Petitgrain bigarade Citrus aurantium Essential Oil

Botanical Origin:

Common name: Bitter Orange

Latin name: Citrus aurantium   L.

Family: Rutaceae.

Other names: Engl.: bitter orange, sour orange, bigarade, bigarade orange, Seville orange. Deu.: Bitterorange, Bittere Orange, Pomeranze. Suom.: pomeranssi, hapanappelsiini. Sven.: pomerans. Fran.: bigarade, bigardier, oranger amer. Span.: naranja agria, naranja amarga. Pharm.: aurantii amari cortex, aurantii flores , folia aurantii, fructus aurantii, oil of neroli, oil of petit-grain, oleum neroli. Bot. syn.: Citrus amara Link, Citrus aurantium L. var. amara L., Citrus bigaradia Duhamel, Citrus bigarradia Loisel., Citrus vulgaris Risso.

Description:

The sour or bitter orange, Citrus aurantium   L, closely resembles the sweet orange, Citrus sinensis L, in general character and appearance of tree and fruit; yet the two represent very distinct botanical species and not merely cultivated varieties of one species. Bitter orange contain many subspecies, one of them is the bigarade, or the true bitter. It is distinguished from the sweet orange most readily by its broadly wing-margined leaf petioles, by the commonly hollow axis or core of its fruit, and by the acidity of its pulp.

The volatile oils in the leaves, flowers, and fruit of the bitter orange possess an odor different from that in the sweet orange and have a different chemical composition.

Range & Habitat:

The sour or bitter orange is, in all probability, a native of Cochin China in Southeastern Asia, whence it spread to India and Persia. Unknown to the Romans, even during the period of their greatest imperial expansion, it was introduced to the Mediterranean countries (Syria, Palestine, Egypt, North Africa, Sicily, Sardinia, Spain, and Southern France) by Arabs in the tenth and eleventh centuries A.D.

The bitter orange tree grows at altitudes below 400 m., in a warm climate, with an optimum average yearly temperature of 22 º to 23 º C. the trees are very sensitive to cold weather, particularly when previously weakened by attacks of insects and diseases. A temperature of – 4 º to – 5 º, maintained for several days, may cause serious damage, affecting the especially the young branches that have not yet lignified. Trees entirely covered with ice may have to be cut down. In some years, late spring frosts destroy a great part of the flower crop. A bitter orange grove should have much sun and air, but must be protected against strong winds.

With a favorable climate, the bitter orange tree may be planted in almost any soil, regularly manured and irrigated during the summer, but not in a soil which is too tightly packed or moist, or one containing excessive lime, clay, or silica.

Planting & Cultivation:

Bitter orange trees are propagated by seed, grafting, or by layering.

The seeds are planted in seed beds in March or April; transplanting takes place early in their second year, when the weather is warm and bright. The young plants are set out 30 cm. apart, in rows 1 m. apart. After two years they are grafted with slips containing buds, the most favorable time being in May or June, when sap flows freely in the trees and when the bark can be loosened easily from the trunk. All this work is done in commercial nurseries, which subsequently sell the young trees to grove owners.

Final planting of the young grafted trees takes place in April – May, at intervals of 4 m. During the first year branch growth must be controlled to keep the foliage sufficiently high above the ground and in well rounded shape, with space between the branches for flower harvesters to reach the center of the tree.

Cultivation consists of hoeing, plowing, manuring, pruning, irrigating, and treating against insects and diseases. The ground should be worked three times each year by fertilizing in spring, hoeing after the harvest, and hoeing during September – October in order to apply slowly decomposing manure. At least two plowings are required each summer. Irrigation is particularly important during the first two years after planting. Undertaken early in the morning or after sunset, or even at night, it varies according to climate, soil, exposure, and atmospheric conditions.

Harvesting and Preparing for the Market:

Flower Harvest:

Flower harvest takes place from the end of April to late May or early June; depending on weather conditions, it lasts from three to four weeks. A small harvest can be gathered also in fall, but compared with the spring harvest it is insignificant. Picking is done mostly by women and children who stand on ladders and drop the flowers on sheets spread on the ground around the trees. The blossoms from one tree are collected and put into a basket, the sheets spread beneath the next tree, the ladders moved, and the picking resumed.

The blossoms must be picked at the proper stage of development, when just beginning to open. Closed buds give an inferior yield of oil with a somewhat “green” odor. Care must be taken to pick only the blossoms and to exclude leaflets and petioles which, although increasing the weight of the flower material, impart a somewhat harsh Petitgrain “by-note” to the distilled Neroli oil.

The blossoms are spread on sheets in a thin layer and delivered early the following morning to the distillers. It is necessary to turn the blossoms over frequently during the overnight storage; otherwise, they develop heat and ferment.

Leaf Harvest:

From late June until early October, the trees are pruned, and the resulting leaf material is used for the distillation of oil of Petitgrain bigarade.

Yield:

Flowers

The flower yield of each tree depends upon its age, the care taken of it, weather conditions, and injury by insects and diseases. Well irrigated orchard begins to produce 3 or 4 years after planting. For the next ten years the orchard produces a medium harvest. The highest yield is obtained in the twentieth or thirtieth years. A ten-year-old tree produces about 6 kg of flowers yearly, an older tree up to 20 kg,

Neroli Oil

1 kg of orange blossoms yields about 1 g of Neroli oil; but the oil content is affected by many factors, and particularly by atmospheric conditions. Warm weather and ample sunshine increase the yield, because the blossoms then contain less water. A belated flower season is usually favorable to the yield of oil. The yield improves as the season progresses; it is lowest (about 0.07%) at the beginning, and highest (about 0.12%) toward the end of the harvest. Flowers from groves on slopes with southern exposure and protected from cold winds give the best yield.

Petitgrain oil:

Five hundred kilograms of leaves yield about 1 kg of petitgrain bigarade oil.

Method of Extraction:

By Steam Distillation.

Neroli Oil:

Flowers are charged to still (with steam jackets or steam coils) and 1.5 times that amount of water. The blossoms must float freely in boiling water (water distillation), as distillation with direct steam would result in an inferior yield. Orange blossoms like roses, clog together on treatment with live steam, the steam then forming channels through the agglutinated mass and escaping without coming in contact with all the blossoms. Distillation is usually carried out in such a way 1 liter (1 kg) of distillation water (“orange flower water”) is obtained per kilograms of charged orange flowers.

Obviously the length of distillation depends upon the quantity of water distilled over; in the usual stills it takes about 3 hr to obtain 1 liter of orange flower water per kilogram of flowers. The oil of Neroli floats on top of the distillation water as a yellowish liquid and is easily is easily separated in the Florentine flask. The distillation water retains, in a dissolved state about 1/3 of the total amount of volatile oil distilled over and is therefore very fragrant.

Petitgrain bigarade oil:

The leaves are charged into stills of 1500 to 2000 liter capacity, and live steam is injected for about 2 to 2.5 hr. The operation is carried out in such a way that 800 g of distillation water are collected per kilogram of plant material charged.

Notes:

• The leaf material to be distilled should originate exclusively from the true bitter (sour) orange tree. Such oils will have a relatively high laevorotation and that the presence of leaves from sweet orange trees will result in oils of lower laevorotation, or even of dextrorotation.
• The leaf material should not contain any wooden branches, nor any small (unripe) fruit. The presence of any such fruit in the leaf material will also result in oils of lower laevorotation, or even of dextrorotation.
• The leaf material should be distilled rapidly and with direct steam, generated in a separate steam boiler. It must not be immersed in boiling water, as this will cause hydrolysis of linalyl acetate, the most important constituent of petitgrain oil.

Adulteration & its Detection:

The oil is subject to much adulteration, especially with: