Natural aroma chemicals for use in foods and beverages - Natural Food Additives, Ingredients and Flavourings - page 213

quantities both in their own right and as the by-products of the juice industry, are of
great commercial importance as sources of natural aroma chemicals (Margetts
2004), some of which are used to prepare other natural aroma chemicals. One
useful differentiator might be that between materials that are directly isolated from
the oil (often mono-terpenes and their derivatives) and those that require additional
processing (usually sesqui- and di-terpenes and their derivatives).
Citrus oils are often 'folded', i.e. the more volatile terpenes (frequently
hydrocarbons that provide little organoleptic impact and have a negative effect on
water solubility) are distilled off, the remaining pot fraction being the 'folded oil'.
For example, grapefruit oil can be folded to give a terpene fraction, which along
with the ubiquitous d-limonene [10.2], contains the grapefruit mercaptan,
p -menthen-8-thiol [10.3]; the less volatile material, the 'folded oil', can be further
processed to give the oxygenated sesquiterpene nootkatone [10.4].

[10.2] [10.3] [10.4]

Orange oil, the cheapest and highest volume of all the oils, can be processed to give
d-limonene, aliphatic aldehydes such as octanal [10.5] and decanal [10.6] from the
terpene fraction, and the sesquiterpene valencene [10.7] from the folded oil.

[10.5] [10.6] [10.7]

￿ ￿ ￿ ￿ ￿

Other examples of 'volatile derivatives' are the pinenes, alpha - [10.8] and
beta - [10.9] from pine oils; these also yield alpha -terpineol [10.10]. Mandarin oil
is unusual in yielding a nitrogen derivative, methyl N -methylanthranilate [10.11].

[10.8] [10.9] [10.10] [10.11]