Influence of Enzymatic Pretreatment and Optimization on Hydro Distillation Recovery of Essential Oils from Allium cepa

The essential oil industry is agro-based and its consumption is increasing very fast. The need to improve its production technology is essential to enhancing the overall yield and quality. An environmentally friendly process is therefore sought which could be achievable via enzyme-based processes. This study produced xylanase and pectinase by solid-state fermentation and applied them in pre-treating milled onions (Allium cepa) for improved essential oil yield. The pre-treated milled onion bulbs were hydro distilled at about 100 C-o and the essential oils obtained characterized using Gas Chromatography - Mass Spectrometry to identify the components. Response Surface Methodology was employed for optimizing the extraction parameters. Results showed that the use of enzymes for pre-treatment of the onions increased the essential oil yield. The xylanase and pectinase function optimally at pH 5.5 and 4.0 respectively and at a temperature of 60 C-o. About 10 compounds were identified in the essential oil obtained from untreated onion with Oleic acid as the main component. The mixed enzyme-treated onions showed 24 compounds in the essential oil which is rich in S-propyl methane thiosulfonate. The response surface methodology gave the optimum extraction time and enzyme quantity for the extraction. Antioxidant activity results indicate that the oil has a protective effect against oxidative stress which is of medical importance. Variability of the components of the extracted essential oils with enzymes makes it expedient to choose a pre-treatment enzyme based on the component of interest.