Cold plasma for the disinfection of industrial food‐contact surfaces: An overview of current status and opportunities

Cold plasma: A nonthermal pretreatment, extraction, and solvent activation technique for obtaining bioactive compounds from agro-food industrial biomass

The present review provides a comprehensive overview of cold plasma treatment and its applications in solvent activation and bioactive component extraction. The study has summarized the principles, types, uses, and mechanisms of cold plasma treatment in activating various solvents, extracting biomolecules, and affecting the characteristics of the extracted compound. This review also explores the environmental benefits of implementing this sustainable technology, highlighting the influence of key parameters such as gas type, treatment time, voltage, and plasma flow rate on the extraction process, providing insights into optimizing these conditions for maximum efficiency. In addition, future trends and research needs for advancing cold plasma-assisted extraction have also been proposed. All biomolecules exhibit specific characteristics; still, the influence of cold plasma treatment varies depending on treatment parameters and product properties, including the source material utilized in the extraction process. Most research has shown that cold plasma treatment can cause cell disruption due to reactive species generation and enhances solvent penetration; thereby, it helps in improving extraction yield with negligible effects on characteristics. With the growing demand for natural bioactive compounds in the nutraceutical, pharmaceutical, and food sectors, cold plasma offers a promising alternative to conventional thermal and chemical extraction techniques. This review concisely discusses the benefits and challenges of cold plasma treatment and the need for additional research.

Cold Plasma-A Sustainable Energy-Efficient Low-Carbon Food Processing Technology: Physicochemical Characteristics, Microbial Inactivation, and Industrial Applications

Nonthermal technologies, mostly utilized for microbial inactivation and quality preservation in food, are attracting increased interest, particularly in nonthermal plasma. Cold plasma (CP) demonstrates favorable results, such as increased germination, enhanced functional and rheological characteristics, and the eradication of microorganisms. Consequently, CP is a novel technology in food processing that has significantly contributed to the prevention of food spoilage. This study highlights contemporary research on CP technology in food processing. This includes its use in microbial decontamination, shelf life extension, mycotoxin degradation, enzyme inactivation, and surface modification of food products. The CP generation techniques under low pressure, including glow discharge, radio frequency and microwave techniques, and atmospheric pressure, including dielectric barrier discharge (DBD), plasma jet, and corona discharge, are discussed. Additionally, the source for the generation of plasma-activated water (PAW) with its significant role in food processing is critically discussed. The CP is an effective method for the decontamination of several food materials like fruits, vegetables, meat, and low-moisture food products. Also, the review addressed the effects of CP on the physicochemical properties of foods and CP for pretreatment in various aspects of food processing, including drying of food, extraction of bioactive compounds, and oil hydrogenation. CP improved the drying kinetics of food, resulting in reduced processing time and improved product quality. Similarly, CP is effective in maintaining food safety and quality, removing the formation of biofilm, and also in reducing protein allergenicity. The review also underscored the importance of CP as a sterilizing agent for food packaging materials, emphasizing its role in enhancing the barrier characteristics of biopolymer-based food packaging materials. Therefore, it is concluded that CP is effective in the reduction of pathogenic microorganisms from food products. Moreover, it is effective in maintaining the nutritional and sensory properties of food products. Overall, it is effective for application in all aspects of food processing. There is a critical need for ongoing research on upscaling for commercial purposes.

Process Technologies for Disinfection of Food-Contact Surfaces in the Dry Food Industry: A Review

The survival characteristics of bacterial pathogens, including Salmonella spp., Listeria monocytogenes, Staphylococcus aureus, and Escherichia coli, in foods with a low water activity (aw) have been extensively examined and reported. Microbial attachment on the food-contact surfaces can result in cross-contamination and compromise the safety of low-aw foods. The bactericidal potential of various conventional and novel disinfection technologies has been explored in the dry food industry. However, the attachment behavior of bacterial pathogens to food-contact surfaces in low-aw conditions and their subsequent response to the cleaning and disinfection practices requires further elucidation. The review summarizes the elements that influence disinfection, such as the presence of organic residues, persistent strains, and the possibility of microbial biotransfer. This review explores in detail the selected dry disinfection technologies, including superheated steam, fumigation, alcohol-based disinfectants, UV radiation, and cold plasma, that can be used in the dry food industry. The review also highlights the use of several wet disinfection technologies employing chemical antimicrobial agents against surface-dried microorganisms on food-contact surfaces. In addition, the disinfection efficacy of conventional and novel technologies against surface-dried microorganisms on food-contact surfaces, as well as their advantages and disadvantages and underlying mechanisms, are discussed. Dry food processing facilities should implement stringent disinfection procedures to ensure food safety. Environmental monitoring procedures and management techniques are essential to prevent adhesion and allow the subsequent inactivation of microorganisms.

Use of dielectric-barrier discharge (DBD) cold plasma for control of bread spoilage fungi

Bread is a greatly consumed bakery product worldwide. Unfortunately, it is an optimal substrate for fungal contamination and deterioration (aw > 0.95), commonly caused by the genera Penicillium, Paecilomyces, and Aspergillus, resulting in significant economic losses. Traditional conservation methods, such as the use of calcium propionate, are rejected by some consumers, leading to investment in alternative methods, such as the use of cold plasma. This study aimed to verify the effectiveness of dielectric-barrier discharge (DBD) cold plasma in inhibiting the growth of bread spoilage fungi. The species Penicillium sumatrense (ML1), Penicillium roqueforti (FML125), Penicillium paneum (FML126), Paecilomyces variotii (FML112), Aspergillus niger (ML2) were used. To assess the effect of plasma on fungi, they were inoculated into swabs, stainless steel coupons, and then small plugs were taken directly from the fungal culture and pan bread slices. All strains were inoculated into swabs and pan bread slices, but only the ML1 strain was used for experiments with coupons and plugs. Regarding the swabs of all strains (System I, 50 W/15 min), in addition to the milder treatments on the plug (System II, 50 W/2.5, 5, 10, and 20 min) and all treatments of ML1 strain coupons (System II, 200 W/15 min, 10 W and 8 W/2.5 and 1.5 min), the cold plasma presented fungistatic properties, delaying mycelial growth from 8 to 30 days and reducing the fungal population by 2.24 log when compared to controls. By analyzing the 200 W treatment with the longest exposure (5, 10, and 20 min) on the plug, plasma showed fungicidal action, completely inactivating mycelial growth. Regarding the pan bread slices, plasma System III, when applied for 45 min, reduced strains FML126 and FML112 by 1 log, FML125 and ML2 by 2 logs, and ML1 by 7 logs, demonstrating potential for use as a control method in the baking industry.

Rapid changes in stress-related gene expression after short exposure of Arabidopsis leaves to cold plasma

Cold Atmospheric Plasma (CAP) technology has emerged as a promising tool in various biological applications due to its ability to generate a composite signal comprising reactive oxygen and nitrogen species, ultraviolet radiation, and electromagnetic fields, all while maintaining a stable temperature. Although CAP treatments have demonstrated significant effects on seed germination and plant growth, the direct molecular responses of plants to CAP exposure remain poorly understood. In this study, young Arabidopsis thaliana leaves were exposed to a brief 5- or 30-s localized CAP treatment, resulting in rapid and localized tissue damage without causing lethal effects on the entire plant. Molecular analyses conducted on the entire plant rosette revealed a notable increase in hydrogen peroxide levels, along with the upregulation of stress-related genes, akin to a wound response. Of particular interest, the activation of RelA/SpoT Homolog (RSH) genes encoding proteins that regulate the synthesis of the stress marker (p)ppGpp, also known as alarmone, and playing a major role in the energic regulation of photosynthesis, occurred shortly after CAP exposure. The expression of RSH genes was up-regulated after 5s CAP exposure, while the wound stress marker ZAT12 remained unaffected, highlighting a specific signalling pathway to activate RSH genes. This finding suggests the potential involvement of the alarmone signalling pathway in the plant's response to CAP exposure, thereby opening avenues for further exploration of metabolic pathways and signalling cascades induced by CAP treatment.

Sustained germination-promoting effect of cold atmospheric plasma on spinach seeds

Cold atmospheric plasma (CAP) irradiation exhibits a sterilizing effect without causing thermal denaturation or leaving behind residual toxicants. CAP also has potential applications in various fields, including agriculture, leading to research efforts in recent years. This study investigated the effects of CAP on the seed germination rate of spinach (Spinacia oleracea), which typically has a low seed germination rate. Our results confirmed that irradiation with N2-CAP and Air-CAP significantly enhanced the germination rate of spinach seeds. Notably, we discovered that CAP irradiation promoted germination even in spinach seeds coated with a fungicide (thiuram) and a disinfectant (Captan), which are commonly used. Additionally, we examined whether the interval between CAP irradiation and the subsequent germination-induction treatment influenced the germination efficiency. We found that the germination-promoting effect of CAP on spinach seeds persisted for at least 30 days, demonstrating the high utility and practicality of CAP in the agricultural sector.

Bioaerosol Inactivation by a Cold Plasma Ionizer Coupled with an Electrostatic Precipitator

Despite best efforts in air purification, airborne infectious diseases will continue to spread due to the continuous emission of bioaerosols by the host/infected person. Hence, a shift in focus from air purification to bioaerosol inactivation is urgently needed. To explore the potential of the cold plasma technology for preventing rapid spread of airborne infectious diseases, we studied a cold plasma ionizer (CPI) device and an electrostatic precipitator (ESP)-coupled CPI (CPI-ESP) device for the inactivation and cleaning of surface-spread microorganisms and bioaerosols, using porcine respiratory coronavirus (PRCV), Escherichia coli (E. coli), and aerosolized E. coli as representatives. We firstly demonstrated that CPI coupled with ESP is an effective technology for inactivating virus and bacteria spread on surfaces in an in-house test chamber. We then demonstrated the efficacy of CPI-coupled ESP for the inactivation of aerosolized E. coli in the same chamber. Furthermore, we have demonstrated the efficiency of a CPI-ESP coupled device for the inactivation of naturally occurring airborne microbials in a few indoor settings (i.e., a living room, a discussion room, a schoolroom, and an office) to determine the treatment duration- and human activity-dependent efficacy. To understand the disinfection mechanism, we conducted a fluorescence microscopy study to reveal different degrees of E. coli bacteria cell membrane damage under CPI treatment.

In-package cold plasma treatment to extend the shelf life of food

Conventional food preservation methods such as heat treatment, irradiation, chemical treatment, refrigeration, and coating have various disadvantages, like loss of food quality, nutrition, and cost-effectiveness. Accordingly, cold plasma is one of the new technologies for food processing and has played an important role in preventing food spoilage. Specifically, in-package cold plasma has become a modern trend to decontaminate, process, and package food simultaneously. This strategy has proven successful in processing various fresh food ingredients, including spinach, fruits, vegetables, and meat. In particular, cold plasma treatment within the package reduces the risk of post-processing contamination. Cryoplasm decontamination within packaging has been reported to reduce significantly the microbial load of many foods' spoilage-causing pathogens. However, studies are needed to focus more on the effects of in-package treatments on endogenous enzyme activity, pest control, and removal of toxic pesticide residues. In this review, we comprehensively evaluated the efficacy of in-package low-temperature plasma treatment to extend the shelf life of various foods. The mechanisms by which cold plasma interacts with food were investigated, emphasizing its effects on pathogen reduction, spoilage mitigation, and surface modification. The review also critically assessed the effects of the treatments on food quality, regulatory considerations, and their potential as viable technologies to improve food safety and packaging life. In-package cold plasma treatment could revolutionize food storage when combined with other sophisticated technologies such as nanotechnology.

Intervention mechanisms of cold plasma pretreatment on the quality, antioxidants and reactive oxygen metabolism of fresh wolfberries during storage

Fresh wolfberries, a nutritious "super fruit", face limited marketing potential due to storage difficulties. This study aimed to enhance their storage stability using dielectric barrier discharge plasma (DBD) pretreatment and investigate the intervention mechanism. The results indicated that the optimal condition of DBD pretreatment for fresh wolfberries was 13.64 kV, 70 s and 2.7 kHz, which extended their shelf from 2 to 5 d at room temperature. This pretreatment reduced decay, weight loss, and firmness reduction by inactivating microorganisms and inhibiting respiration. Additionally, the decline of phenols, flavonoids, ascorbic acid, and antioxidant activity was inhibited, while maintaining high content of polysaccharides, titratable acid, and carotenoids. Interestingly, moderate DBD treatment produced reactive oxygen species (ROS) that triggered the defense response of wolfberries' ROS metabolism system and promoted the biosynthesis of flavonoids, thereby enhancing resistance to decay. The findings offer new insight into plasma effects on fruits and vegetables.

Alternative methods for RuBisCO extraction from sugar beet waste: A comparative approach of ultrasound and high voltage electrical discharge

Ultrasound (US) and high voltage electric discharge (HVED) with water as a green solvent represent promising novel non-thermal techniques for protein extraction from sugar beet (Beta vulgaris subsp. vulgaris var. altissima) leaves. Compared to HVED, US proved to be a better alternative method for total soluble protein extraction with the aim of obtaining high yield of ribulose-1,5-bisphosphate carboxylase-oxygenase enzyme (RuBisCO). Regardless of the solvent temperature, the highest protein yields were observed at 100% amplitude and 9 min treatment time (84.60 ± 3.98 mg/gd.m. with cold and 96.75 ± 4.30 mg/gd.m. with room temperature deionized water). US treatments at 75% amplitude and 9 min treatment time showed the highest abundance of RuBisCO obtained by immunoblotting assay. The highest protein yields recorded among HVED-treated samples were observed at a voltage of 20 kV and a treatment time of 3 min, disregarding the used gas (33.33 ± 1.06 mg/gd.m. with argon and 34.89 ± 1.59 mg/gd.m. with nitrogen as injected gas), while the highest abundance of the RuBisCO among HVED-treated samples was noticed at 25 kV voltage and 3 min treatment time. By optimizing the US and HVED parameters, it is possible to affect the solubility and improve the isolation of RuBisCO, which could then be purified and implemented into new or already existing functional products.

Practice and Progress: Updates on Outbreaks, Advances in Research, and Processing Technologies for Low-moisture Food Safety

Large, renowned outbreaks associated with low-moisture foods (LMFs) bring to light some of the potential, inherent risks that accompany foods with long shelf lives if pathogen contamination occurs. Subsequently, in 2013, Beuchat et al. (2013) noted the increased concern regarding these foods, specifically noting examples of persistence and resistance of pathogens in low-water activity foods (LWAFs), prevalence of pathogens in LWAF processing environments, and sources of and preventive measures for contamination of LWAFs. For the last decade, the body of knowledge related to LMF safety has exponentially expanded. This growing field and interest in LMF safety have led researchers to delve into survival and persistence studies, revealing that some foodborne pathogens can survive in LWAFs for months to years. Research has also uncovered many complications of working with foodborne pathogens in desiccated states, such as inoculation methods and molecular mechanisms that can impact pathogen survival and persistence. Moreover, outbreaks, recalls, and developments in LMF safety research have created a cascading feedback loop of pushing the field forward, which has also led to increased attention on how industry can improve LMF safety and raise safety standards. Scientists across academia, government agencies, and industry have partnered to develop and evaluate innovate thermal and nonthermal technologies to use on LMFs, which are described in the presented review. The objective of this review was to describe aspects of the extensive progress made by researchers and industry members in LMF safety, including lessons-learned about outbreaks and recalls, expansion of knowledge base about pathogens that contaminate LMFs, and mitigation strategies currently employed or in development to reduce food safety risks associated with LMFs.

Production of third generation bio-fuel through thermal cracking process by utilizing Covid-19 plastic wastes

During this pandemic, it has become customary to wear a face waste mask to guard against coronavirus illness (COVID-19). However, huge production of face waste masks, PPE kit and gloves pose environmental risks, since existing disposal methods such as incineration and reclamation which are emitting hazardous substances. In the present study covid-19 medical waste material like waste face waste masks; gloves and PPE kit (personal protective equipment) are considered as the feedstock for the thermal degradation process. Mainly nylon, polyethylene and polypropylene compounds are present in the Covid-19 medical waste compounds, further feedstock material is subjected to physical characterization process like proximate, ultimate and thermo gravimetric analysis (TGA), to determine the moisture, ash, volatile matter and decomposition temperature respectively. The waste waste mask has lower ash content of 9.7 %, whereas gloves and other PPEs has 11.8 and 11.2 % of ash respectively. Similarly volatile matter is also higher for waste waste mask than other feed stocks. Pyrolysis process is carried out between a temperature range of 100 °C to 700 °C and the products of the pyrolysis process are pyrolytic liquid, gas and residue. The maximum pyrolytic oil is produced from waste masks, gloves and other PPE kit at 300, 350 and 320 °C respectively. The calorific value of the pyrolytic oil from waste mask, gloves and other PPE kit possess 40.85,40.11,40.31 MJ/kg respectively, which indicates that all the pyrolytic oil has closer to the diesel fuel. Therefore pyroltic oil obtained from the Covid-19 medical waste can be used as an alternative fuel for CI engine.

Treatment of Fresh Meat, Fish and Products Thereof with Cold Atmospheric Plasma to Inactivate Microbial Pathogens and Extend Shelf Life

Assuring the safety of muscle foods and seafood is based on prerequisites and specific measures targeted against defined hazards. This concept is augmented by 'interventions', which are chemical or physical treatments, not genuinely part of the production process, but rather implemented in the framework of a safety assurance system. The present paper focuses on 'Cold Atmospheric pressure Plasma' (CAP) as an emerging non-thermal intervention for microbial decontamination. Over the past decade, a vast number of studies have explored the antimicrobial potential of different CAP systems against a plethora of different foodborne microorganisms. This contribution aims at providing a comprehensive reference and appraisal of the latest literature in the area, with a specific focus on the use of CAP for the treatment of fresh meat, fish and associated products to inactivate microbial pathogens and extend shelf life. Aspects such as changes to organoleptic and nutritional value alongside other matrix effects are considered, so as to provide the reader with a clear insight into the advantages and disadvantages of CAP-based decontamination strategies.

Convolutional Neural Network for Object Detection in Garlic Root Cutting Equipment

Traditional manual garlic root cutting is inefficient and can cause food safety problems. To develop food processing equipment, a novel and accurate object detection method for garlic using deep learning—a convolutional neural network—is proposed in this study. The you-only-look-once (YOLO) algorithm, which is based on lightweight and transfer learning, is the most advanced computer vision method for single large object detection. To detect the bulb, the YOLOv2 model was modified using an inverted residual module and residual structure. The modified model was trained based on images of bulbs with varied brightness, surface attachment, and shape, which enabled sufficient learning of the detector. The optimum minibatches and epochs were obtained by comparing the test results of different training parameters. Research shows that IRM-YOLOv2 is superior to the SqueezeNet, ShuffleNet, and YOLOv2 models of classical neural networks, as well as the YOLOv3 and YOLOv4 algorithm models. The confidence score, average accuracy, deviation, standard deviation, detection time, and storage space of IRM-YOLOv2 were 0.98228, 99.2%, 2.819 pixels, 4.153, 0.0356 s, and 24.2 MB, respectively. In addition, this study provides an important reference for the application of the YOLO algorithm in food research.