As juicy as a lemon
The lemon is ovoidal and oblong-shaped, with an umbo at the top, the peel is light yellow, the pulp is yellowish and very sour and is divided in eight/ten segments. There are also varieties of lemon with a variegated green and white peel.
The citrus fruit sprouts in the form of a berry, called hesperidium. As regards the physiology of the lemon, in general the epicarp or exocarp (the tough peel that contains the fruit) is thick and coloured, full of glands containing the essential oils. The mesocarp or pith (intermediate layer) is part of the epicarp and is white and spongy.
The endocarp (pulp, interior part) is divided in 8-10 segments by thin membranes. Inside the segments there are cells and vesicles containing a solution of water, sugar and acids. Every segment contains between 4 and 8 ovules, which can produce as many pips. These are whitish, egg-shaped and contain embryos.
According to the variety or cultivar of the plant, the lemon fruits can have different characteristics as regards the dimension, the colour, the thickness and the rugosity of the peel, the juiciness and sourness of the pulp, the presence of pips, etc.
Composition of the fruit
- 40% peel
- 57-58% pulp
- 2-3% pips
Besides the alimentary and culinary use of the fresh fruit, the lemon can be used in different ways. In particular:
- from the pulp they extract the lemon juice, which has numerous uses in the alimentary, chemical field (citric acid) and pharmaceutical field
- from the peel they extract the essential oils
- the pips can be used as pectins or to produce oil.
The pectins are vegetal substances that are drawn from the pulp and, above all, from the peel of the citrus fruit, but also from other fleshy fruit such as the apples. Their industrial classification is E440.
The pectin, as Braconnot discovered in 1825, is the principal constituent element of the fruit, where it is in form of protopectin (pectin bonded with cellulose) and has a high commercial value. As a matter of fact, in an acid solution (usually citric acid) and in the presence of sucrose, the pectins form gelatines: because of this property they are used especially in the alimentary industry (thickeners, emulsifiers, stabilizers) and in the pharmaceutical industry (antidiarrheals haemostats).
In the alimentary mixes pectins can be used in powder or in liquid form (concentrated extract), like, for example, in jams.
Depending on the techniques of industrial production, different kinds of pectins can be obtained:
- quick-setting pectins (ideal for some types of jams; they can be purified further, to be used in the pharmaceutical field)
- slow-setting pectins (used, above all, as alimentary gelatines)
- low methoxy pectins (capable of gelatinizing even in the absence of sugar).