules was maintained mainly through hydrophobic interactions and disulfide bonds. Besides, DC-MF treatment helped to generate a relatively loose and uniform microstructure to trap more water as shown by electron microscope image, which was consistent with the highest WHC at 3.8 mT.

HPLC-DAD fingerprints combined with chemometric techniques for the authentication of plucking seasons of Laoshan green tea.

Laoshan green teas plucked in summer and autumn were measured by high performance liquid chromatography-diode array detector (HPLC-DAD). After baseline correction, the fingerprints data were resolved by multivariate curve resolution-alternating least squares (MCR-ALS) and a total of 57 components were acquired. Relative concentrations of these components were afterwards applied to distinguish plucking seasons using principal component analysis (PCA), support vector machines (SVM) and partial least squares-discriminant analysis (PLS-DA). For both SVM and PLS-DA models, the total recognition rates of training set, cross-validation and testing set were 100%, 91.3% and 100%, respectively. Besides, three variable selection methods were employed to determine characteristic components for the authentication of summer and autumn teas. Results showed that PLS-DA model based on three characteristic components selected by VIP possesses identical predictive ability as the original model. This study demonstrated that our proposed strategy is competent for the authentication of plucking seasons of Laoshan green tea.

Effects of radio frequency heating on water distribution and structural properties of grass carp myofibrillar protein gel.

This study explored effects of radio frequency (RF, 27.12 MHz, 3 kW) heating replacing the first stage (electrode gaps of 120, 140 and 160 mm) or/and the second stage (95 mm) of the water bath heating on water distribution and structural characteristics of grass carp myofibrillar proteins gels. Compared with control, RF heating (140) during the first stage significantly reduced the total time to prepare gels from 70 min to 45.3 min and increased springiness and water holding capacity from 62.9% to 68.3%. It may be attributed to the appropriate RF heating contributing to α-helix turning into random coil and cross-linking via hydrophobic interactions and disulfide bonds, thus forming smooth gels with clear network structures. Structural changes further affected water distribution (immobilized water increasing from 97.8% to 98.7%). Namely, RF (140 mm) heating improved water distribution and structural characteristics of gels, which provided basic information for RF heating surimi gels.

Effect of nanoliposomal entrapment on antioxidative hydrolysates from goose blood protein.

In this study, the encapsulation of goose blood hydrolysate (GBH) was performed within nanoliposomes. We investigated the physicochemical properties, stability, antioxidant indices, the morphology of nanoparticles, the digestion stability in simulated gastrointestinal fluid, differential scanning calorimetry (DSC) analysis, and Fourier transform infrared (FTIR) spectroscopy. GBH was successfully encapsulated into nanoliposomes using reverse-phase evaporation method. The entrapment efficiency of GBH-loaded nanoliposomes was about 70.99 ± 2.85%, the average particle size was 93.3 ± 2.45 nm, the zeta-potential of GBH-loaded nanoliposomes was -30 mV, and the morphology of GBH-loaded nanoliposomes was characterized by transmission electron microscope. Moreover, the results of DSC and FTIR showed that the GBH nanoliposome was more stable than the empty liposomes due to hydrogen bond complexation between liposome and GBH. The release of GBH from nanoliposomes could be significantly controlled, and the release ratios were 48.9 ± 2.96% in simulated gastric fluid and 59.9 ± 5.30% in simulated intestinal fluid, respectively, proving that degradation rate of antioxidant activities of GBH encapsulated in nanoliposomes was decreased. In conclusion, nanoliposomes embedding is a promising and effective way to increase the stability of hydrolysates from GBH and produce various types of functional food.

Low frequency magnetic field plus high pH promote the quality of pork myofibrillar protein gel: A novel study combined with low field NMR and Raman spectroscopy.

This study investigated the combined effects of low frequency magnetic field (LF-MF) (3.8 mT) and pH (5-7) on pork myofibrillar protein (MP) gel quality. With LF-MF applying, the water ratio and migration rate both changed to varying extents. LF-MF modified secondary structure of MP by exposing tryptophan and tyrosine residues to participate in hydrogen bonding with water, as well changing α-helix and ß-sheet to varying extents; LF-MF also drove molecular rearrangement and crosslinking. LF-MF brought gel larger and more ordered network to trap more water. And the water holding capacity of gels significantly increased by 2.50% and 2.47% when LF-MF involved at appropriate pH (pH 6.5 and 7.0). Collectively, our results support an optimum treatment (pH 6.5 or 7.0 with applying LF-MF) for the improvement in gel quality of pork MP, and the combination of physical and chemical treatments casts a new light into improving product quality during meat processing.

Gel properties of myofibrillar proteins heated at different heating rates under a low-frequency magnetic field.

The effects of low-frequency magnetic field combined with different heating rates on pork myofibrillar protein (MP) gels were investigated. Samples were treated under different heating rates (1 °C/min and 2 °C/min) in the presence or absence of 9.5 mT low-frequency magnetic field. The highest levels of intermolecular and intramolecular ionic and hydrogen bonds in MP were observed at the heating rate of 2 °C/min under the 9.5 mT magnetic field. These bonds resulted in decreasing the α-helix and increasing the ß-sheet and ß-turn, which promoted the formation of a more uniform microstructure. It also increased the proportion of bound water, increasing the ability of MP to bind with water. This effect, combined with the weaker hydrophobic interactions, as confirmed by the reduced content of tryptophan and aliphatic residues, explained well the high water-holding capacity of MP induced by heating at 2 °C/min under the 9.5 mT magnetic field.

Degradable porous carboxymethyl chitin hemostatic microspheres.

Lethal hemorrhage could endanger lives. Although many hemostatic agents are commercially available with good clinical effect, it is necessary to develop novel hemostatic materials with high efficacy, biological safety, low cost, easily preparation and excellent biodegradability and biocompatibility. Here, novel biodegradable and uniform microspheres with regular spherical architecture and porous microstructure were prepared by thermosensitive carboxymethyl chitin (CMCH) with low substitution degree and low deacetylation through physical-crosslinking at high temperature without using any toxic crosslinkers. The obtained CMCH microspheres (CMCH-MS) were non-cytotoxic, low hemolytic potential and biodegradable in the presence of lysozyme. In vitro blood clotting evaluation indicated that the porous microsphere network structures and the hydrophilicity of the CMCH could promote hemostasis due to the quick blood absorption and local concentration of the coagulation factors for the CMCH-MS. The CMCH-MS showed much better hemorrhage control than negative control and traditional hemostatic chitosan, similar hemostatic performance as commercialized cross-linked starch microspheres in both rat tail and liver models. Thus, the new biodegradable porous CMCH-MS may hold great potential for hemorrhage control in medical treatment.