Basil is an annual bush belonging to the mint family. The plant grows to a height of 50-120 cm. It has opposite, dull green velvet leaves with an average length of 7-8 cm and breadth of 3-4 cm. It has small white or light-colored flowers arranged in a terminal spike. The leaves possess dot-like oil glands in which the essential oil is stored. The plant emits a light fragrance. When fresh, the herb has a pleasant, minty note, and it has a spicy but mildly pungent and bitter taste.
Basil, being a cold-sensitive plant, grows best in warm, dry weather. Therefore, growing basil in cold regions requires careful selection of the area and the season.
The dried herb consists of about 14% protein, 61% carbohydrate, 4% fat, and 18% fiber. It contains minerals and vitamins, in particular ascorbic acid and vitamin A. However, its most significant component is the volatile oil.
The yield of the essential oil is generally less than 1%. In one report, the yield from the aerial part of the plant is 0.1-0.25%, but the flower top alone gives 0.4%. This indicates that the flower top has the most oil. In a study in Egypt, hydrodistilled volatile oil from the stem, leaf, and inflorescence was obtained (Islam and Salama, 2007). More than 30 components were identified in all three parts, with about 70% of them being oxygenated compounds. Linalool, estragole, cardinol, bornyl acetate, ocimene, and 1,8-cineole were prominent. In a study in China, GC-MS examination of steam- distilled oil showed 54 compounds. The main constituents were anisole, p-allylani- sole, and (+)-epibicyclo-sesquiphellandrene, among other compounds (Lu and Li, 2006). In the oil from the green and purple varieties from Iran, a difference in chemical compositions has been noted (Sajjadi, 2006). The variations in composition of the essential oil for the four different seasons have been studied (Hussain et al., 2008). The yields varied between 0.5 and 0.8%, with the maximum amount being obtained in winter. There are also some differences in the proportions of the various constituents. GC-MS studies conducted on SCF extracts (Filip et al., 2014), on Indian (Srivastava et al., 2013) and on Polish essential oils (Wesolowska et al., 2012) reported an array of minor compounds.
Although they are all labeled basil oil, there are significant differences due to regional, seasonal, and varietal differences, and variations in the stage of maturity. These factors must be carefully considered while standardizing basil oil for flavoring purposes.
European-type oil is obtained by steam distillation of the flowering top or the entire aerial part. Basil oil is a pale yellow mobile liquid with a floral, spicy note and is soluble in fatty oils; however, the Comoros-type basil oil has a more noticeable camphoraceous note.
According to the FCC, Comoros-type basil oil occurs as a light yellow liquid with a spicy odor. It may be distinguished from other types, such as European-type basil oil, by its camphoraceous odor and physicochemical constants.
Basil oil dissolves in fatty oils. It is soluble in mineral oil, forming a turbid solution. While it is insoluble in glycerol, it can be taken into solution by propylene glycol with some haziness.
European-type basil oil, according to the FCC, occurs as a pale yellow liquid with a floral, spicy odor. It may be distinguished from other types such as Comoros or Reunion by its more floral odor and its physicochemical constants. It is soluble in most fixed oils, and in mineral oil but with some turbidity. One milliliter is soluble in 20 mL of propylene glycol with slight haziness, but it is insoluble in glycerin.
Physical characteristics as defined by the FCC are as follows:
Optical rotation -2 to + 2° -5 to -15°
Refractive index 1.512-1.520 at 20 °C 1.483-1.493 at 20 °C
Specific gravity 0.952-0.973 0.900-0.920
Solubility 1 mL dissolves in 4 mL of 80% alcohol