Zitronen oel [German]

Description

Evergreen tree (shrub) native to the Far East; actual growing site questionable. It was introduced into the Mediterranean region at the time of the Crusades. The plant grows to 6 m (20 ft.) high. It has strong, branched roots and an erect trunk with several branches; the lower limbs are sometimes covered with thorns. The tree has alternate oval leaves, white flowers (from February to October), and oval fruits that are yellow when ripe. The rind of the fruits is thin, and the epicarp is rough; the segmented endocarp contains a sour juice and oval seeds. The leaves (and terminal twigs), fruits, and rind are the parts used. Lemon has a character istic lemon-leaf odor and a sour, bitter taste.
Lemon petitgrain is obtained by steam distillation of the leaves. It has small, terminal twigs and small, unripe fruits with yields varying between 0.16 to 0.23%. It is a clear, mobile, pale-yellow or amber liquid exhibiting the characteristic odor of the leaves.
For flavoring use, lemon petitgrain oil must be terpeneless. Its main constituents include d-α-pinene, camphene, d-limonene, dipentene, l-linalool, geraniol, nerol, and the corresponding ace tates, esterified cineol, and citral.
Lemon essential oil is obtained by cold expression (mechanical or manual) of the peel in yields of approximately 4% based on the weight of the fruit. (A less valuable quality of oil is obtained by steam distillation of the peel.) The expressed oil is a mobile, clear liquid that may become turbid on cooling; it is pale yellow or greenish-yellow. The physical-chemical constants of lemon essen tial oil vary, depending on the source of the fruit-Spain, California, Florida, Israel, Italy.
To date more than forty constituents have been identified in the oil, which contains approximately 90% limonene (by weight). Other important terpenes include α- and β-pinene, myrcene, citral, and γ-terpinene. The non-volatile residue contains citropten (or limettin). From the normal essential oil, the terpeneless and ses quiterpeneless oils are obtained by vacuum rectification, washing with dilute alcohol or by column chromatography. Rectification is important to achieve a product with good solubility. Terpeneless oils are also more stable, as they are less sensitive to oxidation.
Soluble essences are prepared by using low-strength ethanol with yields of 1/50, 1/100, 1/200, and 1/400 with reference to formu lated syrups.
Using typical extraction techniques, the derivatives are a fluid extract and a tincture (20% in 70% ethanol) obtained from the dried peel. By properly compounding the essential oil (raw or terpeneless), juice, pectins, and sugars, it is possible to prepare pastes suitable for flavoring carbonated beverages.
The preparation of lemon juice is similar to that of orange.