# Supercritical Fluid CO2 Extraction of Essential Oil from Spearmint Leaves Dried by Vacuum Drying with a Desiccant

## TL;DR

This study improves the extraction of spearmint essential oil using vacuum drying with calcium chloride and optimized supercritical CO2 extraction.

## Contribution

The study introduces a more efficient vacuum drying method and optimizes supercritical CO2 extraction to enhance essential oil yield and quality.

## Key findings

- Using calcium chloride in vacuum drying reduced drying time by 21.1% and costs by 31.0%, while increasing essential oil yield by 11%.
- Lower separator pressure during supercritical CO2 extraction increased essential oil yield by minimizing volatile constituent loss.
- The Chrastil model accurately described essential oil solubility in supercritical CO2, with maximum phenolic content observed at a specific CO2 density.

## Abstract

The essential oil (EO) of Mentha spicata L. (spearmint) exhibits pronounced biological activity, making it valuable for applications in agrochemistry as an insecticidal agent, in perfumery and cosmetics, and as a natural preservative in the food industry. However, maintaining the integrity and yield of EO during post-harvest processing and extraction remains a key technological challenge. This study aimed to enhance the vacuum-drying (VD) process of spearmint using calcium chloride as a desiccant and to optimize the conditions of supercritical CO2 extraction (SC-CO2), including EO separation and the evaluation of its solubility under dynamic extraction conditions. The incorporation of calcium chloride into the VD process reduced drying duration by 21.1% and processing costs by 31.0%, while increasing EO yield by 11%. A decrease in separator pressure from 70 to 10 bar during SC-CO2 extraction resulted in nearly a threefold increase in EO yield by minimizing the loss of volatile constituents. The solubility of spearmint EO in supercritical CO2 was successfully described by the Chrastil model and correlated with carvone solubility. The maximum total phenolic content (72.3 ± 2.2 mg gallic acid equivalent per gram) was observed at a CO2 density of 353.91 kg/m3. The solubility of EO was studied directly using the plant matrix under dynamic conditions.