Antimicrobial activity of gaseous chlorine dioxide against Aspergillus flavus on green coffee beans

Generation, mechanisms, kinetics, and effects of gaseous chlorine dioxide in food preservation

Food preservation is a critical issue in ensuring food safety and quality. Growing concern around industrial pollution of food and demand for environmentally sustainable food has led to increased interest in developing effective and eco-friendly preservation techniques. Gaseous ClO2 has gained attention for its strong oxidizing properties, high efficacy in microorganism inactivation, and potential for preserving the attributes and nutritional quality of fresh food while avoiding the formation of toxic byproducts or unacceptable levels of residues. However, the widespread use of gaseous ClO2 in the food industry is limited by several challenges. These include large-scale generation, high cost and environmental considerations, a lack of understanding of its mechanism of action, and the need for mathematical models to predict inactivation kinetics. This review aims to provide an overview of the up-to-date research and application of gaseous ClO2 . It covers preparation methods, preservation mechanisms, and kinetic models that predict the sterilizing efficacy of gaseous ClO2 under different conditions. The impacts of gaseous ClO2 on the quality attributes of fresh produce and low-moisture foods, such as seeds, sprouts, and spices, are also summarized. Overall, gaseous ClO2 is a promising preservation approach, and future studies are needed to address the challenges in large-scale generation and environmental considerations and to develop standardized protocols and databases for safe and effective use in the food industry.

Bactericidal Mechanisms of Chlorine Dioxide against Beta-Hemolytic Streptococcus CMCC 32210

Chlorine dioxide is a globally recognized green and efficient disinfectant. This study aims to investigate the bactericidal mechanism of chlorine dioxide using beta-hemolytic Streptococcus (BHS) CMCC 32210 as a representative strain. BHS was exposed to chlorine dioxide, the minimum bactericidal concentration (MBC) values of chlorine dioxide against BHS were determined by the checkerboard method in preparation for subsequent tests. Cell morphology was observed using electron microscopy. Protein content leakage, adenosine triphosphatase (ATPase) activity, and lipid peroxidation were determined by kits, and DNA damage was determined using agar gel electrophoresis. The concentration of chlorine dioxide during disinfection showed a linear relationship with the concentration of BHS. Scanning electron microscopy (SEM) results showed that chlorine dioxide caused significant damage to the cell walls of BHS at a concentration of 50 mg/L, but had no significant effect on Streptococcus exposed to different exposure times. Furthermore, the extracellular protein concentration increased with increasing chlorine dioxide concentration, while the total protein content remained unchanged. The activities of Na+/K+-ATPase and Ca2+/Mg2+-ATPase decreased with increasing chlorine dioxide concentration. Chlorine dioxide treatment led to significant lipid peroxidation and DNA degradation in BHS. Leakage of intracellular components indicated that chlorine dioxide damaged the cell membrane of BHS. Chlorine dioxide exposure resulted in oxidative damage to lipids and proteins, which negatively impacted the cell wall and membrane of Streptococcus. This caused increased permeability and inactivation of key enzymes (Na+/K+-ATPase and Ca2+/Mg2+-ATPase) involved in respiratory metabolism, ultimately leading to DNA degradation and bacterial death due to either content leakage or metabolic failure.

Development of chlorine dioxide sustained-release device using carboxymethyl cellulose-polyvinyl alcohol-β-cyclodextrin ternary hydrogel and a new sustained-release kinetic model

Owing to unique physiochemical and biological properties as well as the ability to be combined with a wide variety of materials for both biocompatibility and hydrophilia, carboxymethyl cellulose (CMC) is an excellent choice as a carrier. Loading Chlorine dioxide (ClO₂) into biodegradable carrier for its good disinfection performance and high safety factors has attracted significantattention. Therefore, in this study, we used ClO₂ as a model drug, and a sustained-ClO₂-gas-release gel was developed from degradable materials, such as carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and β-cyclodextrin (βCD), through a simple and benign crosslinking strategy. Notably, the gel had sustained-release property in a wide temperature range of 4-35 ℃ and released ClO₂ gas effectively for more than 30 days. Furthermore, a loss factor was proposed based on the incomplete release of the drug in the sustained release process to a chieve a good fit with the gas diffusion process. A new diffusion model was designed based on the Korsmeyer-Peppas model, and an excellent fit was obtained. This sustained-ClO₂-gas-release gel provides theoretical and technical guidance for the development of sustained-disinfectant-release agents for use in space and offers new insights into the sustained release model of skeleton-soluble hydrogels.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10570-023-05070-6.

Conventional and non-conventional disinfection methods to prevent microbial contamination in minimally processed fruits and vegetables

Pandemic COVID-19 warned the importance of preparing the immune system to prevent diseases. Therefore, consuming fresh fruits and vegetables is essential for a healthy and balanced diet due to their diverse compositions of vitamins, minerals, fiber, and bioactive compounds. However, these fresh products grew close to manure and irrigation water and are harvested with equipment or by hand, representing a high risk of microbial, physical, and chemical contamination. The handling of fruits and vegetables exposed them to various wet surfaces of equipment and utensils, an ideal environment for biofilm formation and a potential risk for microbial contamination and foodborne illnesses. In this sense, this review presents an overview of the main problems associated with microbial contamination and the several chemicals, physical, and biological disinfection methods concerning their ability to avoid food contamination. This work has discussed using chemical products such as chlorine compounds, peroxyacetic acid, and quaternary ammonium compounds. Moreover, newer techniques including ozone, electrolyzed water, ultraviolet light, ultrasound, high hydrostatic pressure, cold plasma technology, and microbial surfactants have also been illustrated here. Finally, future trends in disinfection with a sustainable approach such as combined methods were also described. Therefore, the fruit and vegetable industries can be informed about their main microbial risks to establish optimal and efficient procedures to ensure food safety.

Effect of Gaseous Chlorine Dioxide Treatment on the Quality Characteristics of Buckwheat-Based Composite Flour and Storage Stability of Fresh Noodles

In this study, the effects of gaseous chlorine dioxide treatment on the physicochemical properties of buckwheat-based composited flour (buckwheat-wheat-gluten) and shelf-life of fresh buckwheat noodles (FBNs), as well as the textural qualities and sensory properties of noodles were investigated. Chlorine dioxide treatment significantly reduced the total plate count (TPC) and the total flavonoids content in the mixed flour (p < 0.05), but the whiteness, development time and stability time were all increased. During storage, the microbial growth and darkening rate of FBNs made from chlorine dioxide treated buckwheat-based composite flour (CDBF) were delayed significantly, slowing the deterioration and improving storage stability of buckwheat noodles. In addition, chlorine dioxide treatment had no apparent adverse effect on the cooking loss and sensory characteristics during noodle storage. This finding would provide a new concept for the production of “low bacterial buckwheat-based flour” and have important consequences for the application of gaseous chlorine dioxide in food industry.

Antimicrobial activity of ClO2 gas against Salmonella Enteritidis on almonds

Nuts, including almonds, are occasionally contaminated with Salmonella spp. In this study, we used chlorine dioxide (ClO₂) gas to inactivate S. enterica subsp. Enterica serovar Enteritidis on almonds. Almonds inoculated with a single strain of S. Enteritidis (8.95 log cfu/mL) were exposed to ClO₂ gas generated from 1.0 or 1.5 mL ClO₂ solution in a sealed container at 50 or 60 °C (43% relative humidity) for up to 10 h. The concentration of ClO₂ gas peaked at 354-510 and 750-786 ppm within 0.5 h upon deposition of 1.0 and 1.5 mL of aqueous ClO₂, respectively, and gradually decreased thereafter. Population of S. Enteritidis on almonds treated at 50 °C decreased to 1.70-2.32 log cfu/sample within 1 h of exposure to ClO₂ gas and decreased to below the detection limit (1.7 log cfu/sample) at all ClO₂ concentrations after 8 h. At 60 °C, the microbial population fell below the detection limit within 1 h, regardless of the volume of ClO₂ solution supplied. Microbial survival on almonds treated with ClO₂ gas and stored at 12 or 25 °C was observed for up to 8 weeks and the organism was not recovered from the almonds treated for 10 h and stored at 12 °C for 2-8 weeks. The lightness (L value) and redness (a value) of almonds treated for 10 h were not changed by ClO₂ gas treatment, but yellowness (b value) increased. Results showed that Salmonella on almonds was successfully inactivated by ClO₂ gas treatment and the microbial survival did not occur during storage.

Chlorine Dioxide Controls Green Mold Caused by Penicillium digitatum in Citrus Fruits and the Mechanism Involved

Green mold caused by Penicillium digitatum is the main postharvest disease in citrus fruits. The goal of this study is to evaluate the antifungal activity of chlorine dioxide (ClO₂) against P. digitatum both in vivo and in vitro and to elucidate the underlying mechanism using flow cytometry and scanning electron microscopy. The results showed that 200-1800 mg/L of ClO₂ significantly inhibited the incidence of green mold on kumquats, mandarins, Peru's oranges, and grapefruits caused by P. digitatum. Additionally, 200 mg/L of ClO₂ significantly induced cell apoptosis of P. digitatum by increasing the fluorescence intensity of the mitochondrial membrane potential from 118 to 1225 and decreased the living cell rate from 96.8 to 6.1%. Further study demonstrated that the content of malondialdehyde and nucleic acid leakage (OD₂₆₀) of P. digitatum markedly increased, and the mycelial morphology was seriously damaged with increased ClO₂ concentration. These results indicated that ClO₂ could inhibit fungal growth by destroying the membrane integrity of P. digitatum, and the use of ClO₂ may be an alternative strategy to control green mold in postharvest citrus fruits.

Efficacy of volatile compounds from Streptomyces philanthi RL-1-178 as a biofumigant for controlling growth and aflatoxin production of the two aflatoxin-producing fungi on stored soybean seeds

AIMS

This study aimed to apply the volatile organic compounds from Streptomyces philanthi RL-1-178 (VOCs RL-1-178) as a fumigant to protect soybean seeds against the two aflatoxin-producing fungi in stored soybean seeds.

METHODS AND RESULTS

The antifungal bioassay tests on potato dextrose agar (PDA) dishes showed that 30 g l-1 wheat seed inoculum of S. philanthi RL-1-178 exhibited total (100%) inhibition on Aspergillus parasiticus TISTR 3276 and Aspergillus flavus PSRDC-4. Identification of the VOCs RL-1-178 using GC-MS revealed 39 compounds with the most abundant substances being geosmin (13·75%) followed by l-linalool (13·55%), 2-mercaptoethanol (9·71%) and heneicosane (5·96%). Comparison on the efficacy of the VOCs RL-1-178 (at 30 g l-1 wheat seed culture) and their four major components (100 µl l-1 each) on the suppression of the two aflatoxin-producing fungi on PDA plates revealed that the VOCs RL-1-178 as well as geosmin, l-linalool and 2-mercaptoethanol completely inhibited (100%) mycelial growth while heneicosane showed only 70·7% inhibition. Use of the VOCs RL-1-178 (30 g l-1 ) as a biofumigant on stored soybean seeds resulted in complete protection (100%) against the infection as well as complete inhibition on production of aflatoxin (B1 , B2 and G2 ) (analysed by HPLC) by the two aflatoxin-producing fungi.

CONCLUSIONS

The VOCs RL-1-178 displayed strong inhibitory effects on A. parasiticus TISTR 3276 and A. flavus PSRDC-4 as well as inhibited aflatoxin (B1 , B2 and G2 ) production.

SIGNIFICANCE AND IMPACT OF THE STUDY

These findings suggest that the VOCs RL-1-178 can be applied as a biofumigant to control the two aflatoxin-producing fungi on stored seeds products.

Preparation of Coated Corrugated Box for Controlled-Release of Chlorine Dioxide and Its Application in Strawberry Preservation

Chlorine dioxide (ClO2) has received great attention as a nontoxic and efficient antimicrobial agent for the preservation of fresh fruits and vegetables. A novel two-layer coated corrugated box was developed to release gaseous ClO2 under the trigger of moisture in this study. The inner surface of the box was firstly coated with a mixture of polyvinyl alcohol-NaClO2-diatomite and then with chitosan acetic acid solution. Results showed that ClO2 was successfully released under high humidity due to the reaction of NaClO2, water vapor and acid. The concentration of released ClO2 increased with the increasing NaClO2 content in the coating, while the addition of diatomite stabilized and extended the release. To evaluate the preservation effect, strawberries were packed in the coated box and stored at room temperature. Compared with the control, the decay rate and weight loss of the strawberries packed in the coated box (9 g/L NaClO2) were reduced up to 21.88% and 6.84%, respectively. The surface color, firmness and nutrients content were also better maintained. Therefore, this coated corrugated box with the capability to release ClO2 under the trigger of moisture has great potential to be applied as an antimicrobial packaging for fresh fruits and vegetables.