Natural flavourings from biotechnology for foods and beverages - Natural Food Additives, Ingredients and Flavourings - page 242

intake of 2.3 μ g/kg/day in the US. Carveol may be extracted from caraway seeds,
spearmint, orange juice, mango and eucalyptus oil, where it is present in small
amounts, sometimes esterifi ed, but it can also be prepared from the oxidation of
limonene (Burdock and Fenaroli 2010). Biotransformation processes for
producing natural carveol as the major product have already been reported using
limonene as the substrate and Aspergillus niger (Divyashree et al. 2006) or
Rhodococcus opacus (Duetz et al. 2001) as biocatalysts. One of the highest yields
of carveol described so far is 13.4 mM (~2 g L −1 ) using the bacteria
Cellulosimicrobium cellulans (Wang et al. 2009).
Perillyl alcohol is one of the most prominent and desirable monoterpene
alcohols due to its potential in the treatment of cancers (Koroch et al. 2007). It has
a green-type aroma descriptor, also described as sweet, fatty and woody resembling
linalool (fl oral) and terpineol, with a threshold of 7 ppm (Burdock and Fenaroli
2010). This alcohol is found in small concentrations in essential oils, such as
lavander and bergamot ( S -isomer), caraway ( R -isomer), gingergrass ( R - and S -),
citrus peel, berries, peppermint, hop, cardamom and others. The reported uses of
perillyl alcohol are baked goods, frozen dairy, gelatine, puddings, beverages and
candies in a concentration of 1-2 ppm. The S form may be obtained starting from
β -pinene by reducing perillyl aldehyde with zinc dust and acetic acid, followed by
saponifi cation of the acetate (Burdock and Fenaroli 2010). The biotechnological
production of perillyl alcohol starting from limonene is also feasible. Microbial
biotransformations for the production of perillyl alcohol as the major product
have already been reported using limonene as the substrate from the microorganisms
Aspergillus niger (Menéndez et al. 2002), Mortierella minutissima (Trytek et al.
2009), Bacillus stearothermophilus (Chang and Oriel 1994) or a recombinant
Escherichia coli (Cheong and Oriel 2000). The highest perillyl alcohol production
was found for a recombinant Pseudomonas putida cultivated in biphasic medium.
After 75 hours, a concentration of 6.8 g L −1 of organic phase was reached (van
Beilen et al. 2005).
Menthol is one of the most economically important monoterpene alcohols,
with an annual consumption of ca. 90 tonnes in the US. Its main uses are in
cigarettes, cosmetics, toothpastes, chewing gum, candies and medicines
(Surburg and Panten 2006; Burdock and Fenaroli 2010). Chemically, menthol is a
cyclic monoterpene alcohol with three asymmetric carbon atoms and consequently
four pairs of optical isomers are possible: (+)-and (−)-menthol, (+)- and
(−)-neomenthol, (+)- and (−)-isomenthol, and (+)- and (−)-neoisomenthol, with
(−)-menthol the isomer that occurs most widely in nature (peppermint and
other mint oils). This compound has a mint-like odor and exerts a cooling
sensation when in contact with the skin and mucosal surfaces, which is one
of its most attractive attributes for industry and may confer analgesic properties
(Koroch et al. 2007). Its aroma threshold is between 950 ppb and 2.5 ppm
(Burdock and Fenaroli 2010). Although the major portion of the worldwide
demand is supplied by Mentha oils, several processes exist for the synthesis
of (−)-menthol. Commercially important routes for the synthesis start from
thymol (hydrogenation) (Surburg and Panten 2006; Burdock and Fenaroli 2010)

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