Essential oils chemical/physical properties

Owing to their liquid nature at room temperature, essential oils are called as such. They should not be confused with fixed oils or fatty oils, which are composed of a naturally occurring mixture of lipids which may not necessarily be volatile. Therefore, essential oils differ entirely both in chemical and in physical properties from fatty oils. Essential oil evaporates completely when dropped on filter paper however, fixed oil leaves a permanent stain which does not evaporate even when heated. 

The commonest essential oils, other than those of the add fruits, are considered in Table XXXIV, which indicates the most important physical and chemical properties, determined by the general methods, and also the principal components and the more probable adulterants. 

In the following chapters we will apply what we have learnt concerning physical and chemical changes, molecules and bonding to explore the structures of the molecules that form the essential oils. The structure of the molecules in a compound and the constituent compounds in a chemical have a big impact on its properties and these will also be reflected in the essential oils containing them. 

From thousands of flavor raw materials, 20-50 items are commonly selected and mixed with different ratios to blend a flavor. This is called flavor compounding, which is a kind of formulation. The raw material may be organic chemicals, essential oils, extracts, oleoresins, or processed flavors. Knowledge of their nature, physical and organoleptic properties, and applications is needed by flavorists. Flavor compounding requires at least 3-5 years of training. 

The following are key examples of how microwave thermal processing could affect the physical and chemical properties of a food material being processed. Each example represents major research areas in food processing, for example, fruits and vegetables, dairy products, meat products, marine products, and essential oils. 

Understanding, on the molecular scale, of processes relevant to microwave extraction has not yet reached the maturity of understanding of other topics in chemistry. Such a challenge is somewhat ambitious and requires a special approach. Microwave extraction interferes with polarization effects that cannot be readily separated from the physical and chemical properties of the extracted molecules. In this chapter we have discussed how the concept of microwave extraction has already become an important issue in the chemistry of natural products. Detailed analysis of past and present literature confirms explicitly the usefulness of this extraction technique. We have hope that this chapter will widen the scope of laboratory and commercial success for the potential applications of microwave technology in essential oil extraction. 

The biotic/biological factors are the main topic of this chapter. Natural variability should be de ned as the phenomenon when diverse quality of essential oils is detectable as result of genetical-biological differences of the source plants. Natural variability is, however, a rather complex issue having many aspects as we can see in the succeeding text. In this context, we deal with the essential oil spectrum, quantitative and qualitative composition of the oils, and not discussing other chemical and physical properties. 

The thorough study of essential oils is based on the relationship between their physical and chemical properties and is completed by the assessment of organoleptic qualities. The earliest analytical methods applied in the investigation of an essential oil were commonly focused on quality aspects, concerning mainly two properties identity and purity [17]. 

The differences in structure and the physical and chemical properties of the terpene- and phenylpropane derivatives encountered in essential oils, have been described in the standard works of Gdldemeister-Hoffmann [72], Guenther [82], SmoNSBN [240], deMayo [160], W. Karrer [117] and Moritz [173]. Haaqen-Smit[86] has dealt with sesqui- and diterpenes. Both Steiner and Holtzem [721] and Jones and Hals all [109] have compiled comprehensive articles on triterpenes. 

Chemical Composition and Other Characteristics Fatty Acid Composition Chemical and Physical Properties Nutritive Values Essential Fatty Acids Polyunsaturated vs. Saturated Fats Medium-Chain Triglycerides (MCT Oil)... 

Important to any measurement of citrus juice volatile flavor components is the presence of (i-limonene, since this compound is naturally present as the most concentrated component in all of the natural citrus oils. Also, the solubility of d-limonene in aqueous media must be considered, since after liquid phase saturation, the headspace concentration remains constant. It has long been established for d-limonene and similar nonpolar flavor compounds over water that meaningful headspace measurement techniques [e.g., solid-phase microextraction (SPME)] require equilibrium of the vapor and liquid phase concentrations. Equilibrium may take a number of hours for static (unstirred) experiments and less than 1 hr for stirred systems. These conditions have been discussed elsewhere, and solubility and activity coefficients of d-limonene in water and sucrose solutions have been determined [1,2]. More recently, the chemical and physical properties as well as citrus industry applications of d-limonene and other citrus essential oils have been compiled [3]. Although not specific to d-limonene, important relationships affecting behavior of flavor release and partitioning between the headspace and the liquid phase of a number of food systems have also been discussed [4]. 

Mineral Oil Hydraulic Fluids and Polyalphaolefin Hydraulic Fluids. Limited information about environmentally important physical and chemical properties is available for the mineral oil and water-in-oil emulsion hydraulic fluid products and components is presented in Tables 3-4, 3-5, and 3-7. Much of the available trade literature emphasizes properties desirable for the commercial end uses of the products as hydraulic fluids rather than the physical constants most useful in fate and transport analysis. Since the products are typically mixtures, the chief value of the trade literature is to identify specific chemical components, generally various petroleum hydrocarbons. Additional information on the properties of the various mineral oil formulations would make it easier to distinguish the toxicity and environmental effects and to trace the site contaminant s fate based on levels of distinguishing components. Improved information is especially needed on additives, some of which may be of more environmental and public health concern than the hydrocarbons that comprise the bulk of the mineral oil hydraulic fluids by weight. For the polyalphaolefin hydraulic fluids, basic physical and chemical properties related to assessing environmental fate and exposure risks are essentially unknown. Additional information for these types of hydraulic fluids is clearly needed. 

This constancy may at first seem remarkable, but it is to be expected if one keeps in mind the fact that hydrocarbons axe essentially long chains of CHs groups. Consider two hypothetical crude oils, one consisting of pure octane (CgHis) fl-nd the second of pure dodecane (CxaHso). Tlrese two crudes would have entirely different physical and chemical properties. The first would be an excellent gasoline, whereas the second would have the properties of kerosene. However,... 

The basic properties of corn oil include its pleasing flavor, its high level of polyunsaturated (essential) fatty acids, a low level of saturated fatty acids, and a low level of linolenic acid (4). The other main physical and chemical properties of com oil are summarized in Table 10. 

Hydrogenation is a chemical process in which hydrogen gas is reacted with oils to increase their oxidative and thermal stability by converting liquid components to semisolid fractions. The melting and crystalline characteristics developed are essential for formulating shortenings with specific desirable physical and functional properties. 

---