Combination of aerosolized curcumin and UV-A light for the inactivation of bacteria on fresh produce surfaces.

There is a critical unmet need to improve microbial safety of fresh fruits and vegetables. Current sanitation approaches cannot achieve >2 log inactivation of bacteria on fresh produce. Thus, there is a need to develop antimicrobial strategies that can consistently achieve >2 logs of bacterial inactivation on the surface of diverse fresh produce. Furthermore it is highly desired that these antimicrobial strategies have reduced environmental impact and are clean label solutions for food products. In this study, we evaluated the combination of curcumin and UV-A light radiation for the inactivation of inoculated E. coli O157:H7 and L. innocua bacterial cells on the surface of spinach, lettuce and tomatoes. Curcumin was deposited on the surface of fresh produce by either aerosolization or conventional spray-atomization methods before exposing the contaminated produce to UV-A light for 10 min (total light fluence of 20.4 kJ m-2). Results showed that the proposed combination of aerosolized or sprayed curcumin and UV-A light radiation can reduce the initial Escherichia coli O157:H7 and Listeria innocua load from 6 log CFU cm-2 to approximately 3 log CFU cm-2 on spinach, lettuce and tomato surfaces. Furthermore, there was no significant difference in bacterial reduction between the different types of inoculated fresh produce surfaces (P > .05). Interestingly, subsequent curcumin deposition and UV-A light exposure cycles were not able to further reduce the bacterial load below the observed threshold of approximately 3 log CFU cm-2. Lastly, the combination of aerosolized curcumin and UV-A light radiation did not affect the color or the texture of the treated fresh produce samples. The findings described in this study illustrate the potential of applying aerosolized or sprayed curcumin under UV-A light illumination to improve microbial safety of fresh produce products.

On mechanism behind UV-A light enhanced antibacterial activity of gallic acid and propyl gallate against Escherichia coli O157:H7.

Possible mechanisms behind the enhanced antimicrobial activity of gallic acid (GA) and its ester propyl gallate (PG) in the presence of UV-A light against Escherichia coli O157:H7 were investigated. GA by itself is a mild antimicrobial and has a pro-oxidant ability. We found that the presence of UV-A light increases the uptake of GA by the bacteria. Once GA is internalized, the interaction between GA and UV-A induces intracellular ROS formation, leading to oxidative damage. Concurrently, GA + UV-A also inhibits the activity of superoxide dismutase (SOD), magnifying the imbalance of redox status of E. coli O157:H7. In addition to ROS induced damage, UV-A light and GA also cause injury to the cell membrane of E. coli O157:H7. UV-A exposed PG caused oxidative damage to the cell and significantly higher damage to the cell membrane than GA + UV-A treatment, explaining its higher effectiveness than GA + UV-A treatment. The findings presented here may be useful in developing new antimicrobial sanitation technologies for food and pharmaceutical industries.

Activity of chitosan-encapsulated Eucalyptus staigeriana essential oil on Haemonchus contortus.

Phytotherapy has been described as an alternative method for the control of gastrointestinal nematodes in small ruminants. Goal of the encapsulation of essential oils in biopolymer matrices is to optimize the biological effects of these oils. The aim of the present study was to evaluate the in vitro and in vivo anthelmintic activity of encapsulated Eucalyptus staigeriana essential oil (EncEs) on the eggs and larvae of Haemonchus contortus. Therefore, the egg hatching test (EHT), larval development test (LDT) and worm load evaluation were performed to evaluate Meriones unguiculatus experimentally infected with H. contortus. The chemical constituents of E. staigeriana essential oil (EsEO) and the in vitro oil release profile from the chitosan matrix at a pH of 1.2 and 7.0 were also characterized. EncEs and EsEO inhibited larval hatching by 97.19% and 99.96% at doses of 1.5 and 1.0 mg ml(-1), respectively. In the LDT, EncEs and EsEO induced a larvicidal effect greater than 95% at concentrations of 5.8 and 8 mg ml(-1), respectively. EncEs and EsEO decreased H. contortus load in M. unguiculatus by 40.51% and 46.44%, respectively. The major chemical constituents of EsEO were (+)-Limonene (72.9%), 1,8-Cineole (9.5%) and o-Cimene (4.6%). The release profile of EsEO was 30% in acid and 25% at neutral pH. The similar efficacy of EncEs and EsEO demonstrates that there was no optimization of anthelmintic action following the encapsulation process. Therefore, the use of new encapsulation matrices with controlled release in the pH of the abomasum should be investigated.

Anthelmintic activity of Eucalyptus staigeriana encapsulated oil on sheep gastrointestinal nematodes.

The anthelmintic activity of Eucalyptus staigeriana essential oil has previously been inferred through both in vitro and in vivo tests. Thus, the encapsulation process generally improves oil stability, promotes controlled release in target organs, reduces dosage, and increases efficacy. The aims of this study were to analyze and encapsulate E. staigeriana essential oil and to verify its anthelmintic activity in sheep. The encapsulation process was accomplished through emulsion using a 4% chitosan solution as the matrix. Anthelmintic activity was established through controlled testing using 18 sheep that were separated into three groups: group 1 was treated with a single dose of 365 mg/kg of E. staigeriana encapsulated oil, group 2 was treated with 200 µg/kg of ivermectin, and group 3 was treated with a 4% chitosan solution as a negative control. The sheep were euthanized and necropsied 13 days posttreatment to evaluate worm burden. Limonene was the major oil component (72.91%). The final product was a hydrogel with 36.5% (m/m) E. staigeriana essential oil per gram. Its efficacy on gastrointestinal nematodes was 60.79%. The highest efficacy was against abomasal nematodes, with 83.75% efficacy. Further studies are necessary to explore the possibility of increasing the hydrogel efficacy; nevertheless, we can state that E. staigeriana encapsulated oil had anthelmintic activity and can be used in gastrointestinal nematode control.