[5-1130-P] Food Safety (5th)

[5-1130-P-19] Acaricidal effects of Linear fatty acids against Tyrophagus putrescentiae

*Kosuke Matsuoka¹, Toshinari Koda², Hiroshi Morita¹ (1. The University of Kitakyushu(Japan), 2. Nissan Chemical Corporation(Japan))

Keywords:Tyrophagus putrescentiae, linear fatty acid , acaricidal test

Tyrophagus putrescentiae is one of the cause of allergies and acariasis because they breed in various places in the room such as food, bedding and carpets. Tyrophagus putrescentiae also cause pollution of the food. Previous study has shown that 2-hexyldecanoic acid that is a branched higher fatty acid has an acaricidal effect against Tyrophagus putrescentiae. However, it is necessary to search for samples that has higher acaricidal effects. This study focused on linear fatty acids. We performed acaricidal test using hexadecanoic acid that has same number of carbons with 2-hexyldecanoic acid. After that, we performed same test using hexanoic acid, octanoic acid and decanoic acid that have carbons less than hexadecanoic acid. Tyrophagus putrescentiae were obtained from Earth Chemical Co., Ltd., and maintained in our laboratory without exposure to any acaricides. Hexanoic acid (C6), octanoic acid (C8), decanoic acid (C10) and hexadecanoic acid (C16) were used to the miticidal test as samples. They were obtained from FUJIFILM Wako Pure Chemical Corporation. Ethanol was used as the dilution solvent. In the acaricidal test, Tyrophagus putrescentiae was placed on a black cloth(45 mm × 45 mm) and samples were sprayed. The black cloth (45 mm×45 mm) was fixed on a petri dish with double sided tape, 30 adult mites were placed on the cloth. After that, samples of linear fatty acids (undiluted solution and 350mM) were dropped on the cloth and feed of insects were placed on the cloth. The petri dish was placed into a plastic container containing saturated saline solution. The temperature and humidity inside the container were kept at 25 °C and 75 %. After 24 h, mortality was determined by observation using a microscope. As a result, the mortality of hexanoic acid, octanoic acid and decanoic acid were over 70 %. However, the mortality of hexadecenoic acid was 0 %. These results were suggested that the carbon number of linear fatty acids was related to the mortality of mites. As a problem, linear fatty acids have unpleasant smell. It is necessary to discover compounds that have miticidal effect and not smelling. In addition, it is thought that we remove the smell of linear fatty acids by masking agents as a possible solution.