UV-C Dose Research Articles

Improving inactivation performance of in-duct ultraviolet germicidal irradiation system with ribbed duct walls by optimizing UVC distribution

The in-duct ultraviolet germicidal irradiation system (ID-UVs) with ribs has been revealed to be effective in reducing the risk of biological contamination, and optimization of its UV radiation distribution is expected to further improve the inactivation performance. In this study, the Critical Survival Fraction Probability (CSFP) and Maximal Bearable UVC Dose (MBUD) methods were synergistically employed as evaluation indicators, and Computational Fluid Dynamics (CFD) was used to optimize the lamp array, duct shape, liner reflectivity and number of UV lamps. Results indicated that the optimal lamp array was positioned at 0° to the airflow direction, and square-section ducts were preferred over circular-section ducts. Ribs obstructed the transmission of specular reflected radiation, while diffuse reflection helps to overcome the obstruction. Reducing the number of lamps alone from four to one increased the volume-averaged irradiance by 14.4–25.3 % in the main irradiated region. For renovation projects, ID-UVs equipped with one lamp and galvanized steel ribs proved optimal, exhibiting increased inactivation efficiencies of 39.7 % (CSFP) and 239.4 % (MBUD) against highly UVC-susceptible MS2 Bacteriophage (K = 0.038 J/m2), and up to 341.1 % (MBUD) against low UVC-susceptible MS2 Bacteriophage (K = 0.028 J/m2) compared to the ID-UVs without ribs and featuring four lamps. Moreover, in comparison to conventional conditions that provide equivalent air-cleaning levels, the optimal ID-UVs allowed for a 60–70 % increase in air handling capacity while achieving at least an 83.6 % reduction in annual energy costs. These findings contribute towards advancing practical applications of ID-UVs with ribbed duct walls.

Evaluating UV-C Sensitivity of Calonectria pseudonaviculata in Model Buffer Solution Using a UV-C Light-Emitting-Diode System.

Calonectria pseudonaviculata, responsible for boxwood blight, produces sticky conidia that pose a contamination risk in boxwood production via cross-contamination from tools, equipment, and other resources. This study evaluated UV-C light-emitting-diode (LED) irradiation (263 to 287 nm) as a disinfection method by examining its effectiveness in inactivating conidia and determining the UV-C sensitivity. Conidial suspensions were exposed to quantifiable UV-C doses under a dynamic stirring condition. Average volumetric intensity was quantified by accounting for UV gradients and UV dose was calculated as a product of average fluence rate (mW⋅cm-2) and exposure time (s). UV-C irradiation effectively inactivated the tested pathogen following log-linear + shoulder kinetics as identified by parameters of goodness of model fit (i.e., high R2 and low root mean square error [RMSE] values). The model predicted the UV sensitivity of C. pseudonaviculata conidia as 46.6 mJ⋅cm-2 per log. A total of 2.04 log reductions of the population could be obtained by an exposure of 60 mJ⋅cm-2 of UV-C dose. The calculated decimal reduction dose (D10) was 13.53 ± 0.98 mJ⋅cm-2 (R2 = 0.97, RMSE = 0.14), inactivation rate constant (Kmax) = 0.17 ± 0.01, and shoulder length = 33.06 ± 1.81 mJ⋅cm-2. These findings indicate that UV-C irradiation could be a viable option for disinfecting tools, equipment, and possibly propagation cuttings in nurseries.

West Nile and Usutu viruses are efficiently inactivated in platelet concentrates by UVC light using the THERAFLEX UV-Platelets system.

West Nile virus (WNV) and Usutu virus (USUV) are mosquito-borne flaviviruses (Flaviviridae) that originated in Africa, have expanded their geographical range during the last decades and caused documented infections in Europe in the last years. Acute WNV and USUV infections have been detected in asymptomatic blood donors by nucleic acid testing. Thus, inactivation of both viral pathogens before blood transfusion is necessary to ensure blood product safety. This study aimed to investigate the efficacy of the THERAFLEX UV-Platelets system to inactivate WNV and USUV in platelet concentrates (PCs). Plasma-reduced PCs were spiked with the virus suspension. Spiked PC samples were taken after spiking (load and hold sample) and after UVC illumination on the Macotronic UV illumination machine with different light doses (0.05, 0.1, 0.15 and 0.2 (standard) J/cm2). Virus loads of WNV and USUV before and after illumination were measured by titration. Infectivity assays showed that UVC illumination inactivated WNV and USUV in a dose-dependent manner. At a UVC dose of 0.2 J/cm2, the WNV titre was reduced by a log10 factor of 3.59 ± 0.43 for NY99 (lineage 1) and 4.40 ± 0.29 for strain ED-I-33/18 (lineage 2). USUV titres were reduced at the same UVC dose by a log10 factor of 5.20 ± 0.70. Our results demonstrate that the THERAFLEX UV-Platelets procedure is an effective technology to inactivate WNV and USUV in contaminated PCs.

Life Cycle Assessment as a Decision-Making Tool for Photochemical Treatment of Iprodione Fungicide from Wastewater

Water contamination with various micropollutants is a serious environmental concern since this group of chemicals cannot always be removed efficiently with advanced treatment methods. Therefore, alternative chemical- and energy-intensive oxidation processes have been proposed for the removal of refractory and/or toxic chemicals. However, similar treatment performances might result in different environmental impacts. Environmental impacts can be determined by adopting a life cycle assessment methodology. In this context, lab-scale experimental data related to 100% iprodione (a hydantoin fungicide/nematicide selected as the model micropollutant at a concentration of 2 mg/L) removal from simulated tertiary treated urban wastewater (dissolved organic carbon content = 10 mg/L) with UV-C-activated persulfate treatment were studied in terms of environmental impacts generated during photochemical treatment through the application of a life cycle assessment procedure. Standard guidelines were followed in this procedure. Iprodione removal was achieved at varying persulfate concentrations and UV-C doses; however, an “optimum” treatment condition (0.03 mM persulfate, 0.5 W/L UV-C) was experimentally established for kinetically acceptable, 100% iprodione removal in distilled water and adopted to treat iprodione in simulated tertiary treated wastewater (total dissolved organic carbon of iprodione + tertiary wastewater = 11.2 mg/L). The study findings indicated that energy input was the major contributor to all the environmental impact categories, namely global warming, abiotic depletion (fossil and elements), acidification, eutrophication, freshwater aquatic ecotoxicity, human toxicity, ozone depletion, photochemical ozone creation, and terrestrial ecotoxicity potentials. According to the life cycle assessment results, a concentration of 21.42 mg/L persulfate and an electrical energy input of 1.787 kWh/m3 (Wh/L) UV-C light yielded the lowest undesired environmental impacts among the examined photochemical treatment conditions.

Feasibility analysis of inactivating influenza A(H1N1) virus using UVC robot in classroom environment

BackgroundStarting from 2009, H1N1 has been one of the respiratory diseases that afflict the global population. Concurrently, due to the influence of COVID-19, it has become widely accepted that preventing the virus's spread necessitates personal protection measures and disinfection in public spaces. ExperimentsThis study conducted two experiments. In the classroom experiment, six UVC dose test points were calibrated to test whether the UVC dose at each testing point met the standards for inactivating IAVs and the time required to meet the standards. In the simulated classroom experiment, seven square slides made of IAVs were placed. After 10 min of robot movement, irradiated sterile square slides were made into suspension and injected into chicken embryos. Cultivate chicken embryos and conduct IAVs testing. ResultsClassroom experiment has shown that 5 testing points can meet the standards for inactivating IAVs(3 mJ/cm2), with a required time of 80 min, 40 min, 15 min, 5 min and 10 min. The UVC dose for testing points that do not meet the standards in 80 min is only 0.5 mJ/cm2. The simulation classroom experiment outcomes revealed that 99.99 % of IAVs were deactivated. Furthermore, this study established both a desktop control group and a chair arm control group, both of which yielded identical results, indicating an inactivation logarithm of IAVs≥4log. ConclusionThe study presented that IAVs on the surface of an object can be effectively and rapidly deactivated at an irradiation density of 1.8 mW/cm2. Meanwhile, the study provides evidence of the feasibility of using the GXU robot to inactivate IAVs in a classroom environment.

Assessing the Efficacy of UV-C Light for the Inactivation of Phytopythium and Phytophthora Species in Water: A Mathematical Modeling Approach Using an Ultraviolet Light-Emitting-Diode System

The use of untreated, recirculated irrigation water is a profitable practice, but it can harbor plant pathogens such as Phytophthora ( Pt) cinnamomi, Pt. nicotianae, Phytopythium ( Pp) vexans, and Pp. helicoides, posing disease risks in crop production. UV-C (240 to 290 nm) light-emitting diode (LED) irradiation was evaluated for inactivating the zoospores of oomycetes in water, providing potential for effective treatment. Zoospore suspensions were exposed to quantifiable UV-C doses under dynamic stirring, calculated by multiplying fluence rate (mW cm−2) and exposure time(s). UV-C irradiation effectively inactivated the tested pathogens following linear (logarithmic linear [ Pt. cinnamomi and Pt. nicotianae]) and nonlinear (Weibull and Weibull + tail [ Pp. vexans and Pp. helicoides]) kinetics as identified by parameters of goodness of model fit: high R2 and low root mean square error (RMSE) values. D10 values of Pt. cinnamomi and Pt. nicotianae calculated from the rate constants ( Kmax) of the log-linear models were 5.05 ± 0.38 mJ cm−2 ( R2 = 0.95, RMSE = 0.091, Kmax = 0.49 ± 0.03) and 4.73 ± 0.33 mJ cm−2 ( R2 = 0.96, RMSE = 0.091, Kmax = 0.49 ± 0.03), respectively. The Weibull + tail model best described the inactivation of Pp. vexans ( R2 = 0.97, RMSE = 0.099) and Pp. helicoides ( R2 = 0.96, RMSE = 0.083), and the δ and Nres values were determined to be 9.88 ± 0.12 and 2.06 ± 0.06 and 11.47 ± 0.38 and 2.45 ± 0.05, respectively. These study findings can be applied to develop water disinfection systems, either alone or in combination with other methods, for effective control of pathogens in irrigation systems. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Performance assessment, through numerical simulation and experimental evaluation, of a thin-film ultraviolet reactor for the processing of fruit juices

Abstract The paper presents a numerical approach to investigate the performance of a thin-film ultraviolet reactor in treating three different fruit juices (apple, orange and pineapple) with UV-C radiation, under six flow rate conditions. Minimum, average and maximum doses were calculated for each configuration, by integrating, over time the irradiance over one thousand different streamlines. The presented approach allows for calculating the dose distribution achieved, thus assessing both the fulfilment of regulatory requirements and the uniformity of the treatment. Experimental tests were finally performed on both apple and orange juice, with a flow rate of 80 L/h. For apple juice, more than 3 Log CFU/mL reductions were obtained on Escherichia coli ATCC 11,229, while, for orange juice, a negligible reduction (0.05 Log CFU/mL) was achieved. These results, according to biodosimetry data from other studies, correspond to UV-C dose distributions that confirm those calculated.

Modeling of UV-C survival of foodborne pathogens and predicting microbial inactivation on fresh-cut ‘Tommy Atkins’ mango using CFD

Abstract Shortwave ultraviolet light (UV-C) disinfection is an emerging technology used to enhance food safety by reducing the pathogen load. Computational fluid dynamics (CFD) served as a numerical simulation tool to calculate the average radiation intensity within a disinfection chamber. The resulting CFD data was employed to estimate the UV-C inactivation kinetic parameters for Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes. Experimental procedures involved irradiating bacterial suspensions with UV-C doses ranging from 0 to 6.028 kJ/m2. The inactivation of S. Typhimurium was described using a log-linear equation, while UV-C survival curves for E. coli O157:H7 and L. monocytogenes were best fitted to Weibull model. Subsequently, the integration of CFD simulations and kinetic parameters enabled the estimation of UV-C doses approaching 6 kJ/m2 for the treatment of fresh-cut ‘Tommy Atkins’ mangoes inoculated with the mentioned microorganisms. This integrated approach partially predicted the inactivation of pathogens on the surface of mango spears.

Dose-dependent physiological effects of UV-C radiation on seashore paspalum

Positive effects of ultraviolet-C (UV–C) radiation on plants have been documented in previous literature with a focus on extending shelf life and reducing disease development. However, its effect on plant growth habits has been scarcely explored, especially in turfgrass where a compact shoot growth is a desirable trait. Seashore paspalum (Paspalum vaginatum) is a warm-season perennial turfgrass requiring low fertilizer and pesticide inputs. This project aimed to test the effects of different doses of UV-C radiation on growth and performance of seashore paspalum cv. Seastar. Here, we provide evidence of dose-dependent effects. Lower UV-C doses (6 s and 1 min daily) improved the performance of seashore paspalum, as manifested by higher tiller density, reduced clipping yields, increased chlorophyll level on selected dates as well as enhanced photosynthetic efficiency compared to control. Contrastingly, higher doses (6 min and 30 min daily) resulted in severe damage with 30-min treatment being lethal to seashore paspalum, causing marked declines in all measured parameters. This is the first time that UV-C-induced growth response was reported in turf. Conclusions drawn from this study would shed light into the effects of UV-C radiation on the growth and performance of seashore paspalum and offer exciting potential for the utilization of UV-C at non-lethal dosage in turfgrass management.

Improvement of Drought Resistance of Osteospermum ecklonis Plants as a Physiological and Biochemical Response to Low Doses of UV-C Irradiation

Osteospermum ecklonis DC. NORL. is native to South Africa and is fully adapted to the Mediterranean climate. The aim of the study was to elucidate morphological and developmental changes in O. ecklonis plants associated with drought resistance in response to low doses of UV-C. Growth responses under three levels of drought stress (NW: normal watering, MD: moderate drought stress and SD: severe drought) were recorded. The results showed that 1 kJ m−2 UV-C significantly (p < 0.05) increased resistance to water stress without affecting growth and development or damaging photosystem II. Fresh weights of the upper parts and the root system of the irradiated plants were maintained at similar levels to those of the non-irradiated control plants. Fv/Fm values in the irradiated plants ranged from 0.73 to 0.82 depending on the stress level, while in the non-irradiated plants, the values ranged from 0.69 to 0.83. Differences between UV-C irradiated and non-irradiated plants were recorded in electrolyte leakage (EL), in malondialdehyde (MDA) and in relative water content (RWC) at all drought levels. The EL percentage of the non-irradiated plants at SD was 19.7%, while in the irradiated plants, it was 17.8%. RWC rates in the irradiated plants ranged between 60.6 and 76.4%, while in the non-irradiated plants, they ranged from 54.2 to 63.6%. Superoxide dismutase (SOD) and catalase (CAT) activities increased with UV-C irradiation, suggesting that antioxidant responses were induced and protected cell membranes from lipid peroxidation and damage. The results of the present study showed that UV-C irradiation at 1 kJ m−2 alleviated the drought symptoms of O. ecklonis by reducing oxidative stress and membrane lipid peroxidation.

Investigation of antimicrobial activity of Ultraviolet B radiation and its potential to generate fructose-mediated reactive oxygen species in coconut water

We evaluated the potential antimicrobial activity and inactivation kinetics, photo-reactivation potential and ability to generate reactive oxygen species (ROS) and consequent ascorbic acid degradation in fructose enriched coconut water. UV-B caused 4.5 ± 0.19 log inactivation in E. coli K12 at 0.45 J/cm2 and inactivation kinetics followed Weibull model, compared to log-linear 4 ± 0.05 log reduction at 0.2 J/cm2 dose of UV-C. A lower extent of UV-A (360 nm) induced photo-reactivation was observed in UV-B treated samples compared to UV-C. UV-B mediated microbial inactivation was largely caused by DNA damage and impaired metabolic activity of E. coli. UV-B treatment did not cause membrane damage, or thiol oxidation. Compared to UV-C, UV-B produced lower concentration of ROS from fructose. At a dose required for 4 log reduction of E. coli K12 by UV-B, only 8% ascorbic acid degraded. These results show that UV-B is an attractive alternative to UV-C treatment. Industrial relevanceUV-C irradiation is a cost-effective measure to ensure food safety. However, for fructose-rich products fruit juices, UV-C exposure to photo-sensitive compounds like fructose generates reactive oxygen species that can deteriorate the quality of fructose-rich products. In this context, UV-B provides comparable, albeit slower, antimicrobial effect but provokes milder fructose mediated oxidative stress than UV-C. This study highlights the potential for using UV-B as an alternative to UV-C light treatment for liquid foods.

Effects of germicidal ultraviolet-C light on grape mealybug (Pseudococcus maritimus)

Germicidal ultraviolet-C light (UV–C) has been used to effectively suppress grapevine powdery mildew (Erysiphe necator). However, effects on arthropod pests that would be simultaneously exposed to UV-C during applications directed at E. necator, are poorly understood. The grape mealybug (Pseudococcus maritimus) is one such grapevine pest. We exposed mated P. maritimus adult females in a lab study to UV-C light doses of 100, 200, 500 and 1000 J/m2. UV-C was applied during darkness and was followed by an additional 4 h dark period post-treatment to enhance possible suppressive effects of UV-C. Positive (2% horticultural oil) and negative (untreated) controls were included. Adult female P. maritimus oviposition was observed two weeks after treatment, and hatching of eggs was enumerated four weeks after treatment. UV-C treatment of mated adult females, regardless of dose, did not prevent oviposition or reduce ovisac viability. In a separate lab experiment, first instar P. maritimus nymphs were similarly exposed to UV-C doses of 200 and 1000 J/m2 with and without a 4hr dark period. UV-C treatments were compared to the same positive and negative controls. Nymph mortality was assessed at 24 and 48 h after UV-C treatment. Increasing doses of UV-C treatments, followed by a dark period, had a small, but significant impact on nymph mortality relative to the untreated control. Further studies on the potential sublethal effects (e.g., fecundity or longevity) of single or multiple exposures or increased UV-C doses upon juvenile stages of P. maritimus are warranted, as longer-term and multigenerational effects of UV-C have been observed in other arthropod systems.

Cold sterilization of coconut water by membrane technology and UV-C

Coconut water contains amino acids, vitamins, antioxidants, and mineral, which are beneficial for human health. However, rapid degradation of coconut water due to the presence of protein, fat, and microbes has led to short shelf life and coconut water’s rancidity. Sterilization of coconut water by heat treatment has been proven to be effective in microorganism elimination, but results in major changes of coconut water’s sensory attributes. In this research, cold sterilization of coconut water was conducted by using ultrafiltration membrane and UV-C to preserve the sensory properties and nutritional components in coconut water. The radiation dose of UV-C and operating pressure of ultrafiltration membrane was varied to obtain the optimum operating condition. The sterilization process by UV-C did not remove fat and protein, which are the rancidity-causing components. In ultrafiltration sterilization, fat and protein can be removed by 74% and 31.37%. Superior microorganism elimination by ultrafiltration was obtained at 99.9999%, compared to that by UV-C at 90%. The ultrafiltration also retained the coconut water’s pH, total soluble solid, and flavor, while improved its clarity. At optimum operating pressure of 0.25 bar, the coconut water’s shelf life of 3 days, according to the Standar Nasional Indonesia (SNI), can be achieved.

Inhibitory effect of UV and gamma radiation for fungal biodeterioration of concrete: A short-term study for sustainable conservation

The conservation of concrete-based deteriorated heritage buildings is a big challenging issue worldwide including in India. This study focused on to prevent fungal biodeterioration in concrete using UVC and gamma radiation. M20 graded concrete cubes (5 cm × 5 cm × 5 cm) were infected with Aspergillus tamarii, which was isolated from a 200 years old historic heritage building. M20 signifies a mixture of cement, sand and aggregate (1:1.5:3), made in such a way that the concrete cube has a compressive strength of 20 N/mm2 when examined after 28 days of curing. The fungal growth appeared clearly as calcium oxalate crystals in the Scanning Electron Microscope (SEM) photographs. Several doses of UVC and gamma radiation were applied on concrete cube. The changes in concrete properties were examined after 30 days in terms of weight, compressive strength, Fourier Transform Infrared Spectroscopy (FTIR) and micro Energy Dispersive X-ray Fluorescence (EDXRF). The results exhibited that compressive strength of control (non-infected and non-irradiated), biodeteriorated (infected), UVC (625 µw/cm² × 300 s) and gamma (0.5 KGy) irradiated infected (inhibition) concrete cubes were 19.74 ± 0.46, 18.88 ± 0.43, 20.20 ± 0.34 and 19.93 ± 0.20 N/mm2 respectively whereas negligible weight losses were observed for inhibition cubes compared to biodeteriorated ones. Calcite (1400, 874 and 705 cm−1), one of the major functional band present in concrete became weak after getting infected by Aspergillus tamarii and strong for inhibition samples irradiated with the above doses. The EDXRF analysis exhibited that mass percentage of calcium ions of the biodeteriorated concrete cubes (49.88 ± 0.65%) was lower than that of UV (75.75 ± 0.16%) and gamma (70.95 ± 0.30%) irradiated infected or inhibition concrete cubes. Altogether, the efficacy of the recommended inhibitory dose of ultraviolet and gamma radiation against concrete deterioration in the field of conservation of heritage building was observed to be positive.

UV Reflectance of Spacecraft Materials and Analog Soils: Implications for Bioburden Reductions on the Undersides of Mars Rovers

AbstractThe Mars Sample Return mission architecture will utilize three spacecraft to collect, cache, recover, launch, and return to Earth a diversity of regolith and rock samples. However, no comprehensive Mars Microbial Survival (MMS) model currently exists. As an initial effort in building an MMS model, we examined the UV reflectance of 15 spacecraft materials and seven Mars analog soils within the context of the Perseverance mission. Data were used to predict the times required to achieve one lethal dose (syn., Sterility Assurance Level [SAL]; def. as a bioburden reduction of −12 logs). Results suggest that a single SAL dosage of UVC was achieved on exposed surfaces on the upper deck of Perseverance within a few hours to a few sols post‐landing at Jezero Crater. The overall average for UVC reflectance from spacecraft materials was approximately 10%. The overall UVC reflectance from Mars analog soils was measured at 1.3%. The Adaptive Caching Assembly (ACA) on Perseverance is located on the forward edge of the underbelly of the spacecraft. Modeling of the accumulated UVC dosage for the ACA yielded a prediction of reaching one SAL for downward facing surfaces at 93 sols that receive “single‐bounce” UVC photons from the local terrain. The SAL increases to 930 sols if an additional “bounce” of the solar UV irradiation is required to reach a partially protected site in the ACA hardware. The current study is the first to report the UVC reflectance from a diversity of spacecraft materials.

Applications of Germicidal Ultraviolet Light as a Tool for Fire Blight Management (Erwinia amylovora) in Apple Plantings.

Nighttime applications of germicidal UV light (UV-C) have been used to suppress several fungal diseases of plants, but less is known of UV-C's potential to suppress bacterial plant pathogens. Fire blight of apple and pear, caused by the bacterium Erwinia amylovora, is difficult to suppress using cultural practices, antibiotics, and host resistance. We therefore investigated the potential of UV-C as an additional means to manage the disease. Laboratory assays confirmed that in vitro exposure of cultures E. amylovora to UV-C at doses ranging from 0 to 400 J/m2 in the absence of visible light was more than 200% as effective as cultures exposed to visible light after the same UV-C treatments. In a 2-year orchard study, we demonstrated that with only two nighttime applications of UV-C at 200 J/m2 made at bloom resulted in an incidence of blossom blight and shoot blight equivalent to the results viewed when antibiotic and biopesticide commercial standards were applied. In vitro dose-response studies indicated consistency in pathogen response to suppressive UV-C doses, including pathogen isolates that were resistant to streptomycin. Based on these results, UV-C may be useful in managing bacterial populations with antibiotic resistance. Concurrent measurements of host growth after UV-C applications indicated that the dose required to suppress E. amylovora had no significant (P > 0.05) effects on foliar growth, shoot extension, internode length, or fruit finish but substantially reduced epiphytic populations of E. amylovora on host tissues.

Ultraviolet-C light at 222 nm has a high disinfecting spectrum in environments contaminated by infectious pathogens, including SARS-CoV-2.

Ultraviolet light (UV) acts as a powerful disinfectant and can prevent contamination of personal hygiene from various contaminated environments. The 222-nm wavelength of UV-C has a highly effective sterilization activity and is safer than 275-nm UV-C. We investigated the irradiation efficacy of 222-nm UV-C against contaminating bacteria and viruses in liquid and fabric environments. We conducted colony-forming unit assays to determine the number of viable cells and a 50% tissue culture infectious dose assay to evaluate the virus titration. A minimum dose of 27 mJ/cm2 of 222-nm UV-C was required for >95% germicidal activity for gram-negative and -positive bacteria. A 25.1 mJ/cm2 dose could ensure >95% virucidal activity against low-pathogenic avian influenza virus and severe acute respiratory syndrome coronavirus (SARS-CoV-2). In addition, this energy dose of 222-nm UV-C effectively inactivated SARS-CoV-2 variants, Delta and Omicron. These results provide valuable information on the disinfection efficiency of 222-nm UV-C in bacterial and virus-contaminated environments and can also develop into a powerful tool for individual hygiene.

Evaluating the UV-C sensitivity of Coxiella burnetii in skim milk using a bench-scale collimated beam system and comparative thermal sensitivity study by high-temperature short-time pasteurization

Introduction:Coxiella burnetii is a zoonotic Gram-negative obligate intracellular bacterial pathogen and the causative agent of query (Q) fever in humans. Contamination of milk by C. burnetii, as a consequence of livestock infection, is a significant public health concern. Effective methods to inactivate C. burnetii in milk are a critical aspect of food safety. Implementation of non-thermal UV-C processing technologies in the dairy industry can effectively preserve the sensory and nutritional quality of raw milk products while ensuring their safety, making them a viable alternative to traditional high-temperature short-time (HTST) pasteurization methods.Methods: Optical light attenuation factors, such as the absorption, scattering, and reflection by skim milk (SM) were evaluated using a spectrophotometer. SM inoculated with an avirulent strain of C. burnetii was irradiated using a collimated beam device equipped with a low-pressure UV-C 254 nm lamp at doses from 0 to 12 mJ/cm2. Optical properties were considered for the evaluation of the delivered UV-C dose. The pasteurization treatment was conducted using a lab scale HTST pasteurizer (72°C/15 s). The verification studies were conducted using Escherichia coli ATCC 25922 inoculated in a phosphate buffer (transparent fluid) and humic acid (opaque fluid). Salmonella enterica serovar Muenchen ATCC BAA 1674 inoculated in SM was tested for its suitability as a surrogate for C. burnetii, a bacterium that requires specialized equipment and expertise for experimentation.Results and Discussion: Absorption, reduced scattering coefficient, and the reflectance of SM at 254 nm were measured as 19 ± 0.3/cm, 26 ± 0.5/cm, and 10.6%, respectively. The UV-C results showed a log-linear inactivation of C. burnetii in SM with the UV-C sensitivity (D10) value of 4.1 ± 0.04 mJ/cm2. The results of HTST pasteurization revealed that C. burnetii was heat-sensitive with a D value of 1.75 min. Salmonella Muenchen showed similar UV inactivation kinetics and is, thereby, suggested as a suitable surrogate to C. burnetii for the pilot-scale UV-C processing studies of SM.

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.

Drastic Microbial Count Reduction in Soy Milk Using Continuous Short-Wave Ultraviolet Treatments in a Tubular Annular Thin Film UV-C Reactor.

Vegetative cells of Listeria monocytogenes and Escherichia coli and spores of Bacillus subtilis and Aspergillus niger were inoculated in soy milk at an initial concentration of ≈5 log CFU/mL. Inoculated and control (non-inoculated) soy milk samples were submitted to three types of treatments using a tubular annular thin film short-wave ultraviolet (UV-C) reactor with 1 mm of layer thickness. Treatments applied depended on the flow rate and the number of entries to the reactor, with UV-C doses ranging from 20 to 160 J/mL. The number of entries into the reactor tube (NET) was established as the most determining parameter for the efficiency of the UV-C treatments. Conidiospores of A. niger were reported as the most resistant, followed by B. subtilis spores, while vegetative cells were the most sensible to UV-C, with Listeria monocytogenes being more sensible than Escherichia coli. Treatments of just 80 J/mL were needed to achieve a 5 log CFU/mL reduction of L. monocytogenes while 160 J/mL was necessary to achieve a similar reduction for A. niger spores.