Synergistic effect of the combined treatment with gamma irradiation and sodium dichloroisocyanurate to control gray mold (Botrytis cinerea) on paprika

Disinfection of fungus using X-ray irradiation for the preservation of contaminated organic artifacts of traditional heritage

In disaster situations such as tsunamis, floods, and typhoons, fungal contamination can significantly intensify within 48 h of submersion, rapidly spreading and damaging the value and structural integrity of organic cultural heritage artifacts. Consequently, the application of radiation-based disinfection has been increasingly studied as an effective method for prompt and reliable treatment. In most cases, the fungal species were successfully eradicated at a radiation dose of 5 kGy (gamma rays). Nevertheless, certain fungal strains demonstrated high resistance and survived even at doses ranging from 10 to 15 kGy, making disinfection more challenging. Notably, differences in threshold disinfection doses between gamma rays and electron beams (E-beams) have been reported. Therefore, this study investigated the threshold dose of X-ray radiation required to disinfect representative fungi that damage organic cultural heritage artifacts, including Epicoccum nigrum (high radiation resistance), Cladosporium cladosporioides (moderate resistance), and Aspergillus niger (common resistance). E. nigrum was effectively controlled at a dose of 12.5 kGy, while C. cladosporioides was controlled at 7.5 kGy and A. niger was controlled within the 5 kGy range. The results of this study suggest that at least 12.5 kGy of X-ray radiation should be used to preserve waterlogged traditional Korean art pieces after flooding or other water disasters.

Effect of sodium dichloroisocyanurate treatment on enhancing the biodegradability of waste-activated sludge anaerobic fermentation

In the present study, a novel oxidant (sodium dichloroisocyanurate, NaCl₂(NCO)₃; SDIC) combined with microorganisms was employed to achieve a higher performance of waste-activated sludge (WAS) anaerobic fermentation. Four concentrations of SDIC (0, 0.3, 0.6, and 1.0 mg SDIC/mg SS) were studied in WAS fermentation systems. The results showed that the release of proteins and polysaccharides was enhanced by the addition of SDIC with values of 1002.25 mg COD/L and 680.25 mg COD/L, respectively, and these values increased 14.46-18.07 times (proteins) and 3.74-7.40 times (polysaccharides) compared with that of the blank test. Additionally, the short-chain fatty acids also increased 2.24 times. The rate of extraction of organic substances from the sludge increased from 3.03% to 33.33%. Furthermore, the fermented sludge with the SDIC treatment had higher hydrolytic acidification efficiencies for bovine serum albumin and glucose, increasing from 4.558% to 9.91% and 2.976%-6.764%, respectively. However, SDIC treatment of the conventional fermented sludge resulted in lower hydrolytic acidification efficiencies with values of 4.978%-1.781% and 3.334%-0.582%, respectively. Biological enzyme analysis also showed that SDIC enhanced α-glucosidase and protease activity but inhibited dehydrogenase, alkaline phosphatase, and acid phosphatase activity. Proteobacteria and Comamonas were the main microbial communities observed in the WAS anaerobic fermentation.

Critical Assessment of Mycotoxins in Beverages and Their Control Measures

Mycotoxins are secondary metabolites of filamentous fungi that contaminate food products such as fruits, vegetables, cereals, beverages, and other agricultural commodities. Their occurrence in the food chain, especially in beverages, can pose a serious risk to human health, due to their toxicity, even at low concentrations. Mycotoxins, such as aflatoxins (AFs), ochratoxin A (OTA), patulin (PAT), fumonisins (FBs), trichothecenes (TCs), zearalenone (ZEN), and the alternaria toxins including alternariol, altenuene, and alternariol methyl ether have largely been identified in fruits and their derived products, such as beverages and drinks. The presence of mycotoxins in beverages is of high concern in some cases due to their levels being higher than the limits set by regulations. This review aims to summarize the toxicity of the major mycotoxins that occur in beverages, the methods available for their detection and quantification, and the strategies for their control. In addition, some novel techniques for controlling mycotoxins in the postharvest stage are highlighted.

Sodium dichloroisocyanurate delays ripening and senescence of banana fruit during storage

Banana as a typical climacteric fruit soften rapidly, resulting in a very short shelf life after harvest. Sodium dichloroisocyanurate (NaDCC) is reported to be an effectively antibacterial compound. Here, we investigated the effects of NaDCC on ripening and senescence of harvested banana fruit at physiological and molecular levels. Application of 200 mg L⁻¹ NaDCC solution effectively inhibited the ripening and senescence of banana fruit after harvest. NaDCC treatment reduced greatly ethylene production rate and expressions of genes encoding 1-aminocyclopropane-1-carboxylate synthetase, 1-aminocyclopropane-1-carboxylate oxidase, ethylene-responsive transcription factor and EIN3-binding F-box protein. Meanwhile, NaDCC treatment down-regulated markedly the expressions of xyloglucan endotransglucosylase/hydrolase and pectinesterase genes. Furthermore, NaDCC treatment affected significantly the accumulation of ripening-related primary metabolites such as sugars and organic acids. Additionally, NaDCC treatment decreased the production of hydroxyl radical and increased 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity, reducing power and hydroxyl radical scavenging activity. In conclusion, NaDCC delayed effectively the ripening and senescence of harvested banana fruit via the reduced ethylene effect and enhanced antioxidant activity.

Postharvest Control of Botrytis cinerea and Monilinia fructigena in Apples by Gamma Irradiation Combined with Fumigation

To extend the shelf life of apples in South Korea, we evaluated the effect of gamma irradiation alone or gamma irradiation combined with fumigation on the control of postharvest decay caused by Botrytis cinerea and Monilinia fructigena. An irradiation dose of 1.0 kGy caused the maximal inhibition of B. cinerea and M. fructigena spore germination. The gamma irradiation dose required to reduce the spore germination by 90% was 0.76 and 0.78 kGy for B. cinerea and M. fructigena, respectively. Inhibition of conidial germination of both fungal pathogens occurred at a greater level at the doses of 0.2 to 1.0 kGy compared with the nontreated control; 0.2 kGy caused 90.5 and 73.9% inhibition of B. cinerea and M. fructigena, respectively. Treatment in vitro with the ecofriendly fumigant ethanedinitrile had a greater effect compared with the nontreated control. The in vitro antifungal effects of the gamma irradiation and fumigation treatments allowed us to further study the effects of the combined treatments. Interestingly, when irradiation was combined with fumigation, the percentage of disease inhibition increased more at lower (<0.4 kGy) than at higher doses of irradiation, suggesting that the combined treatments reduced the necessary irradiation dose in phytosanitary irradiation processing under storage conditions.

Control of Postharvest Bacterial Soft Rot by Gamma Irradiation and its Potential Modes of Action

Gamma irradiation was evaluated for its in vitro and in vivo antibacterial activity against a postharvest bacterial pathogen, Erwinia carotovora subsp. carotovora (Ecc). Gamma irradiation in a bacteria cell suspension resulted in a dramatic reduction of the viable counts as well as an increase in the amounts of DNA and protein released from the cells. Gamma irradiation showed complete inactivation of Ecc, especially at a dose of 0.6 kGy. In addition, scanning electron microscopy of irradiated cells revealed severe damage on the surface of most bacterial cells. Along with the morphological changes of cells by gamma irradiation, it also affected the membrane integrity in a dose-dependent manner. The mechanisms by which the gamma irradiation decreased the bacterial soft rot can be directly associated with the disruption of the cell membrane of the bacterial pathogen, along with DNA fragmentation, results in dose-dependent cell inactivation. These findings suggest that gamma irradiation has potential as an antibacterial approach to reduce the severity of the soft rot of paprika.

Effect of X-irradiation on Citrus Canker Pathogen Xanthomonas citri subsp. citri of Satsuma Mandarin Fruits

Citrus canker caused by Xanthomonas citri subsp. citri (Xcc) is one of the most important bacterial diseases of citrus. Because citrus canker is not found in many countries including European Union and Australia, Xcc is strictly regulated in order to prevent its spread. In this study, the effects of X-irradiation on Xcc growth either in the suspension or on the surface of citrus fruits were investigated. The suspension containing 1×10(7) cfu/ml of Xcc was irradiated with different absorbed doses of X-irradiation ranging from 50 to 400 Gy. The results showed that Xcc was fully dead at 400 Gy of X-irradiation. To determine the effect of X-irradiation on quarantine, the Xcc-inoculated citrus fruits were irradiated with different X-ray doses at which Xcc was completely inhibited by an irradiation dose of 250 Gy. The D10 value for Xcc on citrus fruits was found to be 97 Gy, indicating the possibility of direct application on citrus quarantine without any side sterilizer. Beside, presence of Xcc on the surface of asymptomatic citrus fruits obtained from citrus canker-infected orchards was noted. It indicated that the exporting citrus fruits need any treatment so that Xcc on the citrus fruits should be completely eliminated. Based on these results, ionizing radiation can be considered as an alternative method of eradicating Xcc for export of citrus fruits.