2.3. Fruit flavours

Although certain aromatic spicy fruits (coriander, black pepper, white pepper, pimento berry, ...) have a very high content of aromatic compounds which can be obtain as essential oils, the flavour components of table fruits are present at lower concentrations. So, although one can identify and enjoy the taste and the aroma of a specific fruit, for the flavourists or the perfumers these contents limit the use of concentrates of fruit flavours.

Aromatic components

• Alcohols - C1 to C12 with a preponderance of even-numbered carbon atoms.
• Carbonyls - aldehydes and ketones - benzaldehyde (found in many fruits with stone), 5-hydroxy-2-methylfurfural (found in pineapple), furfural (found in strawberries), etc.
• Acids - in the volatile fractions of fruits are limited to formic and acetic acids.
• Esters - the most important and numerous aromatic components of fruit flavour, often characteristic of a given fruit.
• Lactones - are responsible for characteristic aromatic notes of many fruits. Heinz and Jennings (1966) verified that the ratio of various lactones changes during the ripening process.
• Phenols - are present in many fruits in the form of tannins and are responsible for the characteristic astringency. The presence of phenols is more important in unripe fruits, and diminishes as the fruits ripe.

Carbohydrates

The carbohydrates present in fruits are of considerable importance for their quality and edibility.

These compounds are produced by photosynthesis and those of interest to food and flavour industries are:

The principal sugars found in fruits are fructose and glucose which are reducing sugars, and sucrose, a non-reducing sugar.

Glucose	Frutose
Sucrose

The amount of sugars and relative proportions present in a fruit depend on its nature and its degree of maturation.

Acids

Some fruits are particularly rich in organic acids either in the free state or combined as esters.

Aliphatic acids
Monocarboxylic acids	Formic	H COOH
	Acetic	CH3 COOH
	Butyric	CH3 (CH2)2 COOH
	Glycolic	HO CH3 COOH
	Lactic	CH3 CH(OH) COOH
	Glyceric	HO CH2CHOH COOH
	Pyruvic	CH3 CO COOH
	Glyoxylic	CHO COOH
Dicarboxylic acids	Malonic	HOOC CH2 COOH
	Adipic	HOOC (CH2)4 COOH
	Fumaric	HOOC CH CH COOH
	L-Malic	HOOC CH2 CH(OH) COOH
	Tartaric	HOOC CH(OH) CH(OH) COOH
Tricarboxylic acids	Citric	HO C(CH2 COOH)2 COOH
Carbocyclic acids
Benzoic acid

Amino acids are also present and are essential precursors to many of the biochemical systems in plant metabolism (Rohan, 1970).