Diagnostics of plasma reactive species and induced chemistry of plasma treated foods

Application of cold atmospheric plasma for decontamination of toxigenic fungi and mycotoxins: a systematic review

Introduction

Microbial contamination remains a vital challenge across the food production chain, particularly due to mycotoxins-secondary metabolites produced by several genera of fungi such as Aspergillus, Fusarium, Alternaria, and Penicillium. These toxins, including aflatoxins, fumonisins, ochratoxins, and trichothecenes (nivalenol, deoxynivalenol, T2, HT-2). These contaminants pose severe risks to human and animal health, with their potential to produce a variety of different toxic effects. Notably, up to 50% of global cereal production is affected by mycotoxin contamination, leading to significant economic losses. Current research focuses on innovative technologies to mitigate mycotoxins, with cold atmospheric pressure plasma emerging as a promising decontamination method.

Method

This systematic review aimed at describing recent advances in the application of cold atmospheric plasma for the decontamination of toxigenic fungi and mycotoxins.

Results and discussion

Cold atmospheric plasma offers a sustainable and cost effective solution to preserve food quality while inactivating toxigenic fungi and degrading mycotoxins. Through the generation of reactive oxygen and nitrogen species, cold plasma disrupts fungal cell integrity, hinders spore germination, and inhibits toxin biosynthesis. Additionally, cold atmospheric plasma-driven degradation of mycotoxins involves structural modifications, breaking key molecular bonds that reduce toxicity. The effectiveness of cold plasma depends on operational parameters and the specific characteristics of the treated food, with notable efficacy in degrading aflatoxin B1 and deoxynivalenol by converting them into less toxic substances and inhibiting their spores and DNA responsible for their biosynthesis. While the data demonstrates that cold atmospheric plasma has minimal impact on food composition, further research is needed to fully assess the nature of the degradation products of mycotoxins, its influence on food quality attributes and to optimize application strategies for different products.

Oxygen and air cold plasma for the inactivation of Bacillus cereus in low-water activity soy powder

Cold plasma (CP) technology is a promising alternative to thermal treatments for the microbial decontamination of foods with low-water activity. The aim of this work is study the application of low-pressure CP (0.35 mbar) for the inactivation of Bacillus cereus in a soybean powder matrix using O₂ and synthetic air as ionizing gases. The parameters tested were an input power of 100, 200 and 300 W and an exposure time of 10 to 30 min. The excited reactive species formed were monitored by optical emission spectroscopy, and survival data were analyzed using the Weibull mathematical model. Treatments with both gases were effective in inactivating B. cereus. Air plasma resulted in a maximum 3.71-log reduction in bacterial counts at 300 W and 30 min, while O2 plasma showed the strongest inactivation ability, achieving levels higher than 5 log cycles at 300 W and > 25 min. This is likely due to the strong antimicrobial activity of oxygen-derived radicals together with carbon monoxide as an oxidation by-product. In addition, the Weibull distribution function accurately modeled the inactivation of B. cereus. Cold plasma technology is a promising approach for the decontamination of bacteria in low-water activity foods.

Impact of Cold Atmospheric Plasma Pretreatment on the Recovery of Phenolic Antioxidants from Spent Coffee Grounds

In the present study, cold atmospheric plasma (CAP) was employed as a pretreatment method for the extraction of phenolic compounds from spent coffee grounds (SCGs). The impact of CAP treatment conditions, i.e., thickness of the SCGs layer (mm), distance between the plasma source and the SCGs layer (mm) and duration of CAP treatment (min), on the total phenol content, in vitro antioxidant activity, as well as caffeine and chlorogenic acid content of SCGs, was investigated. The process parameters were optimized with the aid of response surface methodology (RSM). After optimizing the CAP pretreatment conditions, the CAP-treated SCGs were subjected to ultrasound-assisted extraction using ethanol as the extraction solvent. The optimum conditions for CAP treatment identified, i.e., thickness, 1 mm; distance, 16 mm; and duration, 15 min, led to a significant enhancement in the recovery of bioactive compounds from SCGs compared to those obtained from untreated SCGs. Total phenolic content and antioxidant activity significantly increased (i.e., TPC from 19.0 ± 0.7 to 24.9 ± 1.4 mg GAE/100 g dry SCGs, ADPPH from 106.7 ± 5.01 to 112.3 ± 4.3 μmol Trolox/100 g dry SCGs, AABTS from 106.7 ± 5.01 to 197.6 ± 5.8 μmol Trolox/100 g dry SCGs, ACUPRAC from 17938 ± 157 to 18299 ± 615 μmol Trolox/100 g dry SCGs). A significant increase in caffeine content from 799.1 ± 65.1 mg to 1064 ± 25 mg/100 g dry SCGs and chlorogenic acid content from 79.7 ± 15.3 mg to 111.3 ± 3.3 mg/100 g dry SCGs, was also observed. Overall, CAP pre-treatment can be used to enhance the recovery of bioactive compounds from SCGs.

Gas plasmas technology: from biomolecule redox research to medical therapy

Physical plasma is one consequence of gas ionization, i.e. its dissociation of electrons and ions. If operated in ambient air containing oxygen and nitrogen, its high reactivity produces various reactive oxygen and nitrogen species (RONS) simultaneously. Technology leap innovations in the early 2010s facilitated the generation of gas plasmas aimed at clinics and operated at body temperature, enabling their potential use in medicine. In parallel, their high potency as antimicrobial agents was systematically discovered. In combination with first successful clinical trials, this led in 2013 to the clinical approval of first medical gas plasma devices in Europe for promoting the healing of chronic and infected wounds and ulcers in dermatology. While since then, thousands of patients have benefited from medical gas plasma therapy, only the appreciation of the critical role of gas plasma-derived RONS led to unraveling first fragments of the mechanistic basics of gas plasma-mediated biomedical effects. However, drawing the complete picture of effectors and effects is still challenging. This is because gas plasma-produced RONS not only show a great variety of dozens of types but also each of them having distinct spatio-temporal concentration profiles due to their specific half-lives and reactivity with other types of RONS as well as different types of (bio) molecules they can react with. However, this makes gas plasmas fascinating and highly versatile tools for biomolecular redox research, especially considering that the technical capacity of increasing and decreasing individual RONS types holds excellent potential for tailoring gas plasmas toward specific applications and disease therapies.

Innovative nonthermal technologies for inactivation of emerging foodborne viruses

Various foodborne viruses have been associated with human health during the last decade, causing gastroenteritis and a huge economic burden worldwide. Furthermore, the emergence of new variants of infectious viruses is growing continuously. Inactivation of foodborne viruses in the food industry is a formidable task because although viruses cannot grow in foods, they can survive in the food matrix during food processing and storage environments. Conventional inactivation methods pose various drawbacks, necessitating more effective and environmentally friendly techniques for controlling foodborne viruses during food production and processing. Various inactivation approaches for controlling foodborne viruses have been attempted in the food industry. However, some traditionally used techniques, such as disinfectant-based or heat treatment, are not always efficient. Nonthermal techniques are considered a new platform for effective and safe treatment to inactivate foodborne viruses. This review focuses on foodborne viruses commonly associated with human gastroenteritis, including newly emerged viruses, such as sapovirus and Aichi virus. It also investigates the use of chemical and nonthermal physical treatments as effective technologies to inactivate foodborne viruses.

Improving food drying performance by cold plasma pretreatment: A systematic review

Drying is an important and influential process to prolong the shelf-life of food in the food industry. Recent studies have shown that cold plasma (CP) as an emerging drying pretreatment technology can improve drying performance, reduce drying energy consumption, and improve dried food quality. This paper comprehensively reviewed the mechanism of CP improving drying performance, related equipment, energy consumption, influencing factors, and impact on drying quality. This review also discusses the advantages and disadvantages and proposes possible challenges and suggestions for future research. Most studies indicated that CP pretreatment could improve the drying rate and quality and reduce the drying energy consumption. CP can promote moisture diffusion and improve drying efficiency by etching the surface and affecting the internal microstructure. In addition, CP can enhance the quality of dried products by reducing drying time and enzyme activity. Further research is needed to explore the drying mechanisms and equipment innovations to promote the application of CP in the food drying industry.

Effect of plasma-activated water on microbial quality and physicochemical properties of fresh beef

This work studies the influence of plasma-activated water (PAW) on the decontamination of beef and its influence on the color, pH, the thiobarbituric acid reactive substance values (TBARS), and total volatile basic nitrogen (TVBN) values of meat. PAW was generated using non-thermal atmospheric pressure plasma jet (NTAPPJ). He + 0.2% N2 and He + 0.2% O2 were used as worker gas to generate PAW. The PAW produced by the He + O2 plasma system exhibited a higher potential for decontamination of beef than that produced by the He + N2 plasma system. The lightness value (L*) of treated beef does not exhibit a noticeable difference with the control one. TBARS values of all treated beef were lower than the rancidity threshold but significantly greater than that of control samples. The TVBN value of control beef samples reached the decay threshold after 18 days of stockpiling, but treated beef remained good. This work reveals that PAW can potentially inhibit the growth of microorganisms in beef.

Impact of cold plasma on the biomolecules and organoleptic properties of foods: A review

Cold plasma is formed by the nonthermal ionization of gas into free electrons, ions, reactive atomic and molecular species, and ultraviolet (UV) radiation. This cold plasma can be used to alter the surface of solid and liquid foods, and it offers multiple advantages over traditional thermal treatments, such as no thermal damage and increased output variation (due to the various input parameters gas, power, plasma type, etc.). Cold plasma appears to have limited impact on the sensory and color properties, at lower power and treatment times, but there has been a statistically significant reduction in pH for most of the cold plasma treatments reviewed (p < 0.05). Carbohydrates (cross linking and glycosylation), lipids (oxidation), and proteins (secondary structure) are more significantly impacted due to cold plasma at higher intensities and longer treatment times. Although cold plasma treatments and food matrices can vary considerably, this review has identified the literary evidence of some of the influences and impacts of the vast array of cold plasma treatment parameters on the biomolecular and organoleptic properties of these foods. Due to the rapidly evolving nature of the field, we have also identified that authors prioritize the presentation of different information when publishing from different research areas. Therefore, we have proposed a number of key physical and chemical cold plasma parameters that should be considered for inclusion in all future publications in the field.

An Ultra-Simple Charge Supplementary Strategy for High Performance Rotary Triboelectric Nanogenerators

Free-standing rotary triboelectric nanogenerators (rTENG) can accomplish special tasks which require both high voltage and high frequency. However, the reported high performance rTENG all have complex structures for output enhancement. In this work, an ultra-simple strategy to build high performance rTENG is developed. With only one small paper strip added to the conventional structure, the output of the TENG is promoted hugely. The voltage is triplicated to 2.3 kV, and the current and charge are quintupled to 133 µA and 197 nC, respectively. The small paper strip, with the merits of ultra-simplicity, wide availability, easy accessibility and low cost, functions as a super-effective charge supplement. This simple and delicate structure enables ultra-high durability with the 2.3 kV voltage output 100% maintained after 1 000 000 cycles. This charge supplementary strategy is universally effective for many other materials, and decouples the output enhancement from any friction or contact on the metal electrodes, emphasizing a critical working principle for the rTENG. Atmospheric cold plasma is generated using the paper strip rTENG (ps-rTENG), which demonstrates strong ability to do bacteria sterilization. This simple and persistent charge supplementary strategy can be easily adopted by other designs to promote the output even further.

Effect of Electron-Beam Radiation and Other Sterilization Techniques on Structural, Mechanical and Microbiological Properties of Thermoplastic Starch Blend

This work investigates the potential application of various sterilization methods for microorganism inactivation on the thermoplastic starch blend surface. The influence of the e-beam and UV radiation, ethanol, isopropanol and microwave autoclave on structural and packaging properties were studied. All the applied methods were successful in the inactivation of yeast and molds, however only the e-beam radiation was able to remove the bacterial microflora. The FTIR analysis revealed no significant changes in the polymer structure, nevertheless, a deterioration of the mechanical properties of the blend was observed. The least invasive method was the UV radiation which did not affect the mechanical parameters and additionally improved the barrier properties of the tested material. Moreover, it was proved that during the e-beam radiation the chain scission and cross-linking occurred. The non-irradiated and irradiated samples were subjected to the enzymatic degradation studies performed in the presence of amylase. The results indicated that irradiation accelerated the decomposition of material, which was confirmed by the measurements of weight loss, and mass of glucose and starch released to the solution in the course of biodegradation, as well as the FTIR and thermal analysis.

Assessing the Biological Safety of Atmospheric Cold Plasma Treated Wheat Using Cell and Insect Models

Atmospheric cold plasma (ACP) is under investigation for an extensive range of biocontrol applications in food biosystems. However, the development of a novel intervention technology requires a thorough evaluation of the potential for negative effects and the implications for the human and animal food chains’ safety. The evaluations were performed using a contained, high-voltage, dielectric barrier discharge plasma system. The cytotoxicity of two types of food models—a liquid model (wheat model medium (WMM)) vs. a solid model (wheat grain extract (WGE)) was compared in vitro using the mammalian cell line CHO-K1. The residual toxicity of ACP treatment of grains for food purposes was assessed using the invertebrate model Tribolium castaneum, by feeding the beetles with flour produced from ACP-treated wheat grains. The cytotoxic effects and changes in the chemistry of the ACP-treated samples were more pronounced in samples treated in a liquid form as opposed to actual wheat grains. The feeding trial using T. castaneum demonstrated no negative impacts on the survivability or weight profiles of insects. Investigations into the interactions of plasma-generated species with secondary metabolites in the food matrices are necessary to ensure the safety of plasma for food applications.

ROS from Physical Plasmas: Redox Chemistry for Biomedical Therapy

Physical plasmas generate unique mixes of reactive oxygen and nitrogen species (RONS or ROS). Only a bit more than a decade ago, these plasmas, operating at body temperature, started to be considered for medical therapy with considerably little mechanistic redox chemistry or biomedical research existing on that topic at that time. Today, a vast body of evidence is available on physical plasma-derived ROS, from their spatiotemporal resolution in the plasma gas phase to sophisticated chemical and biochemical analysis of these species once dissolved in liquids. Data from in silico analysis dissected potential reaction pathways of plasma-derived reactive species with biological membranes, and in vitro and in vivo experiments in cell and animal disease models identified molecular mechanisms and potential therapeutic benefits of physical plasmas. In 2013, the first medical plasma systems entered the European market as class IIa devices and have proven to be a valuable resource in dermatology, especially for supporting the healing of chronic wounds. The first results in cancer patients treated with plasma are promising, too. Due to the many potentials of this blooming new field ahead, there is a need to highlight the main concepts distilled from plasma research in chemistry and biology that serve as a mechanistic link between plasma physics (how and which plasma-derived ROS are produced) and therapy (what is the medical benefit). This inevitably puts cellular membranes in focus, as these are the natural interphase between ROS produced by plasmas and translation of their chemical reactivity into distinct biological responses.