Extraction of essential oils from Mentha piperita using advanced techniques: Microwave versus ohmic assisted hydrodistillation

Ohmic and microwave assisted hydrodistillation (OAHD and MAHD, respectively) are advanced hydrodistillation (HD) techniques utilizing ohmic and microwave heating processes for extraction of essential oils. OAHD and MAHD of essential oils from the aerial parts of peppermint were studied and the results were compared with those of the traditional HD. The results showed that OAHD and MAHD methods require less than half an hour for extraction process while HD require about 1 h. Scanning electron microscopy of mint leaves undergone OAHD and MAHD provided evidences as to a sudden rupture of essential oil glands. GC–MS analysis did not indicate any noticeable changes in the compounds of the essential oils obtained by novel studied methods in comparison with HD. The results introduced OAHD as the greenest technique in terms of energy consumption. MAHD was superior in terms of rate of essential oils accumulation and also extraction duration parameter.     

Effect of extraction methods on kinetic,chemical composition and antibacterial activities of Tunisian Thymus vulgaris. L. essential oil

The present study aims to compare two innovative extraction techniques: microwave-assisted hydrodistillation (MAHD) and solvent-free microwave extraction (SFME) through traditional extraction techniques: hydrodistillation (HD) and steam distillation (SD) for their efficiency in the extraction of the volatile compounds from Tunisian Thymus vulgaris leaves; the kinetic, yield, composition and antibacterial activities of the essential oil were assessed in vitro. Results show that the essential oils extracted by microwaves were quantitatively (yield) similar to those obtained through the conventional methods, but qualitatively, essential oils analysed by gas chromatography–mass spectrometry (GC–MS) presented 17, 11, 11 and 8 compounds obtained through SFME, MAHD, SD and HD, respectively, mostly consisting of carvacrol (89.24–41.17%), followed by γ-terpinene (11.37–1.37%) and para-cymene (27.95–2.05%). The essential oils were screened for antibacterial activity against 5 microorganisms. All essential oils obtained by studied extraction methods showed the same resistance against Gram (?) and Gram (+) bacteria. The SFME method gave the best results: rapid kinetic of extraction (30 min vs. 35 min for MAHD, 120 min for SD, and 180 min for HD), less energy saving and cleanest process.     

A new kinetic model for the common juniper essenstial oil extraction by microwave hydrodistillation

The main objective of the present study was to model the kinetics of essential oil extraction from swelled ground juniper berries by classic hydrodistillation (HD) and microwave-assisted hydrodistillation (MAHD). A new phenomenological kinetic model was developed on the basis of the juniper essential oil extraction mechanism that assumed three mass transfer processes occurring simultaneously: washing, unhindered diffusion and hindered diffusion. The new model was compared to the existing kinetic models. Among the tested models, the new model had the smallest mean relative percentage deviation and the highest corrected Akaike information criterion value. In addition, that, the new model was verified for HD and MAHD of essential oils from some other plant materials. On the basis of the above-mentioned facts, the new model can be recommended for modeling the kinetics of essential oil extraction by both HD and MAHD.     

Optimization of Ultrasonic Enhanced Salt‐Containing Hydrodistillation by Response Surface Methodology

An ultrasonic enhanced salt‐containing hydrodistillation (UESHD) method for separating essential oil from lavender (Lavandula angustifolia) flowers was investigated using response surface methodology (RSM). The experimental data obtained from a 27‐run experiment were fitted to a second‐order polynomial equation. The optimal conditions were determined by the 3D response surface and the contour plots derived from the models. The efficiency of UESHD and conventional hydrodistillation (HD) was compared. The extraction yield of UESHD was two‐fold higher than that of HD. In addition, GC‐MS results indicated some differences in composition and content between the two essential oils from UESHD and HD.     

Extraction of Essential Oil from Laurel Leaves by Using Microwaves

Abstract

The effects of microwave power and time in solvent-free microwave extraction (SFME) on the yield and composition of the essential oil obtained from laurel (Laurus nobilis L.) leaves were studied. The extraction was also performed by hydrodistillation as a control. Specific gravities and refractive indices of the essential oils obtained by different methods and at various conditions were also examined. The main constituent of laurel essential oil was 1,8-cineole (630–730 mg/mL). Essential oils obtained by SFME and hydrodistillation were comparable with respect to both yield and composition while the process time was reduced by 55–60% when SFME was used.     

Enhanced extraction of essential oil from Cinnamomum cassia bark by ultrasound assisted hydrodistillation

Cinnamon essential oil with many bioactivities is an important raw material for the production of various chemicals,and the conventional hydrodistillation(HD) for cinnamon oil extraction always require a longer extraction time. In this work, ultrasound-assisted hydrodistillation extraction(UAHDE) technique was employed to enhance the extraction efficiency of essential oils from cinnamon barks. The parameters with significant effects on the essential oil extraction efficiency(ultrasound time, ultrasound power, extraction time, liquid–solid ratio) were optimized, and the proposed UAHDE was compared with the conventional HD extraction in terms of the extraction time, extraction yield, and physicochemical properties of extracted oils. Compared to the HD extraction, the UAHDE resulted in a shorter extraction time and a higher extraction yield. Using GC–MS analysis, the UAHDE provided more valuable essential oil with a high content of the vital trans-cinnamaldehyde compounds compared with the HD. Scanning electron micrograph(SEM) confirmed the efficiency of ultrasound irradiation for cinnamon oil extraction. In addition, the analysis of electric consumption and CO2 emission shows that the UAHDE process is a more economic and environment-friendly approach. Thus, UAHDE is an efficient and green technology for the cinnamon essential oil extraction, which could improve the quantity and quality of cinnamon oils.     

微波、超声波和水蒸气蒸馏在紫苏籽挥发油分析中的对比研究

采用水蒸气蒸馏法、微波提取和超声波萃取紫苏籽挥发油。运用毛细管气相色谱-质谱联用仪结合计算机检索对所得挥发油成分进行分析和鉴定,用气相色谱峰面积归一法测定各组分的相对质量分数。结果表明,3种方法分别从紫苏籽所得挥发油中鉴定出33、31及29种化合物,各占总峰面积的97.16%、97.38%及96.6%。不同方法所得紫苏籽挥发油化学组成各有异同,但主要成分是正十六酸、(Z,Z,Z)-9,12,15-十八三烯-1-醇和戊基-2-呋喃基酮。     

不同方法提取鸦胆子挥发油化学成分的GC-MS分析

分别采用水蒸气蒸馏法(HD)和微波辅助水蒸气蒸馏法(MAHD)提取鸦胆子挥发油。运用毛细管气相色谱-质谱联用仪结合计算机检索对所得挥发油成分进行分析和鉴定,用气相色谱面积归一法测定各组分的相对质量分数。结果显示,两种方法分别从鸦胆子挥发油中鉴定出42种和37种化合物,分别占总峰面积的94.09%和94.13%。不同方法所得鸦胆子挥发油化学组成不同,但主要成分是黄樟脑、(+)-4-蒈烯、β-香叶烯、丁香油酚甲醚、2,6-二甲氧基甲苯、柠檬烯和甲基胡椒酚。     

Effects of Operating Parameters on the Cinnamaldehyde Content of Extracted Essential Oil Using Various Methods

Supercritical fluid extraction (SFE) of essential oils from commercial cinnamon bark was compared with essential oils that were obtained by hydrodistillation. Effects of operating parameters (pressure, temperature and extraction time of SFE) on the extraction yield and the composition of the extracted volatile oil were studied. Moreover, in the hydrodistillation process, the effect of the pH of the solvent on the concentration of cinnamaldehyde in the extracted volatile oil was studied. The maximum yield of extract in the SFE process is about 7.8 % at 70 °C and 240 bar. The maximum concentration of cinnamaldehyde in the SFE process was obtained at 70 °C and 160 bar, and the maximum concentration of this component in hydrodistillation was achieved at pH = 4.1.     

Comparative Study of Essential Oils Extracted from Algerian Myrtus communis L. Leaves Using Microwaves and Hydrodistillation

Two different extraction methods were used for a comparative study of Algerian Myrtle leaf essential oils: solvent-free-microwave-extraction (SFME) and conventional hydrodistillation (HD). Essential oils analyzed by GC and GC-MS presented 51 components constituting 97.71 and 97.39% of the total oils, respectively. Solvent-Free-Microwave-Extract Essential oils SFME-EO were richer in oxygenated compounds. Their major compounds were 1,8-cineole, followed by α-pinene as against α-pinene, followed by 1,8-cineole for HD. Their antimicrobial activity was investigated on 12 microorganisms. The antioxidant activities were studied with the 2,2-diphenyl-1-picrylhydrazyl (DPPH^•) radical scavenging method. Generally, both essential oils showed high antimicrobial and weak antioxidant activities. Microstructure analyses were also undertaken on the solid residue of myrtle leaves by Scanning Electronic Microscopy (SEM); it showed that the SFME-cellular structure undergoes significant modifications compared to the conventional HD residual solid. Comparison between hydrodistillation and SFME presented numerous distinctions. Several advantages with SFME were observed: faster kinetics and higher efficiency with similar yields: 0.32% dry basis, in 30 min as against 180 min for HD.     

Influence of thyme and clove essential oils on cottonseed oil oxidation

Simple model systems composed of refined cottonseed oil and thyme oil or clove oil, without additives, were designed to approximate conditions in natural oils in order to study their oxidation behavior. Three methods were used to follow cottonseed oil oxidation, i.e., coupled oxidation withβ-carotene, the TBA test and hydroperoxide number. The results illustrate that clove and thyme oils at various concentrations exhibit antioxidant activity and this phenomenon for clove oil is superior to that of thyme oil. Sensory evaluation tests indicate that the addition of thyme oil or clove oil to cottonseed oil at concentrations ranging from 50 to 1200 ppm do not affect the odor note of cottonseed oil. Therefore, thyme and clove essential oils are recommended for use as natural antioxidants to suppress lipid oxidation.     

Effect of Oils Extracted from Plant Seeds on the Growth and Lipolytic Activity of <Emphasis Type="Italic">Yarrowia lipolytica</Emphasis> Yeast

This study was aimed at evaluating the capability of Yarrowia lipolytica W29 for the synthesis of lipolytic enzymes in a medium containing plant oils from non‐conventional sources with some components displaying bioactivity. Oils from almond, hazelnut, and coriander seeds were obtained by using n‐hexane (Soxhlet method) and a chloroform/methanol mixture of solvents (Folch method), and their effect on the growth and lipolytic activity of Y. lipolytica was compared. A comparison of these two extraction methods showed that the extraction with n‐hexane was less effective regarding the oil extraction yields than the extraction conducted according to Folch's procedure. The lipolytic activity of the studied yeast was higher in the culture media containing oils extracted with the Soxhlet method than the Folch method but it was lower compared to olive oil medium. Among all oils tested, almond oil extracted with n‐hexane was the best inducer of extracellular lipases synthesized by Y. lipolytica. Its lipolytic activity achieved the maximum value of 2.33 U/mL after 48 h of culture. After 24 h of culture, it was close to the value obtained for the medium containing olive oil. Almond oil was a source of oleic and linoleic acids, which may determine differences in the lipolytic activity. The linoleic acid content in almond oil was higher than that found in other oils. When n‐hexane was used for extraction, the resultant oils were characterized by lower contents of polyphenols and poorer antioxidative activity.     

Extraction of essential oil from geranium (Pelargonium graveolens) with supercritical carbon dioxide

This study investigated the supercritical fluid extraction (SFE) of geranium essential oil from geranium (Pelargonium graveolens) using supercritical carbon dioxide solvent. The extraction yield was measured as a function of pressure, temperature and carbon dioxide flow rate. At low pressure (10 MPa) and high temperature (343 K), waxes were co‐extracted with the essential oil, resulting in artificially elevated essential oil extraction yields as no method was available with the SFE apparatus used to separate co‐extracted waxes and oil. At high pressure (30 MPa) and low temperature (313 K), the amount of wax co‐extracted decreased. Under these ‘optimum’ conditions, the extraction yield increased with decrease in flow rate giving a maximum extraction yield of 2.53%. All samples were analyzed by gas chromatography–mass spectrometry and the effect of pressure and extraction time on oil composition was studied. The percentage compositions of terpene hydrocarbons, terpenols, geraniol and geranyl esters were significantly affected by pressure and extraction time. The oil samples obtained by SFE were also compared with commercially obtained steam distilled samples. All major components of the commercially obtained oils were present in the SFE‐obtained oils; however, the percentage composition of the major components differed greatly between steam distilled and SFE oils. Copyright © 2005 Society of Chemical Industry     

Rapid Salt‐Assisted Microwave Demulsification of Oil‐Rich Emulsion Obtained by Aqueous Enzymatic Extraction of Peanut Seeds

Aqueous enzymatic extraction (AEE) is an environmentally friendly edible‐oil‐extraction process that can also provide edible protein. However, the AEE process may form a stable emulsion in most cases, which seriously limits the large‐scale industry applications for producing vegetable oils. In this study, the salt‐assisted microwave radiation demulsification of the oil‐rich emulsion prepared with AEE from peanuts is investigated. The microwave demulsification method is compared with other conventional demulsification methods, including heating, and freezing–thawing. The salt‐assisted microwave demulsification of the emulsions shows a greater free oil yield than conventional heating demulsification. Moreover, the microwave demulsification shows a similar free oil yield in less time than freezing–thawing method. Under the optimal operating conditions of demulsification, the free oil yield can reach 92.3% with CaCl₂‐assisted microwave demulsification for only 2 min. In addition, the oxidative properties and the fatty acid compositions of the demulsified peanut oil are investigated. No significant difference in the fatty acid composition is observed among salt‐assisted microwave, freezing–thawing, and heating demulsified oil. The oxidative properties of the salt‐assisted microwave demulsified peanut oil is better than the conventional heating demulsified oil. Thus, salt‐assisted microwave demulsification provides a quick and effective demulsification method to obtain vegetable oils with high quality. Practical Applications: Aqueous enzymatic extraction (AEE) is an environmentally friendly edible‐oil‐extraction process. To solve the problem of stable emulsion formed during AEE process, the salt‐assisted microwave demulsification of the oil‐rich emulsion prepared with AEE is developed with high efficiency (demulsification for 2 min). In addition, the oxidative properties of the microwave demulsified oil is better than the conventional heating demulsified oil.     

Antiradical Efficiency of Essential Oils from Plant Seeds Obtained by Supercritical CO2, Soxhlet Extraction,and Hydrodistillation

The effect of supercritical CO₂ (SCCO₂) extraction conditions (pressure and temperature) on the system performance as well as the antiradical efficiencies of the essential oils from Japanese pepper (Xanthoxylum piperitum DC.), cardamom (Elettaria cardamomum Maton), and fennel (Foeniculum vulgare) seeds were investigated. A control study with the conventional Soxhlet extraction and hydrodistillation was also conducted to compare the performance of those processes. Antiradical efficiencies were investigated by utilizing 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay with a UV-vis spectrophotometer. Higher pressure and temperature had positive effects on the supercritical process performance due to higher CO₂ density and substrate solubility in SCCO₂. Antiradical efficiencies of cardamom and pepper were almost the same, being significantly higher than that of fennel seeds. However, this effect decreased dramatically for all the spices when the extraction method was changed to Soxhlet extraction and hydrodistillation. SCCO₂ extraction was found to yield more quality and effective essential oils than Soxhlet extraction and hydrodistillation.     

Supercritical fluid extraction of wormwood (Artemisia absinthium L.)

The objective of the work was to optimize the extraction of wormwood oil by supercritical fluid extraction (SFE) of growth-controlled plant material. Different extraction conditions, two growth techniques and various crops were tested and the evolution of the extracted oil composition was screened chromatographically. A comparison with conventional techniques such as hydrodistillation (HD) or organic solvent extraction (OSE) was also presented. Particularly, six CO₂ densities ranging from 285.0 kg/m³ to 819.5 kg/m³ were studied in the range of 9.0-18.0 MPa and 40-50 °C. A systematic study was carried out with plant material from 2005, while SFE of 2006, 2008 and aeroponically grown crops was performed for comparative purposes. The effect of ethanol as a modifier of the supercritical fluid extraction was also studied. The major compounds found in the SFE extracts as well as in the HD essential oils were Z-epoxyocimene, chrysanthenol and chrysanthenyl acetate. A model based on mass transfer equations, the Sovová model, was successfully applied to correlate the experimental data.     

Use of Essential Oils From Various Plants to Change the Fatty Acids Profiles of Lipids Obtained From Oleaginous Yeasts

We studied the ability of seven essential oils to alter the fatty acid composition of lipids produced by an oleaginous yeast Rhodosporidium toruloides. All of the essential oils, except thyme, significantly increased the stearic acid content of the lipids. The amount of essential oils in the media determined the fatty acid composition obtained. Subsequently, we studied the effect of the major monoterpenes present in these essential oils. When R. toruloides was grown on limonene, a major monoterpene in orange essential oil, the composition of lipid obtained was found to be quite similar to natural orange essential oil. This proved that limonene has a major role in the changes in fatty acid profiles of the lipids. The effect of orange essential oil on another oleaginous yeast, Cryptococcus curvatus, was also carried out. Although the effect of the essential oil on the fatty acid composition and biomass (cell mass) was similar for both these two yeasts, the reduction of the activity of some enzymes involved in the metabolic pathways was quite different. From these results, it can be concluded that the effect of essential oils differs with species and it is possible to produce lipids with alternate fatty acid profiles suitable for different applications and with good market value.     

Integrating Microwave-Assisted Extraction of Essential Oils and Polyphenols from Rosemary and Thyme Leaves

The extraction of essential oils (EOs) and polyphenols from rosemary and thyme has been done using an integrated process: microwave hydro-diffusion and gravity (MHG) for EOs and microwave-assisted extraction (MAE) for polyphenols. The innovative installation based on the MHG principle allows uniform microwave irradiation field due to a mechanical stirring and experiments done at low pressure. The results of quantitative analysis of the EOs extracted by MHG after 10?min were similar with those obtained by traditional methods (conventional hydro-distillation (CHD) and microwave-assisted hydro-distillation (MHD)) after 150 and 105?min, respectively. The specific energy for MHG was 5–15 times lower compared with these classical methods. The MHG extraction of EOs is also an effective method for plant material pretreatment before polyphenol extraction. Total phenolic content increased from 35 to 55?mg GAE/g DM for rosemary and from 23 to 38?mg GAE/g DM for thyme.     

Optimization of ethanol modified supercritical carbon dioxide on the extract yield and antioxidant activity from Biebersteinia multifida DC

Essential oil of Biebersteinia multifida DC cultivated in Iran was obtained by hydrodistillation (HD) and supercritical fluid extraction (SFE) methods. The oil was analyzed by capillary gas chromatography using flame ionization and mass spectrometric detections. The effects of different parameters such as temperature, pressure, static extraction time, dynamic extraction time, and mole fraction of modifier on the supercritical fluid extraction (SFE) and radical scavenging activity of B. multifida oil were optimized using central composite design. Fifty two compounds were identified in the HD oil. The major components of B. multifida were (E)-Nerolidol (31.45%), Hexadecanoic acid (11.84%), Phytol (17.1%), and 6,10,14-trimethyl-2-pentadecanone (15.4%). However, by using supercritical carbon dioxide in optimum conditions, obtained only four components contain more than 91.74% of the essential oil. The optimum extraction yield and DPPH EC₅₀ via SFE method were 96% (w/w) and 27.19, respectively.     

Optimization of pressurized hot water extraction on the extract yield and antioxidant activity from Biebersteinia multifida DC using a modified supercritical fluid extractor

Essential oil of Biebersteinia multifida DC cultivated in Iran was obtained by hydrodistillation (HD) and pressurized hot water extraction (PHWE) methods. The oil was analyzed by capillary gas chromatography using flame ionization and mass spectrometric detections. The effects of different parameters such as temperature, pressure, static extraction time, dynamic extraction time, and flow rate on the PHWE and radical scavenging activity of B. multifida oil were optimized using circumscribed central composite. Fifty two compounds were identified in the HD oil. The major components of B. multifida were (E)-Nerolidol (31.45%), Hexadecanoic acid (11.84%), Phytol (17.1%), and 6,10,14-trimethyl-2-pentadecanone (15.4%). However, by using pressurized hot water extraction in optimum conditions, obtained only four components contain more than 86% of the essential oil. The optimum extraction yield and DPPH EC₅₀ via PHWE method were 5.1% (w/w) and 28.40, respectively.