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The effect of magnetic field (MF) on the postharvest quality and energy metabolism of green chili was investigated. An MF of 4 mT intensity was applied during the refrigeration of green chili pepper. Conventional refrigeration (CR) was used as a control, and the chili pepper fruit was stored at 10 °C and sampled at 1, 5, 10, 20, and 30 d after harvest. The results showed that MF inhibited the senescence of chili pepper and quality deterioration, as evidenced by higher water content, vitamin C (VC) and flesh firmness as well as lower weight loss and decay incidence. The decrease of hue angle values and the chlorophyll content were remarkably depressed by MF treatment, indicating an efficient delay in the yellowing of chili pepper. In terms of metabolism, MF sustained high adenosine triphosphate (ATP) content, energy charge (EC), and activities of key enzymes engaged in energy metabolism (H+-ATPase, Ca2+-ATPase, succinate dehydrogenase, and cytochrome C oxidase). Additionally, there was an increase in the concentration of major energy metabolites, including citric-acid, isocitric-acid, D-Glucose-6-phosphate, and D-Fructose-6-phosphate. These results suggested that MF may be used as a promising strategy for preventing the decay of postharvest green chilies and prolonging their shelf life. [Display omitted] • MF slowed down senescence and quality deterioration of green chilies. • MF inhibited the loss of chlorophyll and VC content. • MF sustained ATP, EC, and key enzyme activities for energy metabolism. • Major energy metabolites were maintained at high level by MF. [ABSTRACT FROM AUTHOR]

The continuous-flow pasteurization apparatus was presented, and the electric field within orange juice was produced via an oscillating magnetic field at 50 kHz, causing the volumetric heating of the juice with initial conductivity of 6.85 mS/cm and 8.76 mS/cm. The process principle, especially numerical relationships between excitation voltage, magnetic field, induced electric field (IEF), induced current density, and temperature profile were elaborated. When applying a rectangular wave of the voltage at 50–1000 V, the waveforms of the magnetic field and IEF in the juice were sine-like and sawtooth waves, respectively. Through electromagnetic simulation, the model was established, which indicated the indirect heating of orange juice via oscillating magnetic field was feasible. As the magnetic field increased, the outlet temperature and induced current density in the juice was improved. Notably, the 4–5 logs CFU/ml inactivation effects on aerobic bacteria, yeast and mold in orange juice could be achieved at 65 °C for 60 s after the treatment. • Engineering characteristics of induced electric field technology was elaborated. • Electromagnetic simulation model was conduced to verify its thermal effect. • Waveform of magnetic field and induced electric field was investigated. • Difference between experimental and predicted temperature was not significant. • Inactivation effects on aerobic bacteria, yeast and mold was achieved. [ABSTRACT FROM AUTHOR]

A novel electromagnetic heat extraction method was presented, whereby mandarin peels residue solution was located in a winding coil subjected to an oscillating magnetic field, and the pectin was extracted under appropriate conditions. Numerical relationships between applied magnetic field and induced electric field (IEF) in the extraction process were elaborated. The results showed that the induced current density, IEF and terminal temperature increased with increasing magnetic field. The maximum current density of 0.35 A/cm corresponds to the highest terminal temperature of 84.6 °C and IEF intensity of 26.6 V/cm. When magnetic field intensity was 1.39 T and the extraction time was 15 min, the maximum yield of pectin reached 9.16 %. In addition, all treatments impacted the ash content, protein content, water-holding capacity (WHC), and oil-holding capacity (OHC) of the obtained pectin. The pectin extracted by electromagnetic heat had the lowest DE value of 71.3 % with 126.55 kDa molecular weight, while the GalA content was at the highest level of 76.18 %. After different treatments, the composition of pectin monosaccharides changed, but there were slight differences in the composition of pectin polysaccharides. Moreover, the electromagnetic heat extracted pectin had light color and an obvious surface fragmentation of the peel residue. [Display omitted] • Novel electromagnetic heat method was presented for the extraction of pectin. • The maximum yield of pectin reached 9.16 % at 1.39 T and 15 min. • Electromagnetic heat extracted pectin had brighter color and highest GalA level. • There were slight differences in the composition of polysaccharides. [ABSTRACT FROM AUTHOR]

Strawberries are prone to rapid quality deterioration after harvest. Research has confirmed that a magnetic field can improve fruit quality during postharvest storage. However, how the magnetic field impacts the postharvest physiology of strawberries is far from being explored. In this study, the magnetic field (MF, 4 mT, and 50 Hz) was employed during the storage of strawberries at 4 °C for 1, 3, 5, 7, 10, and 15 d, and conventional refrigeration (CR) was used as the control. The results showed that the MF maintained better fruit quality, as indicated by lower decay incidence, declined weight loss, and greater firmness retention. The decrease in soluble solids content and titratable acidity of strawberries caused by respiratory depletion was also alleviated by MF. Furthermore, an improvement in the adenosine triphosphate level, energy charge, activity of enzymes (H+-ATPase, Ca2+-ATPase, succinate dehydrogenase, and cytochrome oxidase) involved in the respiratory metabolism, as well as primary respiratory metabolites (D -glucose, succinic acid, fumaric acid, and citric acid) were observed for the strawberries of MF group. Accumulations of hydrogen peroxide, superoxide anion, and malondialdehyde were suppressed with the application of MF. Overall, the MF contributed to maintaining higher energy and membrane integrity and function, regulating the levels of energy metabolism enzymes, and mitigating reactive oxygen species accumulation, which might be a part of the mechanism involved in retarding the senescence and decay of harvested strawberries. [Display omitted] • MF treatment maintained better strawberries' quality. • MF could maintain ATP content and energy charge. • MF could maintain energy metabolism enzymes activity. • MF treatment alleviated the accumulation of ROS. • MF treatment delayed the postharvest senescence of strawberries. [ABSTRACT FROM AUTHOR]

To promote NaOH pretreatment of corn stalk (CS), a continuous processing system uniting magnetic field and millimeter-scaled channel flow was established. First, four comparative pretreatments were conducted: (I) CS was pretreated with NaOH under traditional agitation; (II) CS was pretreated with NaOH in a flowing state inside the millimeter-scaled channel; (III) CS was pretreated with NaOH in a flowing state and under a static magnetic field; or (IV) CS was pretreated with NaOH in a flowing state and under a rotating magnetic field. By comparison, the highest pentose (121.22 mg/g dry CS) and hexose (287.04 mg/g dry CS) yields were obtained in the shortest pretreatment time with Pretreatment IV (8 h). Accordingly, the key parameters of Pretreatment IV were optimized as 6.71 Hz frequency, 0.50 L/min flow rate, and 1.02% NaOH concentration. Under these conditions, 439.24 mg sugars were released by 1 g dry CS during pretreatment and enzymatic hydrolysis. [ABSTRACT FROM AUTHOR]

Pumpkin polysaccharides are considered as functional materials with bioactivities. However, the conventional aqueous extraction method for pumpkin polysaccharides is limited by long time consumption, low efficiency and potential damage to their bioactivities. To improve the efficiency of pumpkin polysaccharides extraction, we designed a new experimental system combining a rotary magnetic field and flowing conductive solution. Polysaccharide extractions by 1) acidic sample solution with agitation, 2) flowing acidic sample solution, 3) static magnetic field combined with flowing acidic sample solution, and 4) rotary magnetic field combined with flowing acidic sample solution were conducted at pH level of 2–4, temperature of 30–50 °C, and treatment time of 0–180 min. The extraction by use of rotary magnetic field combined with flowing acidic sample solution resulted in the highest polysaccharide yield. Then, the effects of rotational frequency, Reynolds number, pH, and temperature on extraction yield were investigated. The yield increased at first and then decreased with an increase in rotational frequency. The high polysaccharide yield was achieved at large Reynolds number, high temperature, and low pH. From the ultraviolet, Fourier transform-infrared spectrum and chromatographic analysis, the extracts proved to be polysaccharides with an average molecular weight of 1.435 × 10 5 Da. The extracted pumpkin polysaccharides exhibited a dose-dependent radical-scavenging capacity within 0.1 to 5 mg/mL in the order of hydroxyl radical > DPPH radical > superoxide radical. Industrial relevance Rare report on the application of the combined magnetic field and pipe-fluid technique in extraction functional components from food materials. In this study, a novel experimental apparatus combining rotary magnetic field and spiral-pipe flow was designed to accelerate the extraction of pumpkin polysaccharides. In comparison with 1) agitation, 2) flowing acidic sample solution, and 3) static magnetic field combined with flowing acidic sample solution, the method combining rotating magnetic field and flowing acidic sample solution 4) significantly increased the polysaccharide yield. The increments were 40.18%, 32.14%, and 23.32%, respectively, after 180-min extraction. The pumpkin polysaccharides extracted by this novel method possessed a molecular weight of 1.435 × 10 5 Da and showed desirable antioxidant activities in vitro. Therefore, the combined magnetic field and pipe-fluid technique it is a potential method for efficient extraction of valuable compounds from food materials. [ABSTRACT FROM AUTHOR]

The combination of a rotating perpendicular magnetic field and a flowing Ca 2+ solution accelerated the calcium uptake of fresh-cut apple cubes and shortened the time needed for calcium equilibration between the Ca 2+ solution and samples. The influence of operational parameters (Reynolds number of the flowing Ca 2+ solution, magnetic flux density of the magnetic field, rotating frequency of the magnetic field, and temperature) on the calcium uptake rate were investigated. Negative exponential models were used to sufficiently describe the calcium uptake rate of samples. Magnetic flux density and temperature positively affected the calcium uptake rate. Higher Reynolds number and rotating frequency both accelerated the calcium diffusion, but excessively high levels (turbulent flowing at Re = 4134 or rotating frequency at 10 Hz) decreased the calcium content. Neither the flowing Ca 2+ solution alone, nor the magnetic field alone, accelerated the calcium diffusion. This study provides an alternative methodology for the mineral fortification of fresh-cut fruits under the joint action of a rotating magnetic field and a flowing electrolyte solution. [ABSTRACT FROM AUTHOR]

Kiwifruit juice is a popular liquid food with a large consumption. It usually needs high temperature sterilization before packaging and selling. Alternating magnetic field can produce alternating induced electric field, then a thermal effect is triggered. This study aims to explore the inner heating of kiwifruit juice via induced electric field and its impact on the physicochemical properties. Meanwhile, ultra-high temperature instantaneous sterilization (121°C, 5 s), and conventional heat treatment (93°C, 2 min) were conducted as controls, then effects were compared between these treatments. The results showed that the bacterial, mold and yeast colonies were completely eliminated, polyphenol oxidase activity decreased by 94.8%, and peroxidase activity decreased by 92.7%, at 1800 V and 6 mL/min. The induced electric field treatment and ultra-high temperature instantaneous sterilization had no significant effect on pH and titratable acid (P ≥ 0.05). Conventional heat treatment increased soluble solid content by 5.3%. The induced electric field treatment resulted in the closest color and browning index to the fresh juice owing to moderate thermal effect. It also demonstrated minimal loss on total phenols and flavonoids contents after induced electric field treatment (7.1% and 2.7%, respectively). The heating effect caused by induced electric field has great application potential for the treatment of fruit juice. • Induced electric field was utilized for direct heating of kiwifruit juice. • Contact-less thermal effect and temperature rise on kiwifruit juice was evaluated. • The microbe and enzyme could be inactivated within 7.7 s via continuous-flow treatment. • The minimal loss of total phenols and flavonoid was achieved via induced electric field. [ABSTRACT FROM AUTHOR]

The magnetic field‐assisted freezing (MFAF) has been identified as an emerging physical method used for food preservation, characterised by its high penetrability in food materials. However, effects of magnetic fields in different dimensions on food freezing process and its products quality have not been previously compared. Thus, the alternating magnetic fields (4 mT and 50 Hz) were applied in different directions and its impact on the physiochemical properties of frozen avocado puree during the storage were investigated. In comparison with the conventional freezing process, the application of MFAF could reduce the weight loss and soluble solids rise. The transformation between different types of water and their corresponding redistribution were also limited under MFAF. The decrease of total polyphenol content with extended storage time was reduced due to the inhibitory effect of MFAF on the polyphenol oxidase activity. In general, the MFAF of avocado purees presented better texture characteristics and higher sensory qualities than the controls. The more directions the magnetic field was applied, the better it performed in maintaining the quality of avocado puree. This study provides a reference for the application of the MFAF on food cryopreservation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Microbial fermentation is a mainstream method for producing high-value compounds. • Applications of magnetic fields in microbial fermentation were summarized. • Magnetic field assisted microbial fermentation devices were illustrated. • Underlying mechanisms behind biological effects of magnetic fields were elaborated. The magnetic field application is emerging as an auxiliary physical strategy to facilitate rapid biomass accumulation and intracellular production of compounds. However, the underlying mechanisms and principles governing the application of magnetic fields for microbial growth and biotransformation are not yet fully understood. Therefore, a better understanding of interdisciplinary technologies integration, expanded magnetic field application, and scaled-up industrial implementation is crucial. In this review, the magnetic field characteristics, magnetic field-assisted fermentation devices, and the working mechanism of magnetic field have been reviewed comprehensively from both physical and microbiological perspectives. The review suggests that magnetic fields affect the biochemical processes in microorganisms by mediating nutrient transport across membranes, electron transfer during photosynthesis and respiration, enzyme activity and gene expression. Moreover, the recent advances in magnetic field application for microbial fermentation and conversion in biochemical, food and agricultural fields have been summarized. [ABSTRACT FROM AUTHOR]

The novel, previous unreported induction heating technique developed here uses the inverse process of the existing induction heating techniques. The theoretical basis for developing this technique is to determine whether the induced current passing through a winding food coil would induce a magnetic flux or cause an increase in primary current. Therefore, to develop this technique and implement it in the food industry, it is necessary to understand its technical details and engineering characteristics. This study presents the design and development process of the technique, as well as the calculation formulas, including load voltage, induced electric field, induced current density, heating power and energy utilization rate during the heating process. The results reveal that although the application of this innovative inner heating technique has been achieved, the energy efficiency of the current system is low. The thermal effect and non-thermal effect of the induced electric field decreased the total bacterial counts in the samples of grapefruit juice and raw milk. Image 10083 • Innovative induction heating is a sister technology to ohmic heating in the food industry. • Liquid food can act as the secondary winding of a transformer for inner heating. • A thermal effect on liquid foods by an alternating magnetic field was observed. • The development and design process of this novel technique are presented. • Continuous-flow pasteurization of liquid food was achieved by an induced electric field. [ABSTRACT FROM AUTHOR]

In this study, the air gap magnetic field characteristics of external rotor permanent magnet synchronous motors (PMSMs) under both the stator and rotor coordinate systems considering low‐order current harmonics and high‐order sideband current harmonics are analysed. A direct measurement technique (DMT) for air‐gap magnetic field is proposed. First, an analytical model of air gap magnetic field of external rotor PMSMs is established. The spatial order and frequency characteristics of stator/rotor air gap magnetic field are revealed. Then, a 24‐pole 27‐slot external rotor PMSM is taken as an example. The analytical and finite element (FE) results are compared and analysed. The difference of the spatial order and frequency characteristics between the stator and rotor air gap magnetic field are verified. Next, a new DMT is proposed, which can detect the precise distribution and local microscopic characteristics on the order of 10−1 mm with high resolution. The accuracy of analytical and FE model are verified by the DMT and an indirect experimental test of no‐load back electromotive force. Finally, the mechanical challenges of in‐wheel motors and the practicablility of DMT for eccentricity detection are further discussed. [ABSTRACT FROM AUTHOR]

Static magnetic fields (SMFs) exhibit numerous biological effects and regulate the proliferation and differentiation of several adult stem cells. However, the role of SMFs in the self-renewal maintenance and developmental potential of pluripotent embryonic stem cells (ESCs) remains largely uninvestigated. Here, we show that SMFs promote the expression of the core pluripotent markers Sox2 and SSEA-1. Furthermore, SMFs facilitate the differentiation of ESCs into cardiomyocytes and skeletal muscle cells. Consistently, transcriptome analysis reveals that muscle lineage differentiation and skeletal system specification of ESCs are remarkably strengthened by SMF stimuli. Additionally, when treated with SMFs, C2C12 myoblasts exhibit an increased proliferation rate, improved expression of skeletal muscle markers and elevated myogenic differentiation capacity compared with control cells. Together, our data show that SMFs effectively promote muscle cell generation from pluripotent stem cells and myoblasts. The noninvasive and convenient physical stimuli can be used to increase the production of muscle cells in regenerative medicine and the manufacture of cultured meat in cellular agriculture. [ABSTRACT FROM AUTHOR]

Summary: Magnetic field is an appropriate physical field, it can be used as a process parameter for the preservation of meat products. In this study, fresh beef was subjected to an alternating magnetic field of 2 mT during cold storage at 4°C, then microbial indicators, physicochemical properties of beef samples and its protein indicators were investigated. The results showed that the alternating magnetic field could inhibit the microbial growth on beef sample, and TVB‐N content, drip loss and characteristic putrefactive amine were lower than the control. The total bacterial count and TVB‐N value of beef samples in the control exceeded the threshold value on the 8th day, respectively, while the samples in the alternating magnetic field exceeded the threshold value on the 13th day. Meanwhile, it demonstrated that the field could delay the transformation of free amino acids to biogenic amines and inhibit the accumulation of bitter amino acids, so maintaining its nutritional characteristics. With the extension of storage period, the sulfhydryl content of beef myofibrillar proteins subjected to alternating magnetic field was lower than that of the control. It demonstrated that the protein oxidation of samples was inhibited, which would also be the reason the Ca2+‐ ATPase activity of myofibrillar proteins was maintained at a low level during the period. Furthermore, the upward trend of carbonyl group content was delayed. It provides a reference for the application of alternating magnetic field on cold storage of meat. [ABSTRACT FROM AUTHOR]

Due to the serious bacterial infection of skin and the waste of petroleum-based materials, there is an urgent need to develop natural biodegradable wound dressings with high antibacterial activity. Phosvitin (PSV) has shown its natural antioxidant and antibacterial properties, making it an excellent material for preparing wound healing dressings. In this study, we investigated the effect of magnetic field on the preparation of PSV-Microcrystalline Cellulose (MCC) composite hydrogels in 1-Allyl-3-methylimidazolium chloride (AmimCl) system. The results showed that the prepared hydrogels exhibited homogeneous surface structure, suitable swelling capacity and elasticity modulus, and sufficient thermal stability. The excellent antibacterial and antioxidant activities of hydrogels were mainly resulting from AmimCl and PSV, respectively, and the properties were enhanced after magnetic field treatment. The proteomics analysis indicated that AmimCl can readily penetrate the biological membranes of Staphylococcus aureus (S. aureus), upsetting the metabolism and reducing the virulence. The hydrogels showed great blood compatibility. Compared with the commercial materials, the 5 mT-treated hydrogels presented a comparable wound healing rate in the full-thickness skin injury model. On day 7, the wound healing rate of the 5 mT group reached approximately 84.40 %, which was significantly higher than that of the control group, 72.88 % (P < 0.05). In conclusion, our work provides experience for the development of biodegradable materials combined in ionic liquids and magnetic field, and explores their applications in wound healing dressings. [Display omitted] • The AmimCl is a green solvent and shows antibacterial activity against S. aureus. • Magnetic field can enhance the antibacterial and antioxidant properties of the materials. • 5 mT-treated hydrogels present a comparable wound healing rate as compared to the commercial Tegaderm. [ABSTRACT FROM AUTHOR]

To accurately and quickly predict the open-circuit air-gap magnetic field in interior permanent magnet synchronous machines (IPMSMs), an analytical model based on magnetic equivalent circuit (MEC) method is proposed. The analytical model can provide radial and tangential components of open-circuit magnetic field in the slotless air gap. The radial component is obtained from the MEC model, and the tangential component is obtained from boundary conditions of macroscopic equations. Then, a complex relative air-gap permeance is applied to take the effect of slots into account. As a result, an accurate solution of both radial and tangential components of the flux density in the slotted air gap is obtained. Additionally, the no-load back electromotive force (EMF) and cogging torque are calculated based on the open-circuit air-gap magnetic field. All the analytical results are verified by the finite element (FE) analysis and they are well matched. In the end, a direct measurement experiment of open-circuit air-gap magnetic field is proposed to verify the validity of both radial and tangential open-circuit air-gap magnetic fields. [ABSTRACT FROM AUTHOR]