Analysis of the insect-repelling mechanism of star anise extract and its major active compounds against Plodia interpunctella.

One of the major stored product pests, Indian meal moth causes the loss on the agriculture and food industries. This study was conducted to screen the insecticidal activity of ethanolic extracts and fractions partitioned by four different solvents [(1) n-hexane; (2) ether; (3) ethyl acetate; (4) water] from star anise (Illicium verum Hook. f.) against Plodia interpunctella larvae. Among all solvent-partitioned fractions, the strongest repellency was found for the n-hexane fraction of star anise extract. Solvent-solvent partitioning and chromatographic methods were further used to isolate and identify major anti-insect compounds from star anise extract. The results showed that trans-anethole (94.24%) was the major active compound showing an insect-repelling activity against P. interpunctella. Consequently, trans-anethole can be utilized as a main natural insect-repelling agent for controlling the P. interpunctella infestation. Supplementary Information: The online version contains supplementary material available at 10.1007/s10068-022-01053-8.

Development of insect-proof starch adhesive containing encapsulated cinnamon oil for paper box adhesion to inhibit Plodia interpunctella larvae infestation.

The objectives of this study were to develop insect-resistant adhesives and apply them to a cardboard packaging system for preventing Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) larvae infestation. Cinnamon essential oil (CO), an insecticide, was encapsulated with maltodextrin (CS/MD/CO), ß-cyclodextrin (CS/ß-CD/CO), and polyvinyl alcohol (CS/PVA/CO) in corn starch (CS) paste. This resulted in a sustained and gradual release of CO from the starch-based insect-proof adhesives. Penetration pathways of insects into corrugated cardboard boxes were investigated through the use of a screening test for infestation profiling. Microscopic images of encapsulated CO in an oil in water (O/W) emulsion were observed to confirm the morphology of the adhesives. Adhesion forces of CS, CS/CO, CS/MD/CO, CS/ß-CD/CO, and CS/PVA/CO were determined to be 6.2 N, 4.0 N, 3.1 N, 6.0 N, and 5.8 N, respectively. Consequently, significant decreases of adhesion force in the CS/CO and CS/MD/CO were found to be due to the presence of the surfactant (Span® 80) and the low adhesive properties of MD. The duration of the insecticidal activities of the developed adhesives was evaluated by measuring their release rates for 14 days and repellent profiles up to 24 hr and 40 days. As a result, CS/ß-CD/CO and CS/PVA/CO were found to have an inhibited rapid release and sustained repellent profiles. In conclusion, CS/ß-CD/CO and CS/PVA/CO were determined to be suitable for encapsulation models and could be applied to industrial cardboard containers to prevent cases of insect invasion. PRACTICAL APPLICATION: Corn starch-based natural adhesives with an insect-proof property were applied to food containers consisted of corrugated cardboard boxes. Cornflake cereal packaging using insect-proof corrugated cardboard successfully prohibited pest invasion in commercial food distribution simulation model. Developed insecticidal adhesives are able to control insect penetration in distribution and storage steps.

Characterization and Preservation Performance of Multilayer Film with Insect Repellent and Antimicrobial Activities for Sliced Wheat Bread Packaging.

A multilayer film containing star anise essential oil and thymol coating layers (SAEO and TH, respectively), with insect repellent and antimicrobial properties, has been developed using bar coating and adhesive lamination processes. Our previous study reported the in vitro activities of this polypropylene film (PP)/SAEO/polyethylene terephthalate film (PET)/TH/low-density polyethylene film (LDPE) multilayer film. The current study focused on demonstrating the morphological, optical, and mechanical properties of the film, and evaluating its in vivo activities when used as a bread packaging material. The developed film was 15.03% thicker and 1.86% less transparent than the control film (without active agent coating layers: PP/PET/LDPE). While the color values of the developed film were slightly different from the control film, both films appeared similar to the naked eye. The tensile strength in the developed film was somewhat lower than that of the control film, while both films had statistically comparable values for elongation at break. During storage of sliced bread packaged in the developed film, the film both deterred insects from approaching toward and impeded the growth of microorganisms in the bread. These results suggest the potential applicability of the developed film as an active food packaging material with insect repellent and antimicrobial activities. PRACTICAL APPLICATION: A multilayer film incorporated with insect repellent and antimicrobial coating layers was applied in sliced wheat bread packaging. The developed film effectively inhibited approaches of stored-product insects to packaged bread and growth of microorganisms on the bread surface. It can be used as an active food packaging material that improves the safety and shelf-life of foods.

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

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 (Hübner) (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.

Protection of Grain Products from Sitophilus oryzae (L.) Contamination by Anti-Insect Pest Repellent Sachet Containing Allyl Mercaptan Microcapsule.

The purpose of this study was to develop an anti-insect pest repellent sachet to prevent Sitophilus oryzae (L.) (Coleoptera: Curculionidae) contamination in grain packaging. The anti-insect pest activities of essential oils (EOs) from garlic (Allium Sativum), ginger (Zingiber Officinalis), black pepper (Piper nigrum), onion (Allium cepa), and fennel (Foeniculum vulgare) as well as major compounds (allyl disulfide, AD; allyl mercaptan, AM) isolated from of garlic and onion (AD and AM) were measured against S. oryzae. The results revealed that garlic EO, onion EO, AD, and AM showed strong fumigant insecticidal activities. Among these, AM showed the highest acetylcholinesterase (AChE) inhibition rate, indicating that the fumigation insecticidal efficacy of AM is related with its AChE inhibition ability. Subsequently, the microcapsules were produced with a high efficiency (80.02%) by using AM as a core material and rice flour as a wall material. Finally, sachet composed of rice flour microcapsule containing 2% AM (RAM) was produced. Repellent assay was performed to measure anti-insect pest ability of the RAM sachet, showed remarkable repelling effect within 48 h both in the presence or absence of attractant. In a release profile of RAM sachet, it was expected to last over 20 mo during the distribution period of brown rice. Moreover, RAM sachet showed no undesirable changes to the sensory properties of the rice both before and after cooking. Taken together, these results suggest that the newly developed RAM sachet could be used as a packaging material to protect grain products from S. oryzae contamination. PRACTICAL APPLICATION: The rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), causes damages to stored products and its contamination in grain products has become a major problem in cereal market. To preserve brown rice, an anti-insect pest repellent sachet containing 2% allyl mercaptan was newly developed and it showed remarkable repellent abilities against S. oryzae. It could be used as an active food packaging system to protect grain products from insect pest contamination.

Development of Natural Insect-Repellent Loaded Halloysite Nanotubes and their Application to Food Packaging to Prevent Plodia interpunctella Infestation.

The aims of this study were to develop insect-proof halloysite nanotubes (HNTs) and apply the HNTs to a low-density polyethylene (LDPE) film that will prevent Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), commonly known as Indian mealmoth, from infesting the food. Clove bud oil (CO), an insect repellent, was encapsulated into HNTs with polyethylenimine (PEI) to bring about controlled release of CO. Chemical composition and insecticidal effect of CO were examined. The Fourier transform infrared (FTIR) spectrum of encapsulated CO was confirmed. The surface charges of uncoated HNTs (HNTs/CO) and coated HNTs with PEI by the layer-by-layer (LBL) method (HNTs/CO/LBL) were determined to be -37.23 and 36.33 mV, respectively. HNTs/CO/LBL showed slow, controlled release of CO compared to HNTs/CO. After 30 d, the residual amounts of CO in HNTs/CO and HNTs/CO/LBL were estimated to be 13.43 and 28.66 mg/g, respectively. HNTs/CO/LBL showed the most sustainable repellent effect. HNTs applied to gravure printing ink solution did not affect mechanical, optical, or thermal properties of the developed film. Gravure-printed LDPE film containing HNTs/CO/LBL displayed the greatest preventive effect on insect penetration, indicating its potential for use as insect-resistant food packaging materials.

Development of an anti-insect sachet using a polyvinyl alcohol-cinnamon oil polymer strip against Plodia interpunctella.

Plodia interpunctella is a major storage pest that penetrates into food packaging and causes serious economic losses, as well as posing health risks. The goal of this study was to develop effective anti-insect polymer strips against P. interpunctella by using plant essential oil (EO) and polyvinyl alcohol (PVA). The EO of cinnamon (Cinnamomum zeylanicum, CO) bark was used as an insect repellent, and fumigant mortality and the repellent activity of CO were measured to evaluate subsistent anti-insect properties through newly designed traps. Repellent activity was also examined with several foods to simulate the storage environment. The mortality rate with CO after fumigation for 120 h was 63%. In the repellent assay, CO-treated strips, but not control strips, effectively repelled P. interpunctella in both "with foods" and "without foods" groups. A PVA-CO strip sachet (PCO sachet) was developed to control the volatility of CO, and the PCO sachet demonstrated robust repellent activity. The loading contents of CO at the center and edges of strips were 39.41% and 39.59%, respectively, and through the results of FT-IR, it inferred that CO was physically diffused in the PVA polymer matrix, not forming chemical bonds. In a release test using a gas chromatography, the PCO sachet showed remarkable controlled release of CO. These results demonstrate that the anti-insect effects of CO can be maintained throughout the distribution and storage periods of foods using PCO sachets.

Insect-resistant food packaging film development using cinnamon oil and microencapsulation technologies.

UNLABELLED: Insect-resistant films containing a microencapsulated insect-repelling agent were developed to protect food products from the Indian meal moth (Plodia interpunctella). Cinnamon oil (CO), an insect repelling agent, was encapsulated with gum arabic, whey protein isolate (WPI)/maltodextrin (MD), or poly(vinyl alcohol) (PVA). A low-density polyethylene (LDPE) film was coated with an ink or a polypropylene (PP) solution that incorporated the microcapsules. The encapsulation efficiency values obtained with gum arabic, WPI/MD, and PVA were 90.4%, 94.6%, and 80.7%, respectively. The films containing a microcapsule emulsion of PVA and CO or incorporating a microcapsule powder of WPI/MD and CO were the most effective (P < 0.05) at repelling moth larvae. The release rate of cinnamaldehyde, an active repellent of cinnamaldehyde, in the PP was 23 times lower when cinnamaldehyde was microencapsulated. Coating with the microcapsules did not alter the tensile properties of the films. The invasion of larvae into cookies was prevented by the insect-repellent films, demonstrating potential for the films in insect-resistant packaging for food products. PRACTICAL APPLICATION: The insect-repelling effect of cinnamon oil incorporated into LDPE films was more effective with microencapsulation. The system developed in this research with LDPE film may also be extended to other food-packaging films where the same coating platform can be used. This platform is interchangeable and easy to use for the delivery of insect-repelling agents. The films can protect a wide variety of food products from invasion by the Indian meal moth.

Biological control of indianmeal moth and rice weevil by parasitoids with reference to the intraspecific competition pattern.

Biological control of rice weevil, Sitophilus oryzae (L.), and Indianmeal moth, Plodia interpunctella (Hübner), by their parasitoids Anisopteromalus calandrae (Howard) and Bracon hebetor Say was examined while considering the intraspecific competition pattern of the pests. In both experimental and simulation studies, A. calandrae was shown to suppress the rice weevil population, a contest type competitor, regardless of the parasitoid/weevil ratios tested. In contrast, B. hebetor only significantly suppressed the Indianmeal moth, a scramble type competitor, when the parasitoid/moth ratio was >0.05. At ratios lower than 0.05, the role of B. hebetor was negligible, and the correlation coefficients between the number of moths that had emerged and the parasitoid/moth ratio was estimated to be 0.07. The control efficiency of the two parasitoids with respect to the parasitoid/host ratio was estimated using a ratio-response model. To suppress the weevil density to a level that was only 10% of the current density, the ratio was estimated to be 0.02, whereas this value was 0.14 for the Indianmeal moth. However, for the continuous suppression of the Indianmeal moth, periodic and iterative introduction of B. hebetor was required.