Microbial Inactivation and Quality Changes in Orange Juice Treated by High Voltage Atmospheric Cold Plasma

Although atmospheric cold plasma is well known for nonthermal inactivation of microorganisms on surfaces, few studies examine its application to liquid food within a package. This study explores the decontamination efficiency of high voltage atmospheric cold plasma (HVACP) on Salmonella enterica serovar Typhimurium (S. enterica) in orange juice (OJ). Both direct and indirect HVACP treatments of 25-mL OJ induce greater than a 5-log reduction in S. enterica following 30 s of treatment with air and MA65 gas with no storage. For 50-mL OJ, 120 s of direct HVACP treatment followed by 24-h storage induced a 2.9-log reduction of S. enterica in air and a 4.7-log reduction in MA65 gas; 120 s of indirect HVACP treatment followed by 24-h storage resulted in a 2.2-log reduction in air and a 3.8-log reduction in MA65. No significant (P < 0.05) Brix or pH change occurred following 120-s HVACP treatment. Applying 120-s HVACP direct treatment reduced vitamin C by 22% in air (compared to 50% for heat pasteurization) and pectin methylesterase activity by 74% in air and 82% in MA65. These results demonstrate that HVACP can effectively inactivate Salmonella in OJ with minimal quality degradation.     

Effects of plasma-activated water on microbial growth and storage quality of fresh-cut apple

Fresh-cut ‘Fuji’ apples were immersed for 5 min in plasma-activated water (PAW) generated, by plasma generated with sinusoidal voltages at 7.0 kHz with amplitudes of 6 kV, 8 kV, and 10 kV, designated PAW-6, PAW-8, and PAW-10, respectively. The control group was soaked in distilled water for 5 min instead of PAW. The results indicated that the growth of bacteria, molds, and yeasts was inhibited by PAW treatments during storage at 4 ± 1 °C, especially the microbial inactivation with PAW-8, which was the most efficient. PAW-8 reduced the microbial counts by 1.05 log₁₀CFU g⁻¹, 0.64 log₁₀CFU g⁻¹, 1.04 log₁₀CFU g⁻¹ and 0.86 log₁₀CFU g⁻¹ for aerobic bacteria (aerobic plate counts), molds, yeasts and coliforms on day 12, respectively. In addition, the bacterial counts of fresh-cut apples treated with PAW were <5 log₁₀CFU g⁻¹, which did not exceed to the existing China Shanghai local standard (DB 31/2012–2013) during 12 days of storage. PAW treatments reduced superficial browning of fresh-cut apples without affecting their firmness and titratable acidity. In addition, no significant change was observed in antioxidant content and radical scavenging activity between the PAW-treated and control groups. It is suggested that PAW is a promising method for preservation of fresh-cut fruits and vegetables, which is usually beneficial to the quality maintenance of fresh-cut fruits and vegetables during storage.     

Thermal and chemical inactivation of Lactobacillus virulent bacteriophage

The effect of thermal treatments and several biocides on the viability of Lactobacillus virulent phage P1 was evaluated. Times to achieve 99% inactivation (T₉₉) of phage at different treatment conditions were calculated. The thermal treatments applied were 63, 72, and 90°C in 3 suspension media (de Man, Rogosa, Sharpe broth, reconstituted skim milk, and Tris magnesium gelatin buffer). Phage P1 was completely inactivated in 5 and 10 min at 90 and 72°C, respectively; however, reconstituted skim milk provided better thermal protection at 63°C. When phage P1 was treated with various biocides, 800 mg/L of sodium hypochlorite was required for total inactivation (～7.3 log reduction) within 60 min, whereas treatment with 100% ethanol resulted in only a ～4.7 log reduction, and 100% isopropanol resulted in a 5.2-log reduction. Peracetic acid (peroxyacetic acid) at the highest concentration used (0.45%) resulted in only a ～4.-log reduction of phage within 60 min. The results of this study provide additional information on effective treatments for the eradication of potential phage infections in dairy plants.     

Inactivation efficacy of plasma-activated water: influence of plasma treatment time,exposure time and bacterial species

This study aimed to evaluate the influence of plasma treatment time, bacterial exposure time to PAW and bacterial species on the inactivation efficacy of plasma-activated water (PAW), with additional investigation of the inactivation mechanisms of PAW. Six bacterial species, including Listeria innocua, Staphyloccus aureus, Escherichia coli, Pseudomonas fluorescens, Shewanella putrefaciens and Aeromonas hydrophila were selected as the representative bacteria. The initial bacterial concentration was around 7 log CFU ml⁻¹ after mixing with PAW, and the inactivation efficacy was measured after different exposure times during the 4 °C storage. Scanning electron microscopy (SEM) images of the bacteria after PAW treatment were carried out to inspect the cell structure damage, and physicochemical properties of PAW, including pH, conductivity and long-living reactive species of H₂O₂, , and , were examined. The results showed that the inactivation efficacy of PAW was positively correlated with plasma treatment time and bacterial exposure time, and for the species examined in this study, the Gram-negative species were more sensitive to PAW than the Gram-positive species. Cell structure damage, including shrinkage, distortion, or holes, was observed after PAW treatment. The pH of PAW was acidified to 2.5–2.9, and conductivity was significantly increased to 518.0 μs cm⁻¹. and H₂O₂ were reduced during the 48 h storage, while an increased concentration was observed for . This study demonstrated that the processing parameters of plasma treatment time, exposure time and characteristics of bacteria can significantly affect the inactivation efficacy of PAW.     

High hydrostatic pressure effects on bacterial bioluminescence

The mechanism that leads to microbial inactivation by high hydrostatic pressure remains elusive. In this study, a high-pressure system interfaced with a photomultiplier tube (PMT) was developed to monitor cellular metabolism in situ using bioluminescent bacterial strains. Preliminary characterization of the system was performed using Pseudomonas fluorescens 5RL expressing lux proteins from Vibrio fischeri. Stepwise increases in pressure at 34 MPa and above resulted in decreased bioluminescence. Square wave exposure to pressures of 69, 103 and 138 MPa showed bioluminescence reductions greater than 95%, but when cells were returned to ambient pressure bioluminescence returned to 51, 38, and 4% of initial bioluminescence values, respectively. An Escherichia coli strain expressing lux proteins from V. fischeri was constructed to determine whether this reversible effect could be observed in another bacterial genus. Square wave perturbations of 69, 103 and 138 MPa resulted in bioluminescence reductions of about 94% at the highest pressure treatment. Upon decompression, bioluminescence returned to 74, 58 and 30% of the initial bioluminescence values for cells treated at 69, 103 and 138 MPa, respectively. These results suggest that square wave exposure to pressure up to 138 MPa induces reversible cell damage in P. fluorescens 5RL and E. coli VF lux.     

Inactivation of Escherichia coli O157:H7, Salmonella and human norovirus surrogate on artificially contaminated strawberries and raspberries by water-assisted pulsed light treatment

This study investigated the inactivation of Escherichia coli O157:H7, Salmonella and murine norovirus (MNV-1), a human norovirus surrogate, on strawberries and raspberries using a water-assisted pulsed light (WPL) treatment. The effects of combinations of WPL treatment with 1% hydrogen peroxide (H₂O₂) or 100 ppm sodium dodecyl sulfate (SDS) were also evaluated. Strawberries and raspberries were inoculated with E. coli O157:H7 and treated by WPL for 5–60 s. E. coli O157:H7 on both strawberries and raspberries was significantly reduced in a time-dependent manner with 60-s WPL treatments reducing E. coli O157:H7 by 2.4 and 4.5 log CFU/g, respectively. Significantly higher reductions of E. coli O157:H7 were obtained using 60-s WPL treatment than washing with 10 ppm chlorine. Compared with washing with chlorine, SDS and H₂O₂, the combination of WPL treatment with 1% H₂O₂ for 60 s showed significantly higher efficacy by reducing E. coli O157:H7 on strawberries and raspberries by 3.3- and 5.3-log units, respectively. Similarly, Salmonella on strawberries and raspberries was inactivated by 2.8- and 4.9-log units after 60-s WPL–H₂O₂ treatments. For decontamination of MNV-1, a 60-s WPL treatment reduced the viral titers on strawberries and raspberries by 1.8- and 3.6-log units, respectively and the combination of WPL and H₂O₂ did not enhance the treatment efficiency. These results demonstrated that the WPL treatment can be a promising chemical-free alternative to chlorine washing for decontamination of berries destined for fresh-cut and frozen berry products. WPL–H₂O₂ treatment was the most effective treatment in our study for decontamination of bacterial pathogens on berries, providing an enhanced degree of microbiological safety for berries.     

Production,characterization, microbial inhibition,and in vivo toxicity of cold atmospheric plasma activated water

Cold atmospheric plasma activated water (PAW) was produced at various Reactive Nitrogen Oxygen Species (RONS) concentrations. PAW was characterized and in vivo toxicological studies were conducted, using the zebrafish embryo acute toxicity test (OECD 236).Danio rerio (zebrafish), were raised in standard egg PAW of various RONS concentrations and their lethality was monitored. The thresholds for no lethality and simultaneously no obvious morphological phenotypes were determined as approximately 30 mg/L H₂O₂ concentration, while for NO₃⁻ concentration, the values were also correlated to the pH of the solution used. The pH-value of 3.85 was also a measurable threshold for the lethality of the embryos. Toxic and non-toxic PAW were used as medium to assess their inhibitory potential for Escherichia coli and Enterococcus faecium. The results indicated that PAW delayed the recovery time or even resulted in no growth of these microorganisms compared to control samples.     

Effect of plasma-activated water on microbial quality and physicochemical characteristics of mung bean sprouts

The efficacy of nonthermal plasma-activated water (PAW) in the decontamination of mung bean sprouts was evaluated in this work. After being treated with PAW for 30 min, the populations of total aerobic bacteria and total yeasts and moulds on mung bean sprouts were decreased by 2.32- and 2.84- log₁₀ CFU/g, respectively. The PAW treatment had no significant effect on the antioxidant potential of mung bean sprouts as shown by using 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH•) scavenging activity assay, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) method, and ferric reducing antioxidant power (FRAP) assay (p > 0.05). Additionally, the PAW treatment caused no significant changes in the total phenolic and flavonoid contents, nor the sensory characteristics of mung bean sprouts (p > 0.05). Reactive species such as nitrates, nitrites, and H₂O₂ were generated in PAW, which presumably contributed to the disinfection efficacy of PAW. These data show that PAW can be used as a promising nonthermal technology for the control of microbial contamination in sprouts.Industrial relevanceEdible sprouts are common food ingredients across the world. However, sprouts can be contaminated by pathogenic microorganisms, which may result in health risks to humans. Recently, PAW has been shown to be a safe and effective method for food surface sanitation. However, the application of PAW in the microbial control for sprouts is less investigated. In this study, the influences of PAW on the microbial load, chemical and sensory quality of mung bean sprouts were investigated for the first time. The results showed that PAW could effectively inactivate bacteria and yeasts and moulds on mung bean sprouts without resulting in significant changes in the antioxidant capacities, total phenolic and flavonoid contents, and sensory characteristics of mung bean sprouts. These data indicated that PAW can be used as a promising nonthermal technology for reducing microbial populations on sprouts.     

Inactivation of Salmonella typhimurium and Lactobacillus plantarum by UV-C light in flour powder

This research evaluates the potential use of ultraviolet C light (UV-C) as a decontamination method for powdered foods, particularly of refined flour. This technology's lethal effectiveness was evaluated on Salmonella enterica subsp. Enterica serotype Typhimurium and Lactobacillus plantarum in wheat flour, and in laboratory liquid media of different a_w and turbidities to evaluate the action mechanisms of UV-C light in powdered products. Initial results showed a large variability of lethality in flour, obtaining between 0.2 and 3.0 log₁₀ cycles of inactivation. Results obtained in laboratory media and SEM analysis of contaminated flour indicated that the variability was due to a shadow effect on the efficacy of UV-C light and not due to the low water a_w of the flour or starch content. Based on these conclusions, a 2-m vertical tunnel with twelve 480 W UV-C lamps was designed to treat flour by forming a continuous cloud of dust (0.05–2.4 kg/h). Inactivation levels of 4.0 to 1.7 log₁₀ cycles of the population of L. plantarum in flour were achieved at flow rates of 0.2 and 2.4 kg/h respectively, with a maximum residence time of 4 s.Industrial relevanceThis investigation demonstrated the lethal efficacy of the application of UV–C light to inactivate microorganisms, both pathogenic and spoilage, present in flour. 4-log10 cycles of inactivation of both Salmonella Typhimurium and Lactobacillus plantarum were inactivated with UV-C treatments. A UV-C facility was built up which enabled to treat flour in continuous conditions creating a cloud of dust with treatments of 4 s and lethalities of 4-log10 reductions.     

Impact of plasma-activated water washing on the microbial inactivation,color, and electrolyte leakage of alfalfa sprouts,broccoli sprouts,and clover sprouts

This study investigated plasma-activated water (PAW) as a sanitizer for the washing of sprouts. Alfalfa sprouts, broccoli sprouts, and clover sprouts were washed with PAW, chlorine (Cl, 200 ppm), or deionized water. The inactivation of aerobic mesophilic microorganisms and inoculated Escherichia coli DH5α was evaluated. The quality of sprouts was assessed based on visual color change (ΔE) and plant tissue damage (measured by electrolyte leakage). Significant reductions of 1–2 log CFU/g in aerobic mesophilic microorganisms were achieved by PAW and Cl on clover sprouts and alfalfa sprouts. Reductions of E. coli ranging between 1.4 ± 0.4 log CFU/g and 3.5 ± 0.9 log CFU/g were achieved by PAW on the sprouts (original counts: 6.4 to 8.1 CFU/g), which were comparable to Cl except for the case of alfalfa sprouts where Cl achieved the highest inactivation. No significant quality difference in terms of visual color change or electrolyte leakage was observed in sprouts washed by PAW and Cl.     

Evaluating the effects of plasma-activated slightly acidic electrolyzed water on bacterial inactivation and quality attributes of Atlantic salmon fillets

In this study, an intervention non-thermal processing technology plasma-activated slightly acidic electrolyzed water (PASW) was developed to better preserve salmon fillets. Compared to the plasma-activated water (PAW) and slightly acidic electrolyzed water (SAEW), PASW treatment was found to be more effective in inactivating microorganisms. After PAW, SAEW, or PASW treatment for 120 s, the population of Shewanella putrefaciens (S. putrefaciens) was reduced by 2.04, 2.62 and 2.08 Log CFU/mL (P < 0.05) using plate counts, respectively. The test for the leakage of nucleic acids and protein in intracellular contents confirmed that PASW caused serious damage to the microbial cell structural integrity compared to that alone PAW or SAEW. Meanwhile, scanning electron microscopic observations also showed that PASW caused apparent bacterial structural changes. Besides, the PASW treatment did not alter color and textural properties of salmon fillets, and restrained lipid oxidation as compared to the control and SAEW treatments. In all, this study compared the bacterial inactivation mechanisms for PAW, SAEW, and PASW, and suggested that PASW was effective in inactivating S. putrefaciens of salmon fillets.Industrial relevancePlasma-activated slightly acidic electrolyzed water, an emerging technology in food processing, can be a potential green technology for the processing of aquatic food products. PASW treatment had higher disinfection efficacy than that of SAEW or PAW treatment alone, and no adverse effect on the quality of Atlantic salmon fillets. These results boost knowledge in the food preservation field, as well as the application of non-thermal processing in the food industry.     

Efficacy optimization of plasma-activated water for food sanitization through two reactor design configurations

The chemistry, antimicrobial efficacy and energy consumption of plasma-activated water (PAW) was optimized by altering the discharge frequency, ground-electrode configuration, gas flow rate and initial water conductivity for two reactor configurations, i.e., air pin-to-liquid discharge and air plasma-bubble discharge in water. The ratio of NO₂⁻ and NO₃⁻ formation was altered to optimise the antimicrobial effects of PAW, tested against two Gram-negative bacteria. An initial solution conductivity of 0.2 S·m⁻¹ and 2000-Hz discharge frequency with the ground electrode positioned inside the pin reactor showed the highest antimicrobial effect resulting in a 3.99 ± 0.13-log₁₀ reduction within 300 s against Escherichia coli and 5.90 ± 0.24-log₁₀ reduction within 240 s for Salmonella Typhimurium. An excellent energy efficiency of reactive oxygen and nitrogen species (RONS) generation of 10.1 ± 0.1 g·kW⁻¹·h⁻¹ was achieved.Industrial relevancePlasma-activated water (PAW) is deemed as an eco-friendly alternative to chemical disinfection because its bactericidal activity is temporary. Optimizing the design and operation of PAW reactors to achieve high inactivation rates of more than 5-log₁₀ reductions, as demonstrated in this work, will support the industrial application of this technology and the scaleup at industrial level.     

Fluorescent labeling study of plasminogen concentration and location in simulated bovine milk systems

A fluorescent labeling method was developed to study plasminogen (PG) concentration and location in simulated bovine milk. Activity and stability of PG labeled with Alexa Fluor 594 (PG-594) were comparable to those of native PG. The fluorescent signal of PG-594 exhibited pH, temperature, and storage stability, and remained stable throughout typical sample treatments (stirring, heating, and ultracentrifugation). These characteristics indicate broad applicability of the fluorescent labeling technique for milk protease characterization. In an example application, PG-594 was added to simulated milk samples to study effects of heat and β-lactoglobulin (β-LG) on the distribution of PG. Before heating, about one-third of the PG-594 remained soluble in the whey fraction (supernatant) whereas the rest became associated with the casein micelle. Addition of β-LG to the system slightly shifted PG-594 distribution toward the whey fraction. Heat-induced PG-594 binding to micelles in whey-protein-free systems was evidenced by a decrease of PG-594 from 31 to 15% in the whey fraction accompanied by an increase of PG-594 from 69 to 85% in casein micelle fractions. When β-LG was present during heating, more than 95% of PG-594 became associated with the micelle. A comparison with the distribution pattern of PG-derived activities revealed that heat-induced PG binding to micelles accompanies heat-induced PG inactivation in the micelle fraction. Incubation of the casein micelles with the reducing agent β-mercaptoethanol revealed that disulfide bonds formed between PG and casein or between PG and casein-bound β-LG are the mechanisms for heat-induced PG binding to casein micelles. Western blotting and zymography results correlated well with fluorescent labeling studies and activity studies, respectively. Theoretically important findings are: 1) when heated, serum PG is capable of covalently binding to micellar casein or complexing with β-LG in whey and then coadhering to micelles, and 2) PG that associated with micellar casein through lysine binding sites before heating is capable of developing heat-induced disulfide bonds with casein. The overall results are PG covalently binding to micelles and inactivation thereafter. Our results suggest that, instead of thermal denaturation through irreversible unfolding, covalent bond formation between PG and other milk proteins is the mechanism of PG inhibition during thermal processing.     

Inhibition of Listeria monocytogenes and Escherichia coli O157:H7 in liquid broth medium and during processing of fermented sausage using autochthonous starter cultures

The antimicrobial effect of two autochthonous starter cultures of Lactobacillus sakei was evaluated in vitro (in liquid broth medium) and in situ assays. The inactivation of foodborne pathogens Listeria monocytogenes (serotype 4ab No 10) and Escherichia coli O157:H7 ATCC 43888 was investigated during the production of fermented sausage according to a typical Greek recipe using L. sakei strains as starter cultures. The inactivation kinetics were modeled using GInaFiT, a freeware tool to assess microbial survival curves. By the end of the ripening period, the inhibition of L. monocytogenes was significant in treatments with L. sakei 8416 and L. sakei 4413 compared to the control treatment. A 2.2-log reduction of the population of E. coli O157:H7 resulted from the autochthonous starter culture L. sakei 4413 during sausage processing. The use of the autochthonous starter cultures constitutes an additional improvement to the microbial safety by reducing foodborne pathogens.     

Effect of plasma activated water (PAW) on rocket leaves decontamination and nutritional value

Plasma Activated Water (PAW) obtained by exposing water to cold atmospheric pressure plasma, has recently emerged as a promising alternative for food decontamination, compared to the use of traditional chemical sanitizers. The aim of the study was to evaluate the efficacy of PAW treatments for rocket salad decontamination. Washing with PAW for 2, 5, 10 and 20 min was assessed against different endogenous spoilage microorganisms and compared to untreated water and hypochlorite solution. The chemical composition of PAW as a function of treatment and delay time was characterized and the effect on product quality and nutritional parameters was evaluated.Results showed that PAW allowed an average reduction of 1.7–3 Log CFU/g for total mesophilic and psychrotrophic bacteria and Enterobacteriaceae following 2–5 min washing with minimal variation of qualitative and nutritional parameters. Overall, experimental results highlighted the potentiality of PAW treatments as a promising alternative to chlorine having the advantage of a minor adverse impact on environment and consumers' health.Industrial relevanceTo meet consumers demand, the minimally processed fruit and vegetable industry needs to find sustainable solutions as alternative to the use of traditional chemical sanitizers that allow to increase product shelf-life and preserve safety, qualitative and nutritional characteristics.Plasma activated water represents a promising strategy for food decontamination, but its effects on foods have been only limitedly investigated. The present research is the first study on the use of plasma activated water on fresh rocket leaves, providing new and important information on microbial inactivation and quality of the fresh cut product.     

Use of high-power ultrasound combined with supercritical fluids for microbial inactivation in dry-cured ham

The aim of this study was to analyze the application of supercritical carbon dioxide combined with high-power ultrasound (SC-CO₂ + HPU) and the use of a saline solution (SS; 0.85% NaCl) on the microbial inactivation and the quality of dry-cured ham. The effect of temperature, pressure and treatment time was studied using RSM. Physicochemical analyses were carried out after the treatments and during refrigerated storage (30 days / 4 °C). The most significant inactivation of Escherichia coli (3.62 ± 0.20-log CFU/g) was obtained using the SC-CO₂ + HPU + SS (25 MPa, 46-°C and 10-min), with temperature being the most important process variable. Fat content showed a significant (p < 0.05) reduction (46%) after the SC-CO₂ + HPU treatment. The breakage of the muscle fibers, the disorganization in the myofibrils, as well as the enlargement of the interfibrillar spaces led to the ham softening (avg 26.5%). No significant (p > 0.05) changes in color, texture or pH were found during storage. Thus, ultrasonic-assisted SC-CO₂ could be used, in combination or not with SS, to improve the shelf of dry-cured ham.Industrial relevanceSupercritical carbon dioxide (SC-CO₂) inactivation technology has been shown to be highly efficient at reducing different bacteria in liquid media with minimum effect on food quality. This technology is barely applied to solid products and its use is limited by the long processing times and reduced inactivation capacity. The application of high-power ultrasound (HPU) leads to a shorter process time. This technology is useful for the inactivation of ham microbiota and inoculated E.coli. A liquid medium surrounding the treated solid can enhance microbial inactivation for the purposes of improving the effect of ultrasound cavitation, while only minimally affecting the quality of the samples (color, texture, fat and moisture contents).     

Inactivation of Listeria innocua and Escherichia coli in carrot juice by combining high pressure processing,nisin, and mild thermal treatments

This study explored the effectiveness of high pressure (200–500 MPa) alone or in combination with mild thermal treatments (35 and 50 °C) and nisin (25 and 50-ppm) on the inactivation of L. innocua and E. coli in carrot juice. Processing at 500 MPa at 20 °C for 2 min without nisin resulted in 4- and 5-log CFU/mL reduction of L. innocua and E. coli, respectively while incorporating 25-ppm nisin at same pressure and temperature rendered 7-log CFU/mL reduction. There was synergism between high pressure, nisin, and heat in all treatments to inactivate both microorganisms. After a 28-d of refrigerated storage, total plate counts were <2-log CFU/mL in carrot juice treated with combination of 300 MPa and 25-ppm nisin at 35 °C. All combinations resulted in less intense use of pressure, i.e. more energy efficient, cost effective processes while attaining high quality juices. The results of this study suggest that by using selected combinations of high pressure, nisin and mild temperatures, safe, clean-label, high-quality juices can be produced.Industrial relevanceThe results from this study show a synergistic effect on the inactivation of L. innocua and E. coli in carrot juice from the combined application of HPP, nisin, and mild temperatures. By replacing the use of HPP alone by these combinations will allow the use of reduced pressures over shorter period of times to process low-acid juices, lowering energy requirements and increasing throughput. This study will aid the beverage processing industry in the development of clean label juice products with fresh-like quality attributes and using considerable less energy to conventional processing.     

Analysis of bacterial inactivation by intense pulsed light using a double-Weibull survival model

The objective of this study was to measure the inactivation efficiencies of intense pulsed light (IPL) on six types of bacteria and determine how the efficiency values are related to the spectral transmittance of IPL. All of the microorganisms exhibited up to 7-log CFU/mL reductions, and the double-Weibull survival model provided the best fit to the inactivation curves. We obtained 4D_v values (which is the fluence required to inactivate 99.99% of viable cells) and z_v values (which is the increase in lamp voltage required for a 1-log reduction of the 4D_v value) for lamp voltages ranging from 800 to 1800 V (corresponding to total fluences from 0.00 to 11.41 J/cm²). The 4D_v values for Bacillus cereus, Clostridium perfringens, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella Enteritidis, and Shigella sonnei for IPL treatment at 1800 V were 1.57, 0.66, 0.62, 0.79, 0.66, and 1.63 J/cm², respectively, while the corresponding z_v values were 5553, 3590, 3201, 3678, 3672, and 6440 V, respectively. The variations in the sensitivity to IPL were related to differences in the transmittance of the microorganisms. A practical model was developed to predict the 4D_v values of microorganisms based on their transmittance and the IPL lamp voltage.     

High hydrogen peroxide concentration-low exposure time of plasma-activated water (PAW): A novel approach for shelf-life extension of Asian sea bass (Lates calcarifer) steak

A new method for using plasma-activated water (PAW; 100 ppm H₂O₂) to improve the cold (4 °C) shelf-stability of Asian sea bass steaks (ASBS) was established. Soaking with PAW, created utilizing oxygen and argon, for 30–120 s successfully extended the shelf-life of ASBS by suppressing microbial growths below the permissible level (7 log CFU/g) for 25 days, whereas control reached the microbiological limit after 10 days (p < 0.05). PAW-treated samples had lower accumulation rates of total volatile base nitrogen (< 25 mg/100 g), trimethylamine (< 5 mg/100 g), and propanal (< 400 nmol/g) than control (p < 0.05). PAW improved lipid stability (TBARS <2 mg/kg) but promoted protein oxidation (protein carbonyl ~0.01–0.02 nmol/mg). Hardness and water holding capacity of PAW treatments were better preserved during storage than control as indicated by higher breaking force and lesser expressible moisture drip. Although metmyoglobin tended to stay stable during storage, all treatments' surface total color change tended to increase by 2–5 folds. Overall, argon-produced PAW with 100 ppm H₂O₂ and a short soaking time (30 s) seemed to be a promising method for protecting the quality and safety of ASBS.     

Effect of Low-pressure Cold Plasma (LPCP) on the Wettability and the Inactivation of <Emphasis Type="Italic">Escherichia coli</Emphasis> and <Emphasis Type="Italic">Listeria innocua</Emphasis> on Fresh-Cut Apple (<Emphasis Type="Italic">Granny Smith</Emphasis>) Skin

The aim of this study was to investigate the effect of low-pressure cold plasma (LPCP) on the inactivation of Escherichia coli and Listeria innocua on fresh-cut apple skin and its influence on wettability. Cold plasma treatments have shown to be effective to decontaminate foods, but their effect on the wettability has not been well studied. Surface-inoculated apple samples were treated with argon (Ar), nitrogen (N2), oxygen (O₂), and argon-oxygen (Ar-O₂) cold plasma using a commercial LPCP unit. Three different models were used to fit bacterial survival curves after the LPCP treatments. Changes in surface wettability were also determined by measuring the contact angle. The LPCP treatments using Ar, O₂, or Ar-O₂ mixture for 20 min were the most effective to inactivate E. coli with O₂, while the LPCP treatment with N2 for 20 min reduced L. innocua the most for (p?<?0.05). The highest increase in surface wettability was observed in samples treated for 20 min with O₂ and Ar-O₂. Different LPCP treatments have not great effectivity on the inactivation of E. coli and L. innocua on fresh-cut apple surface, but the all treatments changed the surface wettability of apples, making it more hydrophilic. This can be considered as a negative effect of the LPCP treatment because it can facilitate the adhesion and proliferation of re-contaminating microorganisms. More research should be undertaken to explore the use of other gases and complex surfaces.