Natural flavourings from biotechnology for foods and beverages - Natural Food Additives, Ingredients and Flavourings - page 236

many cheeses, butter, beverages nuts, oats, honey and mushroom. (Burdock and
Fenaroli 2010). Although the essential oil of rose can contain up to 60% of
phenylethyl alcohol, it is too valuable to be used as a source of natural
2-phenylethanol for food fl avorings. Many microorganisms, especially yeasts, are
capable of producing 2-phenylethanol by normal metabolism ( de novo synthesis),
but the fi nal concentration of the fl avor in the culture broth generally remains very
low (Etschmann et al. 2002), for example with Getrichum fragans (Damasceno
et al. 2003) and Kluyveromyces marxianus (Fabre et al. 1998). However, a
concentration as high as 453.1 mg L −1 after 16 hours of fermentation by Pichia
fermentans was reported by Huang et al. (2001).
Isoamyl alcohol has a fusel oil, whisky character with a pungent odor and
repulsive taste with an aroma threshold value of 250 ppb to 4.1 ppm, and its uses
comprise alcoholic beverages, gelatins, puddings, baked goods, hard candy,
chewing gum, non-alcoholic beverages, frozen dairy and soft candy. This alcohol
occurs in vinegar, cheeses, butter, cognac, rum, whiskies, cider, sherry, grape
wines, arctic bramble, olive, gin, quince, sake and buckwheat (Burdock and
Fenaroli 2010). The bioproduction of isoamyl alcohol using Neurospora sp. was
reported by Kobayashi et al. (2008), Brown and Hammond (2003), Yamauchi
et al. (1991), Brigido (2000) and Pastore et al. (1994).

11.2.3 Acids and aldehydes
Among the aldehydes, benzaldehyde (almond aroma) and vanillin (see Section
11.3.6) are the most important and widely used by the food industry. Benzaldehyde
is used in aroma compositions due its bitter almond odor and is applied as a
starting material for a large number of aliphatic fragrance and fl avor materials. It
possesses a sweet, fl oral and spice-like odor (Burdock and Fenaroli 2010). It
naturally occurs in many products such as bitter almond, peach, apricot kernel,
cheeses and black tea (Surburg and Panten 2006). This compound can be obtained
in natural form, by extraction and distillation from botanical sources, or
synthesized from benzyl chloride.
Natural benzaldehyde, generally extracted from fruit kernels such as
apricots, is used as an ingredient in cherry and other natural fruit fl avors and
has a market of ~20 tons per year and a price of approximately EUR 240 per kg.
Benzaldehyde obtained from natural cinnamaldehyde can be purchased for
EUR 100 per kg with an estimated market of more than 100 tons per year (Feron
and Waché 2006). The screening of several white rot fungi has shown that
numerous species are able to synthesize benzaldehyde through de novo , such as
Pleurotus sapidus, Polyporus sp. and others (Lomascolo et al. 1999). Berger et al.
(1987) studied the formation of a methoxy benzaldehyde in Ischnoderma
benzoicum .
Methylbutyric acid can be naturally found in the composition of several oils,
such as peppermint and spearmint, and fruits (e.g. apricot, apple, grapes, papaya
and pineapple). This acid has an aroma threshold between 10 to 60 ppb, with notes
of fermented pineapple fruity and lingonberry (Burdock and Fenaroli 2010). It

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