MANUFACTURING AND PACKAGING OF ESSENTIAL OILS AND OLEORESINS ON VARIOUS TYPES OF SPICES, MEDICINES, AROMATICS ITEMS

Essential oils extracted from a wide variety of plants and herbs have been traditionally employed in the manufacture of foodstuffs, cosmetics, cleaning products, fragrances, herbicides and insecticides. Further, several of these plants have been used in traditional medicine since ancient times as digestives, diuretics, expectorants, sedatives, etc., and are actually available in the market as infusions, tablets and/or extracts. Essential oils are also popular nowadays due to aromatherapy, a branch of alternative medicine that claims that essential oils and other aromatic compounds have curative effects. Moreover, in the last decades, scientific studies have related many biological properties (antioxidant, anti-inflammatory, antiviral, antibacterial, stimulators of central nervous system, etc.) of several plants and herbs, to some of the compounds present in the essential oil of the vegetal cells. For example, valerenic acid, a sesquiterpenoid compound, and its derivatives (acetoxyvalerenic acid, hydroxyvalerenic acid, valeranone, valerenal) of valerian extract are recognized as relaxant and sedative; lavender extract is used as antiseptic and anti-inflammatory for skin care; menthol is derived from mint and is used in inhalers, pills or ointments to treat nasal congestion; thymol, the major component of thyme essential oil is known for its antimicrobial activity; limonene and eucalyptol appear to be specifically involved in protecting the lung tissue. Therefore, essential oils have become a target for the recovery of natural bioactive substances. Essential oils are composed by lipophilic substances, containing the volatile aroma components of the vegetal matter, which are also involved in the defense mechanisms of the plants. The essential oil represent a small fraction of plant composition, and is comprised mainly by monoterpenes and sesquiterpenes, and their oxygenated derivatives such as alcohols, aldehydes, ketones, acids, phenols, ethers, esters, etc. The amount of a particular substance in the essential oil composition varies from really high proportions (e.g. around 80-90% w/w of d-limonene is present in orange essential oil) to traces. Nevertheless, components present in traces are also important, since all of them are responsible for the characteristic natural odor and flavor. Thus, it is important that the extraction procedure applied to recover essential oils from plant matrix can maintain the natural proportion of its original components. New effective technological approaches to extract and isolate these substances from raw materials are gaining much attention in the research and development field. Traditional approaches to recover essential oil from plant matrix include steam- and hydro-distillation and liquid-solvent extraction. One of the disadvantages of steam-distillation and hydro-distillation methods is related with the thermo ability of the essential oil constituents, which undergo chemical alteration due to the effect of the high temperatures applied (around the normal boiling temperature of water). Therefore, the quality of the essential oil extracted is extremely damaged. On the other side, the lipophilic character of essential oils requires solvents such as paraffinic fractions (pentane and hexane) to attain an adequate selectivity of the extraction. Further, liquid solvents should have low boiling points, in order to be easily separated from the extract and re-utilized. In this sense, the main drawback is the occurrence of organic toxic residues in the extracted product. Among innovative process technologies, supercritical fluid extraction (SFE) is indeed the most widely studied application. In practice, SFE is performed generally using carbon dioxide (CO2) for several practical reasons: CO2 has moderately low critical pressure (74 bar) and temperature (32oC), is non-toxic, non-flammable, available in high purity at relatively low cost, and is easily removed from the extract. Supercritical CO2 has a polarity similar to liquid pentane and thus, is suitable for extraction of lipophilic compounds. Thus, taking into account the lipophilic characteristic of plant essential oils, it is obvious that SFE using CO2 emerged as a suitable environmentally benign alternative to the manufacture of essential oil products. The commercial production of supercritical plant extracts has received increasing interest in recent decades and has brought a wide variety of products that are actually in the market. As mentioned before, supercritical plant extracts are being intensively investigated as potential sources of natural functional ingredients due to their favorable effects on diverse human diseases, with the consequent application in the production of novel functional foods, nutraceuticals and pharmacy products. The reader is referred to several recent works in which is reviewed the supercritical extraction and fractionation of different type of natural matter to produce bioactive substances. The general agreement is that supercritical extracts proved to be of superior quality, i.e. better functional activity, in comparison with extracts produced by hydro-distillation or using liquid solvents using supercritical CO2 (50ºC and 45 MPa) and ethanol Soxhlet extraction. Extraction yields were, respectively, 3.8 and 9.1%. Nevertheless, the supercritical extract comprised 21% of essential oil, while the alcoholic extract contained only 9% of the volatile oil substances. Furthermore, studies related with the antibacterial and antifungal properties of the extract revealed better activity for the supercritical product. Another example of improved biological activity exhibit by supercritical extracts was reported by Glisic et al. demonstrating that supercritical carrot essential oil was much more effective against Bacillus cereus than that obtained by hydro-distillation. Indeed, numerous variables have singular effect on the supercritical extraction and fractionation process. Extraction conditions, such as pressure and temperature, type and amount of cosolvent, extraction time, plant location and harvesting time, part of the plant employed, pre-treatment, greatly affect not only yield but also the composition of the extracted material. Knowledge of the solubility of essential oil compounds in supercritical CO2 is of course necessary, in order to establish favorable extraction conditions. In this respect, several studies have been reported. Nevertheless, when the initial solute concentration in the plant is low, as is the case of essential oils, mass transfer resistance can avoid that equilibrium conditions are attained. Therefore, pretreatment of the plant become crucial to break cells, enhancing solvent contact, and facilitating the extraction. In fact, moderate pressures (9-12 MPa) and temperatures (35-50oC) are sufficient to solubilize the essential oil compounds. Yet, in some cases, higher pressures are applied to contribute to the rupture of the vegetal cells and the liberation of the essential oil. However, other substances such as cuticular waxes are co-extracted and thus, on-line fractionation can be applied to attain the separation of the essential oil from waxes and also other co-extracted substances. In this review, on the basis of data reported in the literature and own experience, a detailed and thorough analysis of the supercritical extraction and fractionation of plants and herbs to produce essential oils is presented. Furthermore, the supercritical CO2 extraction of several plants (oregano, sage, thyme, rosemary, basil, marjoram and marigold) from Lamiaceae family was accomplished in our supercritical pilot-plant at 30 MPa and 40oC. High CO2 density was applied in order to ensure a complete extraction of the essential oil compounds.