SOIL AND PLANT ANALYSIS (1+1)

CHEMISTRY OF FRUITS

Fruits are valued for their attractive appearance, flavour and texture for a long time. In recent years their vitamin content has been recognized as an important feature. In all these characteristics, sugars either in the free stage or as derivatives play an important role. Flavour is fundamentally the result of the balance between sugars and acids. Certain flavouring constituents which are mostly glucosides also add to the flavour of the fruits.

I. Sugars
The sugar content varies from traces to 61% in fruits. Traces of sugars are present in lime and 61% in date. Sugars other than glucose, fructose and sucrose are rarely present. The average sugar content varies from 5-10%.

Apple	6-16%
Pineapple	8-18%
Grapes	10-19%
Mango	14%
Date	61%
Tomato	2-4%
Lemon	0.9-3.6
II. Proteins
The protein content of fruits is comparatively very low. The protein content varies with species, locality, season, cultural practices and other environmental factors.


Apple	0.2%	Grapes	1.3%
Banana	1.1%	Guava	0.8%
Avocado	2.1%	Lime, mango and pineapple	<1%
Tomato	1.2%	Dates	2.2%

III. Volatile compounds
The characteristic odour of many fruits is due to the presence of certain volatile compounds. These volatile compounds of the fruits are usually less than 100 ppm in concentration.
This group generally includes esters but compounds such as alcohols, aldehydes, ketons etc. are also found to possess pleasant aroma.


Apple	Ethyl 2 methyl butyrate
Grapes	Methyl anthranilate
Banana	Amyl acetate and isopentyl acetate
Grape fruit	Terpenes

Lemon: Hydrocarbon containing isoprene units and their oxygenated derivatives.
Orange: Limonene.

IV. Fruit phenolic compounds
Phenolic compounds are responsible for colour flavour and taste. These compounds give both desirable and undesirable qualities in fruits. The fruit phenolic compounds include both “Flavonoids” and “Cinnamic acid”. The major flavonoids are anthocyanin, leucoanthocyanin, flavones and flavonols. Cinnamic acid and its derivatives are not flavonoids but related to them. The presence of these phenolic substances in fruits gives an astringemt taste.