A supercritical tuneable process for the selective extraction of fats and essential oil from coriander seeds

https://doi.org/10.1016/j.jfoodeng.2011.03.030Get rights and content

Abstract

A selective supercritical CO2 extraction process has been developed in order to extract selectively the vegetal oil and the essential oil from coriander seeds in a consecutive way by tuning experimental conditions. A 4-step process has been set up: (i) seeds preparation by grinding and sieving, (ii) extraction by supercritical CO2 and (iii; iv) selective separation in two separators with different pressure levels. The first part of this study consisted in studying the effects of the operating conditions (T, P, CO2 density, flow rate and particle size distribution of ground seeds) on the yield of extraction. The results showed that the global performance of the process depends mainly on the pressure level of extraction, on the CO2 flow rate and on the size of the ground seeds. An optimization of the parameters led to an extraction ratio of 90%. The second part of this study dealt with the effects of the operating conditions on the quality of extracts, and more precisely on their composition in vegetal oil and essential oil. It was observed that the supercritical extraction had no major effect on the fatty acid composition of the vegetal oil compared to classical extraction techniques, while essential oil is enriched in components such as linalool and that a previous drying of the seeds is deleterious. Finally, we propose a procedure in order to extract separately each oil by adjusting CO2 density and separation conditions.

Introduction

Coriander (Coriandrum sativum L.) is an annual Apiaceae (Umbelliferae) herb, which is widely used in food (Aluko et al., 2001, Burdok and Carabin, 2009), pharmaceutical (Jabeen et al., 2009) and cosmetic (Eyres et al., 2005) industries.

Coriander fruits contain vegetal oil (VO) with a high concentration of monounsaturated fatty acids, especially of petroselinic acid (C18:1 cis-Δ6). This acid can be oxidatively cleaved to produce a mixture of lauric acid (C12:0), a compound useful in the production of detergents, and adipic acid, a C6 dicarboxylic acid, which can be utilized in the synthesis of nylon polymer (Msaada et al., 2009b). Moreover, the essential oil (EO) of coriander has been shown to have antibacterial (Kubo et al., 2004, Matasyoh et al., 2009), antioxidant (Wangensteen et al., 2004), antidiabetic (Gallagher et al., 2003), anticancerous and antimutagenic (Chithra and Leelamma, 2000) activities.

There are three major extraction techniques used to obtain VO and EO from coriander seeds, which are steam distillation, organic solvent extraction (Soxhlet), and supercritical fluid extraction. Each technique has its benefits and drawbacks as far as operating cost, capital cost, yield and quality of the extracts are concerned. Steam distillation is by far the most widely used and the cheapest way of extraction, but it is limited to EO production, and it may induce chemical changes in the extract by oxidation of some compounds (Anitescu et al., 1997, Donelian et al., 2009, Msaada et al., 2007). Organic solvent extraction is intermediate in capital and operating cost, and is used for producing VO from oilseeds. However, concerns about the solvent residues in the oleoresin products, the new regulations of volatile organic solvent emissions in the air, and the extent of further refining that is required after the extraction step restrain the use of this technology (Catchpole and Grey, 1996). Supercritical fluid extraction is the most recent technology that is of increasing importance in the production of EO, VO, and a range of other substances from natural products (Brunner, 2005, Mohamed and Mansoori, 2002, Temelli, 2009). This technique has the highest capital cost of the three techniques, and moderate operating costs. However, neither solvent residues remain in the product after extraction, nor there are any chemical changes due to the processing technique, which gives extract of outstanding quality (Boutin and Badens, 2009, Brunner, 2005, Catchpole and Grey, 1996, Machmudah et al., 2008, Donelian et al., 2009, Perrut and Clavier, 2003).

The review of literature shows that most of the research works related to the extraction of coriander seeds are aimed at extracting either the VO (Msaada et al., 2009a, Msaada et al., 2009b) or the EO (Bandoni et al., 1998, Grosso et al., 2008, Illés et al., 2000, Msaada et al., 2007). The aim of this work is to put forward a new process using supercritical carbon dioxide, which is able to extract selectively the VO and the EO in a consecutive way by tuning experimental conditions. The effects of operating conditions on the yield of extraction and on the quality of extracts will be also studied to optimize the process.

Section snippets

Raw material

Coriander seeds came from Canada and were provided by the laboratory of General Herbalism, Marseille, France. The seeds used were mature and brown. They were stored in a refrigerator at 4 °C before use. The moisture content was about 10%. Their mass content of VO and EO, respectively determined by Soxhlet and steam distillation were 20.8% (w/w) of VO and 0.4% (w/w) of EO. Hence, EO represents 1.9% (w/w) of the total oil content. The crushed coriander seeds (mean size 0.3 mm) were used for Soxhlet

Operating conditions and reproducibility of the results

Different operating conditions were used to study the influence of the pressure, the temperature, the density and the flow rate of CO2 and the mean particle size of ground seeds to be processed on the extraction ratio and the composition of the extract. The tested operating conditions are gathered in Table 1. Experiment 9 is similar to experiment 1, except that seeds were previously dried at 70 °C and 60 kPa for 24 h.

Results of extraction ratio and mass transfer characteristics are gathered in

Conclusion

Coriander seeds were extracted using supercritical carbon dioxide to obtain selectively vegetal oil and essential oil. A process in four steps has been set up. A range of pressures, temperatures, particle diameters and carbon dioxide flow rates were investigated in order to elucidate their effect on the extraction yield and the composition of the extract. Pressure, particle size and flow rate have revealed to have a significant influence on the extraction yield while they have no major effect

Acknowledgments

This work is part of a research project financed with the help of the Région Midi-Pyrénées, France, which is gratefully acknowledged. The CNRS (France) and the DGRS (Tunisia) contributed also to finance this work through their joint program of international cooperation. The authors also thank the team from LCA-ENSIACET Toulouse, France and especially Mr. Thierry Talou for the chromatographic analyses.

References (28)

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