Design of a treatment chamber for low-voltage pulsed electric field sterilization

Application of electric field treatment (EFT) for microbial control in water and liquid food

Water disinfection and food pasteurization are critical to reducing waterborne and foodborne diseases, which have been a pressing public health issue globally. Electrified treatment processes are emerging and have become promising alternatives due to the low cost of electricity, independence of chemicals, and low potential to form by-products. Electric field treatment (EFT) is a physical pathogen inactivation approach, which damages cell membrane by irreversible electroporation. EFT has been studied for both water disinfection and food pasteurization. However, no study has systematically connected the two fields with an up-to-date review. In this article, we first provide a comprehensive background of microbial control in water and food, followed by the introduction of EFT. Subsequently, we summarize the recent EFT studies for pathogen inactivation from three aspects, the processing parameters, its efficacy against different pathogens, and the impact of liquid properties on the inactivation performance. We also review the development of novel configurations and materials for EFT devices to address the current challenges of EFT. This review introduces EFT from an engineering perspective and may serve as a bridge to connect the field of environmental engineering and food science.

Advances in pulsed electric stimuli as a physical method for treating liquid foods

There is a need for alternative technologies that can deliver safe and nutritious foods at lower costs as compared to conventional processes. Pulsed electric field (PEF) technology has been utilised for a plethora of different applications in the life and physical sciences, such as gene/drug delivery in medicine and extraction of bioactive compounds in food science and technology. PEF technology for treating liquid foods involves engineering principles to develop the equipment, and quantitative biochemistry and microbiology techniques to validate the process. There are numerous challenges to address for its application in liquid foods such as the 5-log pathogen reduction target in food safety, maintaining the food quality, and scale up of this physical approach for industrial integration. Here, we present the engineering principles associated with pulsed electric fields, related inactivation models of microorganisms, electroporation and electropermeabilization theory, to increase the quality and safety of liquid foods; including water, milk, beer, wine, fruit juices, cider, and liquid eggs. Ultimately, we discuss the outlook of the field and emphasise research gaps.

Prospects and application of ultrasound and magnetic fields in the fermentation of rare edible fungi

Ultrasound has the potential to be broadly applied in the field of agricultural food processing due to advantages such as environmental friendliness, low energy costs, no need for exogenous additives and ease of operation. High-frequency ultrasound is mainly used in medical diagnosis and in the food industry for the identification of ingredients and production line quality testing, while low-frequency ultrasounds is mainly used for extraction and separation, accelerating chemical reactions, auxiliary microbial fermentation and quality enhancement in food industry. Magnetic fields have many advantages of convenient use, such as non-toxic, nonpolluting and safe. High-intensity pulsed magnetic fields are widely used as a physical non-thermal sterilization technology in food processing, while weak magnetic fields are better at activating microorganisms and promoting their growth. Ultrasound and magnetic fields, due to their positive biological effects, have a wide range of applications in the food processing industry. This paper provides an overview of the research progress and applications of ultrasound and magnetic fields in food processing from the perspectives of their biological effects and mechanisms of action. Additionally, with the development and application of physical field technology, physical fields can now be used to provide significant technical advantages for assisting fermentation. Suitable physical fields can promote the growth of microbial cells, improve mycelial production and increase metabolic activity. Furthermore, the current status of research into the use of ultrasound and magnetic field technologies for assisting the fermentation of rare edible fungi, is discussed.

Inactivation of Bacteria Using Bioactive Nanoparticles and Alternating Magnetic Fields

Foodborne pathogens are frequently associated with risks and outbreaks of many diseases; therefore, food safety and processing remain a priority to control and minimize these risks. In this work, nisin-loaded magnetic nanoparticles were used and activated by alternating 10 and 125 mT (peak to peak) magnetic fields (AMFs) for biocontrol of bacteria Listeria innocua, a suitable model to study the inactivation of common foodborne pathogen L. monocytogenes. It was shown that L. innocua features high resistance to nisin-based bioactive nanoparticles, however, application of AMFs (15 and 30 min exposure) significantly potentiates the treatment resulting in considerable log reduction of viable cells. The morphological changes and the resulting cellular damage, which was induced by the synergistic treatment, was confirmed using scanning electron microscopy. The thermal effects were also estimated in the study. The results are useful for the development of new methods for treatment of the drug-resistant foodborne pathogens to minimize the risks of invasive infections. The proposed methodology is a contactless alternative to the currently established pulsed-electric field-based treatment in food processing.

Strategies for Microbial Decontamination of Fresh Blueberries and Derived Products

Increasing consumption of blueberries is associated with appreciation of their organoleptic properties together with their multiple health benefits. The increasing number of outbreaks caused by pathogenic microorganisms associated with their consumption in the fresh state and the rapid spoilage of this product which is mainly caused by moulds, has led to the development and evaluation of alternatives that help mitigate this problem. This article presents different strategies ranging from chemical, physical and biological technologies to combined methods applied for microbial decontamination of fresh blueberries and derived products. Sanitizers such as peracetic acid (PAA), ozone (O3), and electrolyzed water (EOW), and physical technologies such as pulsed light (PL) and cold plasma (CP) are potential alternatives to the use of traditional chlorine. Likewise, high hydrostatic pressure (HHP) or pulsed electrical fields (PEF) successfully achieve microbial reductions in derivative products. A combination of methods at moderate intensities or levels is a promising strategy to increase microbial decontamination with a minimal impact on product quality.

Inactivation of Pichia rhodanensis in relation to membrane and intracellular compounds due to microchip pulsed electric field (MPEF) treatment

The effect of microchip pulsed electric field (MPEF) treatment on lethal and sublethal injury of Pichia rhodanensis (P. rhodanensis) were employed under 100–500 V for 20–100 pulses and the underlying mechanism of MPEF treatment was investigated as well. A 6.48 log₁₀ reduction of P. rhodanensis was achieved at 500V for 80 pulse. The fluorescent staining with Propidium Iodide (PI) verified that the rate of sublethal injury cells maximum up to 27.2% under 200 V. MPEF can cause the damage of cell morphology and ultrastructure, meanwhile causing a decrease in cellular enzymes, antioxidant enzyme activity and cell membrane fluidity. The leakage of intracellular compounds (protein, nucleic acid, K⁺, Mg²⁺) and Ca²⁺-ATPase gradually increased as the growth of voltage, especially the proportion of protein in the supernatants increased from 2.0% to 26.4%. Flow cytometry analysis showed that MPEF has significant effect on membrane potential, but no obvious influence on non-specific esterase. MPEF can cause the changing of the secondary structure of protein, at the same time, double helix structure of DNA became loose and unwinding. These results provide a theoretical guidance for the widespread using of MPEF technology in the application of a non-thermal processing technique for food.

Identification of spoilage microorganisms in blueberry juice and their inactivation by a microchip pulsed electric field system

Blueberry juice is a healthy and nutritious food that has become increasingly popular worldwide. However, little is known about the microbial groups of this juice that can cause its spoilage. This study aimed to identify the main spoilage microorganisms in blueberry juice and explore whether a microchip pulsed electric field (MPEF) can effectively inactivate them. We performed polymerase chain reaction (PCR) amplification, as well as 16S rDNA, 18S rDNA, internal transcribed spacer (ITS), and 26S rDNA gene sequence analyses. Nine species belonging to eight genera, including Pantoea, Burkholderia, Pichia, Meyerozyma, Cryptococcus, Aureobasidium, Cladosporium, and Penicillium were identified as spoilage microorganisms. Cryptococcus sp., Meyerozyma sp., and Pichia sp. were specific spoilage organisms (SSO) owing to their rising numbers throughout spoilage progression. The effect of MPEF on the potential inactivation of these microorganisms was to induce significant inactivation of viable Cryptococcus sp., Meyerozyma sp., and Pichia sp. This research provides a theoretical basis for the application of MPEF in improving the quality of blueberry juice.