Extraction of natural materials

The microbiological activity attributed to folic acid in extracts of natural materials was largely that of di- and triglutamyl derivatives, one of the facts... 

Current State of Extraction of Natural Materials with Supercritical Fluids and Developmental Trends... 

The present state and the developmental trends concerning the extraction of natural materials with supercritical fluids may be described under the following aspects ... 

Of increasing interest are structural changes in or coatings of natural materials. Thus the volume increase of tobacco resulting from controlled pressure release is already used industrially. The discontinuous extraction of natural materials requires the plant to be depressurised after completion of the process, whereby the non-stationary behaviour of pressure and temperature in the extraction vessel is of great importance for the design of the pressure vessel. 

Particularly, the extraction of natural materials with compressed gases involves the problem of applying results obtained at laboratory or pilot scale to production-scale conditions. In accordance with the required production rate, increases in scale between 1 10 and 1 1000 may result. 

GC, MS, NMR, IR, HPLC, TLC and other techniques, used bofli alone and in combination can analyze, authenticate and identify F F materials. Table II lists the pros and cons of using various analytical techniques to authenticate F F materials, GC using element specific detectors can detect sulfur or nitrogen compounds with high odor impact that occur at low concentration. It is not uncommon for F F extracts of natural materials to contain hundreds of components. GC analysis of off-line rough cut LC separations of a complex extract can help simplify the identification of the many individual components. 

Extraction of natural materials in order to produce extracts with useful flavor, fragrance, nutritional and other pharmacological properties is a centuries old practice. Traditionally, such extracts are isolated from the relevant biomass (flowers, roots, peel, leaves etc.) using a variety of processes ranging from steam distillation through solvent extraction to simple mechanical expression. Many of these initial materials have been subjected to further refinement steps in order to produce a finished product of acceptable quality. 

Mathematical models for reactive extraction of natural materials have been reported in connection with the extraction of lignin materials from bio-mass, in general from wood species. These models assume that, unless otherwise soluble, the availability of the extractable materials are fiilly dependent upon the chemical reactions taking place in the natural matrix. 

Serpil, T.(1997) Modeling and Simulation of Supercritical Fluid Extraction of Natural Materials from Plants, M.S. Tliesis, Bogazi9i University, Bebek, Istanbul, Turkey. 

Extraction of natural materials often produces complex mixtures of products, as described in the Historical Highlight at the end of this chapter, so additional operations are required to separate and purify individual compoimds. These procedures may involve techniques in which the compounds are separated on the basis of their acidic or basic properties (Sec. 5.3) or by chromatographic methods (Chap. 6). Thus, the isolation of pure natural products normally involves a series of complex and time-consuming operations. Fortunately there are some exceptions to this general rule. The isolation of trimyristin (20) from nutmeg is one of them. 

Nutritional studies on aquatic forms are usually of little value unless the forms are cultured in the absence of associated microorganisms. Only then can one arrive at conclusions regarding the limitations of synthetic enzymes, which is the real core of the science of nutrition. Pure cultures (bacteria-free) have been obtained with a small number of animal microorganisms (true Protozoa), but, with one exception, additions of crude extracts of natural materials are necessary to maintain growth. This is the... 

More recently (see Kidder and Dewey ) it has been found that in the completely synthetic medium of Dewey et aZ. thiamine is required for gro i h of T. geleii, even though the unnatural isomers of amino acids are present. Heat- and alkali-treated extracts of natural materials, added to the synthetic medium, allow growth to take place. It appears that there is an unknown factor (or factors) necessary for thiamine biosynthesis even in... 

Resinoids are products obtained by the extraction of natural materials, mostly resins, gum resins and balsams, by solvents other than petroleum ether or petrol. Chlorinated hydrocarbons (dichloromethane and chloroform), acetone, methanol or ethanol are typically used for this. Resinoids have a characteristic smell, which due to the volatile substances (essential oils) present. 

Dissolved Minerals. The most significant source of minerals for sustainable recovery may be ocean waters which contain nearly all the known elements in some degree of solution. Production of dissolved minerals from seawater is limited to fresh water, magnesium, magnesium compounds (qv), salt, bromine, and heavy water, ie, deuterium oxide. Considerable development of techniques for recovery of copper, gold, and uranium by solution or bacterial methods has been carried out in several countries for appHcation onshore. These methods are expected to be fully transferable to the marine environment (5). The potential for extraction of dissolved materials from naturally enriched sources, such as hydrothermal vents, may be high. 

Supercritical fluid extraction (SFE) has been extensively used for the extraction of volatile components such as essential oils, flavours and aromas from plant materials on an industrial as well as an analytical scale (61). The extract thus obtained is usually analysed by GC. Off-line SFE-GC is frequently employed, but on-line SEE-GC has also been used. The direct coupling of SEE with supercritical fluid chromatography (SEC) has also been successfully caried out. Coupling SEE with SEC provides several advantages for the separation and detection of organic substances low temperatures can be used for both SEE and SEC, so they are well suited for the analysis of natural materials that contain compounds which are temperature-sensitive, such as flavours and fragrances. 

This paper is a review of methods for estimating releases of chemicals into the environment in the course of extraction of raw materials, manufacturing, use, storage, transportation, and disposal, as well as by accidents or natural processes. It discusses source types, forms of substances released (solids, liquids, and gases), receiving media (air, water, soil), time pattern of release (continuous versus intermittent, cyclic versus random), and geographic patterns of release (point, line, area, and volume sources). 

The life cycle of some chemicals begins with extraction of raw materials. Activities such as coal and mineral mining, oil production, and forestry can either release chemicals directly or open the land for releases by natural processes that otherwise would be slower. 

A relatively dilute alcoholic extract of natural raw materials in which the solvent is left (in part) as a diluent, e.g. Civet tincture. 

Extractives of resinous materials by a hydrocarbon type solvent. The extractives are both volatile and non-volatile materials, and the resinous substance used is non-cellular in nature, e.g. Olibanum resinoid. 

The current trend of consumer preference towards natural products requires new processing methods for spice-oils and extracts, without the addition of external material. In recent years there has been an increased interest in supercritical and subcritical extraction [26,27], which use carbon dioxide as a solvent [34,35,36]. Carbon dioxide (CO2) is an ideal solvent for the extraction of natural products because it is non-toxic, non-explosive, readily... 

---