UV-C Treatment Research Articles

Ultraviolet-c Radiation Induced Changes on Bioactive Compounds Content, Antioxidant Capacity and Microbial Quality of Minimally Processed Molokhia (Corchorus Olitorius L.) Leaves

Minimally processed or fresh-cut leafy vegetables are very popular for consumption due to their convenience and ready-to-use properties, but they provide an ideal medium for microbial development and degradation of functional properties. Thus, this industry commonly uses chemical agents for disinfection. However, certain problems with the disinfectant agents’ usage have been raised and led to the investigation of alternative sanitization treatments. In this respect, ultraviolet (UV-C) radiation could be of interest because no residues are released and the cost is relatively low. The present study was carried out to investigate the influence of UV-C treatment on bioactive compounds content, antioxidant capacity and microbial quality of minimally processed molokhia (Corchorus olitorius L.) leaves. Data indicated that UV-C irradiation dose (11.35 kJ m−2) of molokhia leaves led to an initial increasing in bioactive compounds including total polyphenols (41.20%), carotenoids (37.41%), flavonoids (26.43%), chlorophyll (11.93%) and lutein (51.73%) in accompanying with slightly decreasing in antioxidant capacity (-11.78%) on processing day. Also, reduction in mesophilic (-11.50), psychrophilic (-18.90) and enterobacteria (-17.10%) counts was also recorded. The initial bioactive compounds and total antioxidant capacity content decreased as well as the bacterium count gradually increased during the storage period in UV-C treated samples for 9 days at 8 0C, especially after 6 days. In conclusion, data of the present study should be taken in our consideration when the UV-C radiation used as alternative to chemical agents for sanitizing minimally processed molokhia leaves and preserving their quality. How to Cite: Yousif A. Elhassaneen, Areeg A. Nour El-Deen, Amal Z. Nasef, 2023. "Ultraviolet-c Radiation Induced Changes on Bioactive Compounds Content, Antioxidant Capacity and Microbial Quality of Minimally Processed Molokhia (Corchorus Olitorius L.) Leaves." Journal of Agriculture and Crops, vol. 9, pp. 309-322.

UV-C Promotes the Accumulation of Flavane-3-ols in Juvenile Fruit of Grape through Positive Regulating VvMYBPA1.

Flavane-3-ol monomers are the precursors of proanthocyanidins (PAs), which play a crucial role in grape resistance. Previous studies showed that UV-C positively regulated leucoanthocyanidin reductase (LAR) enzyme activity to promote the accumulation of total flavane-3-ols in juvenile grape fruit, but its molecular mechanism was still unclear. In this paper, we found that the contents of flavane-3-ol monomers increased dramatically at the early development stage grape fruit after UV-C treatment, and the expression of its related transcription factor VvMYBPA1 was also enhanced significantly. The contents of (-)-epicatechin and (+)-catechin, the expression level of VvLAR1 and VvANR, and the activities of LAR and anthocyanidin reductase (ANR) were improved significantly in the VvMYBPA1 overexpressed grape leaves compared to the empty vector. Both VvMYBPA1 and VvMYC2 could interact with VvWDR1 using bimolecular fluorescence complementation (BiFC) and yeast two hybrid (Y2H). Finally, VvMYBPA1 was proven to bind with the promoters of VvLAR1 and VvANR by yeast one hybrid (Y1H). To sum up, we found that the expression of VvMYBPA1 increased in the young stage of grape fruit after UV-C treatment. VvMYBPA1 formed a trimer complex with VvMYC2 and VvWDR1 to regulate the expression of VvLAR1 and VvANR, thus positively promoting the activities of LAR and ANR enzyme, and eventually improved the accumulation of flavane-3-ols in grape fruit.

The Effect of Stress Hormones, Ultraviolet C, and Stilbene Precursors on Expression of Calcineurin B-like Protein (CBL) and CBL-Interacting Protein Kinase (CIPK) Genes in Cell Cultures and Leaves of Vitis amurensis Rupr

Calcium serves as a crucial messenger in plant stress adaptation and developmental processes. Plants encode several multigene families of calcium sensor proteins with diverse functions in plant growth and stress responses. Several studies indicated that some calcium sensors may be involved in the regulation of secondary metabolite production in plant cells. The present study aimed to investigate expression of calcineurin B-like proteins (CBL) and CBL-interacting protein kinase (CIPK) in response to conditions inducting biosynthesis of stilbenes in grapevine. We investigated CBL and CIPK gene expression in wild-growing grapevine Vitis amurensis Rupr., known as a rich stilbene source, in response to the application of stilbene biosynthesis-inducing conditions, including application of stress hormones (salicylic acid or SA, methyl jasmonate or MeJA), phenolic precursors (p-coumaric acids or CA), and ultraviolet irradiation (UV-C). The influence of these effectors on the levels of 13 VaCBL and 27 VaCIPK mRNA transcripts as well as on stilbene production was analyzed by quantitative real-time RT-PCR in the leaves and cell cultures of V. amurensis. The data revealed that VaCBL4-1 expression considerably increased after UV-C treatment in both grapevine cell cultures and leaves. The expression of VaCIPK31, 41-1, and 41-2 also increased, but this increase was mostly detected in cell cultures of V. amurensis. At the same time, expression of most VaCBL and VaCIPK genes was markedly down-regulated both in leaves and cell cultures of V. amurensis, which may indicate that the CBLs and CIPKs are involved in negative regulation of stilbene accumulation (VaCBL8, 10a-2, 10a-4, 11, 12, VaCIPK3, 9-1, 9-2, 12, 21-1, 21-2, 33, 34, 35, 36, 37, 39, 40, 41-3, 41-4). The results obtained provide new information of CBL and CIPK implication in the regulation of plant secondary metabolism in response to stress hormones, metabolite precursors, and UV-C irradiation.

The Effect of UV-C Rays and An Insect Growth Regulator on the Growth and Development of Potato Tuber Moth Phthorimaea operculella

The study aimed to control the potato tuber moth Phthorimaea operculella (Zeller) by usingInsect Growth Regulator (Match) and UV-C with a wavelength of 254 nm on adults andincomplete stages (eggs and larvae). The results indicated that (1-2) days old eggs treated byUV-C rays with different exposure times (4,8,12 and 16 min.), from a distance of 50 cm andinsect growth regulator had almost the same effect on the eggs' hatching rates. The highest nonhatchingrates of eggs that sprayed by insect growth regulator was 59.30% at a concentrationof 2 ml /L. While the highest non-hatched rates of eggs that exposed to UV-C rays was 62.20%at a 16-minute exposure period. The results also showed that of (1-2) day old eggs treated withultraviolet rays or treated with the insect growth regulator (Match) were more vulnerable thaneggs at (5-6) days old. As the proportionality was direct between the rates of eggs non-hatchingand the duration of exposure to radiation or the concentration of the insect growth regulator.The results showed that the first instar larvae were more affected than the fourth instar larvaeby both insect growth regulator and UV-C treatments, at different concentrations and exposuretimes. The highest mortality rates for first-stage larvae under the influence of growth regulatorwere 42.20% at a concentration of 2 ml/L and 52.20% under the influence of UV-C rays,exposure time of 16 min., compared with 5.33 and 8.33% in the control treatment, respectively.As for the effect of ultraviolet radiation on the adults of the potato tuber moth, the difference infertility results (number of laid eggs / female) decreased dramatically, as the number of eggs208Academic Science JournalP-ISSN: 4612-2958Volume: 19, Issue: 2Manuscript Code: 675Alaid in the control treatment was 113.00 eggs / female. The lowest number of eggs laid was23.55 eggs / female when insects were exposed to UV rays for 16 min., while the percentagesof hatching, pupation and emergence were 76.33, 68.30 and 60.30% in the control treatment,and decreased to 22.30, 18.10 and 8.00% respectively, when insect exposed to UV-C rays for16 minutes. The results indicate the possibility of using UV-C rays and the insect growthregulator (Match) of chemical pesticides to control potato tuber moth.

Synergistic effect of UV-C irradiation and high-pressure processing in reducing microbial load in “Nanglae” pineapple juice compared to conventional heat treatment

Thermal processing is widely used in juice production to ensure microbial safety and to extend juice shelf life; however, it can have an impact on quality attributes such as color and nutritional content. UV-C irradiation and high-pressure processing (HPP) are non-thermal processing methods which causes little impact on the quality of fruit juice compared to conventional heat treatment (CHT). The objective of this study was to investigate the effect of combining UV-C and HPP (UV-C + HPP) treatments on microbial loads and quality of “Nanglae” pineapple juice during cold storage at 5 ± 1°C for 91 days. The treatments were as follows: (1) no treatment; (2) conventional heat treatment (80 ± 5°C, 10 min); and (3) a combination of UV-C (3 kJ/m2) and HPP (600 MPa, 5 min) treatments. The combined treatments of UV-C and HPP reduced the numbers of viable cells of aerobic microorganisms to less than the quantification limit of 1.48 log CFU/mL and yeasts and molds to <1.18 log CFU/mL throughout the 91-day storage period. Pineapple juice treated with CHT contained yeasts and molds exceeding the quantification limit of 1.18 log CFU/mL after 63 days of storage. The UV-C + HPP treatment preserved carotenoids and protein levels comparable to those found in fresh pineapple juice over 91 days of storage, whereas the CHT significantly decreased these values. Throughout the storage period, ascorbic acid levels in the CHT were slightly lower than in the combined treatments. These results clearly demonstrate that the combination of UV-C and HPP can ensure the safety of “Nanglae” pineapple juice while also retaining bioactive compounds. Combining these two technologies could be a new approach to producing healthy and safe juices.

Combined melatonin and UV-C treatment maintains the quality of fresh-cut bamboo shoots during storage by altering microbial diversity and metabolites

The quality of fresh-cut Ma bamboo (Dendrocalamus latiflorus Munro) shoots was evaluated via physicochemical, 16S rRNA gene sequencing, and metabolomic analyses. Lactobacillaceae, Streptococcaceae, and Enterobacteriaceae were the predominant bacteria. Melatonin and UV-C treatments most inhibited Lactobacillaceae and Cyanobacteriales, respectively. Differential metabolic profiling revealed that 47 and 44 metabolites were downregulated and upregulated, respectively, in the shoots during storage. Significant metabolite accumulation, including secondary metabolite precursors related to phenylpropanoid biosynthesis (tyrosine, leucine, and phenylalanine), was detected. This corresponded to the lignin content and firmness. Melatonin and UV-C treatments increased resistance to external stress via the accumulation of fatty acids and flavonoids. UV-C irradiation upregulated 19 of 22 fatty acyls, including ethyl linoleate, ethyl palmitoleate, 2-isopropylmalic acid, and jasmonic acid, whereas melatonin treatment increased 12 of 16 flavonoids, including hildgardtene and butein 4′-arabinosyl-(1->4)-galactoside. A combined melatonin and UV-C treatment exhibited the merits of both and best maintained the quality of the shoots.

The potential of UVC decontamination to prolong shelf-life of par-baked bread.

The effect of UVC (254 nm) treatment on the mould-free shelf-life of par-baked wholemeal, rye and six-grain bread was examined. Currently, these breads are par-baked, wrapped in high-density polyethylene (HDPE)-foil and transported or stored at room temperature for a couple of days before being full-baked and sold/consumed. Generally, after five days, these breads show signs of mould spoilage. A shelf-life increase in one or more days would already offer immense economical and logistic benefits for the baker or retailer. In this study, the parameters fluence rate (irradiation intensity), fluence (UV dose), distance to the UV-lamp (DTL) and number of layers of a common wrapping HDPE-foil (20 µm) were diversified. The breads were subjected to a UVC treatment (0-2502 mJ/cm²), packed and stored at room temperature for a period of 15 days (21.5 ± 0.8 °C). Similar as for the breads, agar plates with mould spores of Aspergillus niger, Aspergillus montevidensis and Penicillium roqueforti were UVC treated (0-1664 mJ/cm²) and checked daily for visible mould growth during 15 days (25 °C). Aspergillus niger showed the strongest resistance towards UVC, a fluence of 800 mJ/cm² was needed to inhibit growth during 15 days of storage, whereas for P. roqueforti and A. montevidensis, respectively, UV levels of 291 and 133 mJ/cm² were found sufficient. Furthermore, the shelf-life of wholemeal, rye and six-grain bread can be prolonged from 5 to 6, 8 and 9 days, respectively, using 2502 mJ/cm². The effect of higher UVC dosage on shelf-life reached a maximal level and was strongly impacted by the wide spread on data of mould-free shelf-life. The main factors influencing the potential of UV decontamination were the rough bread surface, differences in DTL, the possibility of post-contamination and UV permeability of packaging materials.

Gaseous products generated from polyethylene and polyethylene terephthalate during ultraviolet irradiation: Mechanism, pathway and toxicological analyses

The generation of various degradation products from microplastics (MPs) has been confirmed under ultraviolet (UV) irradiation. The gaseous products, primarily volatile organic compounds (VOCs), are usually overlooked, leading to potential unknown risks to humans and the environment. In this study, the generation of VOCs from polyethylene (PE) and polyethylene terephthalate (PET) under UV-A (365 nm) and UV-C (254 nm) irradiation in water matrixes were compared. More than 50 different VOCs were identified. For PE, UV-A-derived VOCs mainly included alkenes and alkanes. On this basis, UV-C-derived VOCs included various oxygen-containing organics, such as alcohols, aldehydes, ketones, carboxylic acid and even lactones. For PET, both UV-A and UV-C irradiation induced the generation of alkenes, alkanes, esters, phenols, etc., and the differences between these two reactions were insignificant. Toxicological prioritization prediction revealed that these VOCs have diverse toxicological profiles. The VOCs with the highest potential toxicity were dimethyl phthalate (CAS: 131–11-3) from PE and 4-acetylbenzoate (3609-53-8) from PET. Furthermore, some alkane and alcohol products also presented high potential toxicity. The quantitative results indicated that the yield of these toxic VOCs from PE could reach 102 μg g−1 under UV-C treatment. The degradation mechanisms of MPs included direct scission by UV irradiation and indirect oxidation induced by diverse activated radicals. The former mechanism was dominant in UV-A degradation, while UV-C included both mechanisms. Both mechanisms contributed to the generation of VOCs. Generally, MPs-derived VOCs can be released from water to the air after UV irradiation, posing a potential risk to ecosystems and human beings, especially for UV-C disinfection indoors in water treatments.

Changes in phenolics and flavonoids in amaranth and soybean sprouts after UV-C treatment.

Sprouts, mainly from cereals, legumes, and some pseudo-cereals, are rich in nutrients and contain biocompounds, making them attractive for consumption. This research study aimed to develop treatments with UV-C light in soybean and amaranth sprouts and evaluate their effect on biocompounds content, compared with chlorine treatments. UV-C treatments were applied at distances of 3 and 5cm and times of 2.5, 5, 10, 15, 20, and 30min, whereas chlorine treatments were applied as immersion in solutions at 100 and 200ppm for 15min. Phenolics and flavonoid content were higher in UV-C-treated sprouts than in those treated with chlorine solutions. Ten biocompounds were identified in soybean sprouts, with increasing in apigenin C-glucoside-rhamnoside (105%), apigenin 7-O-glucosylglucoside (237%), and apigenin C-glucoside malonylated (70%) due to UV-C application (3cm, 15min); for amaranth sprouts, five biocompounds were identified, with higher contents of p-coumaroylquinic acid (17.7%) after UV-C treatment (3cm, 15min). The best treatment to achieve the highest bioactive compounds concentration was UV-C at a distance of 3cm for 15min, without significant modification on the color parameters, Hue and chroma. PRACTICAL APPLICATION: UV-C can be used to increase the biocompound content in amaranth and soybean sprouts. Nowadays, there is UV-C equipment available for industrial applications. In this way, sprouts may be maintained as fresh through this physical technology, and they will retain or increase the concentration of health-related compounds.

Performance of UV-LED and UV-C treatments for the inactivation of Escherichia coli ATCC 25922 in food model solutions: Influence of optical and physical sample characteristics

Shortwave ultraviolet light (UV-C) and ultraviolet light-emitting diodes (UV-LEDs) are emergent technologies to inactivate pathogenic and spoilage microorganisms in food. However, the effectiveness of these technologies is influenced by the optical properties of the treated food. This work aimed to evaluate the effect of the optical properties of nine model food solutions on the efficacy of UV-C (at 255 nm) and UV-LEDs (at 255, 265 or 280 nm) to inactivate E. coli ATCC 25922. Model solutions were formulated with saccharose (SC), tartrazine (TT) and xanthan gum (XG), exposed from 0 to 50 min. The microbial population was reduced after 15 min of UV-C and UV-LED treatment by >6 log CFU/mL for water and TT, and by UV-C for SC, XG, TT + SC, and (XG + TT + SC) m solutions. The inactivation data were correlated using three different models. Colored compound (TT) showed 60% degradation by UV-C compared to 3% by UV-LED at 50 min. Industrial relevanceNon-thermal treatments such as those based on ultraviolet light, UV-C, and UV-LEDs could have high industrial relevance because of their simplicity of operation and reduced by-product formation, being a friendly alternative for food processing. Understanding the effect of different optical and physicochemical properties of liquid food to be treated by UV-based technologies is mandatory for the equipment's efficient design and operation. Furthermore, the proper selection of processing conditions, such as delivered dose and processing time, allows for obtaining safe and high-quality products.

Implementation of an Environmental Cleaning Protocol in Hospital Critical Areas Using a UV-C Disinfection Robot.

Improving the cleaning and disinfection of high-touch surfaces is one of the core components of reducing healthcare-associated infections. The effectiveness of an enhanced protocol applying UV-C irradiation for terminal room disinfection between two successive patients was evaluated. Twenty high-touch surfaces in different critical areas were sampled according to ISO 14698-1, both immediately pre- and post-cleaning and disinfection standard operating protocol (SOP) and after UV-C disinfection (160 sampling sites in each condition, 480 in total). Dosimeters were applied at the sites to assess the dose emitted. A total of 64.3% (103/160) of the sampling sites tested after SOP were positive, whereas only 17.5% (28/160) were positive after UV-C. According to the national hygienic standards for health-care setting, 9.3% (15/160) resulted in being non-compliant after SOP and only 1.2% (2/160) were non-compliant after UV-C disinfection. Operation theaters was the setting that resulted in being less compliant with the standard limit (≤15 colony-forming unit/24 cm2) after SOP (12%, 14/120 sampling sites) and where the UV-C treatment showed the highest effectiveness (1.6%, 2/120). The addition of UV-C disinfection to the standard cleaning and disinfection procedure had effective results in reducing hygiene failures.

Combining the biocontrol agent Meyerozyma guilliermondii with UV-C treatment to manage postharvest gray mold on kiwifruit

Biological and physical controls as eco-friendly methods are being pursued actively to manage postharvest diseases. Postharvest gray mold is one of the major causes of significant economic losses for kiwifruit industry. Effects of the biocontrol yeast Meyerozyma guilliermondii and UV-C to control gray mold and natural infection on kiwifruit were determined in this study. M. guilliermondii or UV-C as an individual treatment inhibited gray mold and natural infection development. The combined treatment of M. guilliermondii and UV-C provided greater control efficacy than each individual treatment. The growth of M. guilliermondii in fruit wounds was not negatively impacted by UV-C. The analysis at the molecular and physiological levels showed that M. guilliermondii and UV-C alone or in combination induced defensive gene expression and total phenolics in kiwifruit. The disease resistance response induced by UV-C may partially contribute to enhancement in the biocontrol effectiveness of M. guilliermondii on kiwifruit. Taken together, these findings suggested that the hurdle technology combining biocontrol and physical controls may represent a promising method to manage gray mold on kiwifruit.

UV-C treatments extend the postharvest quality of ‘0900 Ziraat’ sweet cherries by protecting the physical and biochemical features of the fruits during the storage

Sustainable practices to extend the postharvest quality of horticultural products lead to cost-effective marketing during the prolonged season. Sweet cherries are among the most commonly consumed and traded fruits worldwide although they necessarily deteriorate after harvest. In the present study, the effects of UV-C irradiation in different application durations along with modified atmosphere packaging (MAP) on quality maintenance of the ‘0900 Ziraat’ sweet cherries were investigated for two years (2018 and 2019). The fruits were divided into six application groups; (1) storage in plastic cups control, (2) using MAP (Xtend®) packages, (3) 5 min UV-C exposure, (4) 10 min UV-C, (5) 20 min UV-C, and (6) 30 min UV-C irradiation. Treatment of UV-C was performed at a 15 cm distance using a metal cabinet equipped with 8 UV-C lamps of 15 watts, 230V/50Hz at 254 nm wavelength. The sweet cherries were stored at 1 °C and 90% RH for 35 days. At the end of the storage, the greatest weight loss occurred in the control fruits, while the lowest loss was obtained from the fruits subjected to 10 min of UV-C for both years. Also, 10 min of UV-C provided the highest firmness value for both years. This treatment also has better effects on maintaining several quality features such as pedicel chlorophyll content, titratable acidity in fruit juice, and total phenolic contents compared to the control fruits. General findings indicated that 10 min UV-C irradiation would be a beneficial practice for extending the general quality features of ‘0900 Ziraat’ sweet cherry during cold storage up to 35 d.

A multidisciplinary approach to the comparison of three contrasting treatments on both lampenflora community and underlying rock surface

Removing lampenflora, phototrophic organisms developing on rock surfaces in tourist cavities due to the artificial lighting, is a challenge for sustainable and appropriate long-term management of caves. Photosynthetic-based biofilms usually cause rock biodeterioration and an ecological imbalance in cave ecosystems. In this work, a detailed investigation of the effects of the 3 most commonly used lampenflora cleaning operations (NaClO, H2O2 and UVC) was carried out in Pertosa-Auletta Cave (Italy). The application of NaClO showed good disinfection capability over extended periods of time without causing any appreciable rock deterioration. The H2O2 treatment showed to be corrosive for the rock surfaces covered with vermiculation deposits. The chemical alteration of organic and inorganic compounds by H2O2 did not remove biomass, favoring biofilm recovery after three months of treatment. Both NaClO and H2O2 treatments were effective at removing photoautotrophs, although the bacterial phyla Proteobacteria and Bacteroidetes as well as Apicomplexa and Cercozoa among the Eukaryotes, were found to be resistant to these treatments. The UVC treatments did not show any noticeable effect on the biofilms.

A Review of the Efficacy of Ultraviolet C Irradiation for Decontamination of Pathogenic and Spoilage Microorganisms in Fruit Juices.

Ultraviolet C (UV-C, 200-280 nm) light has germicidal properties that inactivate a wide range of pathogenic and spoilage microorganisms. UV-C has been extensively studied as an alternative to thermal decontamination of fruit juices. Recent studies suggest that the efficacy of UV-C irradiation in reducing microorganisms in fruit juices is greatly dependent on the characteristics of the target microorganisms, juice matrices, and parameters of the UV-C treatment procedure, such as equipment and processing. Based on evidence from recent studies, this review describes how the characteristics of target microorganisms (e.g., type of microorganism/strain, acid adaptation, physiological states, single/composite inoculum, spore, etc.) and fruit juice matrices (e.g., UV absorbance, UV transmittance, turbidity, soluble solid content, pH, color, etc.) affect the efficacy of UV-C. We also discuss the influences on UV-C treatment efficacy of parameters, including UV-C light source, reactor conditions (e.g., continuous/batch, size, thickness, volume, diameter, outer case, configuration/arrangement), pumping/flow system conditions (e.g., sample flow rate and pattern, sample residence time, number of cycles), homogenization conditions (e.g., continuous flow/recirculation, stirring, mixing), and cleaning capability of the reactor. The collective facts indicate the immense potential of UV-C irradiation in the fruit juice industry. Existing drawbacks need to be addressed in future studies before the technique is applicable at the industrial scale.

Effect of Holder pasteurisation and UV-C irradiation on bacteriophage titres in human milk.

Human milk is the optimal nutrition source for infants and contains a complex mix of bioactive compounds and microorganisms. When unavailable, pasteurised donor milk may be provided, particularly to preterm infants. Holder pasteurisation (HP) is typically implemented in human milk banks to prevent pathogen transmission. Given the impact of heat on milk bioactives, ultraviolet-C irradiation (UV-C) is an alternative being explored and has demonstrated effective bactericidal activity. In addition to bacteria, milk contains viruses including primarily bacteriophages (phages) and which likely influence the developing bacterial microbiome of infants. However, the effect of pasteurisation on human milk phages is unknown. This study assessed the effect of HP and UV-C on titres of exogenous bacteriophages inoculated into human milk. Ten donor human milk samples were tested in parallel with water controls. Milk samples or water controls were inoculated to a final concentration of 1× 104 PFU/mL (±1 log) each of a thermotolerant Escherichia coli phage (T4) and a thermosensitive Staphylococcus aureus phage (BYJ20) and subjected to HP and UV-C treatments. UV-C inactivated both phages within milk and water controls, however, HP was ineffective against the thermotolerant T4 phages. Initial data suggests that UV-C treatment may eliminate phage with potential to affect preterm infant gut colonization. Further studies should extend this to other phages.

UV-C treatment: A non-thermal inactivation method for microbiological stabilisation of must and wine

UV-C treatment is discussed as an effective and efficient method to inactivate harmful microorganisms in wine and other viticultural products. In comparison to other stabilisation techniques, the application of UV-C is thought to be beneficial to reduce energy costs and to minimize SO2 addition. The object of this work was to determine the lethal UV-C dose for harmful microorganisms such as Brettanomyces bruxellensis and Acetobacter aceti. The concept of 5-log inactivation was applied and the Weibull model was used to compare different microbial and wine parameters. Microbial relevant UV-C doses and 2-fold overdose treatments and how they affected chemical and sensory changes of wine were investigated. Riesling and Pinot noir wine, which have different absorbance at 254 nm, were individually inoculated with microorganisms at different inoculation numbers. The results showed that the Weibull model is appropriate to predict the lethal UV-C dose. Already at microbially relevant doses, UV-C treatment can lead to significant changes in the colour and concentration of aroma compounds in white wine. Higher concentrations of 2-aminoacetophenone were found with increasing UV-C doses. Hence, UV-C overdosing can cause the “atypical ageing” off-flavour in wine. However, microbially relevant UV-C doses change the sensory properties of wine more towards a typical ageing character.

Effect of UV-C followed by storage on the fungal growth and aflatoxins content and storability characteristics of sesame (Sesamum indicum) seeds

BackgroundUV-C has been suggested as an alternative technology in controlling food spoilage by primary and secondary pests. Its effects on the storability characteristics of sesame seeds during storage were evaluated. MethodsThe UV-C (0, 2.5, 5.0 and 10 kJ m−2) was applied to explore its Effect on the fungal growth, aflatoxin content, water activity (aw), colour and free fatty acid content (FFA) of sesame seeds. ResultsApplying the UV-C caused a significant reduction in the fungal growth, aw, and the lightness (L* value) of sesame seeds in fresh and stored samples. However, significant increases (p < 0.05) in a* and b* values and the FFA of the sesame seeds were observed. Interestingly, the aflatoxins were not detected in the UVC-treated seeds even after storage for 12 months. The Partial Least Squares regression (PLS) analysis indicated that the application of 5.0 kJ m−2 followed by six months of storage reveals the greatest valid dose for UV-C treatments of sesame seeds. ConclusionUV-C treatment potentially shows effective quarantine security as an alternative method to chemical disinfection procedures to prolong the shelf life and improve the storability characteristics of sesame seeds.

Application of UV-C irradiation prevented a severe outbreak of proliferative kidney disease in rainbow trout aquaculture.

There is an urgent need to establish protocols on how to protect salmonids in aquaculture from outbreaks of proliferative kidney disease (PKD). For this purpose, systems for a continuous application of peracetic acid (PAA, 0.1 mg l-1) and of ultraviolet C light (UV-C, 323.5-158.6 mW s cm-2) were installed in the inlet of raceway-channels within a sub-unit of a commercial rainbow trout Oncorhynchus mykiss farm. After 127 d of rearing, a fish health examination was conducted. Fish in the control and PAA treatment groups showed signs of PKD. In contrast, fish in the UV-C treatment group showed almost no signs of disease based on clinical examinations and necropsy. This observation indicates that UV-C irradiation could be a promising tool to protect fish from PKD in the future.

Effectiveness of the Field Application of UV-C for Cucumber Downy Mildew Control

There is growing interest in the application of ultraviolet (UV-C) energy to control crop pathogens. In the present study, the efficacies of UV-C treatments for controlling cucumber downy mildew (Pseudoperonospora cubensis) were investigated on a commercial farm in eastern Massachusetts, USA. Controlled doses of UV-C, delivered by a tractor-mounted array of sources, between 120 and 480 J·m-2 were applied and compared to conventional fungicide treatments as well as to untreated controls, for each of two consecutive years (2020 and 2021). Visual assessments of foliar disease severity in the trial plots were made several times from planting through the end of productive life. In contrast to the successful control of powdery mildew, the UV-C treatments for controlling cucumber downy mildew were not as successful as conventional fungicides. None of the UV-C treatments affected the overall progression rate of downy mildew once the disease became apparent, although disease onset was delayed slightly compared to untreated controls. This delay may have been due to UV-C induced resistance to infection by the host. Unlike powdery mildews, downy mildew spores from P. cubensis are darkly pigmented, possibly decreasing the efficacy of the UV-C treatments for controlling the disease. DM spores may also be only susceptible to UV exposure prior to encysting in the leaves of the host, thereby perhaps limiting the window of opportunity when UV-C treatments can be effective. Although not the primary focus of this study, the use of reflective mulch appeared to delay disease onset relative to black mulch in fields with significant sunlight exposure, perhaps due to lowering plant stress by maintaining a lower soil temperature.