|HOSSAINE, FARAH - Institut National De La Recherche Scientifique (INRS)|
|LACROIX, MONIQUE - Institut National De La Recherche Scientifique (INRS)|
Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2019
Publication Date: 6/13/2019
Citation: Hossaine, F., Follett, P.A., Lacroix, M. 2019. Synergistic effects of nanocomposite films containing essential oil nanoemulsions in combination with ionizing radiation for control of rice weevil Sitophilus Oryzae in stored grains. Journal of Food Science. 84(6):1439-1446.
Interpretive Summary: We developed and tested bioactive packaging films based on chitosan nanocomposites loaded with plant essential oils (EOs) for fumigant activity against the stored product pest rice weevil, Sitophilus oryzae. Eucalyptus oil showed the highest activity against rice weevil, but the combination of oregano and thyme was also effective. Combination of films with EOs with irradiation was also tested. Irradiation at 200 Gy alone caused 69% mortality, and when irradiation at 200 Gy was combined with the bioactive chitosan film containing the oregano-thyme nanoemulsion mortality increased to 100% after 14 days exposure. Thin, bioactive chitosan films were able to provide extended bioactivity of embedded EOs. These bioactive films have many applications for improving the safety and prolonging the shelf life of packaged foods.
Technical Abstract: The fumigant toxicities of eight individual essential oils (EO) (basil, cinnamon, eucalyptus, mandarin, oregano, peppermint, tea tree and thyme) and one binary combination (thyme and oregano) for control of the rice weevil, Sitophilus oryzae, were investigated. In bioassays, all individual and combined essential oils were toxic to the rice weevil. Eucalyptus EO exhibited the highest toxicity among the individual EO treatments, causing 100% mortality at a minimum concentrations of 0.8 µl/mL after 24 h of exposure. The combination treatment of oregano and thyme EO displayed higher fumigant activity than the individual oregano or thyme treatments. A stable oil-in-water nanoemulsion was evaluated using high pressure homogenization (microfluidization) and varying the pressure and number of cycles.The droplet size of the emulsions was found to decrease from 217 nm to 71 nm and encapsulation efficiency (EE %) increased from 37-84% with increasing microfluidization pressure and number of cycles. The optimum conditions for preparing the mixture of oregano and thyme EO nanoemulsions were evaluated to be homogenization pressure of 103 MPa and 3 cycles. Incorporating oregano:thyme nanoemulsions (0.75%) into the biopolymeric films chitosan (CH), methyl cellulose (MC) and poly lactic acid PLA resulted in effective diffusion matrices causing 30-50% rice weevil mortality after 14 days exposure. Irradiation at 200 Gy alone caused 69% mortality and increased to 100% when combined with the the bioactive chitosan film containing the oregano-thyme nanoemulsion.