The trees of jojoba (Simmondsia chinensis or Simmondsia californica) are nut producing, evergreen forest-type trees. They resemble (when pruned yearly to one stem, as done in Palestine) small olive trees, but with faintly green broad leaves rather than the olive color of olive leaves. From a distance, they appear as if they are olive trees.
Being desert trees, jojoba trees grow with a little amount of water, but to produce well, they need annually at least 300 mm of rain or its equivalent by drip irrigation. This is 50% less than what olive trees need (450 mm) for good production. The jojoba tree and its fruits are also known to be resistant to plant diseases and to insects. To produce economically, they do not need any special care except for removing weeds and providing some manure and the minimal quantities of water and organic fertilizer or manure.
Jojoba seeds are produced only by the female plants which begin economic production after four years of yearly fertilization and irrigation equivalent to 300 mm annually. Six years are needed to obtain an economic production (150 kg/hectare) of jojoba seeds from jojoba grown in hilly or marginal arid areas with less than 400 mm annual rainfall and are dry-farmed without irrigation. In more arid environments with low rainfall as in the desert farm of Professor Assaf near the airport in Jordan with less than 150 mm rainfall, a drip irrigation totaling 200mm spread over 10 irrigation times per year was found to be sufficient for a fair amount of jojoba seed production which was found to increase by the addition of organic manure.
Male plants which are planted within the jojoba plot in a distribution representing 10% of the female plants or as a fence around the whole plot are sufficient for pollination of all the female jojoba trees. Jojoba seeds planted in a row to serve as a green fence produce 50% female and 50% male plants. The males produce beautiful yellow flower clusters during the winter season when few other plants are flowering and thus can be well used for greenery in various environmentally needed places, especially where water quantities are limited.
As we elucidated, 50-60% by weight of the dry jojoba seeds is oil which is a liquid wax that may be obtained by pressing without causing any pollution to the surrounding area of the press or the general environment of the area. Pressing of jojoba seeds is done in an electrical screw press made for pressing hard seeds. Such a press and a pump filter is in operation in the town of Arrabeh of the Jenin District of Palestine and it is the only one for pressing hard seeds – as of 2004 – in the Arab World. This electric screw press is different from the centrifugal or the pressure pressing operations done in olive oil extraction. Olives are soft fruits with 45-60% water and yield from 18 to 30% oil, whereas jojoba nuts (seeds) normally have 2-4% water. The only other operation needed to obtain the pure jojoba oil is filtration, and as done in Palestine, cold-pressing is done.
No black watery residue called also vegetable water is produced as in olive pressing, and thus no contamination of environment ever occurs from jojoba oil production. Another 10-12% of jojoba oil may be produced by extraction of the jojoba seeds cake residue (jifit) with hexane or cyclohexane. This second grade oil is used in industrial lubrication and some may use it in mixed cosmetics, such as shampoos, lotions, soaps, etc.
The remaining dry cake residue is not edible “as-is”, but could be used as a natural soil improver and fertilizer, as it has 25-30% protein with nitrogen and fibers.
This dry cake residue also contains the organic substance simmondisine which may be extracted by water and purified by known biochemical techniques with the potential of being utilized as an appetite depressant drug.
Summary of the main characteristics of jojoba trees, their seed production and oil isolation: