Optimization of the Vacuum Fractional Distillation Process for Enhancing the α-Guaiene of Patchouli Oil with Response Surface Methodology

α-guaiene is one of the primary sesquiterpene compounds used as a flavor and fragrance agent in patchouli oil. The fraction of patchouli oil that is rich in α-guaiene has been successfully isolated. In the present work, α-guaiene was isolated from crude patchouli oil through vacuum fractional distillation followed by GC-MS identification. Three important process parameters—feed volume, reflux ratio, and applied run pressure—were investigated and optimized using Box–Behnken design. The research methodology was an experimental laboratory using response surface methodology (RSM) with a feed volume level from 75 mL to 125 mL, a reflux ratio from 10:1 to 30:1, and an applied run pressure from 5 mmHg to 15 mmHg. The α-guaiene-enriched fraction was found in the first distillate fraction patchouli. The optimum condition that generated α-guaiene fraction at 44.70% purity was the treatment with a feed volume of 75 mL, a reflux ratio of 24:1, and applied run pressure of 14.80 mmHg. Results indicated that feed volume did not significantly affect the α-guaiene content, while the applied run pressure and reflux ratio used had a significant effect. A quadratic mathematical model with R2 0.861 and validation 96.14% was suitable for predicting the optimum α-guaiene fraction content during the vacuum fractional distillation process.