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Controlled-release of Chlorine Dioxide in a Perforated Packaging System to Extend the Storage Life and Improve the Safety of Grape Tomatoes

A controlled-release chlorine dioxide (ClO2) pouch was developed by sealing a slurry form of ClO2 into semipermeable polymer film; the release properties ...

USDA, ARS, USHRL

Chitosan coating plus different essential oils was developed and applied to fresh blueberries in order to find more natural treatments to preserve fresh fruit quality and safety during postharvest storage. Studies were 1st performed in vitro where wild-type Escherichia coli and Penicillium digitatum were grown in suitable media, and then subjected to 6 essential oils. Three compounds, carvacrol (CAR), cinnamaldehyde (CIN), and trans-cinnamaldehyde (ECIN) had high antimicrobial capacity and were selected for an in vivo study for postharvest storage of blueberries. The selected essential oils, 0.5% each, were added into a chitosan solution and coated on fresh blueberries. After storage at 5, 10, and 20 °C for various days, fruit firmness and microbial populations were evaluated. The chitosan coating substantially decreased bacteria and yeasts/molds on the fruit, and all 3 essential oils added to the antimicrobial activities. Further dosage experiments showed that the antimicrobial activity remained even when lowering CAR concentration to 0.1% and ECIN to 0.2%. Chitosan, CAR, and ECIN also maintained fruit firmness. Our results suggest that chitosan coatings containing essential oils are effective in extending the shelf life of fresh blueberries.

Effects of chitosan-essential oil coatings on safety and quality of fresh blueberries.

The effect of chlorine dioxide (ClO2) gas on the safety and quality of blueberries was studied. In vitro studies revealed that both ClO2 gas fumigation and ClO2 direct contact in water killed food pathogen bacterium Escherichia coli and fruit decay pathogen fungus Colletotrichum acutatum. In vivo studies were conducted using noninoculated berries and berries inoculated with postharvest decay and foodborne pathogens. Berries were inoculated with either E. coli (5.2 log CFU/g) or C. acutatum (3.9 log CFU/g). Inoculated fruit were dried for 2 h at room temperature in a climate-controlled laboratory and packed in perforated commercial clamshells, with or without ClO2 pads, and stored at 10°C for up to 9 days. The effects of ClO2 on microbial populations and fruit firmness were monitored during storage. In the inoculation experiment, treatment with ClO2 reduced populations of E. coli and C. acutatum by 2.2 to 3.3 and 1.3 to 2.0 log CFU/g, respectively. For the noninoculated blueberries, the initial total aerobic bacteria count and the yeast and mold count were 4.2 and 4.1 log CFU/g, respectively. ClO2 treatment reduced total aerobic bacteria count and yeast and mold count by 1.5 to 1.8 and 1.3 to 1.7 log CFU/g, respectively. The firmness of both inoculated and noninoculated blueberries was maintained by ClO2 treatment. Thus, controlled-release ClO2 gas fumigation technology shows promise as an effective and practical antimicrobial agent in commercial clamshell packaging of blueberry and other fruits.

Antimicrobial activity of controlled-release chlorine dioxide gas on fresh blueberries.

Chitosan films incorporated with various concentrations of the complex of β-cyclodextrin and essential oils (β-CD/EO) were prepared and investigated for antimicrobial, mechanical, and physical properties. Four bacterial strains that commonly contaminate food products were chosen as target bacteria to evaluate the antimicrobial activity of the prepared films. The incorporation of β-CD/EO significantly increased the antimicrobial activities of the chitosan films against Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, and Listeria monocytogenes. It was also found that tensile strength (TS) of chitosan film was significantly increased with the incorporation of the β-cyclodextrin and 0.75% essential oils complex. The elongation at break (EB) decreased with the increasing concentrations of essential oils. Inclusion of the complex of β-cyclodextrin and 0.25% essential oils also significantly decreased water vapor permeability (WVP) of chitosan films. Our results suggest that chitosan films containing β-CD/EO could be used as active food-packaging material.

Antimicrobial and mechanical properties of β-cyclodextrin inclusion with essential oils in chitosan films.

The sponge of Clathria cervicornis is commonly used in traditional medicine. This study aims to identify the active compound in C. cervicornis and to evaluate its antimicrobial activity. The purified active compound was determined to be crambescidin 800 and was found to be highly active against Acinetobacter baumannii (minimal inhibitory concentration, MIC=2 μg/ml), Klebsiella pneumoniae (MIC=1 μg/ml) and Pseudomonas aeruginosa (MIC=1 μg/ml). A potent antimicrobial compound, crambescidin 800, was isolated in Clathria cervicornis. It is extremely active against three common pathogenic bacteria.

Christopher Ference

USDA, ARS, USHRL

Controlled-release of Chlorine Dioxide in a Perforated Packaging System to Extend the Storage Life and Improve the Safety of Grape Tomatoes