March 5, 2021 | Audrey-Maude Vézina
Update : March 8, 2021
A combined treatment of irradiation and essential oil vapors could effectively eliminate insects, bacteria and mold in stored grains.
Professor Monique Lacroix‘s team from the Institut national de la recherche scientifique (INRS) has demonstrated the synergistic effect of this combined process on insects and mold affecting rice. The study was published in the Radiation Physics and Chemistry journal.
Microorganisms and insects are the main enemies of stored grains. Currently, the food industry uses fumigants to destroy them. However, these compounds, which evaporate or decompose into gases into air or water, are threatening human health and the environment. “When grain is fumigated, a small amount of gas is absorbed by the grain and released into the atmosphere. For food irradiation, the treatment is physical. If “new molecules” are produced, they are no different than those produced by normal processes applied to food, such as heat,” says Professor Monique Lacroix.
Food irradiation refers to the exposure of food to ionizing radiation, including gamma rays and X-rays. The research team has determined the effectiveness of these two processes, both with and without essential oils.
The study aimed at testing whether the energy level of the irradiation source with variable flow rate could affect the dose (or treatment time) needed to kill 90% of insects or molds. The research team showed that gamma rays were more effective against insects than X-rays. In addition, a higher dose rate with gamma rays proved to be more effective than a low dose rate. Moreover, by adding eucalyptus and tea tree essential oils, the effectiveness significantly improved.
“With the addition of essential oils, the dose needed was four to six times smaller depending on gamma dose rates. In fact, oils increase the sensitivity of insects to radiation.”Professor Monique Lacroix, expert in sciences applied to food.
Similar results can be seen for bacteria and moulds, even though they are more resistant to radiation. According to a previous study, microorganisms’ sensitivity to irradiation increased by about 1.5 times with the addition of thyme and oregano essential oils.
The team also conducted experiments with essential oil vapors diffused in 5 kg bags of rice. In the future, the team would like to test the process in an industrial setting, through partnership with companies.
The article “Radiosensitization of rice weevil Sitophilus oryzae using combined treatments of essential oils and ionizing radiation with gamma-ray and X-Ray at different dose rates”, by Farah Hossain, Peter Follett, Shiv Shankar, Tofa Begum, Stephane Salmieri and Monique Lacroix, was published in the Radiation Physics and Chemistry journal. The study received financial support from the Natural Sciences and Engineering Research Council of Canada (NSERC), the Ministère de l’Économie et de l’Innovation and the United States Department of Agriculture (USDA).