Microwave hydrodiffusion and gravity for rapid extraction of essential oil from Tunisian cumin (Cuminum cyminum L.) seeds: Optimization by response surface methodology

Highlights

• Microwave hydrodiffusion and gravity (MHG) and hydrodistillation (HD) were compared.

• Both processes were assessed by response surface methodology (RSM).

• Optimal conditions for Both processes were achieved.

• Microwave hydrodiffusion and gravity produced the finest cumin essential oils.

• Microwave hydrodiffusion and gravity was more efficient: rapid kinetic + less energy.

Abstract

Recently, microwave hydrodiffusion and gravity (MHG) pushed the confines of the microwave assisted extraction (MAE) further toward an innovative, quick, efficient, and eco-friendly process for plant secondary metabolites extraction. The goal of this study was to optimize the microwave hydrodiffusion and gravity (MHG) process for the extraction of the essential oils (EO) from Tunisian cumin (Cuminum cyminum L.) seeds. The effects of different parameters: microwave irradiation time (8, 12, and 16 min), microwave irradiation power (150, 200, and 250 W), and moisture content (40, 50, and 60%), on the extraction yield were achieved using the response surface methodology (RSM) with central composite design (CCD). In order to elucidate the efficiency of the MHG, it was compared with conventional hydrodistillation (HD) in terms of kinetic, quantity and quality of obtained EO, environmental impact, and energy consumption. Results showed that, under the optimum conditions defined by the central composite face-centered (CCF) and calculated by the analysis of variance (ANOVA) (16 min of microwave irradiation time, 203.30 W of microwave irradiation power, and 44.67% of moisture content), the yield of cumin essential oil obtained with MHG was 1.579 ± 0.05%. Meanwhile, compared with the HD process, the MHG successfully improved the EO yield (1.579 ± 0.05% versus 1.550 ± 0.07% with HD) in shorter extraction time (16 min versus 150 min with HD), less electrical consumption, lower carbon dioxide emissions (CO₂), and smaller volume of waste water. Using the GC-FID and GC–MS analysis, the MHG provided more valuable EO with high amount of oxygenated compounds compared with the HD. Scanning electron micrograph (SEM) confirmed the efficiency of MHG for EO extraction. Thus, MHG appeared like rapid process, green technology, and desirable alternative protocol to enhance the quantity and the quality of the essential oil extracted from the medicinal and aromatic plants (MAPs).

Introduction

Over the past few years and with the development of the Green Chemistry, the application of the microwave assisted extraction (MAE) gained enormous popularity as a favored environment-friendly process for extraction of secondary metabolism in numerous laboratories and major industries (Filly et al., 2014; Yu et al., 2014). In fact, the MAE improved the quantity and the quality of the extract, reduced the time of extraction, decreased the cost and the energy consumption, and minimized the quantity of carbon dioxide (CO₂) emitted into the atmosphere compared with the conventional extraction methods as hydrodistillation (HD) (Farhat et al., 2011).

Recently, microwave hydrodiffusion and gravity (MHG) pushed the confines of the microwave assisted extraction further toward an innovative, quick, efficient, and eco-friendly process without any degradation in the quality of the extract (López-Hortas et al., 2016; Pérez et al., 2014). In reality, the key property of the MHG extraction was based on the combination of the microwave irradiation and the earth gravity at atmospheric pressure, without adding the solvent or the water (Binello et al., 2014; López-Hortas et al., 2016).

Moreover, the MHG extraction showed the best results addressed in a wide variety of applications focused on the extraction of the active compounds such as: antioxidant molecules, essential oils, colorants, pectin, and polyphenols from the medicinal and aromatic plants (Al Bittar et al., 2013; Boukroufa et al., 2015; Bousbia et al., 2009a; Périno et al., 2016; Zill-e-Huma et al., 2009). The success of the MHG in the laboratory scale pushed the researchers to expand its application area. Périno et al. (2016) used a pilot scale of MHG system for the extraction of the polyphenols from lettuce.

Cumin is one of the medicinal and aromatic species belong to the Apiaceae family (Umbelliferae). It originated in Turkistan, Egypt, and countries neighboring the Mediterranean area (Rebey et al., 2012; Thippeswamy and Naidu, 2005). Cumin is the most popular aromatic spice in the world after pepper (Piper nigrum L.) (Hajlaoui et al., 2010). In fact, cumin and its essential oil were commonly used as an aromatic spice in the food industry due to its strong aromatic quality (Wang et al., 2006). Furthermore, its essential oil was also used in the cosmetics and the perfumery industries (lotions, creams, and perfumes) (Dubey et al., 2017). In particular, the pharmaceutical industry used cumin volatile oil as an excellent antioxidant, antimicrobial, antitumor, cytotoxic, anti-inflammatory, antifungal, and antidiabetic agent (Bettaieb et al., 2011; Rebey et al., 2012; Einafshar et al., 2012; Hajlaoui et al., 2010; Li and Jiang, 2004; Petretto et al., 2018; Sharma et al., 2016).

Since the yield and the chemical composition of the essential oil may differ significantly with: agricultural factors, seasonal variations, ecological situations, and extraction methods (Moghaddam et al., 2015; Telci et al., 2006), the cumin essential oil was extracted in this study by the microwave extraction to improve the quantity and the quality of the volatile oil.

The complete MHG method was herein presented, where the effects of some parameters such as: the microwave irradiation time, the microwave irradiation power, and the moisture content on the MHG extraction were studied using the response surface methodology (RSM) as the powerful statistical method. The yield of Tunisian cumin essential oil was followed as a key parameter to achieve the optimum for MHG extraction. Then, the optimal MHG response was compared with the hydrodistillation (HD) in terms of the extraction kinetic, the quantity and quality of the essential oils, the environmental impact, and the energy consumption. Finally, the morphological of cumin seeds before and after extractions was also done by the scanning electron microscope (SEM) to better understand the effectiveness and the quickness of the MHG on the extraction of the essential oil from the medicinal and aromatic plants (MAPs).