Prolonged Insecticidal Activity of Clove oil-Loaded Halloysite Nanotubes on Plodia interpunctella Infestation and Application in Industrial-Scale Food Packaging

Abstract

Previous study reported the development of insect-proof halloysite nanotubes (HNTs) and food packaging; however, the duration of their insecticidal properties remains unclear. Here, we aimed to (1) demonstrate the duration of repellency of clove bud oil (CO) encapsulated by HNTs for more than 30 days, and (2) manufacture insect-proof film containing HNTs for commercial use. Also, the release behavior of CO from insect-resistant HNTs was evaluated and HNTs were applied to food packaging composed of polypropylene and low-density polyethylene films to prevent Plodia interpunctella (Hubner) (Lepidoptera: Pyralidae) larva infestation. CO, a natural insecticide, was embedded with HNTs and polyethyleneimine (PEI) via vacuum pulling process to cause a slow and gradual release of CO. The sustained release profile of CO from CO-containing HNTs with a PEI coating [(HNTs/CO/layer-by-layer (LBL)] was verified by gas chromatography analysis. The repellent activity of HNTs/CO/LBL was observed for up to 46 days, whereas CO film and HNTs/CO film exhibited no insecticidal activities during the test period. After 30-day exposure, the HNTs/CO/LBL film exhibited a 7-day extension in the penetration test. To evaluate the insecticidal properties of the insect-proof film (HNTs/CO/LBL scale-up film) manufactured in an industrial facility, the inhibitory effects of HNTs/CO/LBL scale-up film on insect infestation was elucidated in both the segregation and combination tests. As a result, HNTs/CO/LBL alone or gravure-printed film treated with HNTs/CO/LBL were capable of protecting food from insect infestation. Practical Application Halloysite nanotubes containing natural insect repellent were applied to industrial production of food packaging. Commercial cornflake cereal packaging using insect-resistant film successfully inhibited pest infestation. Insect-proof film produced at an industrial facility can be utilized to protect processed food from insect infestation.