Citral from lemongrass

Materials for flavoring may be divided into several groups. The most common groupings are either natural or artificial flavorings. Natural materials include spices and herbs essential oils and thek extracts, concentrates, and isolates fmit, fmit juices, and fmit essence animal and vegetable materials and thek extracts and aromatic chemicals isolated by physical means from natural products, eg, citral from lemongrass and linalool from hois de rose. 

A chemical substance or simple mixture of substances obtained from natural sources by distillation or extraction such as citral from lemongrass oil or eugenol from clove bud. 

Isolate The term for a single constituent that has been separated from a mixture of volatiles such as an essential oil, e.g. citral from lemongrass, limonene from citrus oils. 

Gitral Manufacture. Natural sources of citral are lemongrass oil and l itsea cuheha. Both oils contain 70—80 wt % citral. Synthetic citral is made from terpene sources such as nerol and geraniol and in multitonnage quantities from petrochemical sources. 

Isolation from Essential Oils. Citral is isolated by distillation from lemongrass oil and from Litsea cubeba oil. It is the main component of these oils. 

The two oils were formerly the main source of natural citral, obtained as a ca. 4 1 mixture of geranial and neral by distillation [463, 466a]. However, lemongrass oil has declined in commercial importance due to the competitive synthesis of citral and isolation of natural citral from Litsea cubeba oil. Today, some lOOt/yr are still... 

Nature Identical Flavor Matenal A flavor ingredient obtained by synthesis, or isolated from natural products through chemical processes, chemically identical to the substance present in a natural product and intended for human consumption either processed or not eg, citral obtained by chemical synthesis or from oil of lemongrass through a bisulfite addition compound. 

All industrial vitamin A syntheses use p-ionone as the starting compound (36, see page 14) 3S). This monocyclic C13 ketone can be obtained either completely synthetically from acetone and acetylene by consequent use of the C2 and C3 addition reaction, or via citral (59, see page 14) obtainable from natural sources (lemongrass oil). 

Citral occurs in many essential oils such as those of hops, rose, ginger, orange and basil. Its importance stems from its occurrence in lemon and lemongrass, the oils of which both depend heavily on citral for their characteristic odours. It can comprise as much as 85% of lemongrass oil. 

In one of the experiments in this chapter, you isolate the naturally occurring fat trimyristin from nutmeg, a valuable spice. In other experiments in this textbook, you have the opportunity to isolate citral, the odoriferous component of lemongrass oil (Sec. 4.6), and to separate different pigments found in green leaves (Sec. 6.2). You may also examine the two enantiomers of carvone, one of which is found in spearmint and the other in caraway seed oil (Sec. 7.4). The techniques you will use in these experiments serve as an introduction to the methods that are used in research laboratories to isolate natural products having potential value to society. 

In this respect, menthol from citral would be an attractive synthetic route because citral is a renewable raw material mainly obtained by the distillation of lemongrass oil, which contains approximately 70-80% citral. 

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