# Assessment of the Oil Release and Insect Repellent Activity of Spray-Dried Gum Arabic/Citronella Oil Microcapsules

## TL;DR

This study creates microcapsules from gum arabic and citronella oil to effectively repel insects, with optimal conditions yielding high repellent activity.

## Contribution

The study systematically optimizes spray-drying parameters to enhance encapsulation efficiency and insect repellent activity of citronella oil.

## Key findings

- Encapsulation efficiency reached 90% with higher inlet temperatures and feed rates.
- Optimal microcapsules had a wall-to-core ratio of 4:1, temperatures above 150°C, and feed rates above 2.5 mL/min.
- The highest insect repellent activity was 95% against Drosophila melanogaster.

## Abstract

Essential oils are natural insect repellents, which can be microencapsulated and protected by wall materials to provide prolonged protection against insects. The protection and release of these repellents depend on various parameters, including morphology and production conditions. Herein, twenty-seven gum arabic/citronella essential oil (GA/CEO) spray-dried microcapsules were produced by using three wall-to-core ratios (3:1, 4:1, 6:1), three inlet temperatures (120, 150, 180 °C), and three feed rates (1, 2.5, 5 mL/min). The morphology, particle size, encapsulation efficiency, and release rates were evaluated. The insect repellent activity of microcapsules (0.25, 0.5, and 1 g) against Drosophila melanogaster flies was tested. A systematic process optimization was carried out by evaluating the effects of both emulsion concentration and process parameters on the release rates. Microcapsules with smooth surfaces and homogeneous particle sizes were produced. Encapsulation efficiency reached 90% by increasing the inlet temperature and feed rate. Slower release rates (approximately 40%) were achieved with higher concentrations of the wall material and temperatures, generally. Optimal process conditions were determined as a wall-to-core ratio of 4:1, temperatures exceeding 150 °C, and feed rates above 2.5 mL/min. The highest repellent activity achieved was 95%, indicating effectiveness of GA/CEO microcapsules as insect repellent materials.