Germicidal efficacy of the pulsed magnetic field against pathogens and spoilage microorganisms in food processing: An overview

Exploring the role of static magnetic field in supercooling storage from the viewpoint of meat quality and microbial community

In order to explore the application prospects of static magnetic field (SMF) combined with supercooling in meat preservation, this study proposed a novel method of supercooling assisted by a stationary magnetic field (SMF + supercooling) for the preservation of chilled pork, evaluating its cooling rate and quality changes (e.g., water holding capacity, color, pH, and TVB-N), as well as the evolution trend of the microbiota. The results showed that SMF + supercooling significantly (P < 0.05) improved the cooling rate of pork. Compared to chilling and supercooling, SMF + supercooling significantly delayed the increase of TVB-N and TVC on the 12th day of storage (P < 0.05). SMF + supercooling treatment achieves the maintenance of pork water-holding capacity by inhibiting water migration, reducing drip loss, cooking loss, and centrifugal loss of pork. The 16S rDNA bacteria flora analysis demonstrated that SMF + supercooling treatment reduced the relative abundance of spoilage bacteria such as Acinetobacter, Streptococcus, and Pseudomonas, delaying the deterioration of pork quality caused by microbial growth. The SMF + supercooling treatment can be considered a novel refrigeration preservation method that delays the deterioration of pork quality and extends its shelf life.

Intermittent high voltage electrostatic field and static magnetic field assisted modified atmosphere packaging alleviate mildew of postharvest strawberries after simulated transportation by activating the phenylpropanoid pathway

The mildew is a typical symptom of strawberries during storage. The effectiveness of intermittent high voltage electrostatic field combined with static magnetic field (HVEF-SMF) technique in inhibiting the mildew of strawberries (before and after simulation of transport vibrations) was investigated. Intermittent HVEF, SMF and HVEF-SMF treatments inhibited spoilage fungal growth on the surface of strawberries by increasing the membrane permeability and leakage of intracellular materials of spoilage fungal. The HVEF-SMF alleviated mildew in strawberries, which probably via the increase of antifungal compounds (total phenolics and lignin), phenylpropanoid biosynthetic enzyme activities (Phenylalanine ammonia-lyase, 4-coumarate-CoA ligase) and pathogenesis-related proteins enzymes activities (chitinase and β-1,3-glucanase). Overall, HVEF-SMF contributed to alleviating the mildew and disease incidence of strawberries, improving the levels of antimicrobial activity, as well as extending their shelf life from 6 d to 12 d. Therefore, HVEF-SMF treatment is a promising technology for alleviating postharvest mildew in strawberries after transportation.

The importance of supercooled stability for food during supercooling preservation: a review of mechanisms, influencing factors, and control methods

Supercooling can preserve food in its original fresh state below its ice point temperature without freezing. However, the supercooled state is unstable in thermodynamics, state breakdown can occur at any moment, resulting in irregular and larger ice crystals formation, leading to food tissue damage, and loss of quality and nutrients. While the effectiveness of supercooling preservation has been verified in the lab and pilot scale tests, the stability of the supercooled state of food remains an open question, posing a limitation for larger industrial-scale application of supercooling preservation. Based on this background, this review presents the instability mechanisms of supercooling preservation and summarizes the factors such as food properties (e.g., material size, food components, specific surface area, and surface roughness) and preservation circumstances (e.g., cooling rate, temperature variation, and mechanical disturbance) that influence the stability of the supercooled state of food. The review also discusses novel techniques for enhancing the supercooling capacity and their limitations (e.g., precise temperature control and magnetic field). Further studies are necessary to comprehensively evaluate the effects of influence factors and supercooling technologies on supercooling, realizing the true sense of 'no-crystal' food products under subzero temperature preservation conditions in commercial applications.

A review on synthesis and antibacterial potential of bio-selenium nanoparticles in the food industry

Effective control of foodborne pathogen contamination is a significant challenge to the food industry, but the development of new antibacterial nanotechnologies offers new opportunities. Notably, selenium nanoparticles have been extensively studied and successfully applied in various food fields. Selenium nanoparticles act as food antibacterial agents with a number of benefits, including selenium as an essential trace element in food, prevention of drug resistance induction in foodborne pathogens, and improvement of shelf life and food storage conditions. Compared to physical and chemical methods, biogenic selenium nanoparticles (Bio-SeNPs) are safer and more multifunctional due to the bioactive molecules in Bio-SeNPs. This review includes a summarization of (1) biosynthesized of Bio-SeNPs from different sources (plant extracts, fungi and bacteria) and their antibacterial activity against various foodborne bacteria; (2) the antibacterial mechanisms of Bio-SeNPs, including penetration of cell wall, damage to cell membrane and contents leakage, inhibition of biofilm formation, and induction of oxidative stress; (3) the potential antibacterial applications of Bio-SeNPs as food packaging materials, food additives and fertilizers/feeds for crops and animals in the food industry; and (4) the cytotoxicity and animal toxicity of Bio-SeNPs. The related knowledge contributes to enhancing our understanding of Bio-SeNP applications and makes a valuable contribution to ensuring food safety.

Technological innovations enhance postharvest fresh food resilience from a supply chain perspective

Fresh food is rich in nutrients but is usually seasonal, perishable, and challenging to store without degradation of quality. The inherent limitations of various preservation technologies can result in losses in all stages of the supply chain. As consumers of fresh foods have become more health-conscious, new technologies for intelligent, energy-efficient, and nondestructive preservation and processing have emerged as a research priority in recent years. This review aims to summarize the quality change characteristics of postharvest fruits, vegetables, meats, and aquatic products. It critically analyzes research progress and applications of various emerging technologies, which include: the application of high-voltage electric field, magnetic field, electromagnetic field, plasma, electrolytic water, nanotechnology, modified atmosphere packaging, and composite bio-coated film preservation technologies. An evaluation is presented of the benefits and drawbacks of these technologies, as well as future development trends. Moreover, this review provides guidance for design of the food supply chain to take advantage of various technologies used to process food, reduce losses and waste of fresh food, and this improve the overall resilience of the supply chain.

Effect of low voltage electrostatic field combined with partial freezing on the quality and microbial community of large yellow croaker

The effect of low voltage electrostatic field combined with partial freezing (LVEF- PF) treatment on storage quality and microbial community of large yellow croaker was studied. Three different methods including chilled (C), partial freezing (PF) and 6 kV/m electrostatic field combined partial freezing storage were used to preserve large yellow croaker for 18 days. Total viable counts (TVC), sensory evaluation, and physiochemical index including pH, total volatile basic nitrogen (TVB-N), K value and centrifugal loss were examined. During storage, the large yellow croaker was susceptible to microbial growth and spoilage. However, LVEF-PF treatment was found to be effective in enhancing sensory quality, inhibiting microbial growth, and maintaining myofibril microstructure. Low field nuclear magnetic resonance showed that LVEF-PF treatment reduced the migration of immobilized water to free water. At 18th day, the TVC value of LVEF-PF, PF and chilled group were 3.56 log CFU/g, 5.11 log CFU/g, 7.73 log CFU/g, respectively. Therefore, from the results of TVB-N and TVC value, the shelf life of LVEF-PF group was at least 3 days longer than PF group, and 6 days longer than the chilled group. High-throughput sequencing showed that the microbial community diversity significantly decreased during storage. The predominant bacteria in chilled, PF, LVEF-PF group at 18th day were Pseudomonas, Psychrobacter and Shewanella, respectively, and the relative abundance of spoilage bacteria such as Pseudomonas and Psychrobacter were reduced by LVEF-PF treatment, that corresponding with lower values of TVB-N and TVC value. LVEF-PF treatment could be used as a new processing and storage method to delay deterioration and prolong shelf life of large yellow croaker.

External static magnetic field potentiates the reduction of antibiotic resistance genes during swine manure composting

Livestock and poultry manure are repositories of antibiotic resistance genes (ARGs). Accumulating evidence suggests that composting is an important way to effectively attenuate ARGs, but how to reinforce the reduction in ARGs during composting needs to be further investigated. This study explored the influence of an external static magnetic field on ARG mitigation enhancement during swine manure composting. The results showed that a total of 12 high-risk ARGs were identified. A relatively high magnetic field intensity (14.81 mT) was more effective in reducing the abundance of high-risk ARGs, and the removal rate was 20.66-100 %. It also reduced the abundance of 27.14 % of integrons, 79.44 % of insertion sequences, and 8.78 % of plasmids. Partial least squares path modeling showed that a relatively high magnetic field intensity treatment promoted the reduction in ermB by reducing the abundance of Phascolarctobacterium, Streptococcus, and insertion sequences. It also mitigated sul1 expression by reducing the abundance of Acinetobacter and integrons, and it mitigated tetM expression by decreasing Lactobacillus, Streptococcus, insertion sequences, and plasmids. These findings demonstrate that an external static magnetic field is an effective method for intensifying the reduction in ARGs, providing a feasible reference for controlling the potential ARG risk of organic waste composting.

Design and Application of Near Infrared LED and Solenoid Magnetic Field Instrument to Inactivate Pathogenic Bacteria

PURPOSE

This study aims to evaluate the efficiency of infrared LEDs with a magnetic solenoid field in lowering the quantity of gram-positive Staphylococcus aureus and gram-negative Escherichia coli bacteria, as well as the best exposure period and energy dose for inactivating these bacteria.

METHOD

Research has been performed on a photodynamic therapy technique called photodynamic inactivation (PDI), which combines infrared LED light with a wavelength range of 951-952 nm and a solenoid magnetic field with a strength of 0-6 mT. The two, taken together, can potentially harm the target structure biologically. Infrared LED light and an AC-generated solenoid magnetic field are both applied to bacteria to measure the reduction in viability. Three different treatments infrared LED, solenoid magnetic field, and an amalgam of infrared LED and solenoid magnetic field, were used in this study. A factorial statistical ANOVA analysis was utilized in this investigation.

RESULTS

The maximum bacterial production was produced by irradiating a surface for 60 min at a dosage of 0.593 J/cm², according to the data. The combined use of infrared LEDs and a magnetic field solenoid resulted in the highest percentage of fatalities for Staphylococcus aureus, which was 94.43 s. The highest percentage of inactivation for Escherichia coli occurred in the combination treatment of infrared LEDs and a magnetic field solenoid, namely, 72.47 ± 5.06%. In contrast, S. aureus occurred in the combined treatment of infrared LEDs and a magnetic field solenoid, 94.43 ± 6.63 percent.

CONCLUSION

Staphylococcus aureus and Escherichia coli germs are inactivated using infrared illumination and the best solenoid magnetic fields. This is evidenced by the rise in the proportion of bacteria that died in treatment group III, which used a magnetic solenoid field and infrared LEDs to deliver a dosage of 0.593 J/cm² over 60 min. According to the research findings, the magnetic field of the solenoid and the infrared LED field significantly impact the gram-positive bacteria S. aureus and the gram-negative bacteria E. coli.

Aquaphotomics monitoring of strawberry fruit during cold storage - A comparison of two cooling systems

The objective of this study was to use aquaphotomics and near-infrared (NIR) spectroscopy to follow the changes in strawberries during cold storage in the refrigerator with an electric field generator (supercooling fridge, SCF) and without it (control fridge, CF). The NIR spectra of strawberries stored in these refrigerators were collected over the course of 15 days using a portable mini spectrometer and their weight was measured daily. The spectral data in the region of the first overtone of water (1,300-1,600 nm) were analyzed using aquaphotomics multivariate analysis. The results showed a decrease in weight loss of strawberries, but the loss of weight was significantly lower in SCF, compared to the CF. The reduction of weight loss due to exposure to an electric field was comparable to the use of coatings. The aquaphotomics analysis showed that the NIR spectra adequately captured changes in the fruit over the storage period, and that it is possible to predict how long the fruit spent in storage, regardless of the storage type. During aquaphotomics analysis, 19 water absorbance bands were found to be consistently repeating and to have importance for the description of changes in strawberries during cold storage. These bands defined the water spectral pattern (WASP), multidimensional biomarker that was used for the description of the state and dynamics of water in strawberries during time spent in storage. Comparison of WASPs of strawberries in CF and SCF showed that exposure to an electric field leads to a delay in ripening by around 3 days. This was evidenced by the increased amount of structural, strongly bound water and vapor-like trapped water in the strawberries stored in SCF. This particular state of water in strawberries stored in SCF was related to the hardening of the strawberry skin and prevention of moisture loss, in agreement with the results of significantly decreased weight loss.

Origin of static magnetic field induced quality improvement in sea bass (Lateolabrax japonicus) during cold storage: Microbial growth inhibition and protein structure stabilization

To explore the potential application of static magnetic field (SMF) treatment in marine fish preservation, the sea bass (Lateolabrax japonicus) was exposed to SMF (5 mT) and its quality changes during cold storage were evaluated by total viable counts, water holding capacity, pH, color, and textural properties. Characteristics of the protein in the presence of SMF were investigated by measuring total sulfhydryl (SH) content, Ca2+-ATPase activity, secondary structure, and muscle microstructure. SMF treatment exhibited positive effects on fish quality, showing favorable performance on the most quality indicators, especially a significant reduction in the Microbial Counts. Furthermore, higher total SH content and Ca2+-ATPase activity were observed in SMF-treated samples, demonstrating that the oxidation and denaturation of myofibrillar protein (MP) were delayed due to SMF treatment. The transformation of α-helix to random coil was prevented in SMF-treated samples, indicating that the secondary structure of MP was stabilized by SMF treatment. The above changes in protein structures were accompanied by changes in muscle microstructure. More intact and compact structures were observed in SMF-treated samples, characterized by well-defined boundaries between myofibers. Therefore, our findings suggest that under the conditions of this article, SMF treatment could maintain the quality of fish mainly by inhibiting the growth of microorganisms and enhancing the stability of protein structures, and could be a promising auxiliary technology for preservation of aquatic products.

Advances in prepared dish processing using efficient physical fields: A review

Prepared dishes are increasingly popular convenience food that can be eaten directly from hygienic packaging by heating. Physics field (PF) is food processing method built with physical processing technology, which has the characteristics of high efficiency and environmental safety. This review focuses on summarizing the application of PFs in prepared dishes, evaluating and comparing PFs through quality changes during processing and storage of prepared dishes. Currently, improving the quality and extending the shelf life of prepared dishes through thermal and non-thermal processing are the main modes of action of PFs. Most PFs show good potential in handing prepared dishes, but may also react poorly to some prepared dishes. In addition, the difficulty of precise control of processing conditions has led to research mostly at the laboratory stage, but as physical technology continues to break through, more PFs and multi-physical field will be promoted for commercial use in the future. This review contributes to a deeper understanding of the effect of PFs on prepared dishes, and provides theoretical reference and practical basis for future processing research in the development of various enhanced PFs.

The use of the electromagnetic field in microbial process bioengineering

An electromagnetic field (EMF) has been shown to have various stimulatory or inhibitory effects on microorganisms. Over the years, growing interest in this topic led to numerous discoveries suggesting the potential applicability of EMF in biotechnological processes. Among these observations are stimulative effects of this physical influence resulting in intensified biomass production, modification of metabolic activity, or pigments secretion. In this review, we present the current state of the art and underline the main findings of the application of EMF in bioprocessing and their practical meaning in process engineering using examples selected from studies on bacteria, archaea, microscopic fungi and yeasts, viruses, and microalgae. All biological data are presented concerning the classification of EMF. Furthermore, we aimed to highlight missing parts of contemporary knowledge and indicate weak spots in the approaches found in the literature.

Enhancement of Polypeptide Yield Derived from Rapeseed Meal with Low-Intensity Alternating Magnetic Field

The application of physical processing technologies in fermentation is an effective way to improve the quality of substrates. The purpose of the study was to evaluate the feasibility of enhancing the polypeptides of rapeseed meal (RSM) by a low-intensity alternating magnetic field (LF-MF)-assisted solid-state fermentation. A protease-producing strain B16 from RSM was isolated and identified as Bacillus velezensis by analyzing its morphology and 16S rDNA sequencing. Then, it was employed in solid-state fermentation for polypeptide production. The results showed that the neutral protease activity could reach 147.48 U/mL when B.velezensis was cultured under suitable conditions. The protease activity increased rapidly on the 2.5th day of traditional fermentation, while the polypeptide yield reached the maximum on the third day. The highest polypeptides content was achieved by LF-MF-assisted fermentation at magnetic field intensity 140 Gs, treatment 4 h, magnetic field intervention after 16 h of inoculation, and rotation speed 50 rpm/min, which increased by 18.98% compared with traditional fermentation. Therefore, LF-MF-assisted fermentation effectively enhanced the polypeptide yield. The results suggested that LF-MF technology would be widely used to produce bioactive components from agro-industrial by-products.

Inactivation efficacy and mechanisms of atmospheric cold plasma on Alicyclobacillus acidoterrestris: Insight into the influence of growth temperature on survival

The bactericidal effect of dielectric barrier discharge-atmospheric cold plasma (DBD-ACP, 20, and 30 kV) against Alicyclobacillus acidoterrestris on the saline solution and apple juice was investigated. Results show that DBD-ACP is effective for the inactivation of A. acidoterrestris by causing significant changes in cell membrane permeability and bacterial morphology. The effect of culture temperatures on the resistance of A. acidoterrestris to DBD-ACP was also studied. A. acidoterrestris cells grown at 25°C had the lowest resistance but it was gradually increased as the culture temperature was increased (25-45°C) (p < 0.05). Moreover, results from Fourier transform infrared spectroscopy (FT-IR) and Gas Chromatography-Mass Spectrometer (GC-MS) analysis showed that the increase in the culture temperature can gradually cause the decreased level of cyclohexaneundecanoic acid in the cell membrane of A. acidoterrestris (p < 0.05). In contrast, cyclopentaneundecanoic acid, palmitic acid, and stearic acid showed an increasing trend in which the fluidity of the bacterial cell membrane decreased. This study shows a specific correlation between the resistance of A. acidoterrestris and the fatty acid composition of the cell membrane to DBD-ACP.

Application of sonodynamic technology and sonosensitizers in food sterilization: a review of developments, trends and challenges

Food safety and food waste have always been hot topics of discussion in recent years. However, the infection of human pathogenic bacteria and the waste of food resources caused by microbial-contaminated food remains common. Although traditional sterilization technology has been very mature, it causes changes in food flavor and excessive energy consumption to a certain extent. Moreover, the widespread bacterial resistance has also sounded a warning for researchers and finding a new alternative to antibiotics is urgently needed. The application of sonodynamic sterilization technology in medical treatment has aroused the interest of researchers. It provides ideas for new food sterilization technology. As a new non-thermal sterilization technology, sonodynamic sterilization technology has strong penetration, safety, less residue and by-products, and will less change the quality of the food itself. Therefore, sonodynamic sterilization technology has great potential applied in food sterilization technology. This review describes the concept of sonodynamic sterilization technology, the sterilization mechanism of sonodynamic sterilization and the inactivation mechanism of various pathogens, the classification and application of sonosensitizers, and the ultrasonic technology in sonodynamic sterilization in the application over the recent years. It provides a scientific reference for the application of sonodynamic sterilization technology in the field of food sterilization.