Promising applications of cold plasma for microbial safety, chemical decontamination and quality enhancement in fruits

A review on mechanisms and impacts of cold plasma treatment as a non-thermal technology on food pigments

Food characteristics like appearance and color, which are delicate parameters during food processing, are important determinants of product acceptance because of the growing trend toward more diverse and healthier diets worldwide, as well as the increase in population and its effects on food consumption. Cold plasma (CP), as a novel technology, has marked a new trend in agriculture and food processing due to the various advantages of meeting both the physicochemical and nutritional characteristics of food products with minimal changes in physical, chemical, nutritional, and sensorial properties. CP processing has a positive impact on food quality, including the preservation of natural food pigments. This article describes the influence of CP on natural food pigments and color changes in vegetables and fruits. Attributes of natural pigments, such as carotenoids, chlorophyll, anthocyanin, betalain, and myoglobin, are presented. In addition, the characteristics and mechanisms of CP processes were studied, and the effect of CP on mentioned pigments was investigated in recent literature, showing that the use of CP technology led to better preservation of pigments, improving their preservation and extraction yield. While certain modest and undesirable changes in color are documented, overall, the exposure of most food items to CP resulted in minor loss and even beneficial influence on color. More study is needed since not all elements of CP treatment are currently understood. The negative and positive effects of CP on natural food pigments in various products are discussed in this review.

Potential use of cold plasma treatment for disinfection and quality preservation of grape inoculated with Botrytis cinerea

Gray mold caused by Botrytis cinerea is a serious disease of grape (Vitis vinifera) during storage. The aim of this study is to evaluate the effect of atmosphere cold plasma (a novel and nonthermal technology) on inactivation of B. cinerea and preservation of chemical, physical, and mechanical characteristics of grape inoculated with B. cinerea. Herein, different time of cold plasma (0, 10, 20, and 40 s) was firstly considered to be the main factors, besides different storage time (1, 2, 3, 4, and 5 weeks) at 4°C. According to the results, plasma treatment exhibited inhibitory effect on gray mold percentage and microbial load of B. cinerea (log CFU g-1) during postharvest storage. So, in the last week, the gray mold percentage and microbial load in the control were 100% and 3.6 log CFU g-1, and in 40-s plasma were 4.5% and 2.53 log CFU g-1, respectively. Although the minimum infection and microbial load were observed in 40-s plasma, better postharvest quality preservation was observed in short-time cold plasma treatment (≤20 s). Forty-second plasma caused fruit tissue destruction and negatively decreased mechanical indices (Emod: 0.0028, Fmax = 1.78, and W = 3.18) and weight loss (91.9) in comparison with ≤20-s plasma, in which mechanical indices (Emod =0.0077, Fmax = 3.6, and W = 10.06) and weight loss (1/1) were higher. The long-time cold plasma treatment (40 s) had also maximum effects on color changes (10) and surface temperature (2.8°C). Although the highest TSS and TA were observed in 40-s Plasma, but different time of plasma treatments had no effect on pH. Altogether, these results indicate that the short-time cold plasma treatment can inactivate B. cinerea on grape berries and preserve crop quality properties.

Application of cold argon plasma on germination, root length, and decontamination of soybean cultivars

Applying cold discharge plasma can potentially alter plants' germination characteristics by triggering their physiological activities. As a main crop in many countries, soybean was examined in the present study using cultivars such as Arian, Katoul, Saba, Sari, and Williams in a cold argon plasma. This study has been motivated by the importance of plant production worldwide, considering climate change and the increasing needs of human populations for food. This study was performed to inspect the effect of cold plasma treatment on seed germination and the impact of argon plasma on microbial decontamination was investigated on soybeans. Also, the employed cultivars have not been studied until now the radicals generated from argon were detected by optical emission spectrometry (OES), and a collisional radiative model was used to describe electron density. The germination properties, including final germination percentage (FGP), mean germination time (MGT), root length, and electrical conductivity of biomolecules released from the seeds, were investigated after the plasma treatments for 30, 60, 180, 300, and 420 s. The decontamination effect of the plasma on Aspergillus flavus (A.flavus) and Fusarium solani (F.solani) was also examined. The plasma for 60 s induced a maximum FGP change of 23.12 ± 0.34% and a lowest MGT value of 1.40 ± 0.007 days. Moreover, the ultimate root length was 56.12 ± 2.89%, in the seeds treated for 60 s. The plasma exposure, however, failed to yield a significant enhancement in electrical conductivity, even when the discharge duration was extended to 180 s or longer. Therefore, the plasma duration of 180 s was selected for the blotter technique. Both fungi showed successful sterilization; their infectivity inhibition was 67 ± 4 and 65 ± 3.1%, respectively. In general, the cold plasma used for soybeans in the present study preserved their healthy qualities and reduced the degree of fungal contamination.

A review on plasma-activated water and its application in the meat industry

Meat is a nutritious food with a short shelf life, making it challenging to ensure safety, quality, and nutritional value. Foodborne pathogens and oxidation are the main concerns that lead to health risks and economic losses. Conventional approaches like hot water, steam pasteurization, and chemical washes for meat decontamination improve safety but cause nutritional and quality issues. Plasma-activated water (PAW) is a potential alternative to thermal treatment that can reduce oxidation and microbial growth, an essential factor in ensuring safety, quality, and nutritional value. This review explores the different types of PAW and their physiochemical properties. It also outlines the reaction pathways involved in the generation of short-lived and long-lived reactive nitrogen and oxygen species (RONS) in PAW, which contribute to its antimicrobial abilities. The review also highlights current studies on PAW inactivation against various planktonic bacteria, as well as critical processing parameters that can improve PAW inactivation efficacy. Promising applications of PAW for meat curing, thawing, and decontamination are discussed, with emphasis on the need to understand how RONS in PAW affect meat quality. Recent reports on combining PAW with ultrasound, mild heating, and non-thermal plasma to improve inactivation efficacy are also presented. Finally, the need to develop energy-efficient systems for the production and scalability of PAW is discussed for its use as a potential meat disinfectant without compromising meat quality.

In-package cold plasma treatment for microbial inactivation in plastic-pouch packaged steamed rice cakes

In-package atmospheric cold plasma (ICP) treatment was investigated as a method to inactivate microorganisms in Korean steamed rice cakes (SRCs) packaged in plastic pouches. The effect against Escherichia coli O157:H7 increased with increasing ICP treatment power and time and using nylon-containing pouches. Moreover, E. coli O157:H7 growth was effectively inhibited at 4 and 25 °C when SRCs were in a pouch filled with an O₂-CO₂ (70 % and 30 %) gas. Under optimal treatment power (30 W), treatment time (4 min), and headspace-to-SRC volume ratio (7:1) conditions, ICP effectively inactivated E. coli O157:H7, Bacillus cereus spores, Penicillium chrysogenum, and indigenous aerobic bacteria, as well as yeast and molds in SRCs packaged with air in the nylon/low density polyethylene pouch by 2.2 ± 0.2 log CFU/g, 1.4 ± 0.2 log spores/g, 2.2 ± 0.3 log spores/g, 1.1 ± 0.2 log CFU/g, and 1.0 ± 0.1 log CFU/g, respectively. Furthermore, post-treatment storage was effective in preventing the growth of E. coli O157:H7 in SRCs at 4 °C and 25 °C when the pouch was filled with N₂-CO₂ (50 % and 50 %) or O₂-CO₂ (70 % and 30 %). Collectively, these findings indicate that ICP treatment effectively decontaminates SRCs and represents a potential non-thermal microbial decontamination technology for SRCs in pouch packaging.

Plasma Surface Engineering of Natural and Sustainable Polymeric Derivatives and Their Potential Applications

Recently, natural as well as synthetic polymers have been receiving significant attention as candidates to replace non-renewable materials. With the exponential developments in the world each day, the collateral damage to the environment is incessant. Increased demands for reducing pollution and energy consumption are the driving force behind the research related to surface-modified natural fibers (NFs), polymers, and various derivatives of them such as natural-fiber-reinforced polymer composites. Natural fibers have received special attention for industrial applications due to their favorable characteristics, such as low cost, abundance, light weight, and biodegradable nature. Even though NFs offer many potential applications, they still face some challenges in terms of durability, strength, and processing. Many of these have been addressed by various surface modification methodologies and compositing with polymers. Among different surface treatment strategies, low-temperature plasma (LTP) surface treatment has recently received special attention for tailoring surface properties of different materials, including NFs and synthetic polymers, without affecting any of the bulk properties of these materials. Hence, it is very important to get an overview of the latest developments in this field. The present article attempts to give an overview of different materials such as NFs, synthetic polymers, and composites. Special attention was placed on the low-temperature plasma-based surface engineering of these materials for diverse applications, which include but are not limited to environmental remediation, packaging, biomedical devices, and sensor development.

Impact of Non-Thermal Technologies on the Quality of Nuts: A Review

Nuts are widely consumed worldwide, mainly due to their characteristic flavor and texture, ease of consumption, and their functional properties. In addition, consumers increasingly demand natural or slightly processed foods with high quality. Consequently, non-thermal treatments are a viable alternative to thermal treatments used to guarantee safety and long shelf life, which produce undesirable changes that affect the sensory quality of nuts. Non-thermal treatments can achieve results similar to those of the traditional (thermal) ones in terms of food safety, while ensuring minimal loss of bioactive compounds and sensory properties, thus obtaining a product as similar as possible to the fresh one. This article focuses on a review of the main non-thermal treatments currently available for nuts (cold plasma, high pressure, irradiation, pulsed electric field, pulsed light, ultrasound and ultraviolet light) in relation to their effects on the quality and safety of nuts. All the treatments studied have shown promise with regard to the inhibition of the main microorganisms affecting nuts (e.g., Aspergillus, Salmonella, and E. coli). Furthermore, by optimizing the treatment, it is possible to maintain the organoleptic and functional properties of these products.

A comprehensive study on decontamination of food-borne microorganisms by cold plasma

Food-borne microorganisms are one of the biggest concern in food industry. Food-borne microorganisms such as Listeria monocytogenes, Escherichia coli, Salmonella spp., Vibrio spp., Campylobacter jejuni, Hepatitis A are commonly found in food products and can cause severe ailments in human beings. Hence, disinfection of food is performed before packaging is performed to sterilize food. Traditional methods for disinfection of microorganisms are based on chemical, thermal, radiological and physical principles. They are highly successful, but they are complex and require more time and energy to accomplish the procedure. Cold plasma is a new technique in the field of food processing. CP treatments has no or very low effect on physical, chemical and nutritional properties of food products. This paper reviews the effect of plasma processing on food products such as change in colour, texture, pH level, protein, carbohydrate, and vitamins. Cold plasma by being a versatile, effective, economical and environmentally friendly method provides unique advantages over commercial food processing technologies for disinfection of food.

Recent developments for controlling microbial contamination of nuts

In recent years, the consumption of nuts has shown an increasing trend worldwide. Nuts are an essential part of several countries' economies as an excellent source of nutrients and bioactive compounds. They are contaminated by environmental factors, improper harvesting practices, inadequate packaging procedures, improper storage, and transportation. The longer storage time also leads to the greater chances of contamination from pathogenic fungi. Nuts are infected with Aspergillus species, Penicillium species, Escherichia coli, Salmonella, and Listeria monocytogenes. Therefore, nuts are associated with a high risk of pathogens and mycotoxins, which demand the urgency of using techniques for enhancing microbial safety and shelf-life stability. Many techniques such as ozone, cold plasma, irradiation, radiofrequency have been explored for the decontamination of nuts. These techniques have different efficiencies for reducing the contamination depending on processing parameters, type of pathogen, and conditions of food material. This review provides insight into decontamination technologies for reducing microbial contamination from nuts.

Effect of atmospheric pressure non-thermal pin to plate plasma on the functional, rheological, thermal, and morphological properties of mango seed kernel starch

This study aimed to investigate the effect of atmospheric pressure non-thermal pin-to-plate plasma on the functional, rheological, thermal, and morphological properties of mango seed kernel starch. As cold plasma contains highly reactive species and free radicals, it is expected to cause noticeable modifications in the attributes of starch treated. The isolated mango seed kernel starch was subjected to the plasma treatment of input voltages 170 and 230 V for 15 and 30 min of exposure. Water adsorption, swelling, and solubility at lower temperatures. There has been a significant reduction (p < 0.05) in pH values of starch from 7.09 to 6.16 and also the desirable reduction in turbidity values by 42.60%. However, there has been no significant change in the oil and water binding behavior of the starch. The FTIR spectra of MSKS demonstrate the formation of amines which contributes to the better hydrophilic nature of the starch. The structural modification has been adequately confirmed by SEM images. The maximum voltage and time combination, lead to depolymerization of starch which is supported by NMR spectra thus affecting thermal and rheological properties. The application of cold plasma-modified MSKS in food would facilitate stable and smooth textural development.

Cold plasma technology: advanced and sustainable approach for wastewater treatment

Cold plasma has been a potent energy-efficient and eco-friendly advanced oxidation technology which has gained attention in recent decades as a non-thermal approach in diverse forms of applications. This review highlights a comprehensive account of the implementation of this technology in the field of wastewater treatment to resolve certain issues regarding the degradation of numerous aqueous pollutants and water-borne pathogenic microorganisms including viruses up to a significant level. The paper addresses plasma chemistry sources and mechanisms on wastewater treatment and impact on various physical, chemical, and biological characteristics of treated water. Furthermore, studies have revealed that this emerging technology is effective in inactivating SARS-CoV-2 or coronavirus, which serves as a transmission channel for this lethal virus in wastewater. Despite these benefits, the development of cold plasma as a wastewater treatment technique is still hampered by a lack of information like capital investment, proficient application, liveability, and operating cost, thus necessitating additional research for its booming commercialization, as this can be an emerging approach to solving water crises and meeting the demand for fresh or potable water resources.

Application of nonthermal processing technologies in extracting and modifying polysaccharides: A critical review

Polysaccharides are natural polymer compounds widely distributed in plants, animals, and microorganisms, most of which have a broad spectrum of biological activities to promote human health. They could also be used as texture modifiers in food industry due to their excellent rheological and mechanical properties. Many researchers have shown that nonthermal processing technologies have numerous advantages, such as high extraction efficiency, short extraction time, and environmental friendliness, in the extraction of polysaccharides compared with the traditional extraction methods. Moreover, nonthermal technologies could effectively change the physicochemical properties and structural characteristics of polysaccharides to improve their biological activities or processing properties. Therefore, a comprehensive summary about the extraction and modification of polysaccharides by nonthermal technologies, including ultrasound, high hydrostatic pressure, pulsed electric fields, and cold plasma, was provided in this review. In particular, the underlying mechanisms, processing operations, and current application status of these technologies were discussed. In addition, the applications of combining nonthermal techniques with other technological methods in polysaccharide extraction and modification were briefly introduced.

State of the art in nonthermal plasma processing for biomedical applications: Can it help fight viral pandemics like COVID-19?

Plasma processing finds widespread biomedical applications, such as the design of biosensors, antibiofouling surfaces, controlled drug delivery systems, and in plasma sterilizers. In the present coronavirus disease (COVID-19) situation, the prospect of applying plasma processes like surface activation, plasma grafting, plasma-enhanced chemical vapor deposition/plasma polymerization, surface etching, plasma immersion ion implantation, crosslinking, and plasma decontamination to provide timely solutions in the form of better antiviral alternatives, practical diagnostic tools, and reusable personal protective equipment is worth exploring. Herein, the role of nonthermal plasmas and their contributions toward healthcare are timely reviewed to engage different communities in assisting healthcare associates and clinicians, not only to combat the current COVID-19 pandemic but also to prevent similar kinds of future outbreaks.

Application of new technologies in decontamination of mycotoxins in cereal grains: Challenges, and perspectives

Emerging decontamination technologies have been attracted considerable attention to address the consumers' demand for high quality and safe food products. As one of the important foods in the human diet, cereals are usually stored for long periods, resulting in an increased risk of contamination by different hazards. Mycotoxins comprise one of the significant contaminants of cereals that lead to enormous economic losses to the industry and threats to human health. While prevention is the primary approach towards reducing human exposure to mycotoxins, decontamination methods have also been developed as complementary measures. However, some conventional methods (chemical treatments) do not fulfill industries' expectations due to limitations like safety, efficiency, and the destruction of food quality attributes. In this regard, novel techniques have been proposed to food to comply with the industry's demand and overcome conventional methods' limitations. Novel techniques have different efficiencies for removing or reducing mycotoxins depending on processing conditions, type of mycotoxin, and the food matrix. Therefore, this review provides an overview of novel mycotoxin decontamination technologies such as cold plasma, irradiation, and pulse light, which can be efficient for reducing mycotoxins with minimum adverse effects on the quality and nutritional properties of produce.

Modification and improvement of biodegradable packaging films by cold plasma; a critical review

Cold plasma is one of the techniques used in recent years to improve the functionality and interfacial attributes of biopolymers. Employing cold plasma for the treatment and modification of biopolymers possesses several advantages including its biocompatibility, elimination of toxic solvents usage, treatment consistency, and appropriateness for heat-sensitive ingredients. Most studies have presented the efficacious use of cold plasma treatment in improving structural, mechanical and thermal properties of film composites. In addition, cold plasma improves the film surface characteristics, particularly in protein-based films, through bringing up the polar functional groups onto the bio-composite surface, consequently increasing roughness, improving printability, increasing adhesion, and reducing contact angle; while it is not effective in the improvement of water vapor permeability of edible films. Cold plasma-treated edible packaging films experienced significant improvement where exposed to microbial contaminations, mainly due to the non-thermal nature of cold plasma technology leading to the protection of antimicrobial potency of bioactive compounds and antimicrobial constitutes. Therefore, it can be concluded that cold plasma treatment is an innovative strategy to strengthen the edible film characteristics as a promising alternative to the currently used chemical and physical modification approaches.

High Voltage Electrical Discharges as an Alternative Extraction Process of Phenolic and Volatile Compounds from Wild Thyme (Thymus serpyllum L.): In Silico and Experimental Approaches for Solubility Assessment

The objective of this study was to evaluate the potential of green solvents for extractions of bioactive compounds (BACs) and essential oils from wild thyme (Thymus serpyllum L.) using theoretical and experimental procedures. Theoretical prediction was assessed by Hansen solubility parameters (HSPs) and conductor-like screening model for realistic solvents (COSMO-RS), to predict the most suitable solvents for extraction of BACs. An experimental procedure was performed by nonthermal technology high voltage electrical discharge (HVED) and it was compared with modified conventional extraction (CE). Obtained extracts were analyzed for chemical and physical changes during the treatment. Theoretical results for solution of BACs in ethanol and water, as green solvents, were confirmed by experimental results, while more accurate data was given by COSMO-RS assessment than HSPs. Results confirmed high potential of HVED for extraction of BACs and volatile compounds from wild thyme, in average, 2.03 times higher yield of extraction in terms of total phenolic content was found compared to CE. The main phenolic compound found in wild thyme extracts was rosmarinic acid, while the predominant volatile compound was carvacrol. Obtained extracts are considered safe and high-quality source reach in BACs that could be further used in functional food production.