Engineering pineapple peel cellulose nanofibrils with oxidase-mimic functionalities for antibacterial and fruit preservation.

In this study, an antibacterial material (CNF@CoMn-NS) with oxidase-like activity was created using ultrathin cobalt­manganese nanosheets (CoMn-NS) with a larger specific surface area grown onto pineapple peel cellulose nanofibrils (CNF). The results showed that the CoMn-NS grew well on the CNF, and the obtained CNF@CoMn-NS exhibited good oxidase-like activity. The imidazole salt framework of the CNF@CoMn-NS contained cobalt and manganese in multiple oxidation states, enabling an active redox cycle and generating active oxygen species (ROS) such as singlet molecular oxygen atoms (1O2) and superoxide radical (·O2-), resulting in the significant inactivation of Staphylococcus aureus (74.14%) and Escherichia coli (54.87%). Importantly, the CNF@CoMn-NS did not exhibit cytotoxicity. The CNF@CoMn-NS further self-assembled into a CNF@CoMn-NS paper with flexibility, stability, and antibacterial properties, which can effectively protect the wound of two varieties of pears from decay caused by microorganisms. This study demonstrated the potential of using renewable and degradable CNF as substrate combined with artificial enzymes as a promising approach to creating antibacterial materials for food preservation and even extending to textiles and biomedical applications.

Inactivation of Salmonella Enteritidis on Hatchery and Table Eggs Using a Gas-phase Hydroxyl-Radical Process.

Eggs represent a significant vehicle for Salmonella Enteritidis with the pathogen being transferred to chicks in the hatchery, or to consumers via table eggs. In the following, the efficacy of a gas-phase hydroxyl-radical process for decontaminating hatchery and table eggs was evaluated. Recovery of Salmonella was maximized through holding eggs in tryptic soy broth containing 20% w/v glycerol for 1 h prior to plating. By using this technique, it was possible to recover 63% of the theoretical Salmonella inoculated onto eggs. The continuous hydroxyl-radical reactor consisted of a bank of UV-C lamps (254 nm) that generated hydroxyl-radicals from the degradation of hydrogen peroxide (H2O2) mist and ozone gas. The optimal treatment was defined as that which supports a 5 log CFU/egg reduction of Salmonella without negatively affecting egg quality or leaving H2O2 residues. A process of 2% v/v H2O2 delivered at 30 mL/min with a UV-C dose of 19 mJ/cm2 and ozone (20 ppm) with a total treatment time of 10s was selected. The egg quality metrics (Haugh value, yolk index, albumin pH, yolk pH) did not negatively differ over a 35-day shelf-life at 4 or 25℃ compared to washed eggs or nontreated controls. The cuticle layer of eggs remained intact following hydroxyl-radical treatment. Fertilized eggs (n = 61) treated with the hydroxyl-radicals exhibited the same hatchery rate (75%) as nontreated controls (71-79%) with no defects (unhealed navels or red hocks) being observed. The same hydroxyl-radical treatment could be applied to table eggs to support >5 log CFU/egg reduction of Salmonella and was compatible with egg washing regimes practiced in industry. In comparison, the egg washing process based on sodium hydroxide and chlorine supported a 2.76 ± 0.38 log CFU/egg reduction of Salmonella. The hydroxyl-radical treatment represents a preventative control step to reduce the carriage of Salmonella on hatchery and table eggs.

Degradation products of aflatoxin M1 (AFM1) formed by high voltage atmospheric cold plasma (HVACP) treatment.

Cold plasma technology is a novel non-thermal technology that has shown promising results for food decontamination and improving food safety. This study is a continuation of a previous investigation of the treatment of AFM1-contaminated skim and whole milk samples by HVACP. Previous research has shown HVACP is effective in degrading aflatoxin M1 (AFM1) in milk. The goal of this study is to identify the degradation products of AFM1 after HVACP treatment in pure water. An HVACP direct treatment at 90 kV using modified air (MA65: 65% O2, 30% CO2, 5% N2) was performed for up to 5 min at room temperature on a 5.0 mL water sample in a Petri dish artificially contaminated with 2 µg/mL of AFM1. The degradants of AFM1 were analyzed and their molecular formulae were elucidated by using high-performance liquid-chromatography time-of-flight mass spectrometry (HPLC-TOF-MS). Three main degradation products were observed and based on mass spectrometric fragmentation pathways, chemical structures for the degradation products were tentatively assigned. According to the structure-bioactivity relationship of AFM1, the bioactivity of the AFM1 samples treated with HVACP was reduced due to the disappearance of the C8-C9 double bond in the furofuran ring in all of the degradation products.

Changing the IgE Binding Capacity of Tropomyosin in Shrimp through Structural Modification Induced by Cold Plasma and Glycation Treatment.

Tropomyosin (TM) is the major allergen of shrimp (Penaeus chinensis). Previous studies showed that separate cold plasma or glycation have their drawback in reducing allergenicity of TM, including effectiveness and reliability. In the current study, a new processing combining cold plasma (CP) and glycation was proposed and its effect on changing IgE binding capacity of TM from shrimp was investigated. Obtained results showed the IgE binding capacity of TM was reduced by up to 40% after CP (dielectric barrier discharge, 60 kV, 1.0 A) combined with glycation treatment (4 h, 80 °C), compared with the less than 5% reduction after single CP or glycation treatment. Notably, in contrast to the general way of CP prompting glycation, this study devised a new mode of glycation with ribose after CP pretreatment. The structural changes of TM were explored to explain the decreased IgE binding reactivity. The results of multi-spectroscopies showed that the secondary and tertiary structures of TM were further destroyed after combined treatment, including the transformation of 50% α-helix to ß-sheet and random coils, the modification and exposure of aromatic amino acids, and the increase of surface hydrophobicity. The morphology analysis using atomic force microscope revealed that the combined processing made the distribution of TM particles tend to disperse circularly, while it would aggregate after either processing treatment alone. These findings confirmed the unfolding and reaggregation of TM during combined processing treatment, which may result in the remarkable reduction of IgE binding ability. Therefore, the processing of CP pretreatment combined with glycation has the potential to reduce or even eliminate the allergenicity of seafood.

Degradation of Aflatoxin M1 in skim and whole milk using high voltage atmospheric cold plasma (HVACP) and quality assessment.

Cold plasma technology is a novel non-thermal technology that has shown promising results for food decontamination and improving food safety. This study investigates the efficacy of high voltage atmospheric cold plasma (HVACP) system to reduce Aflatoxin M1 (AFM1) in skim and whole milk. A dielectric barrier discharge HVACP was employed at 90 kV using modified air (MA65: 65 % O2, 30 % CO2, 5 % N2) fill gas for 1,3, and 5 min. Skim and whole milk was spiked with 1.0 µg/L AFM1 and exposed to HVACP treatment in both direct or indirect mode with no post-treatment storage or 4.0 h post storage at room temperature. Optimum condition of toxin degradation was chosen as for quality assessment including color, conductivity, total dissolved solid (TDS), pH, viscosity, peroxide value (PV), Thiobarbituric acid reactive substance (TBARS) assay, Fourier-transform infrared spectroscopy (FTIR), as well as nutrient composition. A one-minute HVACP treatment degrades 41.9 % and 37.8 % of AFM1 in skim milk and whole milk, respectively. However, much greater reductions were seen after a short treatment and then post-treatment storage. A greater than 87 % reduction in AFM1 was observed for all samples after a 3 min HVACP treatment with 4.0 h of post treatment. These results suggest that a few minutes of HVACP treatment is sufficient to generate significant reactive plasma species in the milk. Quality changes were less significant with shorter post treatment time and indirect mode of exposure. Overall, HVACP is an effective solution for decontamination of milk from AFM1.

Recent Advances and Potential Applications of Atmospheric Pressure Cold Plasma Technology for Sustainable Food Processing.

In a circular economy, products, waste, and resources are kept in the system as long as possible. This review aims to highlight the importance of cold plasma technology as an alternative solution to some challenges in the food chain, such as the extensive energy demand and the hazardous chemicals used. Atmospheric cold plasma can provide a rich source of reactive gas species such as radicals, excited neutrals, ions, free electrons, and UV light that can be efficiently used for sterilization and decontamination, degrading toxins, and pesticides. Atmospheric cold plasma can also improve the utilization of materials in agriculture and food processing, as well as convert waste into resources. The use of atmospheric cold plasma technology is not without challenges. The wide range of reactive gas species leads to many questions about their safety, active life, and environmental impact. Additionally, the associated regulatory approval process requires significant data demonstrating its efficacy. Cold plasma generation requires a specific reliable system, process control monitoring, scalability, and worker safety protections.

Modelling of inactivation kinetics of Escherichia coli and Listeria monocytogenes on grass carp treated by combining ultrasound with plasma functionalized buffer.

Linear (first-order) and non-linear (Weibull, biphasic, and log-logistic) models were evaluated for predicting the inactivation kinetics of Escherichia coli and Listeria monocytogenes on grass carp treated by a novel technique (UPFB) combining ultrasound (US) with plasma functionalized buffer (PFB). Results showed that UPFB was more effective for inactivating bacteria when compared with individual applications of US or PFB with reductions of 3.92 and 3.70 log CFU/g for Escherichia coli and Listeria monocytogenes, respectively. Compared with the linear model, the three non-linear models presented comparable performances and were more suitable for describing the inactivation kinetics with superior adj-R2 (0.962-0.999), accuracies (0.970-1.006) and bias factors (0.995-1.031), and by assessing the strengths of evidence, weights of evidence and evidence ratios for the models, the biphasic model was identified as the best fit model. The current study provided new insights into the effective evaluation of decontamination methods.

Control of aflatoxin M1 in skim milk by high voltage atmospheric cold plasma.

Cold plasma has potential for the degradation of aflatoxins in corn and hazelnuts; however, this has not been demonstrated for aflatoxin in milk. In this study, the efficacy of high voltage atmospheric cold plasma (HVACP) on the reduction of aflatoxin M1 (AFM1) in skim milk improved with increasing treatment times (1-20 min), using gas containing 65% oxygen (MA65) rather than air, increasing voltage (60-80 kV) and reducing sample volume (30 mL-10 mL). Direct treatment was more effective than indirect treatment. AFM1 in milk was degraded by 65.0 % and 78.9 % by air and MA65 respectively in 20 min with no change in milk colour. The toxicity of AFM1 after treatment was assessed using a brine shrimp model. A five-minute HVACP treatment reduced the toxicity of AFM1 by 83.9 % based on the increase in brine shrimp survival. HVACP is a promising method to reduce AFM1 in milk.

High voltage atmospheric cold plasma inactivation of Listeria monocytogenes in fresh Queso Fresco cheese.

Listeria (L.) monocytogenes is a significant pathogen found in ready-to-eat meat and dairy products. Soft cheeses, such as Queso Fresco cheese (QFC), are particularly sensitive to Listeria contamination, and occasionally serve as a source of food-borne illness outbreaks. In the present study, clinical and cheese isolates of L. monocytogenes were assayed for phenotypic characteristics following sub-lethal high voltage atmospheric cold plasma (HVACP) treatment. Reductions in biofilm formation, swimming motility, and growth dynamics were observed following HVACP treatment. Microbial enumeration of 1-, 10-, and 100-g fresh QFC following 0, 1, 2, or 3 min of HVACP demonstrated significant reductions in L. monocytogenes after 1 min (P-value <0.05), with increasing efficacy with prolonged exposure. A mass-dependent effect was observed between treatments of 1-, 10-, and 100-g QFC in regard to treatment efficacy. This result indicates that greater L. monocytogenes reduction on a larger QFC mass requires greater exposure of the L. monocytogenes to the reactive gas species. Optical absorption spectroscopy confirmed a reduction in reactive gas species for each log increase in QFC mass, however, an equivalent volume of inert foam resulted in increased reactive gas generation compared to QFC. In conclusion, we demonstrate both the application and limitations of HVACP treatments of QFC in the currently defined experimental parameters.

Cytotoxicity assessment of Aflatoxin B1 after high voltage atmospheric cold plasma treatment.

Aflatoxin B1 (AFB1) is a secondary metabolite produced by Aspergillus flavus and A. parasiticus, and is a known carcinogen in humans and animals. High voltage atmospheric cold plasma (HVACP) technology has already shown promise to decontaminate AFB1 in food and feed. This study aimed to investigate the cytotoxicity of AFB1 after HVACP treatment. AFB1 (100 µM) was treated at 85 kV with HVACP for 0, 2, 5, 10, and 20 min. HepG2 cells were exposed to HVACP-treated AFB1 for 72 h and assessed for cell viability, caspase-3 activity, DNA fragmentation, and protein carbonyls for each treatment time. Cell viability, caspase-3 activity, DNA fragmentation levels, and protein carbonyls contents of HepG2 cells exposed to HVACP-treated AFB1 after 20 min was not significantly different compared to non-exposed HepG2 cells (P > 0.05). However, their contents were significantly higher in non-exposed cells compared to the other HVACP treatment times (P < 0.01). Twenty minutes of HVACP treatment for AFB1 significantly reduced AFB1 cytotoxicity and oxidative damage and showed potential as a safe aflatoxin decontamination technology.

High voltage atmospheric cold plasma treatment inactivates Aspergillus flavus spores and deoxynivalenol toxin.

Fungal contamination is a concern for the food industry. Fungal spores resist food sterilization treatments and produce mycotoxins that are toxic for animals and humans. Technologies that deactivate spores and toxins without impacting food quality are desirable. This study demonstrates the efficiency of a high voltage atmospheric cold plasma (HVACP) technology using air to generate reactive oxygen (ROS) and nitrogen (RNS) species for the degradation of Aspergillus flavus cultures and the deoxynivalenol (DON) mycotoxin. Optical emission and absorption spectroscopy demonstrate ionization of hydroxyl groups, atomic oxygen and nitrogen, and confirm production of ROS and RNS, e.g. O3, NO2, NO3, N2O4, and N2O5. Fungal cultures show a depletion in pigmentation and an ~50% spore inactivation after 1-min treatments. Treated spores show surface ablation and membrane degradation by scanning electron microscopy. Twenty-minute direct HVACP treatments of 100 µg of DON in one mL aqueous suspensions resulted in a greater than 99% reduction in DON structure and rescued over 80% of Caco-2 cell viability; however, the same treatment on 100 µg of powdered DON toxin only showed a 33% reduction in DON and only rescued 15% of cell viability. In summary, HVACP air treatment can inactivate both fungal spores and toxins in minutes.

In-package decontamination of chicken breast using cold plasma technology: Microbial, quality and storage studies.

Atmospheric cold plasma (ACP) is a promising non-thermal technology for controlling food spoilage. In this study, ACP treatment at 100 kV for 1, 3 and 5 min was applied to chicken breast samples. Approximately 2 log CFU/g reduction in natural microflora of chicken was achieved within 5 min of treatment and 24 h of storage. The observed reduction was attributed to the reactive oxygen and nitrogen species in cold plasma. For shelf-life study, control and ACP treated samples (100 kV for 5 min) were analysed for the population of mesophiles, psychrotrophs and Enterobacteriaceae as well as sample colour and pH over a storage period of 24 days. On day 24, the population of mesophiles, psychrotrophs and Enterobacteriaceae in treated chicken was respectively 1.5, 1.4 and 0.5 log lower than the control. These results suggest that in-package ACP is an effective technology to extend the shelf-life of poultry products.

Strategy to achieve a 5-log Salmonella inactivation in tender coconut water using high voltage atmospheric cold plasma (HVACP).

This study examined high voltage atmospheric cold plasma (HVACP) technology as a non-thermal intervention for inactivating Salmonella enterica serovar Typhimurium LT2 (ST2) in tender coconut water (TCW). Treatment with HVACP in air at 90 kV for 120 s inactivated 1.30 log10 of ST2. Development of a TCW stimulant suggested an interfering role of magnesium and phosphate salts with HVACP inactivation. Generation of reactive gas species, viz. ozone and hydrogen peroxides were found to be responsible for microbial inactivation. The addition of 400 ppm citric acid to the TCW effectively reduced ST2 by 5 log10 during HVACP treatment. Under these conditions, higher cellular leakage and morphological damage were observed in ST2. Minimal physico-chemical changes in TCW were observed with HVACP treatment, except for an 84.35% ascorbic acid loss (added externally). These results demonstrate a potential pathway for developing highly effective cold plasma treatments to preserve fruit and vegetable juices.

The Effect of Atmospheric Cold Plasma on Bacterial Stress Responses and Virulence Using Listeria monocytogenes Knockout Mutants.

Listeria monocytogenes is an opportunistic intracellular pathogen commonly associated with serious infections and multiple food-borne outbreaks. In this study, we investigated the influence of atmospheric cold plasma (80 kV, 50 Hz) on L. monocytogenes (EGD-e) and its knockout mutants of sigB, rsbR, prfA, gadD, and lmo0799 genes at different treatment time intervals. Further, to ascertain if sub-lethal environmental stress conditions could influence L. monocytogenes survival and growth responses, atmospheric cold plasma (ACP) resistance was evaluated for the cultures exposed to cold (4°C) or acid (pH 4) stress for 1 h. The results demonstrate that both wild-type and knockout mutants were similarly affected after 1 min exposure to ACP (p > 0.05), with a difference in response noted only after 3 min of treatment. While all L. monocytogenes strains exposed to acid/cold stress were hypersensitive to ACP treatment and were significantly reduced or inactivated within 1 min of treatment (p < 0.05). The results indicate sigB and prfA are important for general stress resistance and biofilm, respectively, loss of these two genes significantly reduced bacterial resistance to ACP treatment. In addition, exposure to sub-lethal 1min ACP increased the gene expression of stress associated genes. SigB showed the highest gene expression, increasing by 15.60 fold, followed by gadD2 (7.19) and lmo0799 (8.6) after 1 min exposure. Overall, an increase in gene expression was seen in all stress associated genes analyzed both at 1 min treatment; while long treatment time reduced the gene expression and some cases down-regulated prfA and gadD3 gene expression. By comparing the response of mutants under ACP exposure to key processing parameters, the experimental results presented here provide a baseline for understanding the bacterial genetic response and resistance to cold plasma stress and offers promising insights for optimizing ACP applications.

Effects of Cold Plasma on Food Quality: A Review.

Cold plasma (CP) technology has proven very effective as an alternative tool for food decontamination and shelf-life extension. The impact of CP on food quality is very crucial for its acceptance as an alternative food processing technology. Due to the non-thermal nature, CP treatments have shown no or minimal impacts on the physical, chemical, nutritional and sensory attributes of various products. This review also discusses the negative impacts and limitations posed by CP technology for food products. The limited studies on interactions of CP species with food components at the molecular level offers future research opportunities. It also highlights the need for optimization studies to mitigate the negative impacts on visual, chemical, nutritional and functional properties of food products. The design versatility, non-thermal, economical and environmentally friendly nature of CP offers unique advantages over traditional processing technologies. However, CP processing is still in its nascent form and needs further research to reach its potential.

Recent Advances in the Application of Cold Plasma Technology in Foods.

The past decade has seen a surge in the scientific literature investigating the potential food-related applications of plasma. A multidisciplinary scientific effort has started to demonstrate process efficacy for a range of plasma applications, including antimicrobial, pesticidal, food functionalization, and waste treatment. Insights into the interactions of plasma species with food and the mechanisms of action are also emerging. This review examines the current status of cold plasma technology within the food sector with a particular emphasis on emerging applications. Opportunities and current challenges that need to be addressed for successful adoption of the approach by industry are detailed.

The Potential of Cold Plasma for Safe and Sustainable Food Production.

Cold plasma science and technology is increasingly investigated for translation to a plethora of issues in the agriculture and food sectors. The diversity of the mechanisms of action of cold plasma, and the flexibility as a standalone technology or one that can integrate with other technologies, provide a rich resource for driving innovative solutions. The emerging understanding of the longer-term role of cold plasma reactive species and follow-on effects across a range of systems will suggest how cold plasma may be optimally applied to biological systems in the agricultural and food sectors. Here we present the current status, emerging issues, regulatory context, and opportunities of cold plasma with respect to the broad stages of primary and secondary food production.

Degradation kinetics of organic dyes in water by high voltage atmospheric air and modified air cold plasma.

High voltage atmospheric cold plasma (HVACP) is a novel, non-thermal technology which has shown potential for degradation of various toxic components in wastewater. In this study, HVACP was used to examine the degradation kinetics of methyl red, crystal violet and fast green FCF dyes. HVACP discharge was found to be a source of reactive nitrogen and oxygen species. High voltage application completely degraded all dyes tested in less than 5 min treatment time. Plasma from modified gas (∼65% O2) further reduced the treatment time by 50% vs. plasma from dry air. First order and Weibull models were fitted to the degradation data. The Weibull model was found better in explaining the degradation kinetics of all the treated dyes.

Evaluation of physical and chemical properties and their interactions in fat, oil, and grease (FOG) deposits.

Fat, oil and grease (FOG) blockages in sewer systems are a substantial problem in the United States. It has been estimated that over 50% of sewer overflows are a result of FOG blockages. In this work, a thorough laboratory study was undertaken to examine key variables that contribute to FOG deposit formation under controlled conditions. Physical and chemical properties and their interactions were evaluated and conditions that generated deposits that mimicked field FOG deposits were identified. It was found that 96 of the of 128 reaction conditions tested in the laboratory formed FOG deposits with similar physical and chemical characteristics as field FOG deposits. It was also found that FOG deposits can be created through fatty acid crystallization and not just saponification. Furthermore FOG deposits were found to be more complex than previously documented and contain free fatty acids, fatty acid metal salts, triacylglycerol's, diacylglycerol's and, monoacylglycerol's. Lastly it was found that FOG deposits that only contained saturated fatty acids were on average 2.1 times higher yield strength than deposits that contained unsaturated fatty acids.

Structures of Degradation Products and Degradation Pathways of Aflatoxin B1 by High-Voltage Atmospheric Cold Plasma (HVACP) Treatment.

High-voltage atmospheric cold plasma (HVACP) is a novel nonthermal decontamination technology that has potential for use in the food industry. In this study, HVACP was applied to treat pure aflatoxin B1 (AFB1) powder on a glass slide. AFB1 was degraded by 76% using a 5 min HVACP treatment in air having 40% relative humidity. The degradation products of AFB1 were separated, and their molecular formulas were elucidated using liquid-chromatography time-of-flight mass spectrometry (HPLC-TOF-MS). Six main degradation products were observed. The structures of the degradation products were further clarified via orbitrap mass spectrometry by means of fragmentation of the parental ions. Two degradation pathways were proposed on the basis of the structure of the degradation products. Among the six degradation products, two were ozonolysis products of AFB1. The appearance of the other four degradation products indicates that AFB1 was degraded by other reactive species besides ozone that were generated during HVACP treatment. Reactive oxygen gas species are suggested as the major agents for aflatoxin degradation during HVACP treatment. Two degradation pathways of AFB1 by HVACP treatment were proposed. One pathway involves reactions in which H•, OH•, CHO• radicals are added. The other involves epoxidation by HO2• radicals and oxidation of AFB1by the combined effects of the oxidative species OH•, H2O2, and O3. According to the structure-bioactivity relationship of AFB1, the bioactivity of the AFB1 samples subjected to HVACP treatment is significantly reduced because of the disappearance of the C8═C9 double bond in the furofuran ring in all of the major degradation products as well as the modification of the lactone ring, cyclopentanone, and the methoxyl group.