Essential oils, analysis origin

The traditional method of essential oil analysis is to extract the plant material by steam distillation or with solvent and then fractionally distil the oil or extract and isolate individual components by chromatographic techniques for subsequent identification by spectroscopic methods. At each step the odour of the fractions and isolates is assessed and those with the desired characteristics are investigated further. To answer the enquiry about the key odour components of broom absolute, first a sample of the absolute that is of an acceptable odour quality is obtained. The absolute is the alcoholic extract of the concrete, which is itself the solvent extract of the flowers of Spartium junceum, Spanish broom, often referred to by its French name Genet. The odour of any natural extract can vary according to the geographical origin and quality of the plant material, the time of year it is harvested and the extraction method used. If no sample of adequate quality is commercially available then the fresh flowers would be obtained from the plant and the extraction carried out in the laboratory. 

Several trial compounds may have to be made before a reasonably close analytical match is obtained. One of the problems that arises at this stage is sorting out the contribution that various components can make to the total quantity of a single ingredient found in the analysis. If citronellol is present, it may be because it occurs as a specified component in the formula, because it comes from a number of different essential oils, or because it is included in one or more bases. Many of the terpenes, such as J-limonene, are present in numerous essential oils, any number of which may be present. Trying to get back to the original formula requires considerable deductive powers and ingenuity on the part of the perfumer. 

Carrubba, A., Torre, R., Prima, A.D., Saiano, F. and Alonzo, G. (2002) Statistical analysis on the essential oil of Italian coriander (Coriandrum sativum L.) fruits of different ages and origins. Journal of Essential Oil Research 14, 389-396. 

Figure 4.5 The use of gas chromatography (GC) to distinguish a fake oil from a genuine essential oil. The size of the peaks represents the output of the detector (in this case measured in millivolts) and each peak corresponds to a different constituent separated from the original mixture. The horizontal axis represents the time during the analysis at which that constituent emerged from the GC column (over a total analysis time of 70 minutes).

Analysis of an essential oil will tell us what compounds are present (qualitative analysis) and in what amounts (quantitative analysis). However, when considering the composition of any named oil it is difficult to lay down precise criteria. As with all products of natural origin, there will be variations according to growing conditions and how they are harvested, extracted and stored. Even if the species of plant is defined and the parts used for oil production are carefully controlled, variation in composition will occur. This has previously been explained in terms of chemotypes and will be examined in more detail for other essential oils later in this chapter. Even when examining a particular chemotype there will be differences in the amounts of constituents, although these are usually within a fairly narrow range. 

There are several essential oil producing species available according to their country of origin. Consequently their chemical analysis will show a resultant variation in composition. 

Intermolecular isotopic correlations are thus indicative for the authenticity of natural flavour mixtures. The method for their assessment is GC-C/P-IRMS (combustion/ reductive pyrolysis). As an early example for intermolecular isotope correlations, the result of a GC-C-IRMS analysis of the essential oil from Coriandrum sativum is given in Fig. 6.19 [327]. Further examples are corresponding analyses of oils from Artemisia vulgaris [327], Coriandrum sativum [337] and various lemon oils (Table 6.8) ]325, 338, 339]. In any of these cases typical correlations are found between the compounds of the same origin, even when their average 8-values may differ between... 

Steam distillation is the main commercial extraction procedure for the production of essential oils from almost any type of plant material. Solvent extraction is also used commercially and yields a resinoid, concrete or absolute according to the solvents and techniques used (see Chapter 4). Both steam distillation and solvent extraction are used on a laboratory scale to produce oils and extracts for analysis. Other methods of extraction, such as supercritical fluid extraction (SFE), which uses supercritical CO2 as the extraction solvent, are now being developed and used on both commercial and laboratory scales. The extracts produced by SFE may contain different materials from the steam-distilled oil because of the solvating power of C02 and the lower extraction temperature, which reduces thermal degradation. The C02 extract may therefore have an odour closer to that of the original material and may contain different fragrant compounds. The choice of extraction procedure depends on the nature and amount of material available, and the qualities desired in the extract. Solvent extraction is better suited to small sample amounts or volatile materi-... 

Massoia essential oils prepared from barks of various origins were analyzed after laboratory extraction. Table I summarizes the compositional analysis... 

Faulharber et al (5,6) and other researchers (7-9) have described how the determination of the isotope values of constituents is of increasing importance, especially in view of the demand for authenticity control and origin determination of essential oils and foods. To determine isotope values, g chromatography-isotope ratio mass spectrometry (GC-IRMS) has been used, although not widely. The present authors (70) have studied the possibility of a more convenient and common means of analysis of isotope values, based on the isotope peak in the mass spectrum of a compound. The present study focuses on the development of a new analytical method for the differentiation of quality in commercial citrus oils of various origins. 

These results suggest that, in addition to an enantiomeric analysis, (16,17) this analytical method can be applied to evaluate the genuineness of essential oils. Furthermore, it is expected that this technique of isotope ratio analysis will be applicable to evaluate the origin of citrus essential oils and their products, and also to specify organic compounds from natural resources. 

GC coupled with mass spectrometry proved to be a useful application to identify variations in the composition of essential oil and make comp)arative analysis, in view of their possible use originated on the properties described before. Essential oils obtained by steam-distillation from Schinus molle leaves and young tree branches from the city of Resistencia, Province of Chaco were compared with oils from trees of different backgrounds (Maffei Chialvo, 1990, Menendez et al., 1996, Barroso et al., 2011 Guala et al., 2009). 

Guenther, E., 1972. The Essential Oils—Vol. 1 History—Origin in Plants Production Analysis, reprint of 1st edn. (1948). Malabar, EL Krieger Publishing Company. 

The overall high variation in essential oil compositions can be explained by the fact that quite different products might be generated by small changes in the synthase sequences only. On the other hand, different synthases may be able to produce the same substance in systematically distant taxa. The different origin of such substances can be identified by, for example, the ratio (Mosandl, 1993). Hence, a simple quantitative analysis of the essential oil composition is not necessarily appropriate for estimating genetic proximity even in closely related taxa (Bazina et al., 2002). 

Lawrence, B.M., Progress in essential oils, Petfum. Flavorist, 19(6), p. 57, 1994. Smith, D.M., L. Levi, Treatment of compositional data for the characterizing of essential oils determination of geographieal origins of peppermint oils by gas chromatographic analysis, J. Agric. Food Chem., 9, p. 230, 1961. 

Authenticity assessment of genuine substances of coriander oil (Coriander sativum L.) has been the object of a work dealing with the analysis of 10 authentic coriander essential oil samples of different origins [29]. The techniques used were GC-IRMS and enantioselective two-dimensional GC using a chiral cyclodextrin derivative as the stationary phase. The enantiomer ratio and the 8 C values of 12 characteristic components were compared with those of commercially available... 

Accurate, precise, sensitive, and rapid analytical determinations are as essential in food science and technology as in chemistry, biochemistry, and other physical and biological sciences. In many cases, the same methodologies are used. How does one, especially a young scientist, select the best methods to use A review of original publications in a given field indicates that some methods are cited repeatedly by many noted researchers and analysts, but with some modifications adapting them to the specific material analyzed. Official analytical methods have been adopted by some professional societies, such as the Official Methods of Analysis (Association of Official Analytical Chemists), Official Methods and Recommendation Practices (American Oil Chemists Society), and Official Methods of Analysis (American Association of Cereal Chemists). 

Validated methods are just as important as the availability of reference materials for allergens [21], As peanut allergy is highly prevalent and peanut products may enter into the production of various food matrices, e.g. chocolate, ice cream, biscuits and breakfast cereals, it is essential to have a peanut reference material both for research and routine analysis. Peanuts available in the food sector are derived from various sources, such as peanut vari-eties/types from different geographical origins, and are treated by various technological processes, such as dry and oil roasting at various temperatures for various times. 

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