0.2.1 Processes for oil fruits

Since the oilpalm gives the economically most important tropical oilfruit, the technologies for its extraction can serve as an example in this category.

In the traditional process, the fruit is first removed from the bunches, generally after the bunches have fermented for a few days. The fruit is then cooked and pounded or trampled. The mashed mass is mixed into water. The oil and oilcontaining cell material is separated from the fibre and the nuts by rinsing with excess water and pressing by hand. The oil-containing mass, now floating on the top, is collected and boiled. In this step, the oil separates from the rest and collects on the surface. It is skimmed off and finally dried.

The actual execution of the process may vary somewhat from area to area; most traditional processes, however, have in common the superfluous use of water. Using this process, generally not more than 50% of the oil is obtained. The problems are:

- the digestion by means of pounding or trampling,
- the separation of the oil and oilcontaining material from the fibres and the nuts by means of water and
- the liberation of the oil by cooking afterwards.

The potential for improvement of this technology and thereby the development of small scale extraction equipment in principal depends on

- better cooking by means of steam,
- better digesting using a reheating step with steam and
- more effective pressing in a batch press or continuously working screw press.

The modern process of extracting palm oil, used on a larger scale, starts with the steam sterilization of the bunches. The bunches are threshed and the fruit is digested mechanically, while heated with steam. The mass is then pressed in hydraulic presses or continuously in screw presses. The oil is separated from the press fluid by heating and is finally dried.