by Geoff Folkard and John Sutherland.
A previous article (in Footsteps 20) described the many uses and products of the multi-purpose tree – Moringa oleifera. That article described the use of crushed seed to clean drinking water. This article looks at methods of extracting edible oil from moringa seed.
Vegetable oil is an important part of our diet. It is a concentrated source of food energy. Small amounts added to the diet of young children can provide them with a more varied and nutritious diet. However, most cooking oil is expensive and produced by commercial companies.
The Intermediate Technology Development Group (ITDG) in Zimbabwe have looked at machines appropriate for the small-scale processing of oil seed crops – mainly sunflower. The oil mills introduced have brought many benefits to the surrounding areas. Farmers have a good market for their seed, people benefit from cheaper, good quality cooking oil and the mills bring employment.
Moringa oil has been used in skin preparations and ointments since Egyptian times. The bright yellow oil with a pleasant taste has been compared in quality with olive oil. The kernel contains 35–40% by weight of oil. Recent studies in Ghana show that soap made with moringa oil was extremely good. Trials on extracting oil from moringa were carried out with the enthusiastic assistance of Keith Machell.
Moringa seed has a fairly soft kernel, so the oil can be extracted by hand using a screw press (also known as a ‘spindle’ or ‘bridge’ press). The seed is first crushed, 10% by volume of water is added, followed by gentle heating over a low fire for 10–15 minutes, taking care not to burn the seed. One such test yielded 2.6 litres of oil from 11kg of kernels. Once the best processing conditions are worked out, an extraction efficiency of 65% could probably be expected.
Further trials were carried out using a motor-driven screw-type oil expeller from India. During 2 hours of operation 52kg of seed yielded 12.5 litres of cold pressed oil. A further processing of the oil cake yielded a further 10 litres of oil.
Traditional methods of extracting oil from oil seed crops are often slow and not very efficient. They involve extracting the kernels, pounding them and boiling them for 5 minutes in water. After boiling, strain through a cloth into a clean container. Leave overnight to allow the oil to separate from the water. There may be some debris floating on the surface of the oil. Tribesmen in Oman use this technique to extract oil from Moringa peregrina seed with some success. If you don’t have access to a machine, try out this method.
After the oil is extracted, the rather bitter tasting presscake still has all the properties of fresh seed in treating and cleaning water. With a 60% protein content, it may be used as a soil fertiliser and further study is looking at how it could be used as part of animal and poultry feed.
The authors are grateful for the support of the ODA, the EC Commission and Keith Machell. They would be pleased to hear from readers with queries about Moringa species. Write to them at:
Department of Engineering, University of Leicester, LE1 7RH, UK.