Agriculture Reference
In-Depth Information
which are around 50-60% w/w. Citrus oils provide important raw materials for
the preparation of corresponding citrus fl avours but mostly require further
processing to remove the terpene components. Terpene molecules are relatively
complex hydrocarbons and, although they have distinctive aromas, are very
insoluble in beverages. Additionally they are particularly vulnerable to oxidation
and the products of such oxidative processes usually contribute an unpleasant
character to a beverage.
Citrus oils are processed for use as components of beverage fl avours either by
'washing' or by a fractional distillation process. Washing involves partitioning the
whole citrus oil in an aqueous alcohol mixture. Soluble components pass into the
aqueous alcoholic fraction leaving the less soluble terpene fraction as an upper
layer that is easily removed by separation. Some citrus fl avours are further enhanced
by the addition of individual components such as citral which have been obtained
by fractional distillation from citrus or other essential oils. So-called terpeneless
oils are produced by fractional distillation of whole oil, when the more volatile
terpenic components are removed leaving more oxygenated and thus more soluble
components. Neither washing nor fractional distillation remove all the terpenes and
for that reason citrus fl avours and the beverages produced from them are particularly
vulnerable to oxidation. The shelf lives of whole citrus oils, citrus fl avours and the
beverages produced from them need to take account of this vulnerability to
oxidative fl avour change. The use of carbonation, the addition of anti-oxidants
such as ascorbic acid and the use of appropriate packaging can all assist in reducing
the rate of oxidation. Citrus fl avour components are also very vulnerable to light
degradation and products should be stored away from direct sunlight.
15.3 Natural additives for soft drinks produced by distillation
Reference has already been made to the importance of distilled citrus oil
(particularly lime oil), but the process of distillation in its wider sense is employed
to provide ingredients that become part of the range of fl avours that fi nd application
in soft drinks. Essential oils from a variety of aromatic plants are used in the
preparation of fl avours that are used in beverages. The extraction of essential oils
is carried out by subjecting the plant material to a steam distillation process.
Depending on the plant material to be used the detail of each process will vary
slightly. In some cases, it involves immersing the botanical in water which is then
boiled; in others it may involve passing steam through the plant mass.
Essential oils co-distil with water vapour that is introduced. The vapour is
passed through a condenser into a separating vessel that allows plant essential oil
(which is normally less dense than water) to be separated and dried.
Essential oils are normally present in very small amounts (usually less than
0.5%) in plant material, although this may be greater where the botanical is dried
before processing.
A very wide range of essential oils is available commercially and they are used
in applications that vary from the preparation of fl avours of all types to use in
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