(160f) Minimizing the Environmental Impact through Microwave-Assisted Extraction of Eucalyptus Globulus Essential Oil

During the last decade, the food industry has shown a growing interest in studying essential oils (EOs) of several plants, herbs, and spices; mainly because of their potential as natural antimicrobials and antioxidants. Although conventional methods as steam distillation (SD) and hydrodistillation (HD) have been widely applied for extraction of EOs; emergent methods, such as microwave-assisted extraction (MAE), have been recently explored to improve the extraction yield and reduce the use of solvents and energy requirements. The aim of this work was to determine the optimum conditions for extraction of Eucalyptus globulus essential oil and the environmental impact associated to these process conditions for different extraction processes. Mathematical models for extraction yield and energy requirements were fitted from experimental data. Obtained models were implemented within an optimization problem wherein the objective function was to minimize total cost. Additionally, environmental impact of the different processes was assessed though the Eco-indicator E99 (EI99). Eucalyptus globulus EO MAE was performed in a NEOS System equipment evaluating selected conditions of solid/liquid ratio (1:1, 1:3, or 1:5), stirring speed (0, 200, or 400 rpm) and microwave (MW) power output (360, 450, or 540 W). Conventional HD was performed in a three-neck round bottom flask heated by a stirring heating mantle (480 W, 60 Hz) attached to the same condenser and graduated trap utilized during MAE at same conditions of solid/liquid ration and stirring speed. Steam distillation was performed using a pressurized boiler, evaluating different conditions of solid/liquid ratio (1:0, 1:1, or 1:2) and steam generation (6.1, 7.5, or 8.8 g/min). Obtained data were fitted to polynomial models by using Response Surface Methodology to describe yield and energy requirements. EI99 was utilized to compute environmental impact of the extraction processes; this eco-indicator considers the waste of water and total use of energy, as well as which are the variables that most influence the environmental impact. The best experimental yields (1.26 ± 0.01, 1.19 ± 0.02, and 1.06 ± 0.27 %, for MAE, HD, and SD, respectively) were obtained under the following conditions: for MAE a solid/liquid ratio of 1:3, 400 stirring speed and 360 W of MW power; in the case of HD a solid/liquid ratio of 1:5 and 400 stirring speed; for SD a solid/liquid ratio of 1:2 and 6.7 g/min of steam flow. The EI99 for each case was 7.47±0.4, 16.91±0.3, and 50.86±13.2, respectively. The optimal solution was found for MAE at a solid/liquid ratio of 1:2.5, 250 stirring speed, and 360 W of MW power, obtaining a yield of 1.46% and an associated environmental impact of 4.48 Eco-points per gram of EO extracted. In case of HD the optimal solution was found for a solid/liquid ratio of 1:8 without stirring, obtaining a yield of 1.44% and 13.41 Eco-points per gram of EO. For SD the best operation conditions were found for a solid/liquid ratio of 1:10 and 52.37 Eco-points per gram of EO, obtaining a yield of 1.02%. From these results MAE exhibited the greatest EO yield extraction with a low environmental impact, it also showed that the HD can be improved to get a greater EO yield and a lower environmental impact. For the SD solution, although it requires a greater use of water, had a lower environmental impact than the one experimentally obtained. The tested approach allows to optimize different responses, finding an equilibrium amongst the operating process conditions and environmental goals.