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*The first column, a, gives the mean of the values reported by Afzal et al. (2001) on polar and nonpolar columns. The second column, b, gives the values reported by Akhila and Tewari (1984) for comparison.

The high percentage found by Afzal et al. (2001) for ar-curcumene (17.7%) seems to indicate a rearrangement of P-bisabolene. A very low content of neral and geranial in the two oils was observed in contrast to the results of Ekundayo et al. (1988) (see Table 3.20). The chemical composition of the sesquiterpene hydrocarbons reported by Afzal et al. (2001) corresponds to that for oils from other countries.

Essential Oils from Other Countries (Australia, Brazil, Poland, Mauritius Island, and Tahiti)

GC analysis of ginger oil from Australia obtained by hydrodistillation or steam distillation of dried rhizomes indicated that it was similar to that from other areas (Connell, 1970; Connell and Jordan, 1971). The major constituents are usual sesquiterpene hydrocarbons with a bisabolane skeleton: a-zingiberene (20 to 30%), ar-curcumene (6 to 19%), P-sesquiphellandrene (7 to 12%). These compounds are accompanied by usual monoterpene hydrocarbons and oxygenated derivatives. Of particular interest is the presence of a relatively high proportion of neral and geranial responsible for the distinctive citrus-like aroma of the oil. GC chromatograms on a column coated with Apiezon M at 130 and 147° C were reported as well as the chromatogram of an African oil. Zingiberone and zingiberenol were also identified.

Taveira Magalhaes et al. (1997a,b) studied essential oils and oleoresins of ginger from Brazil. Two kinds of ginger are characterized by the size of their rhizomes: Gigante commercial crop for export and Calpira for household consumption and of Japanese origin. Steam distillation of dried rhizomes gave essential oils that where characterized by their physicochemical constants and GC analysis. Comparative analysis showed differences between Calpira and Gigante gingers depending on the distillation method and the type of rhizomes (fresh or dried). The strong lemony scent due to its neral and geranial contents is more pronounced for Gigante oil than for Calpira oil. Agronomical and market aspects of ginger cultivation of the two varieties were also reported. The same workers reported the chemical composition of the essential oils of these two kinds of ginger. Most important components are given in Table 3.22. Yields of essential oils obtained from dried rhizomes were 1.2 to 2.5% for Gigante and 2.5 to 2.8% for Calpira.

Table 3.22 Gas chromatography analyses of Gigante and Calpira ginger oils from Brazila

Table 3.22 Gas chromatography analyses of Gigante and Calpira ginger oils from Brazila

Compounds

Gigante

Calpira

a-Pinene (+ camphene)

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