Limonene physical properties

Although the different enantiomers of a chiral molecule have the same physical properties, they usually have different biological properties. For example, the (+) enantiomer of limonene has the odor of oranges, but the (-) enantiomer has the odor of pine trees. 

In addition to chemical assays, Basic Protocols 4 through 6 evaluate the physical properties of citms oils. These methods are based on the high percentage of rf-limonene, in which citms oils have characteristic values. Table Gl.5.7 provides the physical and chemical properties defined by Food Chemical Codex (NRC, 1981). 

Terpenes are a class of unsaturated hydrocarbons made up of isoprene C5 units and found in essential oils and oleoresins of plants such as conifers. The two most commonly used as solvents are turpentine and o-limonene. Their physical properties are compared with those of toluene and methylene chloride in Table 5.7. They are both immiscible with water. As can be seen in Figure 5.3, D-limonene and other small terpenes have similar molecular weights and structures to substituted cyclohexanes and toluene and are therefore to likely have solvent properties intermediate between these two VOCs. 

Table 5.7 Some physical properties of D-limonene and turpentine alongside methylene chloride and toluene for comparison.

Effect of d-limonene on physical properties of packaging material... 

The crystallised tetrabromide was formed in the usual way with the portion distilling 175 to 177 C., and these crystals, when purified to constant melting-point with acetic ether, melted at 104 to 105 C. From the physical properties of the several fractions it may be assumed that nearly the whole of the terpene present was laevo-limonene, and that the oil contained about 60 per cent, of that terpene. 

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]. 

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