a study of the quality of a local herbal tea and volatiles of parinari ...

alcohols, aldehydes, esters, ethers, ketones, phenols, oxides and other specific
compounds containing either sulphur or nitrogen (Heath, 1978). While monoterpenes
(C10) are the lower boiling point fraction of essential oils, sesquiterpenes (C15) are mainly
found in the higher boiling point fraction. The diterpenes (C20) and triterpenes (C30) are
generally eliminated by distillation (Croteau, 1980). While terpenes contribute negligibly
to the flavour profile, they act as a carrier of less volatile constituents and thus
influencing odour (Heath, 1978).
2.4 Biogenesis of aroma compounds
Many flavours, especially those in fruits and vegetables, are the secondary products of
various metabolic pathways (Fisher and Scott, 1997). There are three main classes of
compounds in relation to aroma biogeneration; these are fatty acids, amino acids, and
carbohydrates (Sanz et al., 1997). Secondary metabolites act as an interface between the
producing organism and its environment, they may be produced to combat infectious
diseases, to attract pollinators and to discourage or encourage herbivores (Fisher and
Scott, 1997). Several pathways are involved in aroma biosynthesis; these have not been
fully described but appear to be common for different fruits (Sanz et al., 1997).
2.4.1 Metabolism of fatty acids
Fatty acids seem to be the major precursors of volatile compounds responsible for aroma
of most plant products (Sanz et al., 1997). The character impact compound for a
particular flavour or aroma is a unique chemical substance that provides the principal
sensory identity (McGorrin, 2002). Many character impact compounds responsible for
the fresh, green, and fruity notes of fruits and vegetables are derived from fatty acids
(Berger, 2007). Natural plant volatiles, such as aliphatic esters, alcohols, acids and
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