Plant Material

Ajwain is an annual herbaceous plant, growing to a height of 90 cm, with a profusely branched stem. The leaves are primately divided with a size of 24 x 14 cm and with a clasping leaf base. The inflorescence is a compound umbel, each containing a few hundred flowers. The fruit is 2-3 mm long. On drying, the gray-brown fruit becomes the spice, generally referred to as seed. Often, the seed will have a hair-like attachment to the plant. Mild roasting gives it an enhanced aroma.

India is a major producer of ajwain, as it is used in many vegetarian dishes. It is also grown in Egypt, Afghanistan, and Iran. Ajwain consists of 15.4% protein, 18.1% crude fat, 38.6% carbohydrates, and 11.9% crude fiber. It is rich in minerals: calcium 1.42%, phosphorus 0.30%, and iron 14.6 mg % (Pruthi, 1976).

Essential Oil

In India, the seeds are mostly distilled in primitive stills, but there are also modern facilities that produce quality oil. The yield is reported to be 2.5-4%. Early in the twentieth century, some seeds were exported to Europe and the United States for distillation. Most likely this was for the separation of thymol, which has demand in medicinal preparations. However, with the introduction of synthetic thymol, export for this purpose died out.

Table 13.1. Analysis of ajwain oil

Constituent

Content (% v/w)

a-Pinene

0.2-1.0

p-Pinene

2.0-5.0

Limonene

0.1-0.6

p-Cymene

20.0-25.0

y-Terpinene

40.0-45.0

Thymol

20.0-30.0

Some monoterpenes have been reported in the literature (Akhtar et al., 1988). They include a-pinene 1.8%, camphene 0.5%, p-pinene 3.5%, myrcene 0.3%, 8-3-carene 0.5%, limonene 5.1%, a-terpene 34.9%, and p-cymene. The major oxygenated derivatives are thymol (45.2-48.5%) and carvacrol L (4.5-6.8%).

In the author’s laboratory, oil is produced by steam distillation. The oil is a colorless to brownish liquid possessing a characteristic thyme aroma.

Physical characteristics are as follows:

Optical rotation -1 to + 5°

Refractive index 1.490-1.499 at 25 °C Specific gravity 0.895-0.910

No oleoresin is known to be produced.

Results for a sample of oil produced and analyzed, using GC, in the author’s laboratory, are presented in Table 13.1. The major constituents seen are y-terpinene, p-cymene, and thymol. However, to produce the best quality oil, during distillation the first fraction is generally cut off and the second fraction is taken. This will show a thymol content of 40-42%, with corresponding reduction in p-cymene (12-18%) and y-terpinene (30-38%).

Analyses of a sample from Algeria and several samples from India were compiled by Lawrence (2006). The major components are thymol, isothymol, y-terpinene, limonene, and p-cymene. However, there are also some significant minor components.

Uses

Ajwain has a characteristic phenolic/medicinal flavor due to its thymol content. Its herbaceous and acrid taste is used in some vegetarian dishes. Ajwain could be useful in processed foods such as caramelized onion soups and similar dishes, where it can give an interesting flavor variation.

The main uses of ajwain and its oil are in medicinal preparations for stomach and intestinal treatment. It also has use in the treatment of bronchitis and asthma.

References

Akhtar, H.; Virmani, O.P.; Sharma, A.; Kumar, A.; and Misra, L.N. 1988. Major Essential Oil-Bearing Plants of India. Lucknow, India: Central Institute of Medicinal and Aromatic Plants, pp. 1-3.

Lawrence, B.M. 2006. Progress in essential oils. Perfum. Flavor. 31 (6), 60-70.

Pruthi, J.S. 1976. Spices and Condiments. New Delhi: National Book Trust, pp. 6-8.

 
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